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Fanapi, Nolubabalo Hopelorant. "Durability studies of membrane electrode assemblies for high temperature polymer electrolyte membrane fuel cells." University of the Western Cape, 2011. http://hdl.handle.net/11394/5416.
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>Magister Scientiae - MScPolymer electrolyte membrane fuel cells (PEMFCs) among other fuel cells are considered the best candidate for commercialization of portable and transportation applications because of their high energy conversion and low pollutant emission. Recently, there has been significant interest in high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), due to certain advantages such as simplified system and better tolerance to CO poisoning. Cost, durability and the reliability are delaying the commercialization of PEM fuel cell technology. Above all durability is the most critical issue and it influences the other two issues. The main objective of this work is to study the durability of membrane electrode assemblies (MEAs) for HT-PEMFC. In this study the investigation of commercial MEAs was done by evaluating their performance through polarization studies on a single cell, including using pure hydrogen and hydrogen containing various concentrations of CO as fuel, and to study the performance of the MEAs at various operating temperatures. The durability of the MEAs was evaluated by carrying out long term studies with a fixed load, temperature cycling and open circuit voltage degradation. Among the parameters studied, significant loss in the performance of the MEAs was noted during temperature cycling. The effect of temperature cycling on the performance of the cell showed that the performance decreases with increasing no. of cycles. This could be due to leaching of acid from the cell or loss of electrochemically active surface area caused by Pt particle size growth. For example at 160°C, a performance loss of 3.5% was obtained after the first cycle, but after the fourth cycle a huge loss of 80.8% was obtained. The in-house MEAs with Pt-based binary catalysts as anodes were studied for CO tolerance, performance and durability. A comparison of polarization curves between commercial and in-house MEAs illustrated that commercial MEA gave better performance, obtaining 0.52 A/cm² at 0.5V and temperature of 160°C, with in-house giving 0.39A/cm² using same parameters as commercial. The CO tolerance of both commercial and in-house MEA was found to be similar. In order to increase the CO tolerance of the in-house MEAs, Pt based binary catalysts were employed as anodesand the performance was investigated In-house MEAs with Pt/C and Pt-based binary catalysts were compared and a better performance was observed for Pt/C than Pt-alloy catalysts with Pt-Co/C showing comparable performance. At 0.5 V the performance obtained was 0.39 A/cm2 for Pt/C, and 0.34A/cm²,0.28A/cm²,0.27A/cm² and 0.16A/cm² were obtained for Pt-Co/C, Pt-Fe/C, Pt-Cu/C and Pt-Ni respectively. When the binary catalysts were tested for CO tolerance, Pt-Co showed no significant loss in performance when hydrogen containing CO was used as anode fuel. Scanning electron microscopy (SEM) revealed delamination between the electrodes and membrane of the tested and untested MEA's. Membrane thinning was noted and carbon corrosion was observed from the tested micro-porous layer between the gas diffusion layer (GDL) and catalyst layer (CL).
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Flores, Hernández José Roberto. "Optimization of membrane-electrode assemblies for SPE water electrolysis by means of design of experiments /." Stuttgart : Fraunhofer-IRB-Verl, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014175428&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Ecklund-Mitchell, Lars E. "Development of Thin CsHSO4 Membrane Electrode Assemblies for Electrolysis and Fuel Cell Applications." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002627.
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Bonifacio, Rafael Nogueira. "Estudo e desenvolvimento de conjuntos membrana-eletrodos (MEA) para célula a combustível de eletrólito polimérico condutor de prótons (PEMFC) com eletrocatalisadores à base de paládio." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-09012014-144413/.
