Dissertations / Theses: 'Direct Propane Fuel Cell'

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Psofogiannakis, George. "A mathematical model for a direct propane phosphoric acid fuel cell." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26424.

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In direct hydrocarbon fuel cells, a hydrocarbon fuel is oxidised in the anode electrode. This thesis presents a mathematical model to predict the performance of a unit cell that utilises propane as the fuel, oxygen as the oxidant, phosphoric acid as the electrolyte, and platinum as the catalyst, supported on porous carbon electrodes. The phenomena considered include the electrochemical reactions of propane oxidation and oxygen reduction on platinum, the diffusion of the gases in gas-filled electrode pores, the dissolution and diffusion of dissolved gases in liquid-filled electrode pores as well as ionic conduction of protons. The model was based on the multi-layered physical structure of a modern unit fuel cell. The model was first applied to a phosphoric acid fuel cell cathode electrode. Subsequently, the model was applied to a direct propane-oxygen cell. (Abstract shortened by UMI.)

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Parackal, Bhavana. "An Investigation of Low Temperature Direct Propane Fuel Cells." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35896.

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This research is directed toward the investigation of a low temperature direct propane fuel cell (DPFC). Modeling included a parametric study of a direct propane fuel cell using computational fluid dynamics (CFD), specifically FreeFem++ software. Polarization curves predicted by the CFD model were used to understand fuel cell performance. The predictions obtained from the computational fluid dynamics mathematical model for the fuel cell were compared with experimental results. The computational work identified some critical parameters (exchange current density, pressure, temperature) for improving the overall performance of the fuel cell. The model predictions clearly highlighted the role of catalysts in significantly enhancing the overall performance of a DPFC. Experiments were performed using commercial Nafion-Pt based membrane electrode assemblies (MEAs) to obtain a basis for comparison. It is the first report in the literature that a Pt-Ru (Platinum-Ruthenium) MEA was used in the investigation of a DPFC. Also, it was the first study that fed liquid water continuously to a DPFC by using interdigitated flow field (IDFF) at the anode to humidify the dry propane feed gas. During the experiments oscillations were observed at very low current densities i.e. in nA/cm2, which is a rare case and not reported in the literature to date. This observation has raised serious concerns about the existence of absolute open-circuit cell potential difference for a DPFC. The cycling behaviour observed with DPFC indicated the presence of a continuous degradation-regeneration process of the catalyst surface near open-circuit potential. The experimental work further evaluated the performance of fuel cell by measurement of polarization curves.

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Khakdaman, Hamidreza. "A Two Dimensional Model of a Direct Propane Fuel Cell with an Interdigitated Flow Field." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22732.

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Increasing environmental concerns as well as diminishing fossil fuel reserves call for a new generation of energy conversion technologies. Fuel cells, which convert the chemical energy of a fuel directly to electrical energy, have been identified as one of the leading alternative energy conversion technologies. Fuel cells are more efficient than conventional heat engines with minimal pollutant emissions and superior scalability. Proton Exchange Membrane Fuel Cells (PEMFCs) which produce electricity from hydrogen have been widely investigated for transportation and stationary applications. The focus of this study is on the Direct Propane Fuel Cell (DPFC), which belongs to the PEMFC family, but consumes propane instead of hydrogen as feedstock. A drawback associated with DPFCs is that the propane reaction rate is much slower than that of hydrogen. Two ideas were suggested to overcome this issue: (i) operating at high temperatures (150-230oC), and (ii) keeping the propane partial pressure at the maximum possible value. An electrolyte material composed of zirconium phosphate (ZrP) and polytetrafluoroethylene (PTFE) was suggested because it is an acceptable proton conductor at high temperatures. In order to keep the propane partial pressure at the maximum value, interdigitated flow-fields were chosen to distribute propane through the anode catalyst layer. In order to evaluate the performance of a DPFC which operates at high temperature and uses interdigitated flow-fields, a computational approach was chosen. Computational Fluid Dynamics (CFD) was used to create two 2-D mathematical models for DPFCs based on differential conservation equations. Two different approaches were investigated to model species transport in the electrolyte phase of the anode and cathode catalyst layers and the membrane layer. In the first approach, the migration phenomenon was assumed to be the only mechanism of proton transport. However, both migration and diffusion phenomena were considered as mechanisms of species transport in the second approach. Therefore, Ohm's law was used in the first approach and concentrated solution theory (Generalized Stefan-Maxwell equations) was used for the second one. Both models are isothermal. The models were solved numerically by implementing the partial differential equations and the boundary conditions in FreeFEM++ software which is based on Finite Element Methods. Programming in the C++ language was performed and the existing library of C++ classes and tools in FreeFEM++ were used. The final model contained 60 pages of original code, written specifically for this thesis. The models were used to predict the performance of a DPFC with different operating conditions and equipment design parameters. The results showed that using a specific combination of interdigitated flow-fields, ZrP-PTFE electrolyte having a proton conductivity of 0.05 S/cm, and operating at 230oC and 1 atm produced a performance (polarization curve) that was (a) far superior to anything in the DPFC published literature, and (b) competitive with the performance of direct methanol fuel cells. In addition, it was equivalent to that of hydrogen fuel cells at low current densities (30 mA/cm2).

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Vafaeyan, Shadi. "A Density Functional Theory of a Nickel-based Anode Catalyst for Application in a Direct Propane Fuel Cell." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23316.

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The maximum theoretical energy efficiency of fuel cells is much larger than those of the steam-power-turbine cycles that are currently used for generating electrical power. Similarly, direct hydrocarbon fuel cells, DHFCs, can theoretically be much more efficient than hydrogen fuel cells. Unfortunately the current densities (overall reaction rates) of DHFCs are substantially smaller than those of hydrogen fuel cells. The problem is that the exchange current density (catalytic reaction rate) is orders of magnitude smaller for DHFCs. Other work at the University of Ottawa has been directed toward the development of polymer electrolytes for DHFCs that operate above the boiling point of water, making corrosion rates much slower so that precious metal catalysts are not required. Propane (liquefied petroleum gas, LPG) was the hydrocarbon chosen for this research partly because infrastructure for its transportation and storage in rural areas already exists. In this work nickel based catalysts, an inexpensive replacement for the platinum based catalysts used in conventional fuel cells, were examined using density functional theory, DFT. The heats of propane adsorption for 3d metals, when plotted as a function of the number of 3d electrons in the metal atom, had the shape of a volcano plot, with the value for nickel being the peak value of the volcano plot. Also the C-H bond of the central carbon atom was longer for propane adsorbed on nickel than when adsorbed on any of the other metals, suggesting that the species adsorbed on nickel was less likely to desorb than those on other metals. The selectivity of the propyl radical reaction was examined. It was found that propyl radicals

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5

Hamer, P. "Electrocatalysis towards direct fuel cell applications." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676493.

