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1
Yin, Qiushi, Zihao Xu, Tianquan Lian, Djamaladdin G. Musaev, Craig L. Hill, and Yurii V. Geletii. "Tafel Slope Analyses for Homogeneous Catalytic Reactions." Catalysts 11, no. 1 (January 11, 2021): 87. http://dx.doi.org/10.3390/catal11010087.
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Tafel analysis of electrocatalysts is essential in their characterization. This paper analyzes the application of Tafel-like analysis to the four-electron nonelectrochemical oxidation of water by the stoichiometric homogeneous 1-electron oxidant [Ru(bpy)3]3+ to dioxygen catalyzed by homogeneous catalysts, [Ru4O4(OH)2(H2O)4(γ-SiW10O36)2]10− (Ru4POM) and [Co4(H2O)2(PW9O34)2]10– (Co4POM). These complexes have slow electron exchange rates with electrodes due to the Frumkin effect, which precludes the use of known electrochemical methods to obtain Tafel plots at ionic strengths lower than 0.5 M. The application of an electron transfer catalyst, [Ru(bpy)3]3+/2+, increases the rates between the Ru4POM and electrode, but a traditional Tafel analysis of such a complex system is precluded due to a lack of appropriate theoretical models for 4-electron processes. Here, we develop a theoretical framework and experimental procedures for a Tafel-like analysis of Ru4POM and Co4POM, using a stoichiometric molecular oxidant [Ru(bpy)3]3+. The dependence of turnover frequency (TOF) as a function of electrochemical solution potential created by the [Ru(bpy)3]3+/[Ru(bpy)3]2+ redox couple (an analog of the Tafel plot) was obtained from kinetics data and interpreted based on the suggested reaction mechanism.
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Yin, Qiushi, Zihao Xu, Tianquan Lian, Djamaladdin G. Musaev, Craig L. Hill, and Yurii V. Geletii. "Tafel Slope Analyses for Homogeneous Catalytic Reactions." Catalysts 11, no. 1 (January 11, 2021): 87. http://dx.doi.org/10.3390/catal11010087.
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Tafel analysis of electrocatalysts is essential in their characterization. This paper analyzes the application of Tafel-like analysis to the four-electron nonelectrochemical oxidation of water by the stoichiometric homogeneous 1-electron oxidant [Ru(bpy)3]3+ to dioxygen catalyzed by homogeneous catalysts, [Ru4O4(OH)2(H2O)4(γ-SiW10O36)2]10− (Ru4POM) and [Co4(H2O)2(PW9O34)2]10– (Co4POM). These complexes have slow electron exchange rates with electrodes due to the Frumkin effect, which precludes the use of known electrochemical methods to obtain Tafel plots at ionic strengths lower than 0.5 M. The application of an electron transfer catalyst, [Ru(bpy)3]3+/2+, increases the rates between the Ru4POM and electrode, but a traditional Tafel analysis of such a complex system is precluded due to a lack of appropriate theoretical models for 4-electron processes. Here, we develop a theoretical framework and experimental procedures for a Tafel-like analysis of Ru4POM and Co4POM, using a stoichiometric molecular oxidant [Ru(bpy)3]3+. The dependence of turnover frequency (TOF) as a function of electrochemical solution potential created by the [Ru(bpy)3]3+/[Ru(bpy)3]2+ redox couple (an analog of the Tafel plot) was obtained from kinetics data and interpreted based on the suggested reaction mechanism.
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El-Zahry, Marwa R., and Marwa F. B. Ali. "Enhancement effect of reduced graphene oxide and silver nanocomposite supported on poly brilliant blue platform for ultra-trace voltammetric analysis of rosuvastatin in tablets and human plasma." RSC Advances 9, no. 13 (2019): 7136–46. http://dx.doi.org/10.1039/c8ra10415h.
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Tryk, Donald A., Myoung S. Lee, Makoto Uchida, Hiroyuki Uchida, and Masahiro Watanabe. "Tafel Slope Component Analysis of Polymer Electrolyte Fuel Cell Cathode Current-Potential Behavior." ECS Transactions 35, no. 27 (December 16, 2019): 13–23. http://dx.doi.org/10.1149/1.3643348.
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Kambiré, Ollo, Lemeyonouin A. G. Pohan, Konan H. Kondro, and Lassiné Ouattara. "Study of oxygen evolution reaction on thermally prepared xPtOy-(100-x)IrO2 electrodes." Journal of Electrochemical Science and Engineering 10, no. 4 (July 23, 2020): 347–60. http://dx.doi.org/10.5599/jese.806.
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The mixed coupled xPtOy-(100-x)IrO2 electrodes (x = 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100) were thermally prepared at 450 °C on titanium supports. The prepared electrodes were firstly physically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Afterwards, electrochemical characterizations were performed by voltammetric (cyclic and linear) methods in different electrolyte media (KOH and HClO4). It is shown that the prepared electrodes are composed by both PtOy (platinum and platinum oxide) and IrO2 (iridium dioxide). For xPtOy-(100-x)IrO2 electrodes having higher content of IrO2, more surface cracks and pores are formed, defining a higher surface area with more active sites. Higher surface area due to presence of both PtOy and IrO2, is for xPtOy-(100-x)IrO2 electrodes in 1 M KOH solution confirmed by cyclic voltammetry at potentials of the oxide layer region. For all prepared electrodes, voltammetric charges were found higher than for PtOy, while the highest voltammetric charge is observed for the mixed 40PtOy-60IrO2 (x = 40) electrode. The Tafel slopes for oxygen evolution reaction (OER) in either basic (0.1 M KOH) or acid (0.1 M HClO4) media were determined from measured linear voltammograms corrected for the ohmic drop. The values of Tafel slopes for OER at PtOy, 90PtOy-10IrO2 and IrO2 in basic medium are 122, 55 and 40 mV dec-1, respectively. For other mixed electrodes, Tafel slopes of 40 mV dec-1 were obtained. Although proceeding by different OER mechanism, similar values of Tafel slopes were obtained in acid medium, i.e., Tafel slopes of 120, 60 and 39 mV dec-1 were obtained for PtOy, 90PtOy-10IrO2 and IrO2, and 40 mV dec-1 for other mixed electrodes. The analysis of Tafel slope values showed that OER is more rapid on coupled mixed electrodes than on pure PtOy. For mixed xPtOy-(100-x)IrO2 electrodes, OER is more rapid when the molar percent of PtOy meets the following condition: 0 ˂ x ≤ 80. This study also showed that the mixed coupled electrodes are more electrocatalytically active for OER than either PtOy or IrO2 in these two media.
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Huang, Song-Jeng, Adil Muneeb, Palani Sabhapathy, Khasim Saheb Bayikadi, Tahir Murtaza, Kalaivanan Raju, Li-Chyong Chen, Kuei-Hsien Chen, and Raman Sankar. "Two-Dimensional Layered NiLiP2S6 Crystals as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting." Catalysts 11, no. 7 (June 28, 2021): 786. http://dx.doi.org/10.3390/catal11070786.
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The quest of earth-abundant bifunctional electrocatalysts for highly efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential for clean and renewable energy systems. Herein, directed by the experimental analysis, we demonstrate layered nickel lithium phosphosulfide (NiLiP2S6) crystal as a highly efficient water-splitting catalyst in alkaline media. With strained lattice due to stacked layers as observed by TEM and electronic structure analysis performed by XPS showed mixed Ni2+,3+ oxidation states induced by addition of Li as a cation, NiLiP2S6 displays excellent OER (current density of 10 mA cm–2 showed an overpotential of 303 mV vs. RHE and a Tafel slope of 114 mV dec–1) and HER activity (current density of −10 mA cm–2 showed an overpotential of 184 mV vs. RHE and a Tafel slope of 94.5 mV dec–1). Finally, an alkaline media was employed to demonstrate the overall water splitting using NiLiP2S6 as both the anode and the cathode, which attained a 50 mA cm−2 current density at 1.68 V. This bimetallic phosphosulfide, together with long-term stability and enhanced intrinsic activity, shows enormous potential in water splitting applications.
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Murthy, Arun Prasad, Jayaraman Theerthagiri, Jagannathan Madhavan, and Kadarkarai Murugan. "Highly active MoS2/carbon electrocatalysts for the hydrogen evolution reaction – insight into the effect of the internal resistance and roughness factor on the Tafel slope." Physical Chemistry Chemical Physics 19, no. 3 (2017): 1988–98. http://dx.doi.org/10.1039/c6cp07416b.
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Marshall, Aaron T., and Laurent Vaisson-Béthune. "Avoid the quasi-equilibrium assumption when evaluating the electrocatalytic oxygen evolution reaction mechanism by Tafel slope analysis." Electrochemistry Communications 61 (December 2015): 23–26. http://dx.doi.org/10.1016/j.elecom.2015.09.019.
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Levinas, Ramunas, Natalia Tsyntsaru, and Henrikas Cesiulis. "The Characterisation of Electrodeposited MoS2 Thin Films on a Foam-Based Electrode for Hydrogen Evolution." Catalysts 10, no. 10 (October 14, 2020): 1182. http://dx.doi.org/10.3390/catal10101182.
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Molybdenum sulphide is an emerging precious-metal-free catalyst for cathodic water splitting. As its active sites catalyse the Volmer hydrogen adsorption step, it is particularly active in acidic media. This study focused on the electrochemical deposition of MoS2 on copper foam electrodes and the characterisation of their electrocatalytic properties. In addition, the electrodeposition was modified by adding a reducing agent—sodium hypophosphite—to the electrolyte. To reveal the role of hypophosphite, X-ray photoelectron spectroscopy (XPS) analysis was carried out in addition to scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). MoS2 films, electrodeposited at various charges passed through the cell (catalyst loadings), were tested for their catalytic activity towards hydrogen evolution in 0.5 M H2SO4. Polarisation curves and Tafel slope analysis revealed that the electrodeposited MoS2 films are highly active. Namely, Tafel slopes fell within the 40–50 mV dec−1 range. The behaviour of as-deposited films was also evaluated by electrochemical impedance spectroscopy over a wide overpotential range (0 to −0.3 V), and two clear time constants were distinguished. Through equivalent electrical circuit analysis, the experimental data were fitted to the appropriate model, and the obtained values of the circuit components were examined as a function of overpotential. It was found that the addition of NaH2PO2 into the electrodeposition solution affects the intrinsic activity of the material. Finally, a method is proposed to approximate the number of active sites from impedance data.