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Sistemas de PEMFC são capazes de gerar energia elétrica com alta eficiência e baixa ou nenhuma emissão de poluentes, porém questões de custo e durabilidade impedem sua ampla comercialização. Nesse trabalho foi desenvolvido um MEA com eletrocatalisadores à base de paládio. Foram sintetizados e caracterizados eletrocatalisadores Pd/C, Pt/C e Ligas PdPt/C com diferentes razões entre metais e carbono. Foi realizado um estudo da razão entre ionômero de Nafion e eletrocatalisador para formação de triplas fases reacionais de máximos desempenhos, criado um modelo matemático para transpor esse ajuste para eletrocatalisadores com diferentes razões entre metal e suporte, considerando os aspectos volumétricos da camada catalisadora, e então realizado um estudo da espessura da camada catalisadora. Para as caracterizações foram utilizadas as técnicas de Difração de Raios-X, Microscopias Eletrônicas de Transmissão e de Varredura, Energia Dispersiva de Raios-X, Picnometria a Gás, Porosimetria por Intrusão de Mercúrio, Adsorção de Gás, segundo as equações de BET e BJH, Análise Termo Gravimétrica e feitas as determinações de diâmetros de partículas, de áreas de superfície específica e de parâmetros de rede. Todos os eletrocatalisadores foram usados no preparo de MEAs que foram avaliados em célula unitária de 5 cm2 entre 25 e 100 °C a 1 atm; e a melhor composição foi avaliada também a 3 atm. No estudo dos metais para as reações, visando reduzir a platina aplicada aos eletrodos, sem perdas de desempenho, foram selecionados Pd/C para ânodos e PdPt/C 1:1 para cátodos. A estrutura de MEA desenvolvida utilizou 0,25 mgPt.cm-2 e resultou em densidades de potência de até 550 mW.cm-2 e potências de até 2,2 kWe por grama de platina. A estimativa realizada mostrou que houve uma redução de até 64,5 % nos custos em relação à estrutura de MEA previamente conhecida. Em função da temperatura e pressão de operação foram obtidos valores a partir de R$ 3.540,73 para o preparo de MEAs para cada quilowatt instalado. Com base em estudos recentes, concluiu-se que o custo do MEA desenvolvido é compatível às aplicações estacionárias de PEMFC.PEMFC systems are capable of generating electricity with high efficiency and low or no emissions, but durability and cost issues prevent its large commercialization. In this work MEA with palladium based catalysts were developed, Pd/C, Pt/C and alloys PdPt/C catalysts with different ratios between metals and carbon were synthesized and characterized. A study of the ratio between catalyst and Nafion Ionomer for formation of high performance triple-phase reaction was carried out, a mathematical model to implement this adjustment to catalysts with different relations between metal and support taking into account the volumetric aspects of the catalyst layer was developed and then a study of the catalyst layer thickness was performed. X-ray diffraction, Transmission and Scanning Electron Microscopy, X-ray Energy Dispersive, Gas Pycnometry, Mercury Intrusion Porosimetry, Gas adsorption according to the BET and BJH equations, and Thermo Gravimetric Analysis techniques were used for characterization and particle size, specific surface areas and lattice parameters determinations were also carried out. All catalysts were used on MEAs preparation and evaluated in 5 cm2 single cell from 25 to 100 °C at 1 atm and the best composition was also evaluated at 3 atm. In the study of metals for reactions, to reduce the platinum applied to the electrodes without performance losses, Pd/C and PdPt/C 1:1 were selected for anodes and cathodes, respectively. The developed MEA structure used 0,25 mgPt.cm-2, showing power densities up to 550 mW.cm-2 and power of 2.2 kWnet per gram of platinum. The estimated costs showed that there was a reduction of up to 64.5 %, compared to the MEA structures previously known. Depending on the temperature and operating pressure, values from US$ 1,475.30 to prepare MEAs for each installed kilowatt were obtained. Taking into account recent studies, it was concluded that the cost of the developed MEA is compatible with PEMFC stationary application.
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Barron, Olivia. "Gas diffusion electrodes for high temperature polymer electrolyte membrane fuel cells membrane electrode assemblies." University of the Western Cape, 2014. http://hdl.handle.net/11394/4323.
