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Dissertations / Theses on the topic 'Electrosynthesis'
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1
Smith, James Richard. "Electrosynthesis of novel polyheterocycles." Thesis, University of Portsmouth, 1995. https://researchportal.port.ac.uk/portal/en/theses/electrosynthesis-of-novel-polyheterocycles(3e3e0712-3b50-4ca5-a56e-f06585a8d592).html.
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Peacock, Martin James. "The electrosynthesis of diaryliodonium salts." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326302.
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Cox, Philip. "Electrosynthesis on non-metal electrodes." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252664.
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Watkins, John D. "Enhancing triple phase boundary electrosynthesis." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547876.
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The first part of this thesis is concerned with the synthesis, characterisation and applications of surface functionalised carbon nanoparticles. Synthetic techniques are used to modify the existing surface architecture of carbon nanoparticles towards high surface area modified electrodes and pH sensing applications. Electrochemical and synthetic techniques have been used to study triple phase boundaries and enhance their properties towards a bulk synthetic technique, in which an electrolyte phase and redox probe phase are held separate. A salt matrix, ultrasound, high shear force and a carbon fibre membrane have all been used to form unique triple phase boundary environments in which electron and ion transfer processes can be studied and enhanced towards analytical and electrosynthetic applications. A number of electro-reduction reactions have been shown to be feasible using the triple phase boundary methodology. Alkenes, aldehydes and imines have all been successfully electro-reduced, analysed and optimised to elucidate the synthetic triple phase boundary mechanism.
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Belmont, Cecile. "Coplanar interdigitated band electrodes for electrosynthesis." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/13940.
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The behaviour of coplanar cathodic and anodic band electrodes was investigated and their use for standard syntheses was proven to be considerably advantageous, when compared to other techniques. Electrode arrays were fabricated by screen printing platinum, silver or carbon inks. The inter-electrode distances were in the range 1 mm to 250μm for a constant band width of 1 mm. The mass transport was characterised for different inter-electrode distances and flow conditions. Figures compared positively with other cells. Two acceptable mathematical models were derived for the estimation of the resistance between coplanar band electrodes and were compared with results obtained experimentally or by simulation. Due to their excellent physical and chemical properties, platinum electrodes were found to be particularly well suited for the three syntheses investigated. The furan methoxylation, being carried out in a resistive solvent, was chosen to highlight the advantage of minimising the ohmic drop. It was also shown that the formation of by-product could be limited by acid neutralisation on the adjacent band. Vigorous mixing conditions were not crucial. With the 250 μm inter-electrode array, DHDMF could be produced with a current efficiency of 87%. This compared extremely well with other cells and furthermore the energy consumption could be reduced to 1.4kWh.kg<SUP>-1</SUP>, which represented a saving of at least 50%. The importance of having small ohmic losses was also encountered for the Kolbe reaction, where the applied voltage was set at high values. However the printed platinum film was too rugged and a passivation of the electrode was noticed. The advantage of having small inter-electrode distances was stressed by investigating the propylene epoxidation, which is a coupled reaction. Propylene oxide was produced at a rate of 0.12 mol.h<SUP>-1</SUP>.dm<SUP>-2 </SUP>for an energy consumption of 2.0 kWh.kg<SUP>-1</SUP>. This technique was thus found to be very competitive. Finally the possibility of using this method for the production of hypochlorite by electrolysis of sea water was investigated.
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Monti, Marco <1984>. "Electrosynthesis and characterization of structured catalysts." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4781/1/TESI_Marco_Monti.pdf.
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In this research work the optimization of the electrochemical system of LDHs as catalytic precursors on FeCrAlY foams was carried out.
Preliminary sintheses were performed on flat surfaces in order to easily characterize the deposited material. From the study of pH evolution vs time at different cathodic potentials applied to a Pt electrode, the theoretical best working conditions for the synthesis of single hydroxides and LDH compounds was achieved.
In order to define the optimal potential for the synthesis of a particular LDH compound, the collected data were compared with the interval of precipitation determined by titration with NaOH. However, the characterization of the deposited material on Pt surfaces did not confirm the deposition of a pure and homogeneous LDH phase during the synthesis. Instead a sequential deposition linked to the pH of precipitation of the involved elements is observed. The same behavior was observed during the synthesis of the RhMgAl LDH on FeCrAlY foam as catalytic precursor. Several parameters were considered in order to optimize the synthesis.. The development of electrochemical cells with different feature, such as the counter electrode dimensions or the contact between the foam and the potentiostat, had been carried out in order to obtain a better coating of the foam. The influence of the initial pH of the electrolyte solution, of the applied potential, of the composition of the electrolytic solution were investigated in order to improve a better coating of the catalyst support. Catalytic tests were performed after the calcination of the deposited foam for the CPO and SR reactions, showing an improve of performances along with optimization of the precursors synthesis conditions.
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Monti, Marco <1984>. "Electrosynthesis and characterization of structured catalysts." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4781/.
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In this research work the optimization of the electrochemical system of LDHs as catalytic precursors on FeCrAlY foams was carried out.
Preliminary sintheses were performed on flat surfaces in order to easily characterize the deposited material. From the study of pH evolution vs time at different cathodic potentials applied to a Pt electrode, the theoretical best working conditions for the synthesis of single hydroxides and LDH compounds was achieved.
In order to define the optimal potential for the synthesis of a particular LDH compound, the collected data were compared with the interval of precipitation determined by titration with NaOH. However, the characterization of the deposited material on Pt surfaces did not confirm the deposition of a pure and homogeneous LDH phase during the synthesis. Instead a sequential deposition linked to the pH of precipitation of the involved elements is observed. The same behavior was observed during the synthesis of the RhMgAl LDH on FeCrAlY foam as catalytic precursor. Several parameters were considered in order to optimize the synthesis.. The development of electrochemical cells with different feature, such as the counter electrode dimensions or the contact between the foam and the potentiostat, had been carried out in order to obtain a better coating of the foam. The influence of the initial pH of the electrolyte solution, of the applied potential, of the composition of the electrolytic solution were investigated in order to improve a better coating of the catalyst support. Catalytic tests were performed after the calcination of the deposited foam for the CPO and SR reactions, showing an improve of performances along with optimization of the precursors synthesis conditions.
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Hayati, Burhan. "Mass transfer characteristics of adiponitrile multiphase electrosynthesis." Thesis, Teesside University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385888.
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Lai, Min. "Templated electrosynthesis of nanomaterials and macroporous structures." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441665.
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Thomson, Alastair David. "The electrosynthesis and characterisation of functionalised polyindoles." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/13118.
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The aim of the work presented in this thesis was to investigate the electropolymerisation of indole and various substituted indole monomers, with the objective of electrosynthesising, characterising and functionalising indole-based conducting polymers for possible use as sensor devices. It was found that on electropolymerisation, all of the substituted indole monomers studied formed asymmetric cyclic trimer species. A mechanism was proposed invoking a 3-3' dimer intermediate to explain the nature of the trimer formed. These trimers were believed to initially form in solution and then deposit on to the electrode surface where they could link to form a polymer film consisting of linked trimer units. The polymer film then facilitated the formation of trimers on the film surface. The electronic nature of the substituents was found to control the reactivity of the trimers, and a correlation was found between the electron withdrawing / donating nature of the substituent and the observed potential of the trimer one electron redox reaction. The lyophilicity of the trimer substituents was found to affect the relative solubility of the trimers which controlled the rate of initial adsorption of trimers on to the electrode surface and the rate of desorption of free trimers from the polymer film. It was discovered that for the electropolymerisation of indoles with highly solubilising substituents, a pre-formed polymer layer could be used to encourage the deposition of trimers on to the film and decrease their desportion rate. This was also used to limit any passivation effects noted for electropolymerisation on platinum. The linking mechanism of all the substituted cyclic trimers studied is believed to be very similar. This was tested by studies carried out on the electropolymerisation of N-methylindole. These studies showed that the major product of the N-methylindole electropolymerisation was a highly soluble cyclic trimer species, in addition there was also an appreciable amount of linear polymer produced from the energetically destabilised sterically hindered 3-3'dimer. The absence of any linking of the N-methylindole trimers suggested that the nitrogen positions in the trimer are involved in the linking reaction observed for all of the other substituted indoles studied.
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Fotsing, Kamte Marcellin M. "Electrosynthesis and mechanism of copper(I) nitrile complexes." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=974106666.
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Pornputtkul, Yingpit. "Development of chiral conducting polymers for asymmetric electrosynthesis." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060522.113926/index.html.
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Scienza, Lisete. "Electrosynthesis and characterisation of polypyrrole films on aluminium." Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681336.
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Kalu, Eric Egwu. "Simultaneous electrosynthesis of alkaline hydrogen peroxide and sodium chlorate." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/28391.
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Simultaneous electrosynthesis of alkaline hydrogen peroxide and sodium chlorate in the same cell was investigated. The alkaline hydrogen peroxide was obtained by the electroreduction of oxygen in NaOH on a fixed carbon bed while the chlorate was obtained by the reaction of anodic electrogenerated hypochlorite and hypochlorous acid in an external reactor. An anion membrane, protected on the anode side with an asbestos diaphragm was used as the separator between the two chambers of the cell.
The effects of superficial current density (1.2 - 2.4 kA m⁻²), sodium hydroxide concentration (0.5 - 2.0 M) and catholyte flow (0.1 x 10⁻⁶ - 0.5 x 10⁻⁶ m³ s⁻¹) on the chlorate and peroxide current efficiencies were measured. The effect of peroxy to hydroxy mole ratio on the chlorate current efficiency was measured too.
The cell was operated at fixed anolyte flow of 2.0 x 10⁻⁶ m³ s⁻¹, inlet and outlet temperatures of 27/33°C (anode side), 20/29°C (cathode side), cell voltages of 3.0 - 4.2 V (current density of 1.2 - 2.4 kA -m⁻²) and a fixed temperature of 70°C in the anolyte tank. Depending on the conditions, alkaline peroxide solution and sodium chlorate were cogenerated at peroxide current efficiency between 20% and 86%, chlorate current efficiency between 51.0% and 80.6% and peroxide concentration ranging from 0.069 M to 0.80 M. The cogeneration of the two chemicals was carried out at both concentrated (2.4 - 2.8 M) and dilute (0 - 0.5 M) chlorate solutions. A relative improvement on the current efficiencies at concentrated chlorate was observed. A chloride balance indicated negligible chloride loss to the catholyte.
The results are interpreted in terms of the electrochemical and chemical kinetics and the hydrodynamics of the cell .<br>Applied Science, Faculty of<br>Chemical and Biological Engineering, Department of<br>Graduate
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Szanto, Dominic A. "Characterisation of electrochemical filter-press reactors." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286086.
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Nguyen, Tu Ngoc. "Electrosynthesis and characterization of main group and transition metal oxides." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11949.
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Omweri, James Mokaya. "Electrosynthesis of Lithium Borohydride from Trimethyl Borate and Hydrogen Gas." Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1577718541596251.
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Valdes, E. M. "Studies of the Ce(III)/Ce(IV) couple in multiphase media." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380041.
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Batlle, Vilanova Pau. "Bioelectrochemical transformation of carbon dioxide to target compounds through microbial electrosynthesis." Doctoral thesis, Universitat de Girona, 2016. http://hdl.handle.net/10803/399148.