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Modibane, Kwena Desmond, Ngwako Joseas Waleng, Kabelo Edmond Ramohlola, Thabiso Carol Maponya, Gobeng Release Monama, Katlego Makgopa, and Mpitloane Joseph Hato. "Poly(3-aminobenzoic acid) Decorated with Cobalt Zeolitic Benzimidazolate Framework for Electrochemical Production of Clean Hydrogen." Polymers 12, no. 7 (July 16, 2020): 1581. http://dx.doi.org/10.3390/polym12071581.
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A novel composite of poly(3-aminobenzoic acid) (PABA) and a cobalt zeolitic benzimidazolate framework (CoZIF) has been studied for the production of hydrogen through the hydrogen evolution reaction (HER). The structural characteristics and successful synthesis of PABA, CoZIF and the PABA/CoZIF composite were confirmed and investigated using different techniques. Probing-ray diffraction for phase analysis revealed that the composite showed a decrease and shift in peak intensities, confirming the incorporation of CoZIF on the PABA backbone via in situ polymerization, with an improvement in the crystalline phase of the polymer. The thermal stability of PABA was enhanced upon composite formation. Both scanning electron microscopy and transmission electron microscopy showed that the composite had a rough surface, owing to an interaction between the CoZIF and the external surface of the PABA. The electrochemical hydrogen evolution reaction (HER) performance of the synthesized samples was evaluated using cyclic voltammetry and Tafel analysis. The composite possessed a Tafel slope value of 156 mV/dec and an α of 0.38, suggesting that the Volmer reaction coupled with either the Heyrovsky or Tafel reaction as the rate determining step. The fabricated composite showed high thermal stability and excellent tolerance as well as high electroactivity towards the HER, showing it to be a promising non-noble electrocatalyst to replace Pt-based catalysts for hydrogen generation.
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Sathiskumar, Chinnusamy, Shanmugam Ramakrishnan, Mohanraj Vinothkannan, Ae Rhan Kim, Srinivasan Karthikeyan, and Dong Jin Yoo. "Nitrogen-Doped Porous Carbon Derived from Biomass Used as Trifunctional Electrocatalyst toward Oxygen Reduction, Oxygen Evolution and Hydrogen Evolution Reactions." Nanomaterials 10, no. 1 (December 31, 2019): 76. http://dx.doi.org/10.3390/nano10010076.
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Tremendous developments in energy storage and conversion technologies urges researchers to develop inexpensive, greatly efficient, durable and metal-free electrocatalysts for tri-functional electrochemical reactions, namely oxygen reduction reactions (ORRs), oxygen evolution reactions (OERs) and hydrogen evolution reactions (HERs). In these regards, this present study focuses upon the synthesis of porous carbon (PC) or N-doped porous carbon (N-PC) acquired from golden shower pods biomass (GSB) via solvent-free synthesis. Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies confirmed the doping of nitrogen in N-PC. In addition, morphological analysis via field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) provide evidence of the sheet-like porous structure of N-PC. ORR results from N-PC show the four-electron pathway (average n = 3.6) for ORRs with a Tafel slope of 86 mV dec−1 and a half-wave potential of 0.76 V. For OERs and HERs, N-PC@Ni shows better overpotential values of 314 and 179 mV at 10 mA cm−2, and its corresponding Tafel slopes are 132 and 98 mV dec−1, respectively. The chronopotentiometry curve of N-PC@Ni reveals better stability toward OER and HER at 50 mA cm−2 for 8 h. These consequences provide new pathways to fabricate efficient electrocatalysts of metal-free heteroatom-doped porous carbon from bio-waste/biomass for energy application in water splitting and metal air batteries.
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Jiang, Xiao Yu, Jin Chen, and Wen Zhe Chen. "Microwave Synthesis and Characterization of Nanoscale Lanthanum Cobaltite." Advanced Materials Research 476-478 (February 2012): 1322–26. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.1322.
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Nanoscale lanthanum cobaltite with perovskite-type was successfully synthesized by microwave irradiation directly and was characterized by XRD, SEM, XPS and BET analysis. The results show that the size of particle was 18 nm averagely, the surface area to be 31.0 m2 g−1. The electrochemical properties were studied by cyclic voltammetry and steady state polarization. The cyclic voltammogram between 0 and 0.55 V exhibited two pairs of redox peaks prior to the onset of O2 evolution in 1 mol dm−3 KOH. The Tafel slope and the reaction order with respect to concentration of OH− were found to be 60 mV decade−1 and ca. 1, respectively.
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Tryk, Donald A., Katsuyoshi Kakinuma, Makoto Uchida, and Akihiro Iiyama. "A Simple Analytical Approach for Fitting Steady-State Polarization Behavior of Polymer Electrolyte Fuel Cells Using Tafel Slope Component Analysis (TSCA)." ECS Meeting Abstracts MA2020-02, no. 33 (November 23, 2020): 2177. http://dx.doi.org/10.1149/ma2020-02332177mtgabs.
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Vilakazi, Sibulelo, Tebello Nyokong, Takamitsu Fukuda, and Nagao Kobayashi. "Electrocatalytic behavior of cobalt phthalocyanine complexes immobilized on glassy carbon electrode towards the reduction of dicrotophos pesticide." Journal of Porphyrins and Phthalocyanines 16, no. 07n08 (July 2012): 939–45. http://dx.doi.org/10.1142/s1088424612501040.
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Electrocatalytic properties of cobalt phthalocyanine (CoPc), cobalt tetra-carboxy phthalocyanine (CoTCPc) and cobalt octa-carboxy (CoOCPc), towards the detection of dicrotophos have been studied. Catalytic behavior towards the reduction of dicrotophos was found to be dependent on the pH, as well as the substitution on the phthalocyanine ring. Strong electron withdrawing groups on the phthalocyanine ring yielded best catalysis as evidenced by the enhancement of the reduction peak current, (~5 fold) compared to the bare glassy carbon electrode. The analysis gave a good detection limit of 1.25 × 10-7 M, and good linearity for the studied concentration range. A high Tafel slope value was obtained, indicating a strong interaction between dicrotophos and the cobalt phthalocyanine complex.
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Ebadi, Mehrdad. "Electrocatalytic oxidation and flow amperometric detection of hydrazine on a dinuclear ruthenium phthalocyanine-modified electrode." Canadian Journal of Chemistry 81, no. 2 (February 1, 2003): 161–68. http://dx.doi.org/10.1139/v03-012.
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Electrocatalytic oxidation of hydrazine on a dinuclear ruthenium phthalocyanine ((RuPc)2) modified electrode was studied using cyclic voltammetry (CV) and rotating disc electrode (RDE) techniques. At pH = 13, a four-electron oxidation of hydrazine to N2 was observed. A suitable mechanism was proposed by analyzing the rate equation and the Tafel slope. The flow injection analysis was performed to characterize the (RuPc)2-modified electrode as an amperometric sensor for the detection of hydrazine. The electrode displays an excellent accuracy and precision in phosphate solution at pH 12 and 13. The linearity range was from 30 nM to 1 mM with a correlation coefficient of 0.9998.Key words: ruthenium phthalocyanine, electrocatalysis, surface-modified electrode, hydrazine, amperometric sensor.
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Gu, Siyong, Chien-Te Hsieh, Chih-Peng Kao, Chun-Chieh Fu, Yasser Ashraf Gandomi, Ruey-Shin Juang, and Kenneth David Kihm. "Electrocatalytic Oxidation of Glucose on Boron and Nitrogen Codoped Graphene Quantum Dot Electrodes in Alkali Media." Catalysts 11, no. 1 (January 13, 2021): 101. http://dx.doi.org/10.3390/catal11010101.
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A novel solvothermal technique has been developed in the presence of C/N/B precursor for synthesizing B-N-coped graphene quantum dots (GQDs) as non-metal electrocatalysts towards the catalytic glucose oxidation reaction (GOR). Both N-doped GQD and B-N-codoped GQD particles (~4.0 nm) possess a similar oxidation and amidation level. The B-N-codoped GQD contains a B/C ratio of 3.16 at.%, where the B dopants were formed through different bonding types (i.e., N‒B, C‒B, BC2O, and BCO2) inserted into or decorated on the GQDs. The cyclic voltammetry measurement revealed that the catalytic activity of B-N-codoped GQD catalyst is significantly higher compared to the N-doped GQDs (~20% increase). It was also shown that the GOR activity was substantially enhanced due to the synergistic effect of B and N dopants within the GQD catalysts. Based on the analysis of Tafel plots, the B-N-codoped-GQD catalyst electrode displays an ultra-high exchange current density along with a reduced Tafel slope. The application of B-N-codoped GQD electrodes significantly enhances the catalytic activity and results in facile reaction kinetics towards the glucose oxidation reaction. Accordingly, the novel design of GQD catalyst demonstrated in this work sets the stage for designing inexpensive GQD-based catalysts as an alternative for precious metal catalysts commonly used in bio-sensors, fuel cells, and other electrochemical devices.
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Juodkazytė, Jurga, Kȩstutis Juodkazis, and Saulius Juodkazis. "Atoms vs. Ions: Intermediates in Reversible Electrochemical Hydrogen Evolution Reaction." Catalysts 11, no. 9 (September 21, 2021): 1135. http://dx.doi.org/10.3390/catal11091135.