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The aim of this thesis is an in depth study of electro-oxidation of ethanol, but also that of alternate fuels to allow a direct comparison under a range of conditions. Polycrystalline metal electrodes are used in a half cell set up as model environment for the electrochemical studies of several catalytic surfaces. Due to the limited research that has been carried out, for the first time chapters 3 and 4 of the thesis provide electrochemical studies into the electro oxidation of ethanol, ethylene glycol, acetaldehyde and acetic acid on polycrystalline rhodium while simultaneously studying temperature, concentration and electrolyte. Chapter 5 investigates the effect of changing platinum coverage on the surface of polycrystalline rhodium on of ethanol electro-oxidation while also changing temperature and concentration. To the best of my knowledge this is an experiment never before carried out and clearly shows the effect of the varying platinum coverage under a range of conditions. Chapters 6&7 investigate electro-oxidation of C2 molecules on polycrystalline platinum again with varying concentration, temperature and electrolyte. Although Chapter 1 shows similar experiments have been carried out before, using the same electrode for all experiments as well as investigating the effect of varying tin coverage on the platinum surface allows for direct comparisons, as well as providing results to compare with the results of the rhodium experiments. Overall, this thesis provides a systematic and comprehensive study into the electrochemical oxidation of ethanol and other C2 molecules using cyclic voltammetry and chrono amperometry techniques to provide activity and stability information to a degree not reported anywhere else.

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Troughton, Gavin L. "Anodes for the direct methanol fuel cell." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335195.

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Joseph, Krishna Sathyamurthy. "Hybrid direct methanol fuel cells." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44777.

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A new type of fuel cell that combines the advantages of a proton exchange membrane fuel cells and anion exchange membrane fuel cells operated with methanol is demonstrated. Two configurations: one with a high pH anode and low pH cathode (anode hybrid fuel cell (AHFC)),and another with a high pH cathode and a low pH anode (cathode hybrid fuel cell (CHFC)) have been studied in this work. The principle of operation of the hybrid fuel cells were explained. The two different hybrid cell configurations were used in order to study the effect of the electrode fabrication on fuel cell performance. Further, the ionomer content and properties such as the ion exchange capacity and molecular weight were optimized for the best performance. A comparison of the different ionomers with similar properties is carried out in order to obtain the best possible ionomer for the fuel cell. An initial voltage drop was observed at low current density in the AHFC, this was attributed to the alkaline anode and the effect of the ionomers with the new cationic groups were studied on this voltage drop was studied. These ionomers with the different cationic groups were studied in the CHFC design as well. Finally, the use of non platinum catalyst cathode with the CHFC design was also demonstrated for the first time.

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Lam, Vincent Wai Sang. "Development of the direct borohydride fuel cell anode." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42489.

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Direct borohydride fuel cells (DBFC) are a promising technology for meeting increasing energy demands of portable electronic applications. The objective of this dissertation was to contribute to the understanding of borohydride (BH₄⁻) electro-oxidation and the development of the DBFC anode; a component which can influence both the performance and cost of a DBFC system. The first part of the investigation involves the elucidation of the BH₄⁻ electro-oxidation mechanism on Pt. The BH₄⁻ electro-oxidation mechanism was studied by correlating the results obtained by the electrochemical quartz crystal microbalance technique (EQCM) and the rotating disk electrode technique (RDE) with density functional theory (DFT) calculations from the literature. It was found that BH₄⁻ electro-oxidation on Pt resulted in the adsorption of reaction intermediates, such as BH₂OHad and BOHad, which required high oxidizing potentials to desorb/ oxidize from the catalyst surface. It was also found that the BH₄⁻ oxidation mechanisms (Langmuir – Hinshelwood versus Eley - Rideal) were dictated by the availability of Pt-sites and the competitive adsorption of OH⁻ and BH₄⁻. The second part involves an investigation of the performance of three different carbon black supported anode catalysts: Pt, PtRu, and Os, with a focus on Os catalysts. Fundamental electrochemical methods combined with fuel cell experiments revealed that osmium nanoparticles are kinetically superior and stable catalysts for BH₄⁻ electro-oxidation compared to Pt and PtRu. It was also found that supported Os electrocatalysts appear to favour the direct oxidation of BH₄⁻ in comparison to Pt, and PtRu electrocatalysts. The final section of this dissertation focuses on the effect of electrocatalyst support and anode design on the performance of the DBFC anode. It was found that the Vulcan® XC-72 supported catalyst alleviated mass transfer related problems associated with hydrogen generation from BH₄⁻ hydrolysis. The most significant improvement was obtained when using the graphite substrate supported catalysts (three-dimensional anodes). Fuel cell studies revealed power densities of 103 mW cm⁻² to 130 mW cm⁻² achieved by 1.7 mg cm⁻² Os and ~1 mg cm⁻² PtRu three-dimensional electrodes respectively at 333 K, using an O₂ oxidant at 4.4 atm (abs), and a 0.5 M NaBH₄ – 2 M NaOH anolyte composition.

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Nordlund, Joakim. "The Anode in the Direct Methanol Fuel Cell." Doctoral thesis, KTH, Chemical Engineering and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3676.

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The direct methanol fuel cell (DMFC) is a very promisingpower source for low power applications. High power and energydensity, low emissions, operation at or near ambientconditions, fast and convenient refuelling and a potentiallyrenewable fuel source are some of the features that makes thefuel cell very promising. However, there are a few problemsthat have to be overcome if we are to see DMFCs in our everydaylife. One of the drawbacks is the low performance of the DMFCanode. In order to make a better anode, knowledge about whatlimits the performance is of vital importance. With theknowledge about the limitations of the anode, the flow field,gas diffusion layer and the morphology of the electrode can bemodified for optimum performance.

The aim of this thesis is to elucidate the limiting factorsof the DMFC anode. A secondary goal is to create a model of theperformance, which also has a low computational cost so that itcan be used as a sub model in more complex system models. Toreach the primary goal, to elucidate the limiting factors, amodel has to be set up that describes the most importantphysical principles occurring in the anode.

In addition, experiments have to be performed to validatethe model. To reach the secondary goal, the model has to bereduced to a minimum. A visual DMFC has been developed alongwith a methodology to extract two-phase data. This has provento be a very important part of the understanding of thelimiting factors. Models have been developed from a detailedmodel of the active layer to a two-phase model including theentire three-dimensional anode.