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In 2015 the average concentration of CO2 in the atmosphere exceeded 400 ppm. Some technologies, including CO2 capture and storage, are palliative. However, the development of alternatives to burning of fossil fuels focuses on the base of the problem and proposes substantial changes in the energy model. This thesis proposes the use of bioelectrochemical systems to transform CO2 into valuable products. This process is known as microbial electrosynthesis, and is based on the use of bacteria able to use the electrode as an electron donor (biocathode) to drive CO2 reduction. The results show that the production of hydrogen as intermediate is key to allow further CO2 reduction. This thesis has proven methane production, and organic liquid compounds of two (acetic acid) and four (butyric acid) carbons. The results invite to continue investigating to exploit all the potential of BES and enable its industrial scalability<br>El 2015 la concentració mitjana de CO2 a l’atmosfera va superar per primera vegada les 400 ppm. Algunes tecnologies, com la captura i emmagatzematge de CO2, són pal·liatives. En canvi, el desenvolupament d’alternatives a la crema de combustibles fòssils van a l’arrel del problema i proposen canvis substancials en el model energètic. Aquesta tesi planteja l’ús dels sistemes bioelectroquímics per transformar el CO2 en productes amb valor afegit. Aquest procés es coneix com electrosíntesi microbiana, i es basa en la utilització de bacteris capaços d’utilitzar l’elèctrode com a donador d’electrons (biocàtode) per portar a terme la reducció de CO2. Els resultats demostren que la producció d’hidrogen com a compost intermedi es la clau per poder portar a terme la reducció de CO2. Aquesta tesi ha demostrat la producció de metà, i compostos líquids orgànics de dos (acid acètic) i quatre (acid butíric) carbonis. Els resultats esperonen a continuar investigant per aprofitar tot el potencial dels BES i fer possible la seva escalabilitat industrial
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Lisi, Fabrizio. "Microbial electrosynthesis of industrially viable chemicals from carbon dioxide and electricity." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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This master thesis reflected the work done during the internship at Laboratory of Chemical and Environmental Engineering (LEQUIA), a research group of the University of Girona. The research study dealt with biotechnological platforms for CO2 recycling and valorization. In two lab-scale H-type reactors industrially valuable chemicals were produced through microbial electrosynthesis (MES), using only carbon dioxide and electricity. The work was focused on investigating conditions and experimental parameters triggering chain elongation process in MES applications. Plus, the effect of several factors (applied potential, hydraulic retention time and CO2 loading rate) on MES performance was tested. The reactors were run in a three-electrode configuration and connected to a potentiostat. The energy provided to the anode induced water oxidation reaction, which generated the electrons and protons required for the cathodic CO2 reduction into organics catalyzed by microbial cells. In this study, significant acetogenic and solventogenic activity was detected, as well as chain elongation production. The highest concentrations obtained for ethanol, acetic, butyric and caproic acid were 5.28, 12.90, 1.32 and 1.28 g L-1, respectively. For both systems the maximum productivity phase was observed when low nutrient availability was present in the bulk liquid, while CO2 loading rate and applied potential did not represent limiting factors for the overall MES performance. Moreover, the results obtained validated several observations discussed in reference works regarding solventogenic optimal conditions and the influence of production trends on current signal. Finally, the parameters tested in this work showed potential for increasing MES productivity and further combinations should be investigated for the optimization of MES technology towards the production of higher-value organic compounds.
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Patel, Anish P. "The electrochemical activation and incorporation of carbon dioxide into organic molecules." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14424.
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The consumption of large quantities of fossil fuels on a yearly basis for energy purposes has led to the release of vast quantities of carbon dioxide into the Earth s atmosphere leading to global warming. In order to decrease the amount of carbon dioxide entering the atmosphere, procedures such as carbon dioxide capture and storage are currently being implemented, although this process is successful in decreasing atmospheric carbon dioxide concentration it results in the mindless storage of an otherwise synthetically useful reagent. The development of a viable method to capture carbon dioxide, followed by synthetic utilisation often referred to as CCU is currently gaining much attention. The main challenges in the development of a suitable utilisation reaction are energy and cost efficiency as well as the use of environmentally friendly conditions. Previous reports on utilisation include the catalytic incorporation of carbon dioxide into epoxides under electrochemical conditions, however this process had several drawbacks. In this project the shortcomings of this reported procedure have been addressed in order to develop a potentially viable utilisation process. The catalyst free electrocarboxylation of mono-substituted epoxides, using a magnesium anode/copper cathode electrode couple and tetrabutylammonium bromide supporting electrolyte in a sealed single compartment cell, was achieved under mild reaction conditions (1 atmosphere carbon dioxide pressure, 60 milliamperes constant current and 50 degree celsius heating), producing the corresponding 5-membered cyclic carbonate product in excellent yields (65-96%). Interestingly the use of sono-electrolysis allowed the reduction of para-substituted aromatic epoxides. The stoichiometric addition of tetrabutylammonium bromide was key for the effective activation of carbon dioxide and the epoxide. Similar carbon dioxide incorporation into analogous mono-substituted aziridines, synthesised using a modified Wenker synthesis allowed the formation of the corresponding cyclic carbamates in moderate to excellent yields (32-90%). The selective synthesis of 6-membered cyclic carbonates from oxetane substrates was also achieved in good yields (60-70%) as well the non-selective synthesis of polytrimethylene oxide. The electrochemical process also allowed the tandem formation of magnesium carbonate in quantitative yield (85%). Furthermore substrate free electrocarboxylation allowed the synthesis of alternative iron and zinc carbonates in excellent yield (83-85%) as well as the selective synthesis of aluminium oxalate (99%). Coupled with the high recovery of the supporting electrolyte (90%), this work has demonstrated the economical synthesis of industrially useful chemical feed-stocks under green conditions.
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Trinidad, Pedro. "Fluid flow, mass transport and electrosynthesis studies in filter-press electrochemical reactors." Thesis, University of Portsmouth, 2001. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.766481.
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Karlsson, Rasmus. "Theoretical and Experimental Studies of Electrode and Electrolyte Processes in Industrial Electrosynthesis." Doctoral thesis, KTH, Tillämpad elektrokemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177025.
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Heterogeneous electrocatalysis is the usage of solid materials to decrease the amount of energy needed to produce chemicals using electricity. It is of core importance for modern life, as it enables production of chemicals, such as chlorine gas and sodium chlorate, needed for e.g. materials and pharmaceuticals production. Furthermore, as the need to make a transition to usage of renewable energy sources is growing, the importance for electrocatalysis used for electrolytic production of clean fuels, such as hydrogen, is rising. In this thesis, work aimed at understanding and improving electrocatalysts used for these purposes is presented. A main part of the work has been focused on the selectivity between chlorine gas, or sodium chlorate formation, and parasitic oxygen evolution. An activation of anode surface Ti cations by nearby Ru cations is suggested as a reason for the high chlorine selectivity of the “dimensionally stable anode” (DSA), the standard anode used in industrial chlorine and sodium chlorate production. Furthermore, theoretical methods have been used to screen for dopants that can be used to improve the activity and selectivity of DSA, and several promising candidates have been found. Moreover, the connection between the rate of chlorate formation and the rate of parasitic oxygen evolution, as well as the possible catalytic effects of electrolyte contaminants on parasitic oxygen evolution in the chlorate process, have been studied experimentally. Additionally, the properties of a Co-doped DSA have been studied, and it is found that the doping makes the electrode more active for hydrogen evolution. Finally, the hydrogen evolution reaction on both RuO2 and the noble-metal-free electrocatalyst material MoS2 has been studied using a combination of experimental and theoretically calculated X-ray photoelectron chemical shifts. In this way, insight into structural changes accompanying hydrogen evolution on these materials is obtained.<br>Heterogen elektrokatalys innebär användningen av fasta material för att minska energimängden som krävs för produktion av kemikalier med hjälp av elektricitet. Heterogen elektrokatalys har en central roll i det moderna samhället, eftersom det möjliggör produktionen av kemikalier såsom klorgas och natriumklorat, som i sin tur används för produktion av t ex konstruktionsmaterial och läkemedel. Vikten av användning av elektrokatalys för produktion av förnybara bränslen, såsom vätgas, växer dessutom i takt med att en övergång till användning av förnybar energi blir allt nödvändigare. I denna avhandling presenteras arbete som utförts för att förstå och förbättra sådana elektrokatalysatorer. En stor del av arbetet har varit fokuserat på selektiviteten mellan klorgas och biprodukten syrgas i klor-alkali och kloratprocesserna. Inom ramen för detta arbete har teoretisk modellering av det dominerande anodmaterialet i dessa industriella processer, den så kallade “dimensionsstabila anoden” (DSA), använts för att föreslå en fundamental anledning till att detta material är speciellt klorselektivt. Vi föreslår att klorselektiviteten kan förklaras av en laddningsöverföring från ruteniumkatjoner i materialet till titankatjonerna i anodytan, vilket aktiverar titankatjonerna. Baserat på en bred studie av ett stort antal andra dopämnen föreslår vi dessutom vilka dopämnen som är bäst lämpade för produktion av aktiva och klorselektiva anoder. Med hjälp av experimentella studier föreslår vi dessutom en koppling mellan kloratbildning och oönskad syrgasbildning i kloratprocessen, och vidare har en bred studie av tänkbara elektrolytföroreningar utförts för att öka förståelsen för syrgasbildningen i denna process. Två studier relaterade till elektrokemisk vätgasproduktion har också gjorts. En experimentell studie av Co-dopad DSA har utförts, och detta elektrodmaterial visade sig vara mer aktivt för vätgasutveckling än en standard-DSA. Vidare har en kombination av experimentell och teoretisk röntgenfotoelektronspektroskopi använts för att öka förståelsen för strukturella förändringar som sker i RuO2 och i det ädelmetallfria elektrodmaterialet MoS2 under vätgasutveckling.<br><p>QC 20151119</p>
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Starykevich, Maksim. "Electrosynthesis of 1-D metallic nanoparticles from DES using porous anodic templates." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/21694.
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Doutoramento em Ciência e Engenharia de Materiais<br>O método de síntese de nanoparticulas 1-D assistido por um modelo tornou-se um tópico em voga na química após o desenvolvimento de filmes anódicos com poros bem ordenados. Contudo, a maioria dos trabalhos nesta área tem sido feita utilizando filmes porosos destacados devido à presença de uma barreira no fundo dos poros. No entanto, esta estratégia segue demasiados passos, o que aumenta o seu custo, torna mais difícil a execução e impõe várias limitações. Consequentemente, existe a necessidade de uma técnica que permita o enchimento (electrofilling) dos tubos sem remover a camada barreira – esta tese representa o nosso contributo para esse trabalho. Utilizámos uma técnica mais simples que permite a electrodeposição e “electrofilling” de nanoestruturas directamente nos modelos sobre o substrato metálico, utilizando solventes eutécticos profundos à base de cloreto de colina como electrólito. Relativamente à água, os solventes eutécticos profundos demonstram superior estabilidade térmica e uma janela electroquímica mais alargada, o que aumenta o número de materais secundários depositados.