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We present a critical analysis of the mechanism of reversible hydrogen evolution reaction based on thermodynamics of hydrogen processes considering atomic and ionic species as intermediates. Clear distinction between molecular hydrogen evolution/oxidation (H2ER and H2OR) and atomic hydrogen evolution/oxidation (HER and HOR) reactions is made. It is suggested that the main reaction describing reversible H2ER and H2OR in acidic and basic solutions is: H3O++2e−⇌(H2+)adH2+OH− and its standard potential is E0 = −0.413 V (vs. standard hydrogen electrode, SHE). We analyse experimentally reported data with models which provide a quantitative match (R.J.Kriek et al., Electrochem. Sci. Adv. e2100041 (2021)). Presented analysis implies that reversible H2 evolution is a two-electron transfer process which proceeds via the stage of adsorbed hydrogen molecular ion H2+ as intermediate, rather than Had as postulated in the Volmer-Heyrovsky-Tafel mechanism. We demonstrate that in theory, two slopes of potential vs. lg(current) plots are feasible in the discussed reversible region of H2 evolution: 2.3RT/F≈60 mV and 2.3RT/2F≈30 mV, which is corroborated by the results of electrocatalytic hydrogen evolution studies reported in the literature. Upon transition to irreversible H2ER, slowdown of H2+ formation in the first electron transfer stage manifests, and the slope increases to 2.3RT/0.5F≈120 mV; R,F,T are the universal gas, Faraday constants and absolute temperature, respectively.
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Rakočević, Lazar, Irina Srejić, Aleksandar Maksić, Jelena Golubović, and Svetlana Štrbac. "Hydrogen Evolution on Reduced Graphene Oxide-Supported PdAu Nanoparticles." Catalysts 11, no. 4 (April 9, 2021): 481. http://dx.doi.org/10.3390/catal11040481.
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Hydrogen evolution reaction (HER) was investigated on reduced graphene oxide (rGO)-supported Au and PdAu nanoparticles in acid solution. The graphene spread over glassy carbon (rGO/GC) was used as a support for the spontaneous deposition of Au and Pd. The resulting Au/rGO and PdAu/rGO electrodes were characterized using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) techniques. Phase AFM images have shown that the edges of the rGO sheets were active sites for the deposition of both Au and Pd. XPS analysis revealed that the atomic percentages of both Au and PdAu nanoparticles were slightly higher than 1%. The activity of the PdAu/rGO electrode for the HER was remarkably high, with the overpotential close to zero. HER activity was stable over a 3 h testing time, with a low Tafel slope of approx. −46 mV/dec achieved after prolonged hydrogen evolution at a constant potential.
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Milikić, Jadranka, Aldona Balčiūnaitė, Zita Sukackienė, Dušan Mladenović, Diogo M. F. Santos, Loreta Tamašauskaitė-Tamašiūnaitė, and Biljana Šljukić. "Bimetallic Co-Based (CoM, M = Mo, Fe, Mn) Coatings for High-Efficiency Water Splitting." Materials 14, no. 1 (December 28, 2020): 92. http://dx.doi.org/10.3390/ma14010092.
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Bimetallic cobalt (Co)-based coatings were prepared by a facile, fast, and low-cost electroless deposition on a copper substrate (CoFe, CoMn, CoMo) and characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction analysis. Prepared coatings were thoroughly examined for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution (1 M potassium hydroxide, KOH) and their activity compared to that of Co and Ni coatings. All five coatings showed activity for both reactions, where CoMo and Co showed the highest activity for HER and OER, respectively. Namely, the highest HER current density was recorded at CoMo coating with low overpotential (61 mV) to reach a current density of 10 mA·cm−2. The highest OER current density was recorded at Co coating with a low Tafel slope of 60 mV·dec−1. Furthermore, these coatings proved to be stable under HER and OER polarization conditions.
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Giz, M. J., M. C. Marengo, E. A. Ticianelli, and E. R. Gonzalez. "Electrochemical and physical characterization of Ni-Cu-Fe alloy for chlor-alkali hydrogen cathodes." Eclética Química 28, no. 2 (2003): 21–28. http://dx.doi.org/10.1590/s0100-46702003000200003.
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This work describes the development of an alternative acetate bath for the electrochemical codeposition of Ni-Cu-Fe electrodes at low pH that is stable for several weeks and produces electrodes with good performance for chlor-alkali electrolysis. Physical characterization of the electrode surface was made using X ray absorption spectroscopy (XAS), scanning electron microscopy (SEM) and energy dispersive analysis (EDX). The evaluation of the material as electrocatalyst for the hydrogen evolution reaction (her) was carried out in brine solution (160 g L-1 NaCl + 150 g L-1 NaOH) at different temperatures through steady-state polarization curves. The Ni-Cu-Fe electrodes obtained with this bath have shown low overpotentials for the her, around 0.150 V at 353 K, and good stability under continuous long-term operation for 260 hours. One positive aspect of this cathode is that the polarization behavior of the material shows only one Tafel slope over the temperature range of 298 - 353 K.
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Leyva-Noyola, F., and O. Solorza-Feria. "Microwave Assisted Synthesis of Ru3Pd6Pt Cathode Catalyst in a PEM Fuel Cell." Journal of New Materials for Electrochemical Systems 16, no. 3 (July 8, 2013): 147–50. http://dx.doi.org/10.14447/jnmes.v16i3.3.
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Nanoparticles of Ru3Pd6Pt have been previously produced by different synthesis routes that involve high temperatures and relative high pressures and long time. The usage of a conventional microwave assisted synthesis reduces environmental risk impact as well as the cost effective production in large scale with minimum set up modifications. These features are the motivations for the use of microwaves in the synthesis of the Ru3Pd6Pt catalyst for PEM fuel cell applications to reduce the Pt loading. In this communication a tri-metallic electrocatalyst was produced by the reduction of the corresponding metallic salts, RuCl3, PdCl2, and H2PtCl6 in ethylene glycol using a modified conventional microwave device. Oxygen reduction reaction kinetic analysis results conducted to a Tafel slope, (-b = 41.2 ± 1.7 mV dec-1) at low overpotential, and exchange current density (i0 = 3.01 ± 0.39 × 10-5 mA cm-2) in 0.5M H2SO4. This electrocatalyst exhibited good performance and stability in a single H2/O2PEM fuel cell.
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Wei, Yongan, Liangyu Tian, Panpan Sun, Niu Huang, Xiaowei Lv, Liang Fang, and Xiaohua Sun. "Synthesis of Ni3Bi2S2 Coupled with N-Doped Carbon Sheets as Electrocatalyst for Triiodide and Oxygen Reduction." Journal of Nanoscience and Nanotechnology 21, no. 9 (September 1, 2021): 4740–48. http://dx.doi.org/10.1166/jnn.2021.19345.
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Herein, we report a novel composite structure consisting of Ni3Bi2S2 particles coupled with N-doped carbon (NC) sheets. Different from the generally used high vacuum or microwave-assisted technologies, metal-rich Ni3Bi2S2 can be successfully synthesized via a simple pyrolysis procedure, with NC employed as a reducing agent. In addition, the phase purity, size, and dispersity of the Ni3Bi2S2 particles, which were encapsulated by the NC shell, were modulated by the content of NC. The X-ray photoelectron spectroscopy (XPS) analysis demonstrated the metallic state of the Ni and Bi elements, which ensured good Ni3Bi2S2 electrical conductivity. As a result, the resultant Ni3Bi2S2/NC (0.55 II) catalyzed triiodide reduction with a lower charge transfer resistance than commercial Pt/C (1.4 II). Moreover, Ni3Bi2S2/NC catalyzed the oxygen reduction reaction with a positive ORR half-wave potential (0.81 V vs. RHE) and a low Tafel slope (47 mV dec-1). Our study thus provides the novel exploration of the electrochemical performance of Ni3Bi2S2 and indicates its promising application in electrocatalytic reactions.
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Chen, Meng, Yufei Ma, Yanqiang Zhou, Changqing Liu, Yanlin Qin, Yanxiong Fang, Guoqing Guan, Xiumin Li, Zhaoshun Zhang, and Tiejun Wang. "Influence of Transition Metal on the Hydrogen Evolution Reaction over Nano-Molybdenum-Carbide Catalyst." Catalysts 8, no. 7 (July 22, 2018): 294. http://dx.doi.org/10.3390/catal8070294.
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The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising way to solve energy and environment problems. In this work, various transition metals (Fe, Co, Ni, Cu, Ag, and Pt) were selected to support on molybdenum carbides by a simple organic-inorganic precursor carburization process. X-ray diffraction (XRD) analysis results indicated that the β-Mo2C phase was formed in all metal-doped samples. X-ray photoelectron spectroscopy analysis indicated that the binding energy of Mo2+ species (Mo2C) shifted to a lower value after metal was doped on the molybdenum carbide surface. Comparing with pure β-Mo2C, the electrocatalytic activity for HER was improved by transition metal doping on the surface. Remarkably, the catalytic activity improvement was more obvious when Pt was doped on molybdenum carbide (2% Pt-Mo2C). The 2% Pt-Mo2C required a η10 of 79 mV, and outperformed that of pure β-Mo2C (η10 = 410 mV) and other transition metal doped molybdenum carbides, with a small Tafel slope (55 mV/dec) and a low onset overpotential (32 mV) in 0.5 M H2SO4. Also, the 2% Pt-Mo2C catalyst demonstrated a high stability for the HER in 0.5 M H2SO4. This work highlights a feasible strategy to explore efficient electrocatalysts with low cost via engineering on the composition and nanostructure.
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Lv, Yuepeng, Sibin Duan, Yuchen Zhu, Peng Yin, and Rongming Wang. "Enhanced OER Performances of Au@NiCo2S4 Core-Shell Heterostructure." Nanomaterials 10, no. 4 (March 27, 2020): 611. http://dx.doi.org/10.3390/nano10040611.