The results in the thesis show that the microstructure inthe active layer does not limit the performance. Thelimitations are rather caused by the slow oxidation kineticsand, at concentrations lower than 2 M of methanol, the masstransport resistance to and inside the active layer. Theresults also show that the mass transfer of methanol to theactive layer is improved if gas phase is present, especiallyfor higher temperatures since the gas phase then contains moremethanol.

It is concluded that the mass transport resistance lower theperformance of a porous DMFC anode at the methanolconcentrations used today. It is also concluded that masstransfer may be improved by making sure that there is gas phasepresent, which can be done by choosing flow distributor and gasdiffusion layer well.

Keywords: direct methanol fuel cell, fuel cell, DMFC, anode,model

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10

Hogarth, Martin P. "The development of the direct methanol fuel cell." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295055.

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Allen, Ruth Gleave. "New anodes for the direct methanol fuel cell." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413008.

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Dickinson, Angus John. "Development of a direct methanol fuel cell system." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324802.

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13

Lee, Jeong Kyu. "Direct Methanol Fuel Cell Membranes from Polymer Blends." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1134316195.

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Buche, Silvain. "Polymer electrolyte fuel cell diagnostics." Thesis, University of Bath, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285318.

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15

Hacquard, Alexandre. "Improving and Understanding Direct Methanol Fuel Cell (DMFC) Performance." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-050505-151501/.

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16

Sprague, Isaac Benjamin. "Characterization of a microfluidic based direct-methanol fuel cell." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Summer2008/I_Sprague_072208.pdf.

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17

Haraldsson, Kristina. "On direct hydrogen fuel cell vehicles : modelling and demonstration." Doctoral thesis, Stockholm : Department of Chemical Engineering and Technology, Royal Institute of Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147.

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Li, Xiao. "Development of composite membranes for direct methanol fuel cell." Thesis, University of Manchester, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556263.

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Özdinçer, Baki. "Novel support materials for direct methanol fuel cell catalysts." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/novel-support-materials-for-direct-methanol-fuel-cell-catalysts(f7dfe29a-a593-44a6-a9e3-e9e8f5b8b2a2).html.

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This thesis focuses on developing support materials for direct methanol fuel cell (DMFC) catalysts. The approach involves using graphene based materials including reduced graphene oxide (rGO), reduced graphene oxide-activated carbon (rGO-AC) hybrid and reduced graphene oxide-silicon carbide (rGO-SiC) hybrid as a support for Pt and Pt-Ru nanoparticles. Pt/rGO and Pt-Ru/rGO catalysts were synthesized by three chemical reduction methods: (1) modified polyol, (2) ethylene glycol (EG) reduction and (3) mixed reducing agents (EG + NaBH4) methods. The synthesized catalysts were characterized by physical and electrochemical techniques. The results demonstrated that Pt/rGO-3 and Pt-Ru/rGO-3 catalyst synthesized with Method-3 exhibit higher electrochemical active surface area (ECSA) than the other rGO supported and Vulcan supported commercial electrocatalysts. In addition, Pt/rGO-3 and Pt-Ru/rGO-3 catalysts showed better oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) activities, respectively. The DMFC tests under different cell temperature (30, 50 and 70Â°C) and methanol concentration (1, 2 and 4 M) conditions further demonstrated the higher catalytic activity of the catalysts. The peak power density obtained with Pt/rGO-3 cathode and Pt-Ru/rGO-3 anode catalysts at 70Â°C with 1 M methanol was 63.3 mW/cm2 which is about 59 % higher than that of commercial Pt/C and Pt-Ru/C catalysts. The enhanced performance was attributed to the highly accessible and uniformly dispersed nanoparticles on rGO support with large surface area and high conductivity. Pt/rGO-AC (reduced graphene oxide-activated carbon) and Pt-Ru/rGO-AC catalysts were synthesized with various rGO:AC support ratios by using biomass derived AC. The results showed that the catalysts with content of 20 wt. % AC support (Pt/rGO-AC20 and Pt-Ru/rGO-AC20) exhibited higher ECSA, better catalytic activity and stability among all the tested catalysts. With 1 M methanol and 70Â°C cell temperature, the MEA with Pt/rGO-AC20 cathode and Pt-Ru/rGO-AC anode catalysts gave 19.3 % higher peak power density (75.5 mW/cm2), than that of Pt/rGO-3 and Pt-Ru/rGO-3 catalysts. The better DMFC performance was due to the incorporation of AC particles into rGO structure which builds electron-conductive paths between rGO sheets, facilitates the transport of reactant and products and provides higher specific surface area for the uniform distribution of nanoparticles. Pt/rGO-SiC catalysts were synthesized with variable silicon carbide (SiC) content in the hybrid support. Pt/rGO-SiC10 (10 wt. % of SiC support) catalyst showed higher ECSA and better catalytic activity compared to the Pt/SiC, Pt/rGO-3 and Pt/rGO-SiC20 catalysts. In addition, the Pt/rGO-SiC10 gave 14.2 % higher DMFC performance than the Pt/rGO-3 catalyst in terms of power density. The high performance can be attributed to the insertion of the SiC nanoparticles into rGO structure that improves the conductivity and stability of the catalyst by playing a spacer role between rGO layers. In summary, the overall results showed that the catalytic performance of the catalysts followed the trend in terms of support material: rGO-AC20 > rGO-SiC10 > rGO > Vulcan. The study demonstrated that the novel rGO-AC and rGO-SiC hybrids are promising catalyst supports for direct methanol fuel cell applications.

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Lam, Alfred. "Novel direct liquid fuel cell - membraneless architecture and simple power and fuel crossover control." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/12574.