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Philosophiae Doctor - PhDThe need for simplified polymer electrolyte membrane fuel cell (PEMFCs) systems, which do not require extensive fuel processing, has led to increased study in the field of high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) applications. Although these HT-PEMFCs can operate with less complex systems, they are not without their own challenges; challenges which are introduced due to their higher operation temperature. This study aims to address two of the main challenges associated with HT-PEMFCs; the need for alternative catalyst layer (CL) ionomers and the prevention of excess phosphoric acid (PA) leaching into the CL. The first part of the study involves the evaluation of suitable proton conducting materials for use in the CL of high temperature membrane electrode assemblies (HT-MEAs), with the final part of the study focusing on development of a novel MEA architecture comprising an acid controlling region. The feasibility of the materials in HT-MEAs was evaluated by comparison to standard MEA configurations.
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Liang, Zhenxing. "Preparation of high-durability membrane and electrode assemblies for direct methanol fuel cells /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?MECH%202008%20LIANG.
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Sengul, Erce. "Preparation And Performance Of Membrane Electrode Assemblies With Nafion And Alternative Polymer Electrolyte Membranes." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608734/index.pdf.
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Hydrogen and oxygen or air polymer electrolyte membrane fuel cell is one of the most promising electrical energy conversion devices for a sustainable future due to its high efficiency and zero emission. Membrane electrode assembly (MEA), in
which electrochemical reactions occur, is stated to be the heart of the fuel cell. The aim of this study was to develop methods for preparation of MEA with alternative polymer electrolyte membranes and compare their performances with the conventional Nafion®membrane. The alternative membranes were sulphonated polyether-etherketone (SPEEK), composite, blend with sulphonated polyethersulphone (SPES), and polybenzimidazole (PBI). Several powder type MEA preparation techniques were employed by using Nafion®
membrane. These were GDL Spraying, Membrane Spraying, and Decal methods. GDL Spraying and Decal were determined as the most efficient and proper MEA preparation methods. These methods were tried to improve further by changing catalyst loading, introducing pore forming agents, and treating membrane and GDL. The highest performance, which was 0.53 W/cm2, for Nafion®
membrane was obtained at 70 0C cell temperature. In comparison, it was about 0.68 W/cm2 for a commercial MEA at the same temperature. MEA prepared with SPEEK membrane resulted in lower performance. Moreover, it was found that SPEEK membrane was not suitable for high temperature operation. It was stable up to 80 0C under the cell operating conditions. However, with the blend of 10 wt% SPES to SPEEK, the operating temperature was raised up to 90 0C without any membrane deformation. The highest power outputs were 0.29 W/cm2 (at 70 0C) and 0.27 W/cm2 (at 80 0C) for SPEEK and SPEEK-PES blend membrane based MEAs. The highest temperature, which was 150 0C, was attained with PBI based MEA during fuel cell tests.
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Hall, Kwame (Kwame J. ). "An Investigation of Different Methods of Fabricating Membrane Electrode Assemblies for Methanol Fuel Cells." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54474.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 46).
Methanol fuel cells are electrochemical conversion devices that produce electricity from methanol fuel. The current process of fabricating membrane electrode assemblies (MEAs) is tedious and if it is not sufficiently controlled can be very imprecise. The optimization of this process is paramount to the commercialization and mass production of methanol fuel cells. In order to further understanding this process, MEAs were fabricated according to the decal method using different processes to apply the catalyst ink. The performances of fabricated MEAs were evaluated using a potentiostat. Polarization curves and power density curves were produced to compare the performance of the cells and gain insight into the effects of various parameters on fuel cell performance. Finally, based on the difficulties experienced and the lessons learned during the process, recommendations for future experimentation were made.
by Kwame Hall.
S.B.
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Pestrak, Michael Thomas. "The Effect of Catalyst Layer Cracks on the Mechanical Fatigue of Membrane Electrode Assemblies." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/35447.