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Transition metal sulfides have attracted a lot of attention as potential oxygen evolution reaction (OER) catalysts. Bimetallic sulfide possesses superior physicochemical properties due to the synergistic effect between bimetallic cations. By introducing a metal-semiconductor interface, the physicochemical properties of transition metal sulfide can be further improved. Using the solvothermal method, Au@NiCo2S4 core-shell heterostructure nanoparticles (NPs) and bare NiCo2S4 NPs were prepared. The measurement of the OER catalytic performance showed that the catalytic activity of Au@NiCo2S4 core-shell heterostructure was enhanced compared to bare NiCo2S4 NPs. At the current density of 10 mA cm−2, the overpotential of Au@NiCo2S4 (299 mV) is lower than that of bare NiCo2S4 (312 mV). The Tafel slope of Au@NiCo2S4 (44.5 mV dec−1) was reduced compared to that of bare NiCo2S4 (49.1 mV dec−1), indicating its faster reaction kinetics. Detailed analysis of its electronic structure, chemical state, and electrochemical impedance indicates that the enhanced OER catalytic performances of bare Au@NiCo2S4 core-shell NPs were a result of its increased proportion of high-valance Ni/Co cations, and its increased electronic conductivity. This work provides a feasible method to improve OER catalytic performance by constructing a metal-semiconductor core-shell heterostructure.
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Park, Hyerim, Byung Hyun Park, Jaeyoung Choi, Seyeon Kim, Taesung Kim, Young-Sang Youn, Namgyu Son, Jae Hong Kim, and Misook Kang. "Enhanced Electrochemical Properties and OER Performances by Cu Substitution in NiCo2O4 Spinel Structure." Nanomaterials 10, no. 9 (August 31, 2020): 1727. http://dx.doi.org/10.3390/nano10091727.
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In order to improve the electrochemical performance of the NiCo2O4 material, Ni ions were partially substituted with Cu2+ ions having excellent reducing ability. All of the electrodes were fabricated by growing the Ni1−xCuxCo2O4 electrode spinel-structural active materials onto the graphite felt (GF). Five types of electrodes, NiCo2O4/GF, Ni0.875Cu0.125Co2O4/GF, Ni0.75Cu0.25Co2O4/GF, Ni0.625Cu0.375Co2O4/GF, and Ni0.5Cu0.5Co2O4/GF, were prepared for application to the oxygen evolution reaction (OER). As Cu2+ ions were substituted, the electrochemical performances of the NiCo2O4-based structures were improved, and eventually the OER activities were also greatly increased. In particular, the Ni0.75Cu0.25Co2O4/GF electrode exhibited the best OER activity in a 1.0 M KOH alkaline electrolyte: the cell voltage required to reach a current density of 10 mA cm−2 was only 1.74 V (η = 509 mV), and a low Tafel slope of 119 mV dec−1 was obtained. X-ray photoelectron spectroscopy (XPS) analysis of Ni1−xCuxCo2O4/GF before and after OER revealed that oxygen vacancies are formed around active metals by the insertion of Cu ions, which act as OH-adsorption sites, resulting in high OER activity. Additionally, the stability of the Ni0.75Cu0.25Co2O4/GF electrode was demonstrated through 1000th repeated OER acceleration stability tests with a high faradaic efficiency of 94.3%.
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Spring, Stephanie, Pravin S. Shinde, Patricia R. Fontenot, James P. Donahue, and Shanlin Pan. "Self-Assembled Monolayers of Molybdenum Sulfide Clusters on Au Electrode as Hydrogen Evolution Catalyst for Solar Water Splitting." Inorganics 7, no. 6 (June 25, 2019): 79. http://dx.doi.org/10.3390/inorganics7060079.
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Hydrogen evolution reaction (HER) activities of self-assembled monolayers (SAMs) of [Mo3S7(S2CNMe2)3] and several other MoSx molecular clusters are presented on planer Au electrode. Our study suggests that such Mo-S clusters are unstable under HER reaction conditions of a strongly acidic electrolyte. The [Mo3S7(S2CNEt2)3]I monolayer prepared from DMF showed greater stability among all the studied precursors. The X-ray photoelectron spectroscopy (XPS) analysis on a monolayer of [Mo3S7(S2CNMe2)3]I in THF assembled on Au/ITO suggested sulfur-rich composition with S:Mo ratio of 2.278. The Mo-S monolayer clusters resulting from [Mo3S7(S2CNMe2)3]I in THF showed a Tafel slope of 75.74 mV dec−1 and required a lower overpotential of 410 mV to reach a high HER catalytic current density of 100 mA cm−2 compared to the other studied precursors. Surface coverage of the Mo-S clusters on the Au surface was confirmed by cyclic voltammetry (CV) curves from K3Fe(CN)6 and anodization of Au surface. Further, the rotating ring-disk electrode (RRDE) measurements were performed for the monolayer of [Mo3S7(S2CNMe2)3]I prepared in THF to study its reaction kinetics. The HER catalytic activity of such monolayer Mo-S clusters can further be improved by controlling the sulfur vacancy.
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Eckl, Maximilian, Steve Zaubitzer, Carsten Köntje, Attila Farkas, Ludwig Kibler, and Timo Jacob. "An Electrochemical Route for Hot Alkaline Blackening of Steel: A Nitrite Free Approach." Surfaces 2, no. 2 (March 29, 2019): 216–28. http://dx.doi.org/10.3390/surfaces2020017.
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Blackening belongs to the predominant technological processes in preserving steel surfaces from corrosion by generating a protective magnetite overlayer. In place of the commonly used dipping-procedure into nitrite-containing blackening baths at boiling temperatures that are far above 100 °C, here we describe a more environmentally friendly electrochemical route that operates at temperatures, even below 100 °C. After an investigation of the electrochemical behavior of steel samples in alkaline solutions at various temperatures, the customarily required bath temperature of more than 130 °C could be significantly lowered to about 80 °C by applying a DC voltage that leads to an electrode potential of 0.5−0.6 V vs. Pt. Thus, it was possible to eliminate the use of hazardous sodium nitrite economically and in an optimum way. Electrochemical quantification of the corrosion behavior of steel surfaces that were in contact with 0.1 M KCl solution was carried out by linear sweep voltammetry and by Tafel slope analysis. When comparing these data, even the corrosion rates of conventional blackened surfaces are of the same magnitude as a blank steel surface. This proves that magnetite overlayers represent rather poor protective layers in the absence of additional sealing. Moreover, cyclic voltammetry (CV), atomic force microscopy (AFM), scanning electron microscopy (SEM) and auger electron spectroscopy (AES) characterized the electrochemically blackened steel surfaces.
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Quej-Aké, Luis M., Ricardo Galván-Martínez, and Antonio Contreras-Cuevas. "Electrochemical and Tension Tests Behavior of API 5L X60 Pipeline Steel in a Simulated Soil Solution." Materials Science Forum 755 (April 2013): 153–61. http://dx.doi.org/10.4028/www.scientific.net/msf.755.153.
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In this work electrochemical impedance spectroscopy (EIS) and slow strain rate tests (SSRT) were used for the evaluation of API 5L X60 carbon steel in contact with a simulated soil solution called NS4. EIS monitoring before and after performing the tension tests was carried out. SSRT were carried out in NS4 solution at room temperature to simulate dilute ground water that has been found associated with stress corrosion cracking (SCC) of low carbon steel pipelines. A strain rate of 1x10-6 sec-1 was used. According to the analysis of SSRT, the X60 pipeline steel is highly resistant to SCC. In order to perform the electrochemical test, two working electrodes were considered, a complete specimen, before the SSRT and a fractured specimen after the SSRT. The analyses of results show that the electrochemical response was different in each samples. The corrosion rate (CR) obtained by the two corrosion techniques revealed that the CR of the fractured specimen was higher than the CR of the complete specimen. This behavior is attributed to the fact that the fractured specimen present a high degree of tortuosity and this condition activate the corrosion process. In addition, according to the cathodic Tafel slope, the reduction reacction was influenced by a difusion process. A combine fracture type in SSRT was observed: ductil and brittle with a transgranular appearance. Some pits and internal cracks close to the fracture zone were observed. The failure process and mechanism of X60 steel in NS4 solution are controlled by dissolution and hydrogen embrittlement.
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Elezovic, Nevenka, Biljana Babic, Velimir Radmilovic, Ljiljana Gajic-Krstajic, Nedeljko Krstajic, and Ljiljana Vracar. "A novel platinum-based nanocatalyst at a niobia-doped titania support for the hydrogen oxidation reaction." Journal of the Serbian Chemical Society 76, no. 8 (2011): 1139–52. http://dx.doi.org/10.2298/jsc100823100e.
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The kinetics of the hydrogen oxidation reaction (HOR) was studied at Pt nanoparticles supported on niobia-doped titania (Pt/N-T). The catalyst support, with the composition of 0.05NbO2.5-?-0.995TiO2 (0<?<1), was synthesized by a modified sol-gel procedure and characterized by the BET and X-ray diffraction (XRD) techniques. The specific surface area of the support was found to be 70 m2 g-1. The XRD analysis revealed the presence of the anatase TiO2 phase in the support powder. No peaks indicating the existence of Nb-compounds were detected. Pt/N-T nanocatalyst was synthesized by the borohydride reduction method. Transmission electron microscopy revealed a quite homogenous distribution of the Pt nanoparticles over the support, with a mean particle size of about 3 nm. The electrochemical active surface area of Pt of 42?4 m2 g-1 was determined by the cyclic voltammetry technique. The kinetics of the HOR was investigated by linear sweep voltammetry at a rotating disc electrode in 0.5 mol dm-3 HClO4 solution. The determined value of the Tafel slope of 35 mV dec-1 and an exchange current density of 0.45 mA cm-2 per real surface area of the Pt are in good accordance with those already reported in the literature for the HOR at polycrystalline Pt and Pt nanocatalysts in acid solutions. This new catalyst exhibited better activity for the HOR in comparison with Pt nanocatalyst supported on Vulcan? XC-72R high area carbon.