Como materiais a investigar foram escolhidos titânia e alumina dada a sua capacidade para formar estruturas porosas altamente ordenadas, propriedades eletroquímicas distintas e uso generalizado em síntese assistida por padrão. O estudo aqui apresentado encontra-se dividido em duas etapas. Primeiramente, a influência da camada barreira foi investigada em sistemas modelo através da utilização de filmes barreira densos na superfície dos elétrodos. Para os filmes de alumina e titânia, identificaram-se vários parâmetros que afectam a electrodeposição, dos quais se destacam a influência da voltagem de anodização, a espessura da camada de barreira, a dupla camada eléctrica e o perfil de corrente. Durante esta etapa detectaram-se efeitos nefastos, como a formação de uma densa camada orgânica na superfície do eléctrodo, que foram ultrapassados aumentando a temperatura ou alternando o potencial aplicado.
A segunda etapa consistiu em passar de elétrodos planos (primeira etapa) para modelos porosos (segunda etapa). Foi realizado, com sucesso, o preenchimento dos poros de alumina e dos poros de titânia. Parâmetros como o perfil de corrente, temperatura de solução, entre outras, foram ajustadas para melhorar o fator de preenchimento e a homogeneidade do preenchimento. Foi desenvolvido um processo de preenchimento de moldes de alumina anódica em duas etapas, nucleação AC (1º passo) e preenchimento galvanostático (2º passo). Foram utilizadas três condições diferentes de modelos de titânia anódica porosa no “electrofilling”. O primeiro é sem modificação e demonstrou que a electroredução do zinco ocorre de forma aleatória ao longo de todo o comprimento do poro, o que leva ao fecho do poro e a um enchimento não homogéneo. A segunda modificação, cristalização total por têmpera, permite a preparação de estruturas coaxiais devido à deposição uniforme de zinco nas paredes dos poros. A última modificação foi a cristalização selectiva do fundo do poro. Foi descoberto que uma anodização adicional em eletrólitos não agressivos leva à cristalização da parte barreira dos tubos (fundo) e, consequentemente, a maior condutividade na parte inferior do que nas paredes. Este efeito permite um enchimento ascendente dos modelos porosos de titânia.
As estratégias aqui apresentadas alargam a gama de possibilidades para a aplicação de modelos porosos anódicos na electrodeposição de diferentes nanoestruturas.<br>The template assisted method of 1-D nanoparticles synthesis has become a hot topic in Chemistry after the development of high-ordered porous anodic films. Most studies in this field have focused on the use of detached porous films due to the presence of the barrier layer on the pore bottom. However, this strategy follows a great number of steps, which raises its cost while decreasing convenience of operation and imposing several limitations. Consequently, there is a need for a technique which allows electrofilling of tubes without removing the barrier layer – this thesis represents our contribution to that enterprise. We have devised a simpler technique which allows electrodeposition of nanostructures directly in the templates on metallic substrate, using choline chloride based deep eutectic solvents (DES) as electrolyte. Compared to water, DES have improved thermal stability and a wider electrochemical window, dramatically increasing the number of possible secondary materials deposited.
Titania and alumina were chosen as materials under study due to their known capacity to form highly-ordered porous structures, different electrochemical profiles and widespread use in template assisted synthesis. The present work is divided in two parts. First, the influence of the barrier layer has been investigated by using dense barrier films on the electrode surface as a model system. For both alumina and titania films, several parameters affecting the electrodeposition of zinc have been identified, notably the influence of the anodization voltage, barrier layer thickness, electrical double layer and current profile. During this stage, some negative effects have been detected, such as a dense organic layer formation on electrode surface, a hurdle which has been overcome by either increasing the temperature or applying the alternating potential.
The second stage consisted in transferring the method from the flat electrodes (the first stage) to the porous templates. The successful filling of both porous alumina and porous titania, has been achieved. Parameters such as current profile, solution temperature, among others, have been tuned to improve the fill factor and homogeneity of the filling. A two-step porous anodic alumina template filling with AC nucleation (1st step) and galvanostatic filling (2nd step) has been developed. Three different types of porous anodic titania templates have been used for electrofilling. The first one was used as-prepared, showing that zinc electroreduction occurs in random places along all pore length, resulting in pore sealing and non-homogeneous filling. The second modification, full crystallization by annealing, allows the preparation of coaxial structures due to uniform zinc deposition on the pore walls. The last modification is selective bottom crystallization. It has been found that additional anodization in unaggressive electrolytes leads to crystallization of the barrier (bottom) part of the tubes and, thus, to higher conductivity of the bottom part than that of the walls. This effect allows a bottom-up filling of the titania porous template.
The strategies presented here widen the range of possibilities for the application of porous anodic templates in the electrodeposition of different nanostructures.
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Dang, Xuan Dung. "Electrosynthesis and characterization of thin copolymer films based on pyrrole and thiophene derivatives." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1125491701029-31683.
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Die Copolymerisation wurde mit dem Ziel untersucht, polymere Materialien zu synthetisieren, die die individuellen Eigenschaften der entsprechenden Homopolymere kombinieren. Die Dissertation konzentrierte sich auf die Elektrosynthese und Charakterisierung von leitfähigen Copolymerfilmen auf Basis von Pyrrol- und Thiophenderivaten. Mit einer Reihe von elektrochemischen, spektroskopischen und mikroskopischen Untersuchungsmethoden (Zyklovoltammetrie, elektrochemische Impedanz-spektroskopie, photoelektrochemische Spektroskopie, Elektrospray- Ionisations-Massenspektroskopie, Festkörper- NMR, Raman-Spektroskopie, Thermoanalyse und Rasterelektronenmikroskopie) wurde die Bildung echter Copolymere von Pyrrol mit Bithiophen und von 3-Methylthiophen mit Ethyl-3-thiophenazetat nachgewiesen. Die analytischen Ergebnisse bestätigen, dass Random- Copolymere und keine Block-Copolymere gebildet wurden. Die elektronischen und strukturellen Eigenschaften der Copolymerfilme liegen zwischen denen der jeweiligen Homopolymere und sind abhängig von der Copolymerzusammensetzung. Insbesondere die Halbleiterparameter der Copolymerfilme von Pyrrol mit Bithiophen wie Flachband-Potential, Bandlücken-Energie und Ladungsträgerdichte verschieben sich von denen des reinen Polypyrrols bis zum Polybithiophen, wenn der Gehalt an Bithiophen im Copolymerfilm vergrößert wird. Diese Parameter sind einstellbar durch Variation des Monomerverhältnisses oder des Polymerisationspotentials. Außerdem konnten die strukturellen und elektronischen Eigenschaften des funktionalisierten Polymers Ethyl-3-thiophenazetat durch Copolymerisation mit 3-Methylthiophen deutlich verbessert werden. Die synthetisierten leitfähigen Copolymerfilme können in der Sensorik Anwendung finden<br>The copolymerization has been studied as a new strategy to synthesize polymer materials by combining interesting properties of the respective homopolymers. In this dissertation, the work focused on the electrosynthesis and characterization of conducting copolymer films based on pyrrole and thiophene derivatives. A variety of electrochemical, spectroscopic and microscopic techniques such as cyclic voltammetry, electrochemical impedance and photoelectrochemical spectroscopy, electrospray ionization mass spectroscopy, solid state NMR and Raman spectroscopy, thermal analysis and scanning electron microscopy supported the formation of true copolymers of pyrrole with bithiophene and 3-methylthiophene with ethyl-3-thiophene acetate. The analytical results exhibited that random copolymers were produced rather than block copolymers. The electronic and structural characteristics of the copolymer films were intermediate between those of the respective homopolymers and they were dependent on the copolymer composition. In particular, the semiconducting parameters of the copolymer films of pyrrole and bithiophene such as flat band potential, band gap energy and charge carrier density shifted from those of polypyrrole to polybithiophene with increasing bithiophene content of the copolymer films. Such parameters were controlled precisely by alternating either the monomer ratio or the polymerization potential. In addition, the morphological and electronic properties of the functionalized polymers of ethyl-3-thiophene acetate were increased significantly by copolymerization with 3-methylthiophene. The obtained conducting copolymer films were able to be applied in the field of sensoric
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Meyer, Tjark Hannes [Verfasser]. "Merging Electrosynthesis with 3d Transition Metal-Catalyzed C–H Transformations / Tjark Hannes Meyer." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2021. http://d-nb.info/123763346X/34.
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Al-Salih, T. "The electrosynthesis of metal complexes from the molecular substrates, N2̲, H2̲, CO and isocyanides." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377062.
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Folgueiras, Amador Ana Alicia. "Design and manufacture of an electrochemical flow reactor, and its application in organic electrosynthesis." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/110661/.
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Organic electrosynthesis is recognised as a green enabling methodology to perform reactions in an efficient and straightforward way. Electrons are used as the reagent to form anion and cation radical species from neutral organic molecules achieving oxidations and reductions by replacing toxic and dangerous reagents. Within this field, the use of microreactors in continuous flow is also concurrent with electrochemistry because of its convenient advantages over batch, such as: i) low loading or no supporting electrolyte at all, due to the small distance between electrodes, providing significant advantages in downstream processing; ii) high electrode surface-to-reactor volume ratio; iii) short residence time; iv) improved mixing effect. In this thesis, a novel easy-to-machine flow electrochemical reactor has been designed and fabricated. This reactor can be made either of aluminium or polymers, if additive manufacturing employed. The efficiency of the reactor has been shown in the electrosynthesis of nitrogen-containing heterocycles. The products obtained have been further functionalised in a single two-step flow system connected to the electrochemical reactor: For the electrochemical synthesis of benzothiazoles from N-arylthioamides in flow a catalyst- and supporting electrolyte-free method has been developed. A library of benzothiazoles was synthesised only in the presence of solvent and electricity: Finally, a new synthetic method for the electrochemical formation of benzoxazoles from easily accessible and inexpensive resorcinol and nitriles was discovered: In conclusion, flow electrosynthesis has shown to be a promising tool for electroorganic synthesis, improving the outcome of standard batch cells.
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Musella, Elisa <1992>. "Newly developed electrosynthesis of Layered Double Hydroxides: application to sensing, energy storage and conversion." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9603/1/Tesi%20Musella.pdf.
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Layered Double hydroxides (LDHs) have been widely studied for their plethora of fascinating features and applications. The potentiostatic electrodeposition of LDHs has been extensively applied in the literature as a fast and direct method to substitute classical chemical routes. However, it does not usually allow for a fine control of the M(II)/M(III) ratio in the synthesized material and it is not suitable for large anions intercalation. Therefore, in this work a novel protocol has been proposed with the aim to overcome all these constraints using a method based on potentiodynamic synthesis.
LDHs of controlled composition were prepared using different molar ratios of the trivalent to bivalent cations in the electrolytic solution ranging from 1:1 to 1:4.
Moreover, we were able to produce electrochemically LDHs intercalated with carbon nanomaterials for the first time. A one-step procedure which contemporaneously allows for the Ni/Al-LDH synthesis, the reduction of graphene oxide (GO) and its intercalation inside the structure has been developed. The synthesised materials have been applied in several fields of interest.
First of all, LDHs with a ratio 3:1 were exploited, and displayed good performances as catalysts for 5-(hydroxymethyl)furfural electro-oxidation, thus suggesting to carry out further investigation for applications in the field of industrial catalysis. The same materials, but with different metals ratios, were tested as catalysts for Oxygen Evolution Reaction, obtaining results comparable to LDHs synthesised by the classical co-precipitation method and also a better activity with respect to LDHs obtained by the potentiostatic approach. The composite material based on LDH and reduced graphene oxide was employed to fabricate a cathode of a hybrid supercapacitor coupled with an activated carbon anode. We can thus conclude that, to date, the potentiodynamic method has the greatest potential for the rapid synthesis of reproducible films of Co and Ni-based LDHs with controlled composition.