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Mechanical fatigue testing has shown that MEAs (membrane electrode assemblies) fail at lower stresses than PEMs (proton exchange membranes) at comparable times under load. The failure of MEAs at lower stresses is influenced by the presence of mud cracks in the catalyst layers acting as stress concentrators. Fatigue testing of MEAs has shown that smaller-scale cracking occurs in the membrane within these mud cracks, leading to leaking during mechanical fatigue testing and the failure of the membrane. In addition, this testing of MEAs has further established that the cyclic pressurization pattern, which affects the viscoelastic behavior of the membranes, has a significant effect on the relative lifetime of the MEA. To investigate this behavior, pressure-loaded blister tests were performed at 90 °C to determine the biaxial fatigue strength of Gore-Primea® Series 57 MEAs. In these volume-controlled tests, the leak rate was measured as a function of fatigue cycles. Failure was defined as occurring when the leak rate exceeded a specified threshold. Post-mortem characterization FESEM (field emission scanning electron microscopy) was conducted to provide visual documentation of leaking failure sites. To elucidate the viscoelastic behavior of the MEA based on these results, testing was conducted using a DMA to determine the stress relaxation behavior of the membrane. This data was then used in a FEA program (ABAQUS) to determine its effect on the mechanical behavior of the MEAs. A linear damage accumulation model used the ABAQUS results to predict lifetimes of the membrane in the MEAs. The models showed that under volume-controlled loading, the stress decays with time and the stress dropped towards the edges of the blisters. The lifetimes of the MEAs varied depending on the cycling pattern applied. This is important for understanding failure mechanisms of MEAs under fatigue loading, and will help the fuel cell industry in designing membranes that better withstand imposed hygrothermal stresses experienced during typical operating conditions.Master of Science
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von, Kraemer Sophie. "Membrane Electrode Assemblies Based on Hydrocarbon Ionomers and New Catalyst Supports for PEM Fuel Cells." Doctoral thesis, KTH, Tillämpad elektrokemi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9208.
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The proton exchange membrane fuel cell (PEMFC) is a potential electrochemicalpower device for vehicles, auxiliary power units and small-scale power plants. In themembrane electrode assembly (MEA), which is the core of the PEMFC single cell,oxygen in air and hydrogen electrochemically react on separate sides of a membraneand electrical energy is generated. The main challenges of the technology are associatedwith cost and lifetime. To meet these demands, firstly, the component expensesought to be reduced. Secondly, enabling system operation at elevated temperatures,i.e. up to 120 °C, would decrease the complexity of the system and subsequentlyresult in decreased system cost. These aspects and the demand for sufficientlifetime are the strong motives for development of new materials in the field.In this thesis, MEAs based on alternative materials are investigatedwith focus on hydrocarbon proton-conducting polymers, i.e. ionomers, and newcatalyst supports. The materials are evaluated by electrochemical methods, such ascyclic voltammetry, polarisation and impedance measurements; morphological studiesare also undertaken. The choice of ionomers, used in the porous electrodes andmembrane, is crucial in the development of high-performing stable MEAs for dynamicoperating conditions. The MEAs are optimised in terms of electrode compositionand preparation, as these parameters influence the electrode structure andthus the MEA performance. The successfully developed MEAs, based on the hydrocarbonionomer sulfonated polysulfone (sPSU), show promising fuel cell performancein a wide temperature range. Yet, these membranes induce mass-transportlimitations in the electrodes, resulting in deteriorated MEA performance. Further,the structure of the hydrated membranes is examined by nuclear magnetic resonancecryoporometry, revealing a relation between water domain size distributionand mechanical stability of the sPSU membranes. The sPSU electrodes possessproperties similar to those of the Nafion electrode, resulting in high fuel cell performancewhen combined with a high-performing membrane. Also, new catalystsupports are investigated; composite electrodes, in which deposition of platinum(Pt) onto titanium dioxide reduces the direct contact between Pt and carbon, showpromising performance and ex-situ stability. Use of graphitised carbon as catalystsupport improves the electrode stability as revealed by a fuel cell degradation study.The thesis reveals the importance of a precise MEA developmentstrategy, involving a broad methodology for investigating new materials both as integratedMEAs and as separate components. As the MEA components and processesinteract, a holistic approach is required to enable successful design of newMEAs and ultimately development of high-performing low-cost PEMFC systems.QC 20100922
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Dawson, Craig. "Materials for direct methanol fuel cells: inhibition of methanol crossover using novel membrane electrode assemblies." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/materials-for-direct-methanol-fuel-cells-inhibition-of-methanol-crossover-using-novel-membrane-electrode-assemblies(843284c4-3620-4cac-9118-06671d7bb420).html.