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Shams Ghahfarokhi, Zahra, Mojtaba Bagherzadeh, Ebrahim Ghiamati Yazdi, and Abbas Teimouri. "Surface modification of graphene-coated carbon steel using aromatic molecules for enhancing corrosion resistance; comparison between type of aryl substitution with different spatial situations." Anti-Corrosion Methods and Materials 65, no. 3 (May 8, 2018): 249–62. http://dx.doi.org/10.1108/acmm-06-2017-1808.
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Purpose The purpose of this paper is study of the type of functional group and its situation on phenyl molecule, in increasing the corrosion protection of modified graphene layers by it. Corrosion protection efficiency of graphene was raised via modifying the surface of graphene-coated carbon steel (CS/G) by using aromatic molecules. Phenyl groups with three different substitutions including COOH, NO2 and CH3 grafted to graphene via diazonium salt formation route, by using carboxy phenyl, nitro phenyl and methyl phenyl diazonium salts in ortho, meta and para spatial situations. Design/methodology/approach Molecular bindings were characterized by using X-ray diffractometer, fourier-transform infrared spectroscopy (FTIR), Raman and scanning electron microscopy (SEM)/ energy dispersive X-ray analysis (EDXA) methods. Anti-corrosion performance of modified CS/G electrodes was evaluated by weight loss and electrochemical techniques, potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy, in 3.5 per cent NaCl solution. Findings The obtained results confirmed covalently bonding of phenyl groups to the graphene surface. Also, the observed results showed that substitution spatial situations on phenyl groups can affect charge transfer resistance (Rct), corrosion potential (Ecorr), corrosion current density (jcorr) and the slope of the anodic and cathodic reaction (ßa,c), demonstrating that the proposed modification method can hinder the corrosion reactions. The proposed modification led to restoring the graphene surface defects and consequently increasing its corrosion protection efficiency. Originality/value The obtained results from electrochemical methods proved that protection efficiency was observed in order COOH < NO2 < CH3 and MPD in the para spatial situation and showed the maximum protection efficiency of 98.6 per cent in comparison to other substitutions. Finally, the ability of proposed graphene surface modification route was further proofed by using surface methods, i.e. SEM and EDXA, and contact angles measurements.
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Bhalothia, Dinesh, Sheng-Po Wang, Shuan Lin, Che Yan, Kuan-Wen Wang, and Po-Chun Chen. "Atomic Pt-Clusters Decoration Triggers a High-Rate Performance on Ni@Pd Bimetallic Nanocatalyst for Hydrogen Evolution Reaction in Both Alkaline and Acidic Medium." Applied Sciences 10, no. 15 (July 27, 2020): 5155. http://dx.doi.org/10.3390/app10155155.
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The development of inexpensive and highly robust nanocatalysts (NCs) to boost electrochemical hydrogen evolution reaction (HER) strengthens the implementation of several emerging sustainable-energy technologies. Herein, we proposed a novel nano-architecture consisting of a hierarchical structured Ni@Pd nanocatalyst with Pt-clusters decoration on the surface (denoted by Ni@Pd-Pt) for HER application in acidic (0.5 M H2SO4) and alkaline (0.1 M KOH) mediums. The Ni@Pd-Pt NC is fabricated on a carbon black support via a “self-aligned” heterogeneous nucleation-crystal growth mechanism with 2 wt.% Pt-content. As-prepared Ni@Pd-Pt NC outperforms the standard Pt/C (30 wt.% Pt) catalyst in HER and delivers high-rate catalytic performance with an ultra-low overpotential (11.5 mV) at the cathodic current density of 10 mA∙cm−2 in alkaline medium, which is 161.5 mV and 14.5 mV less compared to Ni@Pd (173 mV) and standard Pt/C (26 mV) catalysts, respectively. Moreover, Ni@Pd-Pt NC achieves an exactly similar Tafel slope (42 mV∙dec−1) to standard Pt/C, which is 114 mV∙dec−1 lesser when compared to Ni@Pd NC. Besides, Ni@Pd-Pt NC exhibits an overpotential value of 37 mV at the current density of 10 mA cm−2 in acidic medium, which is competitive to standard Pt/C catalyst. By utilizing physical characterizations and electrochemical analysis, we demonstrated that such an aggressive HER activity is dominated by the increased selectivity during HER due to the reduced competition between intermediate products on the non-homogeneous NC surface. This phenomenon can be rationalized by electron localization owing to the electronegative difference (χPt > χPd > χNi) and strong lattice mismatch at the Ni@Pd heterogeneous binary interfaces. We believe that the obtained results will significantly provide a facile design strategy to develop next-generation heterogenous NCs for HER and related green-energy applications
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Quej-Ake, L. M., A. Contreras, and Jorge Aburto. "The effect of non-ionic surfactant on the internal corrosion for X52 steel in extra-heavy crude oil-in-water emulsions." Anti-Corrosion Methods and Materials 65, no. 3 (May 8, 2018): 234–48. http://dx.doi.org/10.1108/acmm-03-2017-1770.
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Purpose The purpose of this research is to study different extra-heavy crude oil-in-water emulsions that can be found in practice for corrosion process of X52 steel adding 60 mg.L-1 of non-ionic surfactant and a corrosion inhibitor (CI). Electrochemical impedance spectroscopy and Tafel plots are carried out. Thus, Bode-modulus and Bode-phase angle plots are discussed. Adsorption isotherms obtained from corrosion rate (CR) values are taken into account. Design/methodology/approach Two-electrode arrangement is used to characterize the pseudo-capacitance values for X52 steel exposed to water and crude oil phases, mainly. Electrochemical evaluations for X52 steel exposed to extra-heavy crude oil-in-water emulsions are recorded in a conventional three-electrode cell to study the corrosion process as was documented in detail by Quej-Ake et al. (2015). Therefore, all electrodes are placed as close as possible to eliminate the iR-drop. Findings Pseudo-capacitance analysis shows that X52 steel immersed in oilfield produced water was more susceptible to corrosion than that immersed in ocean water solution and extra-heavy crude oil phase. After being analyzed, the X52 steel surface coverage and adsorption process for surfactant and CI could be concluded that surfactant could protect the metal surface. In a coalescence extra-heavy crude oil-in-water emulsion, the water medium generated a new solution that was more corrosive than the original water phase. Wash crude oil process was provoked in emulsion systems to sweep up the salts, mainly. Thus, corrosive species that can be recovered inside extra-heavy crude oil may appear, and in turn a new more corrosive solution could be obtained. Taking into account the straight line obtained in Bode-modulus plot for X52 exposed to extra-heavy crude oil, it is possible to point out that the negative value of the slope or R2 can be related to a coefficient (Jorcin et al., 2006). It is important to mention that electrochemical responses for X52 steel exposed to extra-heavy crude oil-in-water under coalescence emulsions revealed that corrosion and diffusion processes exist. Therefore, a possible good inhibitor is surfactant in emulsion systems. Originality/value CR and anodic and cathodic slopes suggest that the surfactant acted as mixed CI. Of these, susceptible anodic (MnS and perlite or cementite) and cathodic (ferrite) sites on steel surface could be affected, due to which physicochemical adsorption could happen by using electrochemical parameters analysis. Thus, no stable emulsions should be taken into account for extra-heavy crude oil transportation, because corrosion problems in atmospheric distillation process of the crude oil due to stable emulsion cannot be easily separated. In this manner, coalescent emulsions are more adequate for transporting extra-heavy crude oil because low energy to separate the water media is required.
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Aleksandrov Fabijanić, Tamara, Marin Kurtela, Matija Sakoman, and Mateja Šnajdar Musa. "Influence of Co Content and Chemical Nature of the Co Binder on the Corrosion Resistance of Nanostructured WC-Co Hardmetals in Acidic Solution." Materials 14, no. 14 (July 14, 2021): 3933. http://dx.doi.org/10.3390/ma14143933.
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The electrochemical corrosion resistance of nanostructured hardmetals with grain sizes dWC < 200 nm was researched concerning Co content and the chemical nature of the Co binder. Fully dense nanostructured hardmetals with the addition of grain growth inhibitors GGIs, VC and Cr3C2, and 5 wt.%Co, 10 wt.%Co, and 15 wt.%Co were developed by a one cycle sinter-HIP process. The samples were detailly characterized in terms of microstructural characteristics and researched in the solution of H2SO4 + CO2 by direct and alternative current techniques, including electrochemical impedance spectroscopy. Performed analysis revealed a homogeneous microstructure of equal and uniform grain size for different Co contents. The importance of GGIs content adjustment was established as a key factor of obtaining a homogeneous microstructure with WC grain size retained at the same values as in starting mixtures of different Co binder content. From the conducted research, Co content has shown to be the dominant influential factor governing electrochemical corrosion resistance of nanostructured hardmetals compared to the chemical composition of the Co binder and WC grain size. Negative values of Ecorr measured for 30 min in 96% H2SO4 + CO2 were obtained for all samples indicating material dissolution and instability in acidic solution. Higher values of Rp and lower values of icorr and vcorr were obtained for samples with lower Co content. In contrast, the anodic Tafel slope increases with increasing Co content which could be attributed to more pronounced oxidation of the higher Co content samples. Previously researched samples with the same composition but different chemical composition of the binder were introduced in the analysis. The chemical composition of the Co binder showed an influence; samples with lower relative magnetic saturation related to lower C content added to the starting mixtures and more W dissolved in the Co binder during the sintering process showed better corrosion resistance. WC-5Co sample with significantly lower magnetic saturation value showed approximately 30% lower corrosion rate. WC-10Co sample with slightly lower relative magnetic saturation value and showed approximately 10% lower corrosion rate. Higher content of Cr3C2 dissolved in the binder contributed to a lower corrosion rate. Slight VC increase did not contribute to corrosion resistance. Superior corrosion resistance is attributed to W and C dissolved in the Co binder, lower magnetic saturation, or WC grain size of the sintered sample.