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Li, Winton. "Hydrogen peroxide electrosynthesis in solid polymer electrolyte (spe) reactors with and without power co-generation." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62136.
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For applications that require small amounts of H₂O₂ or have economically difficult transportation means, an alternate, on-site H₂O₂ production method to the current industrial anthraquinone auto-oxidation process is needed. Thus far neutral production of H₂O₂ has been limited to bench-top laboratory scaled research with low yield of H₂O₂ [1]. To produce neutral H₂O₂ on-site and on-demand for drinking water purification, the electroreduction of oxygen at the cathode of a solid polymer electrolyte (SPE) cell could be a possible solution. The work presented here has utilized a SPE cell operating in either fuel cell mode (power generating) or electrolysis mode (power consuming) to produce H₂O₂. The SPE cell reactor is operated with a continuous flow of cathode carrier water flowing through the cathode to remove the product H₂O₂. Two catalysts were chosen for further study in this work, one is the inorganic cobalt-carbon composite catalyst, to be used in both fuel cell mode and electrolysis mode operation. The other is the riboflavin-anthraquinone-carbon composite catalyst, to be used in only the electrolysis mode operation.
Through parametric experiments in both modes of operation, the Co-C catalyst was able to achieve peroxide production rate of ~200 μmol hr-¹ cm-² and 4 mW cm-² operating at a cell temperature of 60°C with a current density of 30 mA cm-² and 30% current efficiency in fuel cell mode operation. Long term recycle experiments over a period of 72 hours showed an accumulated H2O2 concentration of over 1400 ppm. Investigation of both catalysts in electrolysis mode operation showed that the AQ-C catalyst achieved maximum H₂O₂ production of 580 μmol hr-¹ cm-² operating at 40°C and a current density of 240 mA cm-² with an 8% current efficiency; while the Co-C catalyst had a maximum H₂O₂ production rate of 360 μmol hr-¹ cm-² operated at 240 mA cm-² with 8% current efficiency. Long term recycle study of both catalysts in electrolysis mode generated maximum H₂O₂ concentrations of over 3000 ppm in 72 hours. Water sample analysis showed no degradation of the catalysts in either mode of operation.<br>Applied Science, Faculty of<br>Chemical and Biological Engineering, Department of<br>Graduate
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Eiras, Carla. "Eletrossíntese e propriedades ópticas e morfológicas de filmes de poli-p-fenileno e derivados." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-11112013-150338/.
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Nesta tese, estudamos a eletrossíntese de polímeros conjugados eletroluminescentes no azul. Filmes de poli(p-fenileno) (PPP), co-poli(p-fenileno-pirrol) (CPPI) e co-poli(p-fenileno-3-metiltiofeno) (CFMET) foram preparados por voltametria cíclica em eletrodos de vidro condutor (ITO) em uma solução não-aquosa de acetonitrila e perclorato de tetrabutilamônio contendo os monômeros e pares de co-monômeros a diferentes concentrações. Durante a síntese dos filmes de PPP, CPPI e CP3MET, a célula eletroquímica foi posicionada dentro de uma caixa seca contendo CaCl2 como agente secante e em atmosfera de N2(g) super-seco com o objetivo de reduzir a umidade do ar no meio de síntese. A baixa umidade do ar obtida durante as medidas permitiu o controle de parâmetros de crescimento dos filmes de PPP e de seus derivados (CPPI e CP3MET). A morfologia dos filmes foi correlacionada aos seus valores de espessura e de rugosidade obtidos por microscopia de força atômica (AFM). As propriedades ópticas dos filmes foram também investigadas por espectroscopia no UV-VSNIR em função do número de ciclos da varredura obtidos durante a eletrossíntese. As respostas eletroquímicas, dos filmes de FPP, CPPI e CP3MET foram obtidas por voltametria cíclica em uma solução livre de monômero. Estes filmes tiveram ainda a confirmação de suas estruturas químicas por meio de resultados obtidos por espectroscopia no infravermelho (FTIR) e por microespectroscopia e mapeamento Raman<br>This work describes the electrochemical synthesis of poly(p-phenylene) (PPP), p-phenylene-pyrrole copolynier (GPPIC) and p-phenylene-3methylthiophene copolymer (CP3MET). The main interest in studying these materials comes from its blue-electroluminescent properties, which make them suitable for application in electroluminescent devices. The polymerization was carried out using cyclic voltammetry in an acetonitrile non-aqueous medium containing tetrabutylammonium perchlorate and different concentration of each monomer. All the films were synthesized onto indium-tin-oxide covered glass (EO) electrodes. In order to enhance the film quality, electropolymerization was carried out within a glove box containing CaCl2, which was added as a drying agent, and under N2 atmosphere. The low amount humidity during the measurements allowed us to correlate the morphological, electrochemical and optical properties of the films of PPP and derivatives (CPPI and CP3MET). The optical properties of the films were investigated by UV-VIS-NIR spectroscopy after varying the number of cyclos reached during the preparation of the films. The electrochemical response of the films was analyzed via cyclic voltammetry using a monomer-free electrolytic solution. The morphology of the films was correlated to their values of thickness and roughness as obtained by using atomic force microscopy (AFM) and the structural characterization of PPP e their derivatives were obtained by micro-Raman spectroscopy and Raman mapping.
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Tietje-Girault, J. "The influence of cell design and electrolysis parameters on the electrosynthesis of carboxylic acids from carbon dioxide and 1,3-butadiene." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374585.
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Soler, Salas Sergio. "Reacciones de arilación promovidas electroquímicamente." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/461158.
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La reducción catódica de 4-fluorobenzonitrilo, 4-yodobenzonitrilo, 4-cianofenil triflato, 4--yodonitrobenceno, 3--yodonitrobenceno, 2--yodonitrobenceno y yodobenceno en DMF/Benceno (20/80)+0.6 M Bu4NBF4, durante una electrolisis en discontinuo y en un solo paso a temperatura ambiente, da lugar al producto de acoplamiento cruzado correspondiente: 4-fenilbenzonitrilo, 4--fenilnitrobenceno, 3--fenilnitrobenceno, 2--fenilnitrobenceno y bifenilo con rendimientos de bajos a moderados. El mecanismo propuesto, investigado por voltametría cíclica, y análogamente a lo descrito en ausencia de benceno, implica la formación del anión arilo. El anión arilo reacciona con benceno para formar el σH-complejo que es oxidado en las condiciones de reacción, esta reacción compite con la protonación del anión arilo, en todos los casos. La reactividad de cada anión arilo determina, entre otros, la viabilidad de la reacción. Así, en las mismas condiciones experimentales, 4-cianofenil tosilato, 4-cianofenil mesilato, 4-yodotolueno y 4-yodoanisol no muestran la formación de los productos de acoplamiento cruzado correspondientes.
Los productos de acoplamiento cruzado obtenidos se reducen a potenciales muy próximos o más positivos que los reactivos. Lo que ha motivado el estudio de la sustitución de la electrólisis en batch por la electrólisis en continuo. Para ello se ha construido un reactor modular de flujo del tipo ‘plate-to-plate’ con un cuerpo no conductor y con una placa de carbono vítreo de 1 cm x 10 cm como electrodo de trabajo y una placa de cobre de 1 cm x 10 cm sobre la que se deposita electroquímicamente una capa de Pt como contraelectrodo. Diversos parámetros electroquímicos (tales como potencial o carga consumida) y parámetros de celda (tales como caudal volumétrico, distancia inter-electródica o geometría del canal) han sido evaluados y optimizados. Se ha escogido como ejemplo la síntesis de 4,4’-dinitroestilbeno mediante la electrorreducción de 4,4’-dinitrobibencilo en DMF+0.1 M Bu4NBF4. Los resultados obtenidos son comparables, pero no mejoran en esta primera aproximación, a los obtenidos en batch.<br>The electrochemical reduction of 4-fluorobenzonitrile, 4-iodobenzonitrile, 4-cyanophenyl triflate, 4-iodonitrobenzene, 3-iodonitrobenzene, 2-iodonitrobenzene and iodobenzene in DMF/Benzene (20/80)+0.6 M Bu4NBF4, in one-pot reaction and at room temperature, leads to the corresponding cross-coupling product: 4-phenylbenzonitrile, 4-phenynitrobenzene, 3-phenynitrobenzene, 2-phenynitrobenzene and biphenyl with low to moderate yields. The proposed mechanism involves the formation of the aryl anion that is consistent with the number of transferred electrons. The aryl anion reacts with benzene to form a σH-complex that is oxidized to the cross-coupling product in the reaction conditions. In identical conditions, 4-cyanophenyl tosylate, 4-cyanophenyl mesylate, 4-iodotolune and 4-iodoanisole do not show the formation of the corresponding cross-coupling products.
The obtained cross-coupling products are reduced at very close or more positive potential than the reagents. This fact has motivated the substitution of batch electrolysis with flow electrolysis. For this purpose, a plate-to-plate modular flow reactor with a non-conducting housing with 1 cm x 10 cm glassy carbon plate as working electrode and a 1 cm x 10 cm copper plate with completely electrodeposited Pt has been built. Several electrochemical parameters (as potential or charge) and cell parameters (as flow rate, inter-electrodic distance or geometry of the channels) are evaluated and optimized. Synthesis of 4,4’-dinitrostilbene via electroreducion of 4,4’-dinitrobibenzyl in DMF+0.1 M Bu4NBF4 is presented. The obtained results are comparable to obtained batch electrolysis results.
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Boriosi, Lorenzo. "Preparazione di catalizzatori strutturati per la reazione di ossidazione parziale del metano." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/6084/.
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Questo lavoro di tesi ha avuto come obiettivo la preparazione di catalizzatori attivi nella reazione di ossidazione parziale catalitica, CPO, del metano per produrre gas di sintesi.
I catalizzatori sono stati preparati tramite sintesi elettrochimica di composti di tipo idrotalcite a base di Rh/Mg/Al utilizzando come supporto schiume metalliche costituite da FeCrAlY. L’impiego di questo tipo di supporto comporta una serie di vantaggi, dallo sviluppo del catalizzatore all’ottimizzazione del processo catalitico in termini di prestazioni catalitiche, diminuzione degli “hot spots” termici, diminuzione delle perdite di carico e costi del catalizzatore.
La sintesi del catalizzatore è stata effettuata per mezzo di una cella elettrochimica innovativa, che lavora in flusso, e quindi permette la continua rigenerazione della soluzione di sintesi, a differenza di quanto avviene in una cella elettrochimica standard a singolo comparto. La precipitazione dei composti di tipo idrotalcite si ottiene grazie alla tecnica di elettrogenerazione di basi, ovvero grazie alla generazione di un pH basico all’interno della cella elettrochimica a seguito dell’applicazione di un potenziale catodico. Il pH generato è il parametro più importante e determina la natura e la qualità del materiale depositato. È sorta quindi la necessità di sviluppare un sensore potenziometrico miniaturizzato per la determinazione istantanea del pH durante la sintesi, da installare all’interno della schiuma stessa.