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This thesis focuses on developing an alternative system for membrane electrode assembly (MEA) formation to use with a direct methanol fuel cell (DMFC). The approach involves incorporating inorganic fillers with an industry standard Nafion polymer as part of a methanol resistant composite barrier layer at the anode/membrane interface of MEA featuring Nafion 117 membranes. This procedure is used to reduce the fuel cell losses related to the crossover of un-oxidised methanol through the membrane and prevent its subsequent reaction at the cathode. The inorganic filler used within this study was mordenite that has Si/Al ratio of 5 and by incorporating this into the barrier layer a superior DMFC performance has been achieved in comparison to a standard MEA featuring a Nafion 117 membrane. The voltage, current density and power density used as a measure of DMFC performance under a range of methanol molarities (1M-4M) and cell temperatures (40°C-70°C) have been taken for both the novel and standard MEA. Linear sweep voltammetry (LSV) and AC impedance spectroscopy (ACIS) were used to give some insight into what was occurring within the MEA with regards to methanol crossover current and the proton conductivity within the DMFC. To obtain the best possible DMFC performance a range of mordenite loadings from 0wt%1.0wt% were utilised and an optimum loading of 0.5wt% was reached. MEA which featured mordenite that had undergone ion exchange into a protonated form (from the sodium form) and had a silane functional group (glycidoxypropyltrimethoxysilane) grafted onto the surface, gave DMFC performances that were as much as 50% better than the standard. The highest power density obtained with this MEA was 43.6mW/cm-2 compared to the 35mW/cm-2 obtained using the standard. Values obtained for the methanol crossover current and proton conductivity under working DMFC operating conditions showed that this novel MEA had as much as 16% lower methanol permeability compared to the standard combined with comparable proton conductivity when using a 1M methanol feed. The durability of a novel MEA featuring the 0.5wt% functionalised H-mordenite composite barrier layer was tested in the DMFC and compared to a standard MEA at a constant current of 50mA/cm-2 over 100 hours. The cell potential fell by 0.1mV/h in comparison to a 0.23mV/h loss observed with the standard. The work reported within this study aims to show that by incorporating a thin Nafion/mordenite composite layer at the anode/membrane interface within an MEA will result in improvements in DMFC performance. The development of this technology has led to the application for a patent due to the potential for the commercial development of DMFC using this novel approach.
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ANDREA, VINICIUS. "Estudos de durabilidade de conjuntos eletrodo-membrana-eletrodo (MEAs) produzidos por impressão à tela para uso em células a combustível do tipo PEM." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10514.
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Made available in DSpace on 2014-10-09T12:41:22Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:06:21Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Tse, Laam Angela. "Membrane Electrode Assembly (MEA) Design for Power Density Enhancement of Direct Methanol Fuel Cells (DMFCs)." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11522.
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Micro-direct methanol fuel cells (micro-DMFC) can be the power supply solution for the next generation of handheld devices. The applications of the micro-DMFCs require them to have high compactness, high performance, light weight, and long life. The major goal of this research project is to enhance the volumetric power density of direct methanol fuel cells (DMFCs). A performance roadmap has been formulated and showed that patterning the planar membrane electrode assembly (MEA) to 2-D and 3-D corrugated manifolds can greatly increase the power generation with very modest overall volume increases. In this project, different manufacturing processes for patterning MEAs with corrugations have been investigated. A folding process was selected to form 2D triangular corrugations on MEAs for experimental validations of the performance prediction. The experimental results show that the volumetric power densities of the corrugated MEAs have improved by about 25% compared to the planar MEAs, which is lower than the expected performance enhancement. ABAQUS software was used to simulate the manufacturing process and identify the causes of deformations during manufacture. Experimental analysis methods like impedance analysis and 4 point-probes were used to quantify the performance loss and microstructure alteration during the forming process. A model was proposed to relate the expected performance of corrugated MEAs to manufacturing process variables. Finally, different stacking configurations and issues related to cell stacking for corrugated MEAs are also investigated.
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Dreyer, Herbert Morgan Evans. "A comparison of catalyst application techniques for membrane electrode assemblies in SO2 depolarized electrolysers / Dreyer H.M.E." Thesis, North-West University, 2011. http://hdl.handle.net/10394/7373.