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Silva, L. A. da, V. A. Alves, M. A. P. da Silva, S. Trasatti, and J. F. C. Boodts. "Morphological, chemical, and electrochemical properties of Ti/(TiO2 + IrO2) electrodes." Canadian Journal of Chemistry 75, no. 11 (November 1, 1997): 1483–93. http://dx.doi.org/10.1139/v97-178.
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Electrodes of general composition IrxTi(1−x)O2 with 0.2 ≤ x ≤ 1.0 were prepared on a Ti support by calcination of the chlorides at 450 °C. Ex situ and in situ characterization included the use of techniques such as scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). EDX showed a surface enrichment with Ti. The voltammetric charge was found to go through a maximum at 60% IrO2. O2 evolution was studied in 1.0 mol dm−3 HClO4 by determining Tafel slopes and impedance parameters. Tafel slopes were found to vary between 40 and 60 mV depending on the overpotential range and the oxide composition. Solution and film resistance, film and double layer capacitance, and charge transfer resistance were determined as a function of potential and oxide composition. A reaction mechanism has been proposed. Separation of geometric and electronic effects has been attempted. Keywords: oxygen evolution, oxide electrode, electrocatalysis, electrochemical impedance spectroscopy, iridium dioxide.
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Xu, Lin, Jie Xu, Ming-biao Xu, Si-yang Li, Shuai Liu, Yue Huang, and Fu-chang You. "Corrosion Behavior of 3% Cr Casing Steel in CO2-Containing Environment: A Case Study." Open Petroleum Engineering Journal 11, no. 1 (February 28, 2018): 1–13. http://dx.doi.org/10.2174/1874834101811010001.
Full textAbstract:
Introduction: The production casing of 3% Cr steel has encountered severe internal corrosion in Huizhou Oilfield. To disclose corrosion behavior of inner casing, a series of corrosion exposure tests were systematically conducted on 3% Cr coupons in terms of in-field conditions. Material and Methods: Influence of exposure time, temperature, and water-cut on the CO2 corrosion of 3% Cr steel was investigated, and analyses on weight loss, composition and morphology of corrosion product, and Tafel polarization curves were further carried out. Result: The results showed that the corrosion rate of 3% Cr steel increased with increasing temperature, but such trend descended when the temperature exceeded 65°C due to formation of an compact and adherent corrosion product film on the surface of 3% Cr coupons. While varying exposure time from 7 days to 14 days, the corrosion rate decreased, and the Cr and O enrichment was determined in the corrosion products. The corrosion rate of 3% Cr steel increased with a continuous increment of water-cuts, especially when the water-cut was larger than 40%. Conclusion: The localized corrosion can happen at the lower water-cut due to the presence of amorphous films. The main corrosion products were FeCO3, Cr5O12, Fe2O3, and Fe-Cr. Entry of CO2 to the simulated formation water caused an increase in the anodic Tafel slope, and accelerated dissolution of 3% Cr steel.
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Aliaga, Juan, Pablo Vera, Juan Araya, Luis Ballesteros, Julio Urzúa, Mario Farías, Francisco Paraguay-Delgado, Gabriel Alonso-Núñez, Guillermo González, and Eglantina Benavente. "Electrochemical Hydrogen Evolution over Hydrothermally Synthesized Re-Doped MoS2 Flower-Like Microspheres." Molecules 24, no. 24 (December 17, 2019): 4631. http://dx.doi.org/10.3390/molecules24244631.
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In this research, we report a simple hydrothermal synthesis to prepare rhenium (Re)- doped MoS2 flower-like microspheres and the tuning of their structural, electronic, and electrocatalytic properties by modulating the insertion of Re. The obtained compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Structural, morphological, and chemical analyses confirmed the synthesis of poorly crystalline Re-doped MoS2 flower-like microspheres composed of few stacked layers. They exhibit enhanced hydrogen evolution reaction (HER) performance with low overpotential of 210 mV at current density of 10 mA/cm2, with a small Tafel slope of 78 mV/dec. The enhanced catalytic HER performance can be ascribed to activation of MoS2 basal planes and by reduction in charge transfer resistance during HER upon doping.
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Fahidy, Thomas Z. "Some Applications of Bayes' Rule in Probability Theory to Electrocatalytic Reaction Engineering." International Journal of Electrochemistry 2011 (2011): 1–5. http://dx.doi.org/10.4061/2011/404605.
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Bayesian methods stem from the principle of linking prior probability and conditional probability (likelihood) to posterior probability via Bayes' rule. The posterior probability is an updated (improved) version of the prior probability of an event, through the likelihood of finding empirical evidence if the underlying assumptions (hypothesis) are valid. In the absence of a frequency distribution for the prior probability, Bayesian methods have been found more satisfactory than distribution-based techniques. The paper illustrates the utility of Bayes' rule in the analysis of electrocatalytic reactor performance by means of four numerical examples involving a catalytic oxygen cathode, hydrogen evolution on a synthetic metal, the reliability of a device testing the quality of an electrocatalyst, and the range of Tafel slopes exhibited by an electrocatalyst.
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Kear, Gareth, Hãi-Zhèn Wú, Mark S. Jones, and Frank C. Walsh. "Direct-Current Methods for the Estimation of Corrosion Rates in Aqueous Timber Preservatives." Australian Journal of Chemistry 61, no. 6 (2008): 455. http://dx.doi.org/10.1071/ch07429.
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As part of a program to assess the durability of metals in timber preservatives, direct-current electrochemical analyses have been carried out using mild steel, American Iron and Steel Institute 316 stainless steel and galvanized steel immersed in three liquid timber preservatives containing dissolved copper as a biocide. The aqueous preservatives examined were copper–chrome–arsenate (Cu–Cr–As), copper azole (Cu-Tebucanazole), and alkaline copper quaternary (Cu-didecylthyl ammonium chloride). These preservatives are known commercially as CCA, CuAz, and ACQ-B, respectively. Despite previous assumptions, neither polarization resistance- nor Tafel slope-based analyses are suitable methodologies for the universal derivation of absolute values of corrosion rate. An alternative approach is suggested based on anodic linear sweep voltammetry. The results show that the hot-dipped zinc coating was found to be the most active material in terms of the polarization behaviour, especially within the CCA-based electrolyte. There is a strong qualitative correlation between the electrochemical data and corrosion rates estimated using the American Wood Preservers’ Association E-17 standard test for aqueous treatment solutions.
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HENDI, R., H. SAIFI, K. BELMOKRE, and M. OUADAH. "Impacts of the black clay soil moisture on the corrosion and cathodic protection performance of the API X70 Pipeline." Algerian Journal of Signals and Systems 5, no. 2 (June 15, 2020): 106–11. http://dx.doi.org/10.51485/ajss.v5i2.104.
Full textAbstract:
The impact of the black clay soil moisture of Skikda (East of Algeria), on the corrosion cathodic protection performance of the API X70 pipeline was studied in this paper. To achieve this objective, first, electrochemical analysis has been carried out. Then, in order the show impact of the black clay soil moisture of Skikda on the cathodic protection of the API X70 Pipeline, the corrosion parameters of the API X70 steel pipeline obtained by electrochemical measurements such as Tafel slopes, corrosion current densities, and corrosion potentials were used as boundary conditions in the elaborated cathodic protection model. The obtained results show that the corrosion current I corr is directly proportional to the moisture content up to 50 wt. %, with a potential shift towards the more electronegative values. The cathodic protection perfermance has been well proven in black soil at 100 wt. % moisture contents.
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Drazic, Dragutin, Jovan Popic, B. Jegdic, and D. Vasiljevic-Radovic. "Electrochemistry of active chromium, part IV: Dissolution of chromium in deaerated sulfuric acid." Journal of the Serbian Chemical Society 69, no. 12 (2004): 1099–110. http://dx.doi.org/10.2298/jsc0412099d.
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Chromium dissolution in aqueous sulfuric acid solutions in the pH range 0.5 ?3 was studied electrochemically by the potentiostatic or very slow potentiodynamic method, and by the analyses of the Cr ion concentrations in the electrolyte formed during the experiments. It was shown that the electrochemical anodic dissolution follows a common Tafel line with a slope of ca. 120 mVdec-1, independent of the solution pH and the hydrodynamics while the passivation potentials and passivation currents were independent on hydrodynamics but strongly dependent on the pH. In parallel with the electrochemical dissolution, a considerable "anomalous" or chemical Cr dissolution process occurs, as evidenced by the spectrophotometric analyses of the electrolytes for Cr ions after prolonged potentiostating of the electrodes at different potentials, as well as by measuring the electrode weight losses. All these results indicate the existence of a potential independent reaction of Cr dissolution occurring in parallel to the anodic dissolution process. Mechanisms for both the electrochemical and the chemical process are proposed. The consequences of these phenomena on the behavior of some practical systems where chromium or a chromium alloy (e.g., stainless steels) are used are discussed.
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Diaz, E. F., C. Cuevas-Arteaga, N. Flores-García, S. Mejía Sintillo, and O. Sotelo-Mazón. "Corrosion Performance of AISI-309 Exposed to Molten Salts V2O5-Na2SO4at 700°C Applying EIS andRpElectrochemical Techniques." Journal of Spectroscopy 2015 (2015): 1–12. http://dx.doi.org/10.1155/2015/826759.