È possibile correlare le prestazioni catalitiche dei catalizzatori sintetizzati con la cella elettrochimica in flusso, alle loro caratteristiche di morfologia superficiale ed alla composizione chimica, e confrontare le stesse prestazioni catalitiche con quelle ottenute sintetizzando i catalizzatori con la cella elettrochimica standard a singolo comparto.
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Oliveira, Barbara de. "Estudo eletroquimico do efeito de surfactantes na eletrogeração de peroxido de hidrogenio." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265249.
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Orientador: Rodnei Bertazzoli<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica<br>Made available in DSpace on 2018-08-08T23:20:02Z (GMT). No. of bitstreams: 1
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Previous issue date: 2007<br>Resumo: Este trabalho apresenta o estudo do comportamento dos surfactantes catiônicos cloreto de tricaprilmetilamônio (Aliquat® 336) e cloreto de metiltributilamônio (Aliquat® 175) na eletrossíntese de peróxido de hidrogênio. Inicialmente, foram realizados experimentos de medida de tensão superficial pelo método do anel de du Noüy, com o objetivo de encontrar a concentração micelar crítica dos surfactantes. As medidas foram realizadas em solução de K2SO4 0,1 mol L-1, em pH 3,5, a 25 ± 1°C. Uma CMC de a 4,0 10-5 ± 1,0 10-5 mol L-1 para o tensoativo A336 e 3,2 10-2 ± 1,0 10-2 mol L-1 para A175 foram consideradas. Em seguida, foram feitas voltametrias de varreduras lineares em solução de K2SO4 0,1 mol L-1, em pH 3,5, a 25 ± 1°C em solução saturada de oxigênio para diferentes concentrações dos surfactantes com o uso de um eletrodo de carbono vítreo monolítico (CVM). A partir dos voltamogramas obtidos, foram comparadas as separações entre os patamares de redução do O2 observados para as diferentes concentrações dos tensoativos. Também foram obtidos os gráficos de Levich, observando que o processo de redução é controlado por transporte de massa. A partir de relação linear destacada pelo gráfico de Levich, obtiveram-se os valores do coeficiente de difusão do oxigênio, que foram comparados com valores já obtidos na literatura. Os dados foram explorados acerca dos valores de CMC encontrados para os surfactantes. Posteriormente, foi realizada a redução direta do O2 à H2O2 em solução ácida na presença dos surfactantes em um reator eletroquímico de batelada com recirculação com catodo de carbono vítreo reticulado (CVR), sob diferentes concentrações dos tensoativos. Os experimentos foram conduzidos em solução de K2SO4 0,1 mol L-1, em pH 3,5, a 17 ± 1 °C em potencial constante a -1,6 V vs. Pt. A vazão de oxigênio gasoso em solução foi mantida em 6 L min-1 durante todos os ensaios. A máxima concentração de peróxido de hidrogênio gerado foi de 521,5 mg L-1 para a concentração de 1,0 10-5 mol L-1 do surfactante A336 durante 2 horas de eletrólise, com um consumo energético de 3,5 kWh kg-1 e uma eficiência de corrente de 72 %. Já para o surfactante A175, sob as mesmas condições, o máximo de peróxido gerado foi de 471,0 mg L-1 para a concentração de 1,0 10-5 mol L-1 do surfactante<br>Abstract: As a first step of the investigation, experiments of surface strength measurement were performed by using the du Nouy method, to determine of the surfactants¿ Critical Micelle Concentration (CMC). Concentrations ranging 4.0 10-5 ± 1.0 10-5 mol L-1 and from 3.2 10-2 ± 1.0 10-2 mol L-1 for A336 and A175, respectively, were considered. Experiments were carried out in a K2SO4, 0.1 mol L-1 solution, pH 3.5 and temperature of 25 ± 1 oC. Then, linear sweep voltammetry technique was used to record i/E couples on vitreous carbon disc electrode in oxygen saturated 0.1 mol L-1 K2SO4 solution, pH 3.5, in a cell of three electrode. By the examination of the voltammograms for oxygen reduction were identified a dependence of the surfactant concentration. I/E values in the region of mass transfer control were organized in Levich plots, which through at the oxygen diffusion coefficients were calculated as a function of the surfactants concentration. In a sequence of the investigation, the electrosynthesis of hydrogen peroxide was carried out in a flow electrochemical reactor in which the O2 saturated solution was recirculated through a reticulated vitreous carbon cathode. Different concentrations of surfactants were used. Potential selected for the runs was ¿1.6V vs. Pt and oxygen flow rate was 6 L min-1. In two hours of electrolysis, 521.5 mg L-1 of H2O2 was generated using 1,0 10-5 mol L-1 of A336. Current efficiency was 72% and energy consumption was 3.5 kWh kg-1 of hydrogen peroxide. By using the same concentration of A175, hydrogen peroxide concentration was 471.0 mg L-1<br>Mestrado<br>Materiais e Processos de Fabricação<br>Mestre em Engenharia Mecânica
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Cassidy, Kevin D. "Electrosynthesis of Hydrogen Peroxide in an Acidic Environment with RuO2 as a Water Oxidation Catalyst & Silver Nanoparticles in Zeolite Y: Surface Enhanced Raman Spectroscopic (SERS) Studies." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1292365863.
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Davis, Jake Ryan. "Production of Expendable Reagents from Raw Waters and Industrial Wastes." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/344216.
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A couple of processes for electrosynthetic production of expendable reagents, namely acids, bases, and oxidants, from the native salt content of raw waters and industrial wastes were investigated, and the composition of mixed acids and bases made of sodium sulfate or sodium chloride salts were predicted using a model predicated on conservation principles, mass action relations, and Pitzer equations. Electrodialysis with bipolar membranes (BMED) was used to produce acids and bases in a single pass. Product concentration was limited only by the salt content of the feed water. The current efficiency for acid production was slightly higher than that for base, but neither dropped below 75%. Acid and base current utilization showed the same trends with respect to feed salt content and flow velocity, with higher efficiency at higher feed salt concentrations and flow velocities. Operating the BMED stack near the limiting current density of the bipolar membrane (BLCD) or above the limiting current density of the diluate compartment (LCD) decreased current efficiency and increased electrical power dissipation. Electrodialytic acid and base production was approximately10 times cheaper than the chemicals' f.o.b. unit costs as quoted on Alibaba.com. The mechanism and cost of on site peroxodisulfuric acid production by electrolysis of sulfuric acid solutions with boron doped diamond film anodes was investigated experimentally and with molecular dynamics (MD) and density functional theory (DFT) simulations. The cost of on site peroxodisulfate production was approximately 4 times less expensive than purchasing a 25 lb bag. It was shown that direct discharge of sulfate species produces sulfate radicals, which subsequently combined to form peroxodisulfuric acid. The likely hood of these reactions was dependent on electrode surface condition. Sulfate radicals could also be produced in solution by reaction with hydroxyl radicals generated by water discharge.
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Bouvet, Sébastien. "Vers l'introduction douce de groupes fluorés émergents oxygénés et soufrés." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLV007/document.
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Les travaux s’articulent autour du développement de nouveaux agents de fluoration et sur l’étude de leurs réactivités au cours de différentes réactions.Dans une première partie, nous décrivons la synthèse de nouvelles sources réactives de fluorure à partir de liquides ioniques de type imidazolium possédant un fluor en partie anionique. Les deux liquides ioniques [bmim][F] et [bdmim][F] obtenus ont ensuite été testés dans différents processus de monofluoration et de fluorodésulfuration oxydative.Une deuxième partie concerne le développement de réactifs de trifluorométhoxylation.Dans un premier temps, nous nous sommes attachés à synthétiser des nouveaux précurseurs de carbène possédant un groupement OCF3. Nous avons ensuite évalué leur réactivité au cours de différents processus. Dans un second temps, nous nous sommes axés sur la réactivité d’un composé FAR (Fluoroalkyl Amino Reagent) dans des réactions d’acylation aromatique.Enfin, le dernier chapitre rapporte l’étude du comportement électrochimique en réduction du gaz SF6, le but étant d’obtenir une nouvelle source radicalaire de SF5. Après une première partie analytique, l’hexafluorure de soufre a été engagé dans des processus d’électrosynthèse pour tenter de piéger les intermédiaires réactionnels issus de sa réduction<br>The manuscript deals the development of new fluorinating reagents and their reactivity in various reactions.In the first part, we were interested in developing new fluoride sources from ionic liquids with imidazolium as the cationic part, and associated to the fluoride as anion. Two ionic liquids, [bmim][F] and [bdmim][F], were obtained. They were then tested in monofluoration and fluorodesulfurization reactions.The second chapter concerns the development of new trifluoromethoxylation reagents.We began by synthetizing new carbene precursors with an OCF3 group. We then evaluated their reactivities in different processes. A second part was centered on a FAR compound and its reactivity in aromatic acylation reactions.Finally, the last chapter describes the behavior of SF6 in electrochemistry reduction with different conditions, the aim being to have a new source of SF5 radical. After a first part concerning analytical studies of the sulfur hexafluoride, the aforementioned compound was engaged an electrosynthetic process to trap intermediate species coming from its reduction
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Blasco, Gómez Ramiro. "Steering CO2 bio-electrocycling into valuable compounds through inline monitoring of key operational parameters." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/670848.
Full textAbstract:
Microbial Electrochemical Technologies (METs) are a promising alternative for capturing and in-situ reducing CO2 through the use of renewable electricity. Microorganisms grown in autotrophic conditions use CO2 as an electron acceptor and an electrode provides them electrons in the form of electricity. In this process, known as microbial electrosynthesis (MES), different compounds are produced depending on the metabolic possibilities of the microorganisms present in the system. The potential of this technology is high: a culture enriched with selected electroactive microorganisms is able to effectively transform CO2 into high value-added compounds.
This Doctoral Thesis investigated reliable operational procedures for the monitoring of the performances of METs to produce suitable substrates for economically viable downstream applications. The cathodes of two different designs of bioelectrochemical systems (BESs) were inoculated with an enriched culture of a carboxydotrophic strain and were operated until stable conversion of CO2 into acetate, ethanol and small amounts of butyrate.<br>Les tecnologies microbianes electroquímiques (METs) són una alternativa prometedora per capturar i reduir in situ el CO2 a través de l’ús d’electricitat renovable. Microorganismes cultivats en condicions autotròfiques usen CO2 com a acceptor d’electrons i un elèctrode aporta electrons en forma d’electricitat. En aquest procés, conegut com a electrosíntesi microbiana (MES), es produeixen diferents compostos en funció de les possibilitats metabòliques dels microorganismes presents al sistema. El potencial d’aquesta via és alt: un cultiu enriquit de microorganismes electroactius seleccionats pot fer possible la transformació del CO2 en compostos d’alt valor afegit.
En aquesta tesi s'han estudiat diferents paràmetres d'operació que a través d'un monitoratge exhaustiu durant la transformació de l'CO2 mitjançant reactors MET. Es van utilitzar dos dissenys de reactor diferents (tubular i pla) de sistemes bioelectroquímics (BES; sigles en anglès) que van ser inoculats amb un cultiu enriquit amb una soca carboxidotrófica electroactiva i es van operar fins aconseguir l’electro-conversió estable de el CO2 en acetat, etanol i petites quantitats de butirat.