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The convergence of multiple functions in portable electronics is resulting in greater power requirements and a reduced operation time. The incumbent battery technology is not projected to accommodate these requirements. An attractive alternative is the direct liquid fuel cell, in particular the polymer electrolyte membrane (PEM) based direct methanol fuel cell (DMFC), as it does not suffer from the disadvantages associated with conventional battery technology and has the potential for extended and continuous operation. However, the wide spread adoption of the DMFC is prevented by a significant number of barriers that include: fuel crossover, catalyst and fuel utilization, efficiency, overall cost and size. The research presented in this thesis aims to address these areas through the development of simplified cell architectures and operational methods. In a conventional membrane electrode assembly (MEA), a PEM is compressed between an anode and cathode electrode. In this research a new branch of simplified architectures that is unique from those that have been reported in literature has been developed by eliminating and/or integrating key components of a conventional MEA. The membraneless 3D anode approach was shown to be fuel independent and scaleable to a conventional bipolar fuel cell arrangement and exhibits comparable performance to a conventional passive DMFC at ambient conditions (25C, 1 atm). The single electrode supported DMFC was fabricated through a sequential deposition of an anode catalyst layer, an electrically insulating layer and a cathode catalyst layer onto a single carbon fibre paper substrate. This resulted in a 42% reduction in thickness and a 104% improvement in volumetric specific power density over a two electrode DMFC configuration. In addition, simple methods to control fuel crossover and power output were developed and characterized. A perforated graphitic diffusion barrier with engineered properties reduced fuel crossover in the range of ~73% to ~94%. The power output of the membraneless DMFC was controlled through a selective activation/deactivation of triple phase boundary regions on the electrode assembly with a physical guard. This method enabled the DMFC to operate at a single optimized condition where the voltage, current density, crossover and overall efficiency were constant at any power level.

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Fan, Simon Shun Ming. "Performance characterization of the high temperature direct alcohol fuel cell." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42437.

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A fuel cell that promotes the direct use of alcohol fuels such as methanol and ethanol is attractive because these fuels are friendlier than other fuels, such as gasoline, to the end-user and are renewable. Therefore, these fuel cells continue to receive much interest from academia and industry who actively seek alternative energy sources and comprehensive energy supply solutions. However, one of the barriers to the performance improvement of the alcohol fuel cell is the CO-like poisoning intermediates that hinder the alcohol electro-oxidations. This thesis project has validated several different advanced approaches to eliminate the CO-like intermediates from the catalyst surface. A 3-electrode electrochemical glass cell, a half-cell and a single fuel cell have been used to study the effects of these approaches (i.e., introduction of oxidant additives, increased operating temperature, electrochemical pulse techniques, and fuel starvation) on intermediates. A 3-way relationship between the onset potential for electro-oxidation of alcohols, the CO oxidizing potential, and temperatures was determined, and conditions required for a performance benefit were identified. A higher temperature Direct Alcohol Phosphoric Acid Fuel Cell (DAPAFC) using Phosphoric Acid/Silicon Carbide (SiC) as an electrolyte/separator was investigated. Parametric studies were conducted to determine the effects of factors such as higher temperature operation (120-180ºC), etc. A reduced performance gap between PtRu and Pt catalyst at higher temperatures ((>120°C) was shown. Comprehensive studies were also conducted to demonstrate the performance effects of the gas diffusion layer and the micro-porous layer. It was shown that the structure improvement of the phosphoric acid electrode assembly significantly improved the durability and could also improve the cell performance. A higher temperature Direct Alcohol Alkaline Fuel Cell (DAAFC) was also developed to demonstrate the effectiveness of the alcohol electro-oxidation in alkaline medium. An advantage for this system was the use of pure fuel operation which provides at least a 10% improvement in performance compared to dilute fuel operation. In general, the higher temperature direct alcohol vapor fed fuel cells show significantly improved performance using a simple inexpensive separator approach. It appears that this is a new approach which could have a number of advantages.

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Ren, Qiao. "Tungsten carbides as anode electrocatalyst of direct methanol fuel cell." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 97 p, 2007. http://proquest.umi.com/pqdweb?did=1400426011&sid=12&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Thesis (M.S.)--University of Delaware, 2007.
Principal faculty advisors: Jingguang G. Chen, Dept. of Chemical Engineering; and Thomas P. Beebe, Jr., Dept. of Chemistry & Biochemistry. Includes bibliographical references.

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DeLuca, Nicholas William Elabd Yossef A. "Nafion® blend membranes for the direct methanol fuel cell /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2710.

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Jackson, Christopher Leslie. "Performance and optimisation of the direct methanol fuel cell (DMFC)." Thesis, University of Newcastle Upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432490.

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Argyropoulos, Panagiotis. "Performance and modelling of the direct methanol fuel cell (DMFC)." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247913.

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Eccarius, Steffen. "Approaches to Passive Operation of a Direct Methanol Fuel Cell." [S.l. : s.n.], 2007. http://digbib.ubka.uni-karlsruhe.de/volltexte/1000007109.

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Wurtele, Matthew. "Ethane Conversion to Ethylene in a Direct Hydrocarbon Fuel Cell." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/38818.

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Direct hydrocarbon fuel cells are fuel cells than use hydrocarbons directly as fuel instead of the most commonly used fuel in a fuel cell, hydrogen. Studies are being done on direct hydrocarbon fuel cells because they have the potential to be energetically more efficient than hydrogen fuel cells. There are many different hydrocarbons that are available to use as a feed stock and each one reacts at different reaction rates. As the current density of a fuel cell is linked to the reaction rate, it is important to know the energetics of an oxidation reaction that is occurring. Density Functional Theory (DFT) is a technique that can be used to predict the energy states of intermediate reaction steps in a given mechanism. The focus of this study is the using DFT to explore the energetics of the oxidation of ethane to ethylene in a nickel-anode catalyst fuel cell. DFT was used in adsorption runs to optimize the geometries beginning (adsorbed ethane) and end (adsorbed ethylene) of the oxidation reaction. DFT was then used to calculate the energy of transition states by varying bond lengths. It was determined the removal of the second hydrogen from the ethyl radical is the most energy intensive step and, thus, the rate limiting step. Hydrogen, ethane, and ethylene were all explored in this study. The heats of adsorption varied from largest to smallest in the order of ethylene, hydrogen, and ethane. It was determined that the heat of adsorption of hydrogen is sufficient to meet the energy requirements for the dissociation reaction. This may help explain why hydrogen reacts so readily in fuel cells. Conversely, the heats of adsorption for the hydrocarbons did not meet the energy requirements for the dissociation reactions. This may help explain why ethane and ethylene react more slowly in a fuel cell as compared to hydrogen. Also, the oxidation of ethane to ethylene requires two large activation energies. These two additional activation energies may help explain why ethylene reacts more readily than ethane in a fuel cell.

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Nash, Scott. "The development of a membraneless direct borohydride alkaline fuel cell." Thesis, Lancaster University, 2017. http://eprints.lancs.ac.uk/88376/.