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Hydrogen production via the electrolysis of water has gained a lot of attention in the last couple of years. Research related to electrolysers is mostly aimed towards decreasing the noble–metal catalyst content.
In this study the presently used catalyst application techniques were reviewed and critically examined to find commercially applicable and effective methods. Selected methods were then practically applied to determine their feasibility and to gain “know–how” related to the practical application of these techniques. The selected techniques were the hand paint, inkjet print, screen print and spray paint techniques.
Meaningful comparisons were made between the methods in terms of parameters such as practicality, waste of catalyst and microstructure. The results point out that the hand paint and spray paint methods are feasible methods although there are improvements to be made.
The hand paint method was improved by applying a carbon micro porous layer to the gas diffusion layer before the painting is carried out. The addition of the carbon layer reduced the soaking of the catalyst–containing ink through the gas diffusion layer.
A method not initially investigated was identified an evaluated and showed promising results in lowering the mass of catalyst applied. This method comprised of sputtering a layer of catalyst material onto a prepared gas diffusion layer.
It also came to light from the results that electrodes, and therefore membrane electrode assemblies, can be produced at a much lower cost than the commercial available membrane electrode assemblies.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012.
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Chailuecha, Chatkaew. "Methanol barrier layers : modified membrane electrode assemblies for the improvement of direct methanol fuel cell performance." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/methanol-barrier-layer(2c347cde-c81d-4024-90b0-a62e1bf94918).html.
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The direct methanol fuel cell (DMFC) performance has been improved via two approaches. The first approach reduces methanol crossover in the membrane electrode assemblies (MEAs) by incorporating a methanol barrier layer onto an anode electrode of the MEA. The second approach increases the triple phase boundaries via the modified morphology of catalyst layers in the MEA. Methanol barrier layers containing a composite layer of Nafion/mordenite (MOR), Nafion/zeolite Y (ZY), Nafion/montmorillonite (MMT) or Nafion/titanate (TN) were distributed onto the anode of an MEA. The performance of these MEAs were tested in a single cell DMFC for temperatures between 30-80 °C and methanol concentrations of 1 M-4 M and compared with a standard MEA to identify changes in power output. At 2 M methanol concentration and 80 °C, the MEAs featuring with Nafion/0.50 wt% MMT and Nafion/0.50 wt% TN delivered higher power densities, 19.76% and 26.60%, respectively, than that of standard MEA. The catalyst morphology has been adjusted by the dilution of catalyst ink to prevent an agglomeration of catalyst particles, resulting in the increased triple phase boundaries which are the phases for electrochemical reactions and for the transportation of electron and proton products. The new-standard MEA presented the best improvement in power density of 81.15% over the conventional counterpart at 80 °C and 2 M methanol concentration. This modified procedure was further utilised for MEAs fabrication. Further investigation has been carried out by the selected Nafion/MMT layer. The MMT loading of 0.25 wt%-1.00 wt% were incorporated onto the barrier layer where the Nafion/0.25 wt% MMT layer illustrated the best performance. This MEA attributed the highest power density of 69.14 mW cm⁻² which is 2.76% higher than 67.23 mW cm⁻² of the new-standard MEA at 80 °C and 2 M methanol concentration. The best improvement in power density, 27.09%, was obtained at low temperature and low methanol concentration of 30 °C and 1 M. The power density was 25.30 mW cm⁻² when compare to 19.91 mW cm⁻² of the new-standard MEA. These results suggest that the methanol barrier layer and the modified morphology of catalyst layer accomplish the aim of improving DMFC performance.
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Mohseninia, Arezou [Verfasser]. "Modifications of membrane electrode assemblies to understand and improve water management and performance in PEM fuel cells / Arezou Mohseninia." Ulm : Universität Ulm, 2021. http://d-nb.info/1232323845/34.
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Talukdar, Krishan [Verfasser], and K. Andreas [Akademischer Betreuer] Friedrich. "Development and characterization of low Pt-loaded membrane electrode assemblies with focus on performance and durability / Krishan Talukdar ; Betreuer: K. Andreas Friedrich." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1226762492/34.