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OLIVEIRA, Jadson de Lira. "Eletrossíntese de 2,2’- bipiridinas e 3,3’- bipiridazinas em célula eletroquímica de cavidade composta de nanotubos de carbono e grafite em pó." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/16899.
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Previous issue date: 2015-10-07<br>CNPq<br>PDSE<br>CAPES<br>No presente trabalho foi estudada uma nova metodologia eletroquímica para
a síntese de 2,2’-bipiridinas e 3,3’-bipiridazinas através da reação de
homoacoplamento catalisada por um complexo de Ni, em eletrodo constituído por uma
mistura de materiais carbonáceos (grafite e nanotubos de carbono). Tal metodologia
envolveu o uso de uma célula de cavidade e uma pequena quantidade de solvente.
Foi constatado que a adição de nanotubos de carbono à composição da matriz
catódica, aumentou a área efetiva do eletrodo e a condutividade, contribuindo para o
aumento da intensidade da corrente e difusão de espécies iônicas. Foi possível
trabalhar com uma solução aquosa de KCl 0,1 mol.L-1 no compartimento anódico com
uma redução significativa do uso de solvente orgânico na cavidade catódica
(dimetilformamida, 65 vezes menor que uma reação clássica). Também foi possível
diminuir a quantidade de solvente necessário para extração e purificação dos produtos
(diclorometano/hexano, 100 vezes menor), obtendo-se bons rendimentos para os
produtos de acoplamento (83-89%), com exceção das eletrólises que envolveram
reagentes di-halogenados (32-79%). Foi observado que a eficiência de corrente variou
de acordo com o método de eletrólise (potencial ou corrente controlada), sendo mais
efetivo a potencial controlado. Outros catalisadores (Pd e Co) foram testados
proporcionando baixos rendimentos de homoacoplamento (<45%). O limite de
reutilização do cátodo foi atestado através da análise por XPS de amostras do material
coletadas ao longo de quatro eletrólises (sem uso de quantidades adicionais do
catalisador e do eletrólito de suporte). E revelou uma redução na atividade do
catalisador de níquel, possivelmente provocada pela mudança na sua composição
após sucessivas eletrólises.<br>In the present work, it was investigated a new electrochemical method for the
synthesis of 2,2'-bipyridines and 3,3’-bipyridazines through the homocoupling reaction
catalyzed by a Ni complex, into an electrode comprising a mixture of carbonaceous
materials (graphite and carbon nanotubes). This methodology involved the use of a
cavity cell and a small amount of solvent (dimethylformamide 300L). The addition of
carbon nanotubes to the cathode matrix composition increased the effective area of
the electrode and conductivity, thus contributing increment of the current intensity and
diffusion of ionic species. It was possible to work with a 0.1 mol.L-1 KCl aqueous
solution in the anode compartment, with a significant reduction of organic solvent used
in the cathodic cavity (dimethylformamide, 65 times lower than the classical reaction).
It was also possible to reduce the amount of solvent needed for extraction and
purification of the product (dichloromethane/hexane, 100 times lower), resulting in
good yields of the coupling product (83-89%), except with electrolysis involving dihalogenated
reagents (32-79%). It was also observed that the current efficiency varies
with the electrolysis method (controlled potential or current), being more efficient at
controlled potential. Other catalysts (Pd and Co) were tested providing low yields of
the homocoupling product (<45%). The recycling limit of the cathode was attested by
XPS analysis of the material collected over four electrolysis (without the use of
additional amounts of the catalyst and supporting electrolyte), which revealed a
reduction in the nickel catalyst activity; possibily caused by the change in its
composition after successive electrolysis.
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Blanchet, Elise. "Conception d'un procédé d'électrosynthèse microbienne." Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/15853/1/Blanchet_elise.pdf.
Full textAbstract:
L’électrosynthèse microbienne est une technologie innovante qui permet de convertir le dioxyde de carbone en molécules organiques en utilisant une cathode comme source d’électrons de la réduction microbienne du CO2. Le procédé «Biorare» propose de coupler l’électrosynthèse microbienne avec l’oxydation de déchets à l’anode afin d’augmenter le rendement énergétique du procédé. Il devient ainsi possible de traiter un effluent à l’anode et de valoriser du CO2 à la cathode. La thèse a eu pour objectif d’améliorer les performances de la bioanode et de la biocathode séparément, afin de réaliser in fine un prototype de procédé «Biorare» à l’échelle du laboratoire. Parmi plusieurs types de déchets testés, les boues biologiques se sont avérées bien adaptées pour une utilisation à l’anode en assurant des densités de courant jusqu’à 10 A/m2. Toutefois, ces performances étant peu reproductibles, nous avons choisi d’exploiter des biodéchets, dont le gisement représente plus de 22 millions de tonnes en France et la valorisation est aujourd’hui obligatoire. Leur utilisation brute n’a pas permis de dépasser 1 A/m2 mais une méthode innovante de formation des bioanodes a permis d’augmenter les densités de courant jusqu’à 7 A/m2, de façon reproductible et dans des conditions extrapolables. Les travaux sur les biocathodes ont révélé que l’hydrogène est un intermédiaire réactionnel clé pour le transfert d’électrons de la cathode vers les microorganismes qui réduisent le CO2. Cela a conduit à découpler le procédé initial en deux étapes : l’hydrogène est produit dans une cellule d’électrolyse microbienne qui oxyde les biodéchets et, en aval, un bioréacteur gaz-liquide utilise l’hydrogène pour convertir le CO2 en acétate, éthanol, formiate, ou butyrate, suivant les systèmes microbiens. Cette stratégie permet d’augmenter les performances d’un facteur 24 avec une vitesse de production d’acétate de 376 mg/L/j et des concentrations jusqu’à 11 g/L.
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Urgin, Karene. "Préparation de dérivés aryl- et hétéroaryl- pyridazine(s) par voies organométalliques chimiques ou électrochimiques." Thesis, Paris Est, 2010. http://www.theses.fr/2010PEST1094.
Full textAbstract:
Les hétérocycles aromatiques sont des motifs structuraux rencontrés dans un grand nombre de substances d'intérêts biologiques ou pharmacologiques. Plus particulièrement, les pyridazines substituées font l'objet d'un intérêt grandissant pour leurs propriétés pharmaceutiques (antibactériens, anti-inflammatoires, médicaments cardiovasculaires…). De plus, les structures comportant des pyridazines peuvent également être utilisées en tant qu'agents chélatants de cations métalliques et s'ordonner en édifices utilisés en chimie supramoléculaire.Nous nous sommes donc intéressés à l'élaboration d'éléments de base comportant des cycles pyridaziniques de type aryl ou hétéroarylpyridazines. La mise au point de méthodes impliquant des espèces organométalliques a été l'un de nos objectifs primordial. L'élaboration de ces composés a été réalisée par formation de liaisons C-C. Une approche électrochimique d'hétérocouplage associé à une catalyse au nickel a été utilisée. Quelques limites à cette méthode ont cependant été observées dans le cas des couplages mettant en jeu des 3,6-dihalogénopyridazines. Une étude par électrochimie analytique a permis d'en comprendre les raisons. La seconde partie de notre travail a consisté en l'étude de la réactivité d'arylzinciques ou de triarylbismuths vis-à-vis de 3,6-dihalogénopyridazines<br>Heteroaromatic rings are present in various biological and pharmacological active molecules. Substituted aryl-pyridazines have given rise to considerable interest because of their diverse pharmacological properties (antibacterial, anti-inflammatory, cardiovascular drugs…). Moreover, structures which contain pyridazines are used in supramolecular chemistry for their applications through self-assembly processes in the presence of metal ions.In order to elaborate building blocks containing pyridazine rings such as aryl or heteroaryl-pyridazines, we turned our intention on the development of complementary methods involving organometallic reagents. Transition metal-catalyzed cross-coupling reaction of organometallic compounds with organic halides is one of the most powerful methods for the generation of C-C bonds.We chose to develop the most straightforward method involves heterocoupling reaction of aryl/heteroaryl compounds under electrochemical conditions (sacrificial anode process) associated to a nickel catalysis. However some limitations have been pointed out when 3,6-dihalogenopyridazines are involved in the cross-coupling reaction. An electrochemical study was investigated in order to propose some mechanistic considerations. A second part of this work consisted in the study of arylzinc and triarylbismuths reagents toward 3,6-dihalogenopyridazines
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SOUZA, Ronny Francisco Marques de. "Acoplamento eletroquímico de Haletos Alilícos e Prenílicos com Aldeídos e Cetonas em cátodo de pó de grafita." Universidade Federal de Pernambuco, 2014. https://repositorio.ufpe.br/handle/123456789/16581.
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Previous issue date: 2014-12-19<br>Na primeira parte do trabalho foi investigado o acoplamento eletroquímico da mistura de haletos alílicos a compostos carbonílicos adsorvidos em cátodo de pó de grafita na presença ou ausência de aditivos (AgNO3 ou TBABF4), usando um anólito aquoso em célula de cavidade. Foram utilizadas as técnicas eletroquímicas de voltametria de varredura linear e eletrólise com potencial ou corrente constante. O uso de quantidades catalíticas dos sais de AgNO3 ou TBABF4, misturados à grafita, melhoraram significativamente a formação dos álcoois homoalílicos. As eletrólises com o cloreto de alila levaram aos melhores resultados, quando comparadas às eletrólises com o brometo de alila. A reação de alilação mostrou-se sensível a efeitos estéricos e eletrônicos. Os potenciais e correntes mais negativas favoreceram o heteroacoplamento. Os aldeídos aromáticos (67 - 99%) e a 1,1,1-trifluoroacetofenona (95%) levaram aos melhores resultados, já os rendimentos na presença de aldeídos alifáticos (28%) ou cetonas (7%) não foram satisfatórios. Na segunda parte do trabalho foi investigado o acoplamento eletroquímico da mistura de haletos prenílicos ao benzaldeído, nas mesmas condições descritas na primeira parte, utilizando as técnicas eletroquímicas de voltametria de varredura linear e eletrólise com potencial constante. O uso de quantidades catalíticas dos sais de AgNO3 ou TBABF4 misturado à grafita, influenciaram na proporção dos produtos de acoplamento (isômeros α e γ). Os melhores resultados na formação do isômero α, 1-fenil-4-metil-3-penten-1-ol (28%, proporção α:γ igual 74:26 ) foram alcançados com o brometo de prenila e os melhores resultados na formação do isômero γ, 1-fenil-2,2-dimetil-3-buten-1-ol (45%, proporção α:γ igual 6:94) com o cloreto de prenila. Dentro deste estudo, também foram investigados os efeitos da variação da quantidade de reagentes, potencial, corrente, aditivos e tipo de anólito nas reações de acoplamento eletroquímico estudadas. Do ponto de vista preparativo, os resultados são comparáveis aos da literatura e apresentam-se como uma alternativa verde, visto que o cátodo de grafita elimina solventes orgânicos e ânodo sacrificial tradicional de métodos eletrossintéticos. Do ponto de vista mecanístico, deve prevalecer o mecanismo aniônico para a reação de alilação, enquanto na reação de prenilação a competição entre o mecanismo radicalar e aniônico pode ser direcionado para a formação dos isômeros α e γ.<br>In the first part of this work, the electrochemical coupling of a mixture of allylic halides and carbonyl compounds was investigated. The reagents were adsorbed on graphite powder cathode, in the presence or absence of additives (AgNO3 or TBABF4) using aqueous anolyte and a cavity cell. Electrochemical techniques of linear sweep voltammetry and potential or constant current electrolyses were used. The use of catalytic amounts of AgNO3 or TBABF4 added to the graphite powder, have significantly improved the formation of homoallylic alcohols. The electrolysis with allyl chloride gave to the best results when compared to the allyl bromide electrolysis. The allylation reaction was sensitive to steric and electronic effects. More negative currents or potentials favored the heterocoupling. The aromatic aldehydes led to the best results (67 - 99%) and the1,1,1-trifluoroacetofenone (95%), the yields in the presence of aliphatic aldehydes (28%) or ketones (7%) were not satisfactory. In the second part, the electrochemical coupling of a mixture of prenylic halides and benzaldehyde was investigated under the same conditions described in the first part of this work, using electrochemical techniques of linear sweep voltammetry and constant potential electrolysis. The use of catalytic amounts of AgNO3 or TBABF4, added to the graphite powder, has influenced the proportion of the coupling products (α and γ isomers). The best results for the α isomer, 4-methyl-1-phenyl-3-penten-1-ol (28%, ratio α:γ equal 74:26 ) were achieved with prenyl bromide and the best results for the γ isomer, 2,2-dimethyl-1-phenyl-3-buten-1-ol (45%, ratio α:γ equal 6:94) in the presence of prenyl chloride. The effects of the amount of reactants, potential, current, and type of additives and anolyte solution, were also investigated for all electrochemical coupling reactions studied. From the preparation point of view, the results are comparable to the literature and appear as a green alternative, since the graphite powder cathode eliminates organic solvents and sacrificial anodes of traditional electrosynthetic methods. From the mechanistic point of view, the anionic mechanism predominates for the allylation reaction, while in the prenylation reactions take place a competition between radical and anionic mechanism in the formation of α and γ isomers.