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Fuel cells offer the potential for the generation of clean, renewable energy source for a wide variety of applications. Low temperature fuel cells (< 150 °C) are most suitable for portable applications, out of these the alkaline fuel cell (AFC) shows increased electrode kinetics over other fuel cell types. The direct borohydride alkaline fuel cell (DBAFC), a derivative of the AFC, can provide increased power output and improved safety features afforded using borohydride in place of hydrogen gas. However, relatively little research has been conducted on DBAFC, particularly membraneless DBAFC. This work aims to address this and describes an investigation into every aspect of DBAFC to evaluate their deployment on an industrial scale. As such, candidate electrocatalysts were assessed for their electrocatalytic activity towards the oxidation of borohydride in alkaline media for use in DBAFCs using cyclic voltammetry. The candidate electrocatalysts, including Pt, Pd and Ru on activated C and cathode electrocatalysts were then developed into a screen printable electrode ink, a method which could be easily upscaled for mass manufacture. A screen-printed anode developed outperformed commercially available AFC anodes with the developed cathode performing sufficiently when evaluated using electrochemical polarisation. Computer simulations were used to design individual components of a DBAFC, which were built and tested experimentally through operational use and electrochemical impendence analysis. The developed DBAFC performed well, with theoretically low ionic leakage when in a stack, good distribution of electrolyte and air and a low cell weight. Finally, a system was designed to evaluate different electrolyte flow methods and operating conditions and produced a flexible testing system for DBAFC suitable for scale up. The results generated indicate that DBAFCs are a viable alternative to other low temperature fuel cells. Using an effective anode electrocatalyst and system design, DBAFC could be used for a variety of applications.

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Kim, Hyea. "High energy density direct methanol fuel cells." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37106.

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The goal of this dissertation was to create a new class of DMFC targeted at high energy density and low loss for small electronic devices. In order for the DMFC to efficiently use all its fuel, with a minimum of balance of plant, a low-loss proton exchange membrane was required. Moderate conductivity and ultra low methanol permeability were needed. Fuel loss is the dominant loss mechanism for low power systems. By replacing the polymer membrane with an inorganic glass membrane, the methanol permeability was reduced, leading to low fuel loss. In order to achieve steady state performance, a compliant, chemically stable electrode structure was investigated. An anode electrode structure to minimize the fuel loss was studied, so as to further increase the fuel cell efficiency. Inorganic proton conducting membranes and electrodes have been made through a sol-gel process. To achieve higher voltage and power, multiple fuel cells can be connected in series in a stack. For the limited volume allowed for the small electronic devices, a noble, compact DMFC stack was designed. Using an ADMFC with a traditional DMFC including PEM, twice higher voltage was achieved by sharing one methanol fuel tank. Since the current ADMFC technology is not as mature as the traditional DMFCs with PEM, the improvement was accomplished to achieve higher performance from ADMFC. The ultimate goal of this study was to develop a DMFC system with high energy density, high energy efficiency, longer-life and lower-cost for low power systems.

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Ilicic, Alan Bartol. "Investigation of a direct methanol redox fuel cell with design simplification." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/23499.

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A key objective of this work is to address a number of the central issues associated with the direct methanol fuel cell (DMFC) through the investigation of a redox flow battery (RFB) / DMFC hybrid fuel cell. The air cathode (Pt/carbon) of the DMFC is substituted by a Fe²⁺/Fe³⁺ redox couple cathode (carbon) with no platinum-group metal (PGM) catalyst. In this configuration, referred to as the direct liquid redox fuel cell (DLRFC), the Fe²⁺/Fe³⁺ redox couple cathode is selective to the redox couple reaction and fuel crossover does not cause cathode depolarization. A wide range of anolyte fuel concentrations were tested (2-24 M CH₃OH) and the best DLRFC performance was obtained at 16.7 M CH₃OH (equimolar CH₃OH / H₂O). A significant improvement in the DLRFC performance and catholyte charge density was obtained by switching from a sulfate-based iron salt to a perchlorate-based iron salt. This led to a greater than 150% increase in the solubility of the redox couple, greater than a 200 mV increase in the equilibrium half-cell potential of the redox couple and a greater than 200% improvement in the DLRFC peak power density (79 mW/cm² vs. 25 mW/cm²) relative to the sulfate-based system. The selective nature of the redox cathode enabled the demonstration and characterization of a novel mixed-reactant DLRFC (MR-DLRFC) where a mixed electrolyte containing methanol and the redox couple is fed to the cathode and fuel crossover is the mode of fuel supply. A non-optimized peak power density of 15 mW/cm² was obtained with this system. A novel in-situ redox couple regeneration approach was also demonstrated and characterized, which involved substituting the methanol anolyte by an air stream. This approach exploits the hybrid nature of the DLRFC and utilizes the PtRu catalyst at the DLRFC anode as an O₂ reduction cathode during regeneration. Eliminating the use of PGM catalysts at the fuel cell cathode and enabling the use of high fuel concentrations are decisive advantages of DLRFC technology. Furthermore, the ability to extend DLRFC technology to a mixed-reactant architecture where fuel crossover is desirable paves new ground for the future of fuel cell research.

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Sanii, Sanam. "Anode catalyst layer engineering for the direct formic acid fuel cell." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/31849.

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Direct formic acid fuel cells (DFAFC) are promising alternatives to hydrogen proton exchange membrane fuel cells for microelectronic applications. Compared to direct methanol fuel cell (DMFC), the main advantages of direct formic acid fuel cell (DFAFC) are higher theoretical open circuit voltage (1.45 V at 298 K), lower fuel cross over towards cathode and reasonable power densities at room temperature that make DFAFCs a viable alternative for micropower applications. The operation of DFAFCs on Pd-based catalysts at ambient temperature showed lower fuel permeation from anode to cathode that resulted in better fuel utilization when running on high formic acid concentrations (~10M). However, Pd suffers an unacceptable loss of performance with time that decreases the cell power density by about 50% in a few hours. The aim of the present work is to create an extended reaction zone anode structure to improve the utilization of the catalyst and to modify the electrode surface characteristics in order to reduce performance losses. The novel catalyst deposition technique involved electroless (chemical) deposition of Pd particles directly onto the carbon paper substrate (AvCarbTM P50) in the presence of Nafion® solution. It was found that the use of 4.66 g L⁻¹ of pure Nafion® as an additive to the electroless bath and Shipley pre-treatment resulted in 1.6 mg cm⁻² and 0.07 mg cm⁻² Pd and Sn mass loadings respectively with Pd average particle size of 0.45 to 0.55 μm. When pre-treating in nitric acid solution, the surface coverage was found to be uniform with dense particulate-like structure. The surface nitric acid pre-treatment method in conjunction with 2.46 g L⁻¹ Nafion® additive in the electroless solution were resulted in 4.5 mg cm⁻² Pd mass loading on AvCarbTM P50 and enhanced electrochemical performance at current densities larger than 500 A m⁻² at 333 K . Comparing the Pd/C and PdSn/C performances in DFAFC tests, the Pd/C anode with higher Pd mass loading (4.5 mg cm⁻²) and OCV stayed fairly stable on ~ 0.55 V up to 3.5 hours of constant current draw(100 A m⁻² at 333 K).