Full textAbstract:
The corrosion performance of AISI-309 exposed 5 days to molten salts 50 mol% V2O5-50 mol% Na2SO4at 700°C is reported in this paper. Such evaluation was made using three electrochemical techniques: potentiodynamic polarization curve (PC), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (Rp). FromPC, the Tafel slopes,Icorr, andEcorrwere obtained. From Nyquist and Bode plots, it was possible to determine two different stages; the first one showed just one loop, which indicated the initial formation of Cr2O3layer over the metallic surface; after that, the dissolution of Cr2O3formed a porous layer, which became part of the corrosion products; at the same time a NiO layer combined with sulfur was forming, which was suggested as the second stage, represented by two capacitive loops. EIS plots were in agreement with the physical characterization made from SEM and EDS analyses. Fitting of EIS experimental data allowed us to propose two electrical circuits, being in concordance with the corrosion stages. Parameters obtained from the simulation of EIS data are also reported. From the results, it was stated that AISI-309 suffered intergranular corrosion due to the presence of sulfur, which diffused to the metallic surface through a porous Cr2O3layer.
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TAHERIAN, NILOOFAR, and SOHRAB SANJABI. "ELECTROCATALYTIC ACTIVITY OF Ni–Mn–Sn ALLOY FOAMS FOR OXYGEN EVOLUTION REACTION (OER)." Surface Review and Letters 27, no. 03 (July 23, 2019): 1950122. http://dx.doi.org/10.1142/s0218625x19501221.
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This study carried out to examine electrocatalytic activity of Ni–Mn–Sn alloy foams for oxygen evolution reaction (OER) in alkaline media. As the first step, Ni–Mn–Sn alloy foams were prepared of sulfate bath on copper substrate. Next, after optimization of electrodeposition condition by cyclic voltammetry (CV) test, foams were electrodeposited at different current densities 100, 120, 140 and 180[Formula: see text]mA[Formula: see text]⋅[Formula: see text]cm[Formula: see text]. Then, they were characterized by field emission scanning electron microscopy (FE-SEM) along with energy disperse x-ray spectroscopy (EDS) to investigate surface morphologies and chemical compositions. According to FE-SEM results, it was revealed that formation of foam like structures were due to the presence of dynamic hydrogen bubbles template (DHBT). To survey their structure, grazing incidence X-ray diffractometer (GIXRD) analysis was performed. The resulted diffraction pattern determined not only FCC nickel structure of foams, but also mixed phases composed. Following this, Ni–Mn–Sn alloy foams were placed in 0.1 M KOH and related CV tests were applied to measure their electrocatalytic activity for OER. This study demonstrated good electrocatalytic activity for Ni–Mn–Sn alloy foams by showing favorable oxygen evolution overpotenitals and Tafel slopes.
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Abdel Hamid, Zeinab, H. B. Hassan, and Mohamed Sultan. "Electrodeposition of Ni-W and Ni-W-P films using a pulse current technique and their application for hydrogen evolution in an acidic solution." Anti-Corrosion Methods and Materials 67, no. 1 (January 6, 2020): 38–47. http://dx.doi.org/10.1108/acmm-09-2019-2176.
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Purpose The improvement of the hydrogen evolution reaction (HER) performance requires more efficient and inexpensive electrocatalysts. The purpose of this study is to prepare Ni-W and Ni-W-P thin films using the electrodeposition technique using a pulse current and investigate their behaviors toward HER in an acidic solution. Design/methodology/approach The aim is to prepare Ni-W and Ni-W-P films by the electrodeposition technique using a pulse current and estimate their performance for the HER. The surface morphologies and chemical compositions of the deposited films were assessed using scanning electron microscopy, energy-dispersive X-ray analysis and X-ray diffraction. Linear sweep voltammetry, chronoamperometry, Tafel plots and electrochemical impedance spectroscopy were used to evaluate the prepared electrodes toward the hydrogen evolution process. Findings The main conclusion is that the surface morphology of Ni–W deposited film is a crystalline structure, while that of Ni-W-P deposit is an amorphous structure. HER activity on Ni-W electrodes increases with decreasing the Wt.% of W to 7.83 Wt.% in the prepared electrodes. In addition, the presence of P enhances HER activity, which increases with increasing the Wt.% of P in the prepared Ni-W-P electrodes. Both Ni-W (7.83 Wt.% W) and Ni-W-P (20.34 Wt.% P), which have been prepared at 8 A dm−2 display the best performance toward HER compared to the other prepared electrodes. They exhibit high catalytic activities toward HER, which is evidenced by high hydrogen evolution current density values of 9.52 and 33.98 mA cm−2, low onset potentials of −0.73 and −0.63 V, low Tafel slopes of −125 mV/dec, high exchange current densities of 0.058 and 0.20 mA cm−2, low charge transfer resistances (Rct) of 226.28 and 75.8 ohm·cm2 for Ni-W (7.83 Wt.% W) and Ni-W-P (20.34 Wt.% P), respectively; moreover, they exhibited considerable stabilities too. Originality/value The results presented in this work are an insight into understanding the performance of the prepared Cu electrodes coated by Ni-W and Ni-W-P films toward HER. In this work, a consistent assessment of the results achieved on laboratory scale has been conducted.
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Caballero-Manrique, Griselda, Julia Garcia-Cardona, Enric Brillas, Juan A. Jaén, John Manuel Sánchez, and Pere L. Cabot. "Synthesis and Evaluation of PtNi Electrocatalysts for CO and Methanol Oxidation in Low Temperature Fuel Cells." Catalysts 10, no. 5 (May 19, 2020): 563. http://dx.doi.org/10.3390/catal10050563.
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Pt(Ni)/C and PtRu(Ni)/C catalysts were synthesized by electroless deposition of Ni on a carbon dispersion followed by sequenced Pt deposition and spontaneous deposition of Ru species. The structural analyses of the catalysts with 88:12 and 98:2 Pt:Ni atomic ratios pointed out to the formation of small hexagonal Ni crystallites covered by thin cubic Pt surface structures with no evidence about PtNi alloy formation. The onset potentials for CO oxidation on Pt(Ni)/C and PtRu(Ni)/C were about 0.10 and 0.24 V more negative than those of Pt/C, thus indicating their better CO tolerance. The surface Ru species appeared to have the major effect by facilitating the CO removal by the bifunctional mechanism. The onset potential for the methanol oxidation reaction (MOR) of Pt(Ni)/C was about 0.15 V lower than that of Pt/C. The mass and specific activities together with the exchange current densities of the Pt(Ni)/C catalysts were also higher than those of Pt/C, making in evidence their higher activity in front of the MOR. The Tafel slopes for the MOR on Pt(Ni)/C suggested different reaction mechanism than on Pt/C. The electronic (ligand) effect of Ni on Pt was considered the main reason to explain the higher activity of Pt(Ni)/C in front of the CO oxidation and the MOR.
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Obradovic, Maja, Biljana Babic, Nedeljko Krstajic, and Snezana Gojkovic. "Effect of tungsten carbide in carbon Pt catalyst support on electrochemical oxygen reduction in acid solution." Chemical Industry 67, no. 2 (2013): 303–11. http://dx.doi.org/10.2298/hemind120307063o.
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Tungsten carbide was synthesized by calcination of carbon cryogel with embedded tungsten in a form of metatungstate. This material was used as a support for Pt nanoparticles. XRD pattern of W-C support indicates the presence of WC, W2C, and unreacted W, as well as graphitized carbon. According to the previous TEM analysis of W-C support, it contains particles with core-shell structure, where W particle was covered with the shell of a mixture of WC and W2C. The average Pt grain size calculated from XRD pattern was about 6 nm. Cyclic voltammogram of W-C support was recorded within potential range relevant for its application as a catalyst support in fuel cells. Pair of anodic/cathodic peaks close to the negative potential limit could be ascribed to the intercalation of hydrogen within hydrous tungsten oxide, which is always present on the surface of WC in aqueous solutions. Cyclic voltammogram of Pt/W-C indicated that tungsten oxide species are present on tungsten carbide shell as well as on the surface of Pt nanoparticles. Pt surface is only partially covered by hydrous tungsten oxide. Hydrogen intercalation in hydrous tungsten oxide is enhanced in the presence of Pt nanoparticles. Also, the presence of hydrated tungsten oxide leads to the decrease of OH chemisorbed on Pt surface. Stripping of underpotentially deposited copper was used for the assessment of Pt surface area and the specific surface area of Pt was estimated to 41 m2 g-1. Electrochemical oxygen reduction reaction was examined on the synthesized Pt/W-C catalyst and compared with the results on the commercial Pt/C catalyst. It was found that the current densities at Pt/W-C are almost double as those on Pt/C. The Tafel plots for both catalysts are characterized with two Tafel slopes: -0.060 V dec-1 at low current densities, and -0.120 V dec-1 at high current densities. From the rotational dependence of the reaction rate, it was found that oxygen reduction on both Pt/W-C and Pt/C follows the first order kinetics with respect to O2 and that four electrons are transferred per O2 molecule. The results show that the presence of tungsten carbide in support material i.e. hydrous tungsten oxide on Pt surface, leads to promotion of oxygen reduction on the Pt/W-C catalyst. It was assumed that oxophilic hydrated tungsten oxide hinders OH adsorption on Pt surface, thus increasing Pt surface area available for O2 adsorption and its electrochemical reduction.
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Lucatero, Luis Manuel Becerra, David Turcio Ortega, Thangarasu Pandiyan, Narinder Singh, Harpreet Singh, and Tejinder Pal Singh Sarao. "Corrosion inhibition studies of cigarette waste on the iron surface in acid medium: electrochemical and surface morphology analysis." Anti-Corrosion Methods and Materials 63, no. 4 (June 6, 2016): 245–55. http://dx.doi.org/10.1108/acmm-05-2014-1384.