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PASSOS, Sergio Gonçalves Batista. "Desenvolvimento de um método eletroquímico para síntese aquosa de pontos quânticos em célula de cavidade." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17384.
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Previous issue date: 2015-01-16<br>FACEPE<br>Neste trabalho foi desenvolvido um novo método eletroquímico de síntese de PQs de CdTe
estabilizados por ácido mercaptopropiônico (AMP) e cisteamina (CYS). O método consiste na
redução eletroquímica do telúrio metálico em pó em célula de cavidade. O Te0 foi misturado ao
grafite em pó (material do cátodo) e submetido a uma corrente controlada (-30 mA), que
permitiu a geração das espécies reduzidas Te2- e Te2
2-. As espécies reduzidas de telúrio migram
para um compartimento intermediário da célula de cavidade e na presença de sal de cádmio e
um agente estabilizante orgânico (AMP ou CYS) possibilitaram a formação do CdTe coloidal
em única etapa; para posterior obtenção dos PQs através de tratamento térmico à 90°C.
CdTe/CdS-AMP e CdTe/CdS-CYS foram obtidos em meio aquoso pH=12 e 5,5,
respectivamente. Esse método mostrou ser de fácil aplicação, rápido, eficiente, reprodutível e
dispensa o uso de agentes redutores químicos, podendo ser estendido para síntese de outros
PQs. Os PQs sintetizados apresentaram nanocristais de alta qualidade, muito estáveis e com
carga superficial negativa no caso do estabilizante AMP (potencial zeta = -30mV) e positiva na
presença da CYS. Foi observado que o tamanho das partículas aumenta proporcionalmente com
o tempo de aquecimento, apresentando fluorescência com emissão nas cores entre o verde (522
nm) e o vermelho (643 nm). Foi determinado um tamanho médio de partícula de 4,1 nm para o
CdTe/CdS-AMP após 120 minutos de tratamento térmico, com rendimento quântico de 11%.<br>A new electrochemical method was developed for the CdTe quantum dots (QDs) synthesis,
stabilized by mercaptopropionic acid (MPA) and cysteamine (CYS). The method comprises the
electrochemical reduction of tellurium powder in a cavity cell. The Te0 was mixed to graphite
powder (cathode material) and subjected to a controlled current (-30 mA) electrolysis, which
allowed the generation of Te2- Te2
2-. These tellurium reduced species migrate to an intermediate
compartment of the cavity cell containing Cd2+/organic stabilizer (AMP or CYS) aqueous
solution pH 13, which enabled the formation of colloidal CdTe in one pot process. The QDs
are retrieved after heat treatment at 90°C. CdTe/CdS-AMP e CdTe/CdS-CYS were obtained in
aqueous medium adjusting the pH to 12 and 5.5, respectively. This method proved to be easy,
fast, efficient, reproducible and avoids the use of chemical reducing agents. It can also be
extended to the synthesis of other QDs. The synthesized QDs presented a good quality
nanocrystals, with high stability and negative charge surface in the case of the AMP stabilizer
(zeta potential = -30mV) and positive in the presence of CYS. It was observed that the particle
size increases proportionately with the heating time, showing fluorescence emission in the
colors between green (522 nm) and red (643 nm). It was determined an average size of 4.1 nm
particle for CdTe / CdS-AMP after 120 minutes of heat treatment, with a quantum yield of 11%.
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Nogueira, Fred Augusto Ribiero. "Síntese e caracterização eletroquímica de derivados de polipirrol para aplicação em dispositivos eletrocrômicos e capacitores." Universidade Federal de Alagoas, 2014. http://www.repositorio.ufal.br/handle/riufal/2179.
Full textAbstract:
In this research were studied electrochemical properties of films polypyrrole, poly[(12-pyrrol-1’yldodecanoic acid)], poly[1-(3-brominepropylpyrrole)], poly[1-(3-iodinepropylpyrrole) and poly[4-(3-pyrrolyl)butyric acid] prepared by electrochemical methods and deposited onto Indium Tin doped Oxide. The polymers were obtained from the electrochemical deposition methods potentiodynamic, potentiostatic and galvanostatic and characterized by electrochemical and spectroscopic techniques.
The polypyrrole and poly [4 - (3-pyrrolyl) butyric acid] showed capacitive behavior as poly[(12-pyrrol-1’yl dodecanoic acid)] e poly[1-(3-iodinepropylpyrrole) presented a redox couple attributed to the process of doping - undoping of polymers. The capacitive properties of the polymer were obtained from calculations coulombic efficiency and specific capacitance obtained from the charge-discharge curves of the films. The values obtained for these parameters demonstrated the possibility of application of these films in capacitors. All films showed color variations depending on the applied potential and the UV-Vis spectra for the films showed characteristic absorption bands and decrease of the energy gap by increasing the doping level of the polymer. The films were characterized by atomic force microscopy and showed good homogeneity. The values obtained for these parameters demonstrated the possibility of application of these films in electrochromic devices.<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Neste trabalho foram estudadas as propriedades eletroquímicas dos filmes de polipirrol, poli[ácido(12-pirolildodecanóico)], poli[1-(3-bromopropilpirrol)], poli[1-(3-iodopropilpirrol)] e de poli[ácido4-(3-pirrolil)-butírico] preparados por métodos eletroquímicos e depositados sobre eletrodos de óxido de índio dopado com estanho. Os polímeros foram obtidos através dos métodos eletroquímicos de deposição potenciodinâmico, potenciostático e galvanostático e caracterizados por técnicas eletroquímicas e espectroscópicas. O polipirrol e poli[ácido-4-(3-pirrolil)-butírico] apresentaram comportamento capacitivo enquanto o poli [ácido (12-pirolildodecanóico)], poli[1-(3-bromopropilpirrol)] e o poli[1-(3-iodopropilpirrol)] apresentaram um par redox atribuído ao processo de dopagem-desdopagem dos
polímeros. As propriedades capacitivas dos polímeros foram investigadas através de cálculos da eficiência coulômbica e da capacitância específicas obtidas a partir das curvas de carga-descarga dos filmes. Os valores obtidos para esses parâmetros demonstraram a possibilidade de aplicações destes filmes em capacitores. Todos os filmes apresentaram variações de coloração conforme o potencial aplicado e os espectros por UV-Vis para os filmes mostraram bandas de absorção características
e diminuição da energia de gap pelo aumento do nível de dopagem dos polímeros. Os filmes foram caracterização por microscopia de força atômica e apresentaram boa homogeneidade. Os valores obtidos para esses parâmetros demonstraram a possibilidade de aplicações destes filmes em dispositivos eletrocrômicos.
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Gonçalves, Camila dos Santos. "Redução eletroquímica de cinamatos de metila orto-substituídos." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/46/46135/tde-03102006-205141/.
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Neste trabalho são descritas a síntese e a redução eletroquímica em DMF de alguns cinamatos de metila substituídos no anel aromático. O objetivo deste estudo foi verificar a influência de vários substituintes sobre o curso da reação de eletro-hidrodimerização (EHD). Os substratos utilizados foram os o-metil- (1), o-cloro- (2), o-nitro- (3), m,p-dicloro- (4), m-cloro- (5) e p-cloro- (6), m-nitro- (7), o-metoxicarbonil- (8) cinamatos de metila. As técnicas empregadas foram a voltametria cíclica (verificação dos potenciais de redução) e eletrólises preparativas a potencial controlado. Quando o substrato 1 foi eletrolisado, uma mistura de dois estereoisômeros do 4,5-bis-(o-metilfenil)-2-oxo-ciclopentanocarboxila-to de metila, ainda não descritos na literatura, foi obtida, um resultado diferente das EHD de cinamatos descritas que conduzem a um único estereoisômero com elevada diastereosseletividade. O o-clorocinamato de metila (2) investigado em dois potenciais diferentes, sofreu uma desalogenação e forneceu o cinamato de metila (-1,25 V vs. Ag/AgI) e este foi transformado em seu hidrodímero cíclico em 1,45 V vs. Ag/AgI. Nos substratos 4 e 6 ocorreu uma competição entre a desalogenação e a dimerização enquanto que no caso de 5 somente foi observada a EHD. Foi sugerido um mecanismo para a desalogenação. Após eletrólises em vários potenciais, os nitroderivados 3 e 7 conduziram a misturas dos reagentes de partida e os ácidos carboxílicos correspondentes, mas não foram observados produtos de EHD. As eletrólises do o-metoxicinamato de metila (8) não forneceram o dímero esperado na redução de cinamatos, mas compostos policíclicos inéditos cuja formação pode ser convenientemente explicada por meio de ciclizações de Dieckmann que envolvem o grupo metoxicarbonílico do anel aromático.<br>The synthesis and electrochemical reduction in DMF of some ring substituted cinnamic esters are described. The main objective if this work is to verify the influence of the substituents on the electrohydrodimerization (EHD). The substrates studied were the methyl esters of o-methyl- (1), o-chloro- (2), o-nitro- (3), m,p-dichloro- (4), m-chloro- (5), p-chloro- (6), m-nitro- (7) and o-methoxycarbonyl- (8) cinnamic acids. Their electrochemistry was investigated employing cyclic voltammetry (determination of the reduction potentials) and preparative electrolysis at controlled potential. When substrate 1 was electrolyzed, a mixture of two stereoisomers of methyl 4,5-bis-(o-methylphenyl)-2-oxo-cyclopentane-carboxylate, not yet described in literature, was obtained, a result which differs from the usual EHD of cinnamates, which lead to only one stereoisomer with high diastereoselectivity. Methyl o-chlorocinnamate (2) electrolysed at 1,25 V vs Ag/AgI was dehalogenated and afforded methyl cinnamate. When the electrolysis was performed at 1,45 V, the main product was the cyclic expected hydrodimer of methyl cinnamate. In the case of substrates 4 and 6 a competition of dehalogenation and cimerization was observed whereas for 5 only the EHD occurred. A mechanism for the dehalogenation is suggested. Several electrolysis at different potentials, of the nitro-derivatives 3 and 7 yielded mixtures of starting material and the corresponding carboxylic acids. In this no EHD products were observed. The electrochemical reduction of methyl o methoxycarbonyl-cinnamate (8) did not lead to the expected EHD dimer, but new polycyclic compounds were isolated. Their formation is conventiently explained by Dieckmann cyclization which involve the methoxycarbonyl group of the aromatic ring.