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32

Zellner, Michael. "Tungsten carbides as potential alternative direct methanol fuel cell anode electrocatalysts." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 213 p, 2006. http://proquest.umi.com/pqdweb?did=1172119451&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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33

Oedegaard, Anders. "Development and characterisation of a portable direct methanol fuel cell stack." Gerhard-Mercator-Universitaet Duisburg, 2006. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-03012006-080812/.

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This thesis deals with the development and characterisation of a portable direct methanol fuel cell stack. In addition, calculations of the transport of methanol and water in the membrane are compared with experimentally determined values. It also includes investigations of the behaviour of single-cells and some of its components, as the anode gas diffusion layer and the anode flow-field. For the addition of methanol to the anode feed loop, a passive concept based on a permeable tube was developed and verified by both experiments and simulations.

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34

Shivhare, Mahesh Ratanlal. "Design of experiments and modelling of the direct methanol fuel cell." Thesis, University of Newcastle Upon Tyne, 2008. http://hdl.handle.net/10443/749.

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Environmentally friendly polymer electrolyte membrane fuel cells (PEMFCs) have the potential to revolutionise mobile power sources. One of the more promising PEMFC candidates is the direct methanol fuel cell (DMFC). Significant commercial interest has been expressed in the DMFC as a consequence of it becoming a possible replacement technology for batteries and internal combustion engines. The DMFC is a simple system that utilises liquid fuel and which requires minimal ancil lary equipment, and hence are more suited to the logistics of portable and vehicular applications than hydrogen fuel cells. However, significant technological challenges remain that must be addressed prior to the DMFC becoming more commercially exploitable. These challenges include improving the poor anode kinetics of methanol oxidation and reducing methanol crossover. To aid the understanding of the various factors limiting the widespread application of the DMFC, the statistical method of design of experiments was applied. A fractional factorial design was implemented to understand the main effects and interactions of a number of operating parameters on the overall performance of the DMFC, in which the effect of the crossover of methanol through the membrane was considered. The statistical models developed facilitated the detection of key two-factor interactions of temperature with methanol concentration, type of oxidant and cathode back pressure, which suggested that an improvement in DMFC performance was achievable by reducing the effect of methanol crossover. Based on the outcomes of the parametric study, response surface methodology was applied to optimise catalyst layer formulation. The response surface method highlighted the significance of high catalyst loading and the non-linear behaviour of the Nafion@ content. Furthermore, the advantage of adding PTFE in the anode catalyst formulation, to make the anode morphology favourable for carbon dioxide gas evolution, was demonstrated. Steady state semi empirical models for the anode based on methanol oxidation kinetics and cathode considering the effect of methanol crossover through the membrane were also developed. The kinetic models for the anode illustrated the significance of water and surface intermediates in the methanol oxidation reaction on a dual site Pt-Ru catalyst and highlighted the subtle balance between the methanol adsorption-dehydrogenation step and the subsequent oxidative removal step. The cathode model developed provided insight into the effect of methanol crossover on the cathode open circuit potential and helped in reliable estimation of the cathode polarisation curve. Finally a combination of these two models was used in the prediction of the cell polarisation characteristic as a function of cell potential, temperature and amount of methanol crossed over through the membrane

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35

Suwatchara, Danu. "Development of composite binding layer for direct methanol fuel cell application." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/development-of-composite-binding-layer-for-direct-methanol-fuel-cell-application(067b0dac-ec04-4adf-b1f6-64e0de37584d).html.

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Novel composite membrane systems have been devised for use in direct methanol fuel cell (DMFC) with the ultimate aim of improving overall fuel cell performance in terms of achievable power density. The composite membrane system takes the form of a multilayered structure composing of commercial Nafion117 membrane and a novel composite binding layer situated between the anode and the membrane. Within the composite binding layer, inorganic filler particles are evenly dispersed throughout the Nafion matrix presenting a barrier that impedes methanol crossover. Through the current research, three novel membrane electrode assemblies (MEA) have been fabricated, each employing the composite binding layer system with different filler. Mass of filler used is kept constant at 0.5 wt% of Nafion117 membrane. When tested in a DMFC system, the first MEA which utilizes hydrogen form mordenite filler particles yields optimum power density of 60 mW/cm2 with the operation at 90°C, 1M methanol fuel concentration. This represents an improvement of 34.7% compared to the standard MEA which do not include the composite binding layer. Silanefunctionalized hydrogen form mordenite filler is used in the second MEA which yields optimum power density of 64 mW/cm2 at 90°C, 1M methanol, outperforming the standard MEA by 42.5%. The third MEA makes use of TS-1 particles as fillers. This yields an optimum performance of 38 mW/cm2 at 90°C, 1M methanol, a 14.3% reduction in performance compared to the standard. Through the results obtained, it can be deduced that the novel composite binding layer presents a valid approach in reducing methanol crossover, however, the nature of filler particles used exerts a great influence on its performance. Therefore, further research is recommended in exploring new filler materials for use within the composite membrane system.

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36

Wright, Emma Victoria. "Investigation of a novel solid oxide fuel cell interconnect." Thesis, Keele University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265019.

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37

Naidoo, Sivapregasen. "Synthesis of multi-metallic catalysts for fuel cell applications." Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_6275_1241512064.

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The direct methanol fuel cell or DMFC is emerging as a promising alternative energy source for many applications. Developed and developing countries, through research, are fast seeking a cheap and stable supply of energy for an ever-increasing number of energy-consuming portable devices. The research focus is to have DMFCs meeet this need at an affordable cost is problematic. There are means and ways of making this a reality as the DMFC is found to be complementary to secondary batteries when used as a trickle charger, full charger, or in some other hybrid fuel cell combination. The core functioning component is a catalyst containing MEA, where when pure platinum is used, carbon monoxide is the thermodynamic sink and poisons by preventing further reactions at catalytic sites decreasing the life span of the catalyst if the CO is not removed. Research has shown that the bi-functional mechanism of a platinum-ruthenium catalyst is best because methanol dehydrogenates best on platinumand water dehydrogenation is best facilitated on ruthenium. It is also evident that the addition of other metals to that of PtRu/C can make the catalyst more effective and effective and increase the life span even further. In addition to this, my research has attempted to reduce catalyst cost for DMFCs by developing a low-cost manufacturing technique for catalysts, identify potential non-noblel, less expensive metallic systems to form binary, ternary and quarternary catalysts.