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Huang, Wei-Chieh, and 黃威傑. "Catalyst layer structures of PEMFC membrane electrode assemblies." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/06674145030388869653.
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碩士元智大學
化學工程與材料科學學系
98
This thesis Nafion-212 was used to prepare membrane electrode assemblies(MEAs) consisting of various catalyst layer structures. Four different catalyst layer structural MEAs were prepared, including : (a) traditional GDL- Pt/C - membrane - Pt/C - GDL five-layers structure ; (b) GDL - P t- Pt/C -membrane - Pt/C - Pt-GDL seven-layers structure ; (c) GDL - Pt/C - Pt - membrane - Pt - Pt/C - GDL seven-layers structure ; (d) GDL - Pt - Pt/C - Pt - membrane - Pt - Pt/C - Pt - GDL nine-layers structure. The advantage of traditional catalyst layer MEA is easy and time-saving for preparation. But the high thickness of the electrode caused high catalyst resistance and low utilization of catalyst leading to low fuel cell performance. In order to reduce the thickness of catalyst and lower the resistance of catalyst layer, MEAs with low catalyst layer thickness, i.e. structures (b), (c) and (d), were prepared. The PEMFC testing results showed the fuel cell performance decreased in the sequence of : structure d > c > b > a.
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Tsai, Li-Duan, and 蔡麗端. "Proton conductive composite membranes and related membrane electrode assembly (MEAs) for fuel cell applications." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/49277048815811611446.
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博士國立交通大學
應用化學系碩博士班
101
Abstract (in English) In this study, we focus on the modification of materials and their application on fuel cells. 1. Poly(ethylene glycol) modified activated carbon for high performance proton exchange membrane fuel cells A high water retention membrane is developed by co-assembling poly(ethylene glycol) (PEG) grafted activated carbon (AC-PEG) with Nafion. The AC-PEG is prepared via a sol-gel process. The use of PEG as a transporting medium in AC-PEG shows a largely improved water retention ability, a higher proton conductivity and a reduced swelling ratio, making it well suited for proton exchange membrane fuel cells (PEMFCs). Further, the composite membranes show improved mechanical properties at high temperature, thus ensuring the structural stability of membranes during the fuel cell operation. Compositional optimized AC-PEG/Nafion composite membrane (15 wt% compared to Nafion) demonstrates a better performance than the commercially available counterpart, Nafion 212, in fuel cell measurements. To identify the key factor of the improved performance, current interrupt technique is used to quantitatively verify the changes of resistance under different relative humidity environment. 2. Sulfonated graphene oxide/Nafion composite membranes with low methanol permeability An easy and effective method for producing low methanol-crossover membranes is developed by dispersing sulfonated graphene oxide (SGO) into a Nafion matrix. A SGO/Nafion mixture with low SGO content exhibits unique viscosity behaviour and allows for better SGO dispersion within the Nafion. After film casting, the composite membranes show lower methanol and water uptakes, a reduced swelling ratio, improved proton conductivity in low relative humidity, and extremely high methanol selectivity, which can be implemented in direct methanol fuel cells (DMFCs). 3. Novel Bilayer Composite Membrane for Passive Direct Methanol Fuel Cells with Pure Methanol The bilayer composite membrane composed of the sulfonated graphene oxide (SGO)/Nafion and sulfonated activated carbon (SAC)/Nafion composite membrane is designed and prepared by repeatedly bar-coating. With the carefully chosen of solvent, the bilayer composite membrane has shown identical thickness on SEM observation. The SGO/Nafion side has a low methanol permeability ascribed to the unique selectivity of the SGO. Moreover, the SAC side has good water retention which can facilitate the back diffusion water produced by the cathode. The unique design of composite membranes confers low methanol crossover and high proton conductivity at the same time. The bilayer composite membrane shows better power density than Nafion 212 and Nafion 115 and the performance monitored for 24h to ensure the stable power density and the durability of the membrane.