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Valim, Ricardo Bertholo. "Estudo do comportamento eletroquímico de carbono Printex 6L modificado com 2-terc-butil-9,10-antraquinona e 2-etil-9,10-antraquinona para a eletrogeração de H2O2 em meio ácido." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/75/75135/tde-01032013-141330/.
Full textAbstract:
Neste trabalho foi estudado o comportamento eletroquímico de materiais à base de carbono Printex 6L, sem e com a adição de compostos orgânicos da classe das quinonas (2-terc-butil-9,10-antraquinona (TBA) e 2-etil-9,10-antraquinona (EA)) para a produção de peróxido de hidrogênio (H2O2) a partir da reação de redução do oxigênio gasoso (O2). Na primeira etapa, foi utilizada a técnica de microcamada porosa depositada sobre um eletrodo de disco/anel rotatório, sendo que a partir dos resultados obtidos foram confeccionados eletrodos de difusão gasosa (EDG) para a eletrogeração de H2O2. Os melhores resultados utilizando a microcamada porosa foram para os materiais com a adição dos modificadores, sendo que o material com 1,0% (m/m) de TBA na demonstrou ser o mais eficiente na geração de peróxido de hidrogênio, apresentando eficiência 20% maior comparado ao Printex 6L sem modificador. Com o eletrodo de difusão gasosa confeccionado com o composto orgânico escolhido, na melhor porcentagem de adição mássica de modificador, obteve-se a concentração de 301 mg L-1, sendo que com o eletrodo confeccionado com Printex 6L sem modificador obteve-se a concentração de 175 mg L-1, sob as mesmas condições experimentais. A eficiência cinética também apresentou os mesmos resultados quanto à eficiência dos materiais escolhidos, sendo de 5,94 mg L-1 min-1 para o material com 1,0% de TBA, no potencial de -1,0 V (vs. ECS), e de 3,05 mg L-1 min-1 para o eletrodo de difusão gasosa sem modificador, no potencial de -0,8 V (vs. ECS).<br>In this work, the electrochemistry behavior of the materials prepared with Printex 6L, with and without addition of organic compounds of the class of quinones, being the compounds: 2-tert-butyl-9,10-anthraquinone (TBA) and 2-ethyl-9,10-anthraquinone (EA). These materials were used to promote the electrogeneration of hydrogen peroxide through the oxygen reduction reaction. In the first phase, it was used the technique of porous microlayer deposited on the rotating ring/disk electrode, and after has been confectioned gas diffusion electrodes (GDE). The best results using the porous microlayer were for the materials with addition of modifiers, and the material with 1.0% (m/m) of 2-terc-butyl-9,10-anthraquinone was demonstrated to be the most efficient in generating hydrogen peroxide, presenting an efficiency 20% higher when compared to Printex 6L without the modifier. The gas diffusion electrode made with the chosen organic compound, in the best massic percentage of modifier, obtained the concentration of 301 mg L-1, and the electrode made with Printex 6L without the modifier obtained the maximum concentration of 175 mg L-1, under the same experimental conditions. The kinect efficiency also demonstrated the same results regarding the efficiency of the chosen materials, which means 5.94 mg L-1 min-1 for the material with 1.0% of 2-terc-butyl-9,10-anthraquinone, in the potential of -1.0 V(vs. SCE), and 3.05 mg L-1 min-1 for the gas diffusion electrode without the modifier, in the potential of -0.8 V (vs. SCE).
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Wang, Shaopeng. "Part I. Spirodienones via a thermal (1,3) oxygen to carbon migration ; Part II. Spirodienones via a photochemical (1,3) oxygen to carbon migration ; Part III. Mechanistic studies on the anodic oxidation of 3,4-dimethoxybenzene and the electrosynthesis.. /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487686243821522.
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Aït, Lyazidi Hamida. "Electrosyntheses organiques a partir d'acides carboxyliques hydroxyles." Paris 6, 1993. http://www.theses.fr/1993PA066288.
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Cette these a ete consacree a l'etude des reactions d'electrosynthese a partir d'acides-alcools, principalement derives des sucres. La premiere partie concerne la reduction electrochimique des groupes carboxyliques en aldehyde en milieu aqueux. La transformation de l'acide salicylique en salicylaldehyde avec une electrode de mercure a ete reprise et optimisee. Les resultats obtenus ont ete appliques a la reduction des acides gluconique et galactonique en glucose et galactose. Les rendements sont restes modestes. La deuxieme partie concerne l'oxydation des groupes hydroxyles en du groupement carboxylique. L'oxydation chimique peut etre obtenue de facon limitee en utilisant l'oxygene et un catalyseur platine depose sur charbon. Nous avons demontre que la reaction d'oxydation de l'acide lactique en acide pyruvique peut etre conduite en utilisant une suspension de charbon platine dans un compartiment anodique dont le collecteur de courant est polarise a une tension inferieure a celle du degagement d'oxygene, principal responsable de la desactivation du catalyseur. Les conditions optimales de l'electrosynthese ont ete determinees. Ce travail permettra d'aborder le probleme de l'oxydation selective en des groupes carboxyliques
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Zhang, Lin. "Co-immobilisation du complexe (2,2'-bipyridyl) (pentaméthylcyclopentadiényl)-rhodium et de déshydrogénases NAD-dépendantes pour l’électrosynthèse enzymatique énantiosélective." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0283/document.
Full textAbstract:
Dans ce travail, nous avons développé différentes méthodes pour la co-immobilisation sur des électrodes poreuses de carbone de déshydrogénases NAD-dépendantes avec le complexe (2,2'-bipyridyle)(pentaméthylcyclopentadiényl)-rhodium ([Cp*Rh(bpy)Cl]+) pour des applications de synthèse électroenzymatique d’alcools et de sucres chiraux. L'objectif était d'éviter la dégradation de l'activité enzymatique provenant de l'interaction entre les groupes fonctionnels de surface de l'enzyme (-SH, -NH2) et le complexe [Cp*Rh(bpy)Cl]+, et également de permettre le recyclage des catalyseurs. L’électrogreffage de sels de diazonium a été utilisé pour introduire des fonctions alcène et/ou azoture sur une surface de carbone (carbone vitreux plan, feutre de carbone poreux ou couches de nanotubes de carbone). La chimie click « thiol-ène » a été utilisée pour lier de manière covalente une D-sorbitol déshydrogénase modifiée par un tag cystéine (soit 1 ou 2 fragments cystéine à l'extrémité N-terminale de la chaîne polypeptidique) à des électrodes de carbone. Ensuite, la réaction de cyclo-addition de Huisgen alcyne-azoture a été utilisée pour lier le complexe [Cp*Rh(bpy)Cl]+ à l’électrode. Ensuite la co-immobilisation des enzymes redox (D-sorbitol et galactitol déshydrogénases) avec le complexe [Cp*Rh(bpy)Cl]+ a été testée par l'encapsulation des protéines dans une couche de gel de silice, à l'intérieur d'un feutre de carbone poreux préalablement fonctionnalisé par le complexe de rhodium. Le catalyseur est alors stable pendant plusieurs semaines pour la réaction de régénération de NADH, mais cette architecture d'électrode conduit à l'inhibition de l'activité enzymatique, probablement causée par un microenvironnement local (augmentation du pH et de la concentration du produit). La combinaison des chimies clicks « thiol-ène » et cyclo-addition de Huisgen a ensuite été étudiée pour l'immobilisation séquentielle de [Cp*Rh(bpy)Cl]+ et d’une D-sorbitol déshydrogénase porteuse d’un tag cystéine, sur une électrode poreuse bi-fonctionnalisée par les groupes azoture et alcène. Enfin, compte tenu de la différence de durée de vie des enzymes et du complexe [Cp*Rh(bpy)Cl]+ et de la nécessité d'améliorer la séparation de ces éléments du système bioélectrochimique, l’assemblage optimal a été obtenu en associant une couche poreuse de silice dans laquelle est immobilisée l’enzyme avec un papier de nanotubes de carbone fonctionnalisé par le complexe de rhodium. Le catalyseur [Cp*Rh(bpy)Cl]+ pour la régénération de NADH peut être réutilisé successivement avec plusieurs couches de protéines. Ce système optimal a finalement été appliqué à la conversion bioélectrochimique du D-fructose en D-sorbitol<br>In this work we developed methods for the co-immobilization of NAD-dependent dehydrogenases and the (2,2'-bipyridyl) (pentamethylcyclopentadienyl)-rhodium complex ([Cp*Rh(bpy)Cl]+) on porous carbon electrodes for application in the electroenzymatic synthesis of chiral alcohols and sugars. The goal was to avoid the degradation of the enzymatic activity coming from the interaction of functional groups from the enzyme surface (eg.-SH, -NH2) with [Cp*Rh(bpy)Cl]+ and to promote the recyclability of the catalyst. Diazonium electrografting was used to introduce alkene and azide groups on a carbon surface (flat glassy carbon, porous carbon felt or carbon nanotubes layers). Thiol-ene click chemistry was applied to bind a D-sorbitol dehydrogenase with cysteine tags (either 1 or 2 cysteine moieties at the N terminus of the polypeptide chain) onto carbon electrodes. Azide-alkyne Huisgen cyclo-addition reaction was used to bind an alkyne-modified [Cp*Rh(bpy)Cl]+. Then co-immobilization of the redox enzymes (D-sorbitol and galactitol dehydrogenase) with the complex [Cp*Rh(bpy)Cl]+ was tested by encapsulation of the proteins in a silica gel layer, inside a rhodium-functionalized porous carbon felt. The immobilized [Cp*Rh(bpy)Cl]+ was stable over weeks for NADH regeneration, but this electrode architecture led to the inhibition of the enzymatic activity, possibly because of the local environment (increase of pH and product accumulation in the porous electrode). The combination of ‘thiol-ene’ and Huisgen cyclo-addition was then investigated for sequential immobilization of [Cp*Rh(bpy)Cl]+ and cysteine-tagged D-sorbitol dehydrogenase on an azide-alkene bi-functionalized electrode. Finally, considering the different lifetime of enzymes and [Cp*Rh(bpy)Cl]+ catalyst, and the need for a better separation of these elements from the bioelectrochemical system, the best configuration was achieved by associating a porous silica layer with the immobilized enzyme with a bucky paper of carbon nanotubes functionalized with [Cp*Rh(bpy)Cl]+. The reusability of this functionalized electrode was proved and the designed bioelectrode was successfully applied to a bioelectrochemical conversion of D-fructose to D-sorbitol