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38

Pan, Yining. "Immobilized Viologen Polymer for Use in Direct Carbohydrate Fuel Cells." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3524.

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Glucose and other carbohydrates are some of the most abundant renewable energy sources in the world. The oxidation of carbohydrates in a fuel cell allows their chemical energy to be converted directly into electrical energy. Viologen has been indentified and shows promising ability as an electron-transfer catalyst or mediator for carbohydrate oxidation in an alkaline carbohydrate fuel cell. Building on the previous results, the objective of this work was to develop an immobilization chemistry of viologen onto an electrode and to investigate the catalytic activity for carbohydrate oxidation in direct carbohydrate fuel cells.The immobilization was achieved by electropolymerizing a novel viologen monomer onto an electrode surface. The novel viologen monomer, which functions as a monosubstituted viologen, was synthesized and isolated in-house. Gold-plated nickel wire and graphite disks were used as the substrates for the electropolymerization. SEM, EDAX, XPS and water-contact-angle measurement were used to verify the formation of the coating on the gold and graphite surfaces. The catalytic activity of the immobilized viologen on graphite disk surface was examined using a fuel-cell-like device. The test was operated within the desired pH range for an operating fuel cell; it was found that the immobilized viologen polymer has a low catalytic activity toward oxidizing carbohydrates. In addition, the electrochemical properties of the novel viologen monomer were investigated by the method of cyclic voltammetry, as well as for that of two aminoviologens synthesized in-house. Redox potentials, diffusion coefficients, and heterogeneous electron-transfer rate constants were determined.

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39

Luo, Hongze. "Proton conducting polymer composite membrane development for Direct Methanol Fuel Cell applications." Thesis, University of Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1362_1262901908.

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The objective of this study was thus to prepare highly proton condictivity membranes that are cheap to manufacture and have low methanol permeability.

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40

Dara, Mohammad Saad. "Novel direct redox fuel cell : membraneless low precious metal catalyst electrode assembly." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43469.

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The direct fuel redox fuel cell (DFRFC) substitutes the oxygen reduction cathode of low temperature fuel cells such as polymer electrolyte membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC) with an iron redox cathode of a redox flow battery. This approach helps address many of the issues with low temperature fuel cells. For both the PEMFC and DMFC the iron redox cathode eliminates precious metal content from the cathode. With respect to the PEMFC the inherent liquid nature of the iron redox cathode provides both heat and water management to the system which significantly reduces the balance-of-plant components. On the other hand, the issues of fuel crossover for the DMFC are no longer a concern as methanol is not electrochemically active at the carbon cathode used for the ferric reduction reaction. However, the use of metal redox ions in conjunction with a membrane of the same polarity introduces issues of membrane contamination which significantly reduce membrane conductivity resulting in increased ohmic overpotentials and losses in fuel cell performance. In addition, crossover of the redox catholyte can result in anode depolarization. In this a work a novel membraneless direct liquid redox fuel cell is demonstrated. The membraneless design utilizes 3-D electrode(s), the engineering of which allows control of the reactant concentration gradients. This control of the reactant gradient allows for more complete reactant utilization which mitigate catholyte crossover and allow for the elimination of the PEM. The PEM in the DFRFC used in this work is replaced with an open-spacer and liquid acid electrolyte. In addition, this novel membraneless electrode assembly design is completely scalable and flexible to different platforms, fuels, oxidants and electrolytes. In this work a membraneless direct hydrogen redox fuel cell and membraneless direct methanol redox fuel cell based on the 3-D electrode concept and controlled concentration gradient are demonstrated. In addition, the use of the liquid acid electrolyte in the membraneless direct hydrogen redox fuel cell allowed for improved ionic conductivity to the anode catalyst layer. This allowed for significant reductions in precious metal catalyst content to be made from the hydrogen oxidation anode.

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41

Havránek, Aleš. "Relationship between structure and electrochemical properties of direct methanol fuel cell anodes." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=982891725.

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42

Vernersson, Thomas. "Mass transport in proton conducting membranes for the direct methanol fuel cell." Licentiate thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-309.

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43

Wu, Chen-Yi, and 吳貞儀. "Study on Fuel Reforming of Direct Propane Solid Oxide Fuel Cell." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/33755570526316075214.

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44

Chin, Huang Yi, and 黃逸群. "Fuel cell and direct injection engine." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/77710618315974751850.

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45

Liu, Tao-Chun, and 劉陶鈞. "Flexible Mini-Direct Methanol Fuel Cell." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/2h6sgp.

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46

Lee, Huang-Yu, and 李皇諭. "High Performance Direct Methanol Fuel Cell Catalysts." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/83528877736594153250.

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博士
國立中央大學
化學研究所
100
Direct methanol fuel cells (DMFC) shows potential as a new energy source due to its relatively high energy density, easy to store, transport, and reload. However, the low catalyst efficiency, insufficient durability and high manufacture cost are hurdles for immediate commercialization. The first aim of the research covered in this thesis was to improve the catalytic activity and to extend catalyst durability by using polyaniline (PANi) coated on both carbon nanotube (CNT) and ground active carbon (ACg) surface to form PCNT and PACg nanocomposites, and later we examine the different effects of polyaniline, polypyrrole, and polythiophene coating on Vulcan XC-72 to form P1X, Ppy1X and Pth1X nanocomposites as the anode catalysts supports for direct methanol fuel cell. A second part of the study was to examine a novel cathode catalyst, PtPb alloy, which exhibited high activity and tolerance corrosion in acid media. All the anode electrocatalysts were prepared by depositing Pt-Ru alloy nanoparticles on nanocomposites surface through borohydride reduction. The alloying Pt-Pb nanoparticles were supported on ACg and P1CNT by a mild reduction procedure under temperatures below 200oC. Using polyaniline coating on Vulcan XC-72 as the support to form anode catalyst yielded methanol oxidation catalytic activity higher than polypyrrole and polythiophene nanocomposites catalysts. In comparison, the polyaniline coating on different the type carbon supports, the PtRuP1CNT showed highest methanol oxidation performance due to P1CNT formed 3D porous framework catalyst layer, afforded more active sites and easier transport of methanol and CO2. The platinum-lead alloys tended to follow mainly a 4-electron mechanism, which implied reduced H2O2 formation and first order with respect to the dissolved oxygen. PtPbACg catalyst showed high stability including low ECSA change ratio and carbon corrosion under consecutive scan in 0.1 M HClO4. In summary, present study demonstrated that the PANi coating prevented aggregation, loss of Pt particles, and thereby improved long-term stability of fuel cell catalysts on both anode and cathode. It also unveiled a new design of more durable catalysts by coating conducting polymer layer on carbon support which improved catalytic activity, CO tolerance and stability over other catalysts based on the current method technique. PtPb binary alloy nanoparticles could be used as a new potential cathode catalyst metal for both PEMFC and DMFC

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47

Kao, Tzu-Min, and 高資閔. "Plasma splitting of direct methanol fuel cell." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41816354261673033557.