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Purpose The purpose of this paper is to study the corrosion inhibition tendency of cigarette waste (water extracts of cigarette butts, WECB) on an iron surface in an acid medium. Design/methodology/approach The electrochemical impedance spectroscopy and polarization techniques were used to analyze the performance of WECB on the iron working electrode. Electrochemical polarization curves were used to determine the intensity of the metal corrosion, specifically to see the effectiveness of the anodic and cathodic reactions in the corrosive medium having WECB. Moreover, the electrochemical impedance of WECB with electrode was analyzed qualitatively. The electrochemical data that relate isotherm adsorption of WECB with iron were analyzed; furthermore, the scanning electron microscope was used to analyze morphology change during the corrosion inhibition. Findings After analyzing the impedance data, it is seen that there exists a single capacitive semicircle at the higher frequency range corresponding to a one-time constant in the Bode-phase plot. In the polarization curves studies (Tafel slopes), the current densities of both cathodic and anodic branches are greatly affected in the presence of WECB in the corrosive medium, suggesting that WECB performs as a mixed inhibitor. The free energy data and Temkin adsorption isotherm process show that the adsorption process of WECB on the metal surface follows a physisorption. Furthermore, the WECB-coated metal surface analyzed by scanning electron microscopy confirms the corrosion inhibition of WECB in the acid medium. Research limitations/implications An in-depth characterization of the corroded scales is recommended to endorse the results of this study. Social implications There may be some people who may challenge that the research may encourage smoking; however, if taken positively, the research offers a very cost-effective and eco-friendly solution to tackle the cigarette waste. Originality/value Idea of the present work is to reuse the WECB as corrosion inhibitors for the metal surface, as this waste contains large amount of nicotine, which exhibits corrosion inhibition properties. The present work deals with the study of corrosion inhibition properties of WECB on the iron surface in acid medium. The findings of this study can be very useful from scientific, as well as industrial application point of view. Moreover, the research is important as there is no proper recycling process for this waste so as to maintain a clean environment.
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Prabowo, Danar, Max Rudolf Muskananfola, and Frida Purwanti. "ANALISIS KERENTANAN PANTAI MARON DAN PANTAI TIRANG KECAMATAN TUGU, KOTA SEMARANG (Analysis of Coastal Vulnerability on the Maron Beach and Tirang Beach at Tugu Subdistrict, Semarang City)." Management of Aquatic Resources Journal (MAQUARES) 6, no. 4 (July 25, 2018): 555–63. http://dx.doi.org/10.14710/marj.v6i4.21348.
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Pantai Maron dan Pantai Tirang merupakan daerah wisata di wilayah pesisir Semarang. Nilai kerentanan pantai tersebut perlu diketahui agar pemanfaatannya tidak terganggu. Pantai Maron dan Pantai Tirang Kecamatan Tugu, Kota Semarang, dianalisis menggunakan metode CVI (Coastal Vulnerability Index), dilakukan pada bulan Mei sampai dengan Juni 2017. Tujuan penelitian ini adalah mengidentifikasi kondisi kerentanan Pantai Maron dan Pantai Tirang, dan mengetahui nilai indeks kerentanan ekosistem Pantai Maron dan Pantai Tirang, Kecamatan Tugu, Kota Semarang. Metode CVI (Coastal Vulnerabilty Index), dilakukan dengan cara menilai kerentanan pantai pada variabel kemiringan pantai, jarak tumbuhan dari pantai, pasang surut rata-rata, tinggi gelombang rata-rata, dan erosi/akresi pantai berdasarkan tabel indeks kerentanan pantai pada lima sel pantai. Hasil penelitian menunjukkan bahwa nilai CVI Pantai Maron antara 6,45 – 9,13 termasuk dalam kategori kerentanan pantai yang rendah (>20,5), sedangkan nilai CVI Pantai Tirang yaitu 10,21 dan 22,82 termasuk dalam kategori kerentanan rendah dan menengah (20,5 – 25,5). Kesimpulan yang dapat disampaikan adalah nilai kerentanan Pantai Maron dan Pantai Tirang, Kecamatan Tugu, Kota Semarang berdasarkan variabel fisik termasuk dalam kategori rendah dan menengah. Maron and Tirang beaches are tourism area in the coastal area of Semarang. The value of vulnerability of the coast should be known so its utilization will not be disturbed. The Maron Beach and Tirang Beach used Coastal Vulnerability Index method. The research was carried out from Mei to June, 2017. The aims of this study are to identify vurnerability conditions of Maron Beach and Tirang Beach, and to know vulnerability index value of Maron Beach and Tirang Beach, Tugu Subdistrict, Semarang City. CVI method used by scoring coastal vulnerability on variables of coastline slope, plants distance from the coast, average tidal range, average wave height, and coastline changes (accresion/erosion) based on table of coastal vulnerability index at five coastal cells. The research show that the CVI value of the Maron Beach 6,45 into 9,13 that include in the low coastal vulnerability category (<20,5), while CVI value of the Tirang Beach 10,21 and 22,82 that include in the low and middle coastal vulnerability category (20,5-25,5). Conclusion of this research is coastal vulnerability index of Maron Beach and Tirang Beach, Tugu Subdistrict, Semarang City based on physical variables belong to low and middle vulnerability. GMT Detect languageAfrikaansAlbanianAmharicArabicArmenianAzerbaijaniBasqueBelarusianBengaliBosnianBulgarianCatalanCebuanoChichewaChinese (Simplified)Chinese (Traditional)CorsicanCroatianCzechDanishDutchEnglishEsperantoEstonianFilipinoFinnishFrenchFrisianGalicianGeorgianGermanGreekGujaratiHaitian CreoleHausaHawaiianHebrewHindiHmongHungarianIcelandicIgboIndonesianIrishItalianJapaneseJavaneseKannadaKazakhKhmerKoreanKurdishKyrgyzLaoLatinLatvianLithuanianLuxembourgishMacedonianMalagasyMalayMalayalamMalteseMaoriMarathiMongolianMyanmar (Burmese)NepaliNorwegianPashtoPersianPolishPortuguesePunjabiRomanianRussianSamoanScots GaelicSerbianSesothoShonaSindhiSinhalaSlovakSlovenianSomaliSpanishSundaneseSwahiliSwedishTajikTamilTeluguThaiTurkishUkrainianUrduUzbekVietnameseWelshXhosaYiddishYorubaZulu AfrikaansAlbanianAmharicArabicArmenianAzerbaijaniBasqueBelarusianBengaliBosnianBulgarianCatalanCebuanoChichewaChinese (Simplified)Chinese (Traditional)CorsicanCroatianCzechDanishDutchEnglishEsperantoEstonianFilipinoFinnishFrenchFrisianGalicianGeorgianGermanGreekGujaratiHaitian CreoleHausaHawaiianHebrewHindiHmongHungarianIcelandicIgboIndonesianIrishItalianJapaneseJavaneseKannadaKazakhKhmerKoreanKurdishKyrgyzLaoLatinLatvianLithuanianLuxembourgishMacedonianMalagasyMalayMalayalamMalteseMaoriMarathiMongolianMyanmar (Burmese)NepaliNorwegianPashtoPersianPolishPortuguesePunjabiRomanianRussianSamoanScots GaelicSerbianSesothoShonaSindhiSinhalaSlovakSlovenianSomaliSpanishSundaneseSwahiliSwedishTajikTamilTeluguThaiTurkishUkrainianUrduUzbekVietnameseWelshXhosaYiddishYorubaZulu Text-to-speech function is limited to 200 characters Options : History : Feedback : DonateClose
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Limaye, Aditya M., Joy S. Zeng, Adam P. Willard, and Karthish Manthiram. "Bayesian data analysis reveals no preference for cardinal Tafel slopes in CO2 reduction electrocatalysis." Nature Communications 12, no. 1 (January 29, 2021). http://dx.doi.org/10.1038/s41467-021-20924-y.
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AbstractThe Tafel slope is a key parameter often quoted to characterize the efficacy of an electrochemical catalyst. In this paper, we develop a Bayesian data analysis approach to estimate the Tafel slope from experimentally-measured current-voltage data. Our approach obviates the human intervention required by current literature practice for Tafel estimation, and provides robust, distributional uncertainty estimates. Using synthetic data, we illustrate how data insufficiency can unknowingly influence current fitting approaches, and how our approach allays these concerns. We apply our approach to conduct a comprehensive re-analysis of data from the CO2 reduction literature. This analysis reveals no systematic preference for Tafel slopes to cluster around certain "cardinal values” (e.g. 60 or 120 mV/decade). We hypothesize several plausible physical explanations for this observation, and discuss the implications of our finding for mechanistic analysis in electrochemical kinetic investigations.
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"Tafel Slope Component Analysis of Fuel Cell Cathode Current-Potential Behavior." ECS Meeting Abstracts, 2011. http://dx.doi.org/10.1149/ma2011-01/41/1915.
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Rufino, Élen, Mario Santana, Luiz Faria, and Leonardo Silva. "Influence of lead dioxide electrodes morphology on kinetics and current efficiency of oxygen-ozone evolution reactions." Chemical Papers 64, no. 6 (January 1, 2010). http://dx.doi.org/10.2478/s11696-010-0062-2.
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AbstractInfluence of electrode morphology on electrochemical properties of lead dioxide electrodes (β-PbO2) for oxygen-ozone evolution reactions in acid medium was investigated using scanning electronic microscopy (SEM), cyclic voltammetry (CV), polarization curves (PC), and determination of the current efficiency (Φ). Experimental findings revealed that application of high electrodeposition current densities furnishes more rough β-PbO2 films. Surface characteristics were verified by SEM images and the analysis of interfacial pseudo-capacitances and morphology factor (φ). Kinetic study of the overall electrode process (O2 + O3) based on the analysis of the Tafel slope revealed that the electrode morphology and electrolyte composition considerably affect the electrode kinetics. In most cases, the existence of two Tafel slopes distributed in the low and high overpotential domains was observed. Abnormal Tafel slopes (b ≠ 120 mV) obtained for the primary water discharge step during water electrolysis were interpreted considering the apparent charge transfer coefficient (α apa). Optimum conditions for the ozone production were obtained for the less rough β-PbO2 electrode immersed in a sulfuric acid solution (1.0 mol dm−3) containing KPF6 (30 × 10−3 mol dm−3), where the current efficiency of 15 mass % for the ozone production was obtained.