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碩士
國立高雄應用科技大學
機械與精密工程研究所
101
This study use plasma splitting methanol vapor to produce fuel cells hydrogen fuel，In the experiment, different splitting times were introduced into the fuel cell with a different amount of oxygen required for comparison. The plasma splitting time were five minutes and three minutes, the fuel cell reaction oxygen are 10cc/min and 5cc/min. We are comparison with splitting time and the amount of oxygen fed, the hydrogen fuel were making at five and three minutes of the produces maximum voltage have no special difference, but the amount of oxygen have great difference. The fuel cell generate maximum power of different splitting time produce fuel ,and same splitting time different oxygen flow in fuel cell reaction was no different.

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48

楊添福. "Technology development of direct methanol fuel cell." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/68754338815228066787.

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Lin, Chung-Min, and 林崇民. "Analytical model of Direct Methanol Fuel Cell." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/89864024467111962961.

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碩士
國立臺灣大學
化學工程學研究所
95
It has become an important issue to search for alternative energy source due to energy crisis and pollution of the natural environment in recent years. Direct methanol fuel cell (DMFC) is one of the attractive energy supplies. There are some technical challenges for DMFC such as low efficiency due to methanol crossover, low methanol oxidation rate, low power density, and the need for excessive water and heat management, etc. For a better description of the cell operation and optimization of performance, it would be important to develop an accurate and quick mathematical model for DMFC. In this research, a 2D analytical mathematical model of a direct methanol fuel cell was developed to describe not only electrochemical reactions on the anode and cathode electrodes, but also transport phenomena within the fuel cell, operating isothermally at steady state. One could use this model to understand the cell performance such as polarization curve, efficiency, power density and concentration profile. Further, we could predict cell performance and understand how to deal water management when methanol input concentration changes. Compared with other models in the literature, our model allows for prediction of the open circuit voltage of the DMFC. This model contains forty three parameters; most of them are decided by cell structure and operation condition. Only seven parameters(transfer coefficient of electron、resistance of material interface、porosity、thickness of catalyst layer and diffusion coefficient of oxygen) are obtained by regressing to experiment data. The theoretical prediction was in good agreement with experiments from three different fuel cells (including different cell structure, operating condition). This indicates that this model is robust and reliable. With this model, one could better understand electrochemical reactions and mass transport phenomena in fuel cell, including methanol crossover and reactant transport in membrane electrode assembly (MEA), and how these phenomena affect cell performance. The knowledge provided from such an analytical model may help one search for the key factors to improve DMFC performance.

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50

Wang, Chen-Hao, and 王丞浩. "High Performance of Direct Methanol Fuel Cell." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/61418648922028241665.

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博士
國立清華大學
材料科學工程學系
95
The direct methanol fuel cell (DMFC) is an attractive and promising power generator, which generates electricity by an electrochemical redox reaction of methanol and oxygen, enabling a wide range of applications from small sensors, portable electronic devices, to automobiles. However, the slow methanol electro-oxidation and severe methanol crossover undermine the DMFC performance. On the other hand, a high loading of noble metal electrocatalysts make it too expensive for commercialization. In this thesis, two solutions are proposed to tackle these issues: an efficient anode with a low loading of noble metal electrocatalysts to enhance the methanol electro-oxidation; a proton exchange membrane coated with a methanol blocking layer to reduce the methanol crossover. Firstly, the study demonstrated the feasibility of a high-performance membrane-electrode-assembly (MEA), with low electrocatalyst loading on carbon nanotubes (CNTs), which were grown directly on carbon cloth as an anode. The direct growth of CNTs was realized by microwave plasma-enhanced chemical vapor deposition using CH4/H2/N2 as precursors. The cyclic voltammetry and electrochemical impedance measurements with 1 mM Fe(CN)63-/4- redox reaction reveal a fast electron transport and a low resistance on the direct grown CNT. The electrocatalysts, platinum and ruthenium, were coated on CNTs by sputtering technique to form the Pt-Ru/CNTs-CC anode (Pt-Ru/CNTs-CC). The MEA, the sandwiched structure which comprises 0.4 mg cm-2 Pt-Ru/CNTs-CC as the anode, 3.0 mg cm-2 Pt black as the cathode and Nafion 117 membrane at the center, performs very well in a direct methanol fuel cell (DMFC) test. The micro-structural MEA analysis shows that the thin electrocatalyst layer is uniform, with good interfacial continuity between membrane and the gas diffusion layer. Secondly, protonated polyaniline (PANI), a stable and electrically conducting polymer, was directly polymerized on a Nafion 117 membrane (N117), forming a composite membrane, to act as a methanol blocking layer (PANI/N117), whose was evaluated to reduce the methanol crossover in the DMFC. A PANI layer coated on the N117 has a thickness of 100 nm, with an electrical conductivity of about 13.24 S cm-1. The methanol permeability of the PANI/N117 is 41% less than that of the N117 at room temperature, suggesting that the PANI/N117 can effectively reduce the methanol crossover in the DMFC. The MEAs using the conventional N117 (N117-based MEA) and the new developed PANI/N117 (PANI/N117-based MEA) were compared to the feeding of 1, 2, 4, 6 and 8 M methanol at 60 oC. The output power of the N117-based MEA is reduced at higher methanol concentration, which is due to the methanol crossover of the N117. However, the PANI/N117-based MEA exhibits higher output power at higher methanol concentration. The maximum power density of the PANI/N117-based MEA is 70 mW cm-2 at 6 M methanol solution. This value is double that of the N117-based MEA under identical conditions. This work also suggests that the methanol-crossover rate of the PANI/N117-based MEA is about 60% lower than that of the N117-based MEA from 1 M to 6 M methanol solutions. The PANI/N117-based MEA performs well at elevated methanol concentration, suggesting the potential for long-term operation of small-scale DMFCs.

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