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Wang, Hsin-Chun, and 王信君. "Fabrication and Evaluation of Membrane Electrode Assemblies for Fuel Cells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/00471927352223249178.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
98
The effect of catalyst ink concentration and various methods of coating catalyst ink on carbon paper upon the gas diffusion electrode (GDE) properties of fuel cell were investigated. The ratio of Isopropanol to H2O in solvent blends was 1.5 to 1 by weight. The composition of Pt-C/Nafion/solvent in catalyst ink, were 2/20/320、2/20/200、2/20/150、2/20/100 (g/g/g), respectively. The coating methods including coating catalyst on carbon paper with a brush, a comma coating machine and an ultrasonic spray system were carried out. The GDEs were characterized by Field-emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), thermogravimetric analysis (TGA), and cyclic voltammetry (CV) measurements. From EDS images, the electrode made of carbon paper with Pt coating was fabricated by ultrasonic spray method and the Pt particles are spread onto the surface of carbon paper. However, the Pt particles permeated into the carbon paper for the electrodes which were fabricated by the other two coating methods. The TGA results showed the Pt content in electrode which was fabricated by ultrasonic spray method had a higher value than the others. From CV analysis, electrochemical active surface area (ESA) was in the order of ultrasonic spray > brush coating > comma coating. According to the above results, the preparation of GDE with ultrasonic spray is a more proper coating method for the electrode preparation for fuel cell.
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Koraishy, Babar Masood. "Continuous manufacturing of direct methanol fuel cell membrane electrode assemblies." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2554.
Full textAbstract:
Direct Methanol Fuel Cells (DMFC) provide an exciting alternative to current energy storage technologies for powering small portable electronic devices. For applications with sufficiently long durations of continuous operation, DMFC’s offer higher energy density, the ability to be refueled instead of recharged, and easier fuel handling and storage than devices that operate with hydrogen. At present, materials and manufacturing challenges impede performance and have prevented the entry of these devices to the marketplace. Higher-performing, cost-effective materials and efficient manufacturing processes are needed to enable the commercialization of DMFC.
In a DMFC, the methanol-rich fuel stream and the oxidant are isolated from one another by a proton-conducting and electrically insulating membrane. Catalysts in the electrodes on either side of the Membrane Electrode Assembly (MEA) promote the two simultaneous half-reactions which allow the chemical energy carried in the fuel and oxidant to be converted directly into electricity. The goal of this research effort is to develop a continuous manufacturing process for the fabrication of effective DMFC MEAs.
Based on the geometry of the electrode and materials used in the MEA, we propose a roll-to-roll process in which electrodes are coated onto a suitable substrate and subsequently assembled to form a MEA. Appropriate coating methods for electrode fabrication were identified by evaluating the requirements of continuous manufacturing processes; an appropriate set of these processes was then reduced to practice on a custom-designed flexible test bed designed explicitly for this project. After establishing baseline capabilities for several candidate methods, a spraying process was selected and a continuous manufacturing process concept was proposed. Finally, key control parameters of the spraying process were identified and their influence tested on actual MEAs to define optimal operating conditions.text
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CHIEH, HSU JEN, and 徐人傑. "On the Study of Dry Layer Preparation of Membrane Electrode Assemblies." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/34360117095061487529.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
92
This research focuses on the study of electricity generation center of proton exchange membrane fuel cell — the development of low platinum content dry process for Membrane Electrode Assembly (MEA). The catalyst of this process is not prepared from any organic solvent; therefore the time of preparation can be drastically reduced. Only the suction method is used to produce the electrodes. Experimental analysis and observation is performed on the characteristics of attraction force to the micro-structure of catalyst layer. Pressure setting of the experiment is obtained by using the self-made lab equipment. To reduce the influence from other factors during the manufacturing process, the selection of material for the exchange membrane electrode assembly from pre-processing, including cleaning of exchange membrane, and carbon cloth filtering processing, to post-processing, including hot pressure temperature and pressure control, as well as the choices of other parameters are determined through repeated experiments. This research uses Nafion 117 as the main body for producing membrane electrode assembly (MFA). The amount of platinum catalyst is controlled under 0.4 mg/ cm2. From the result of the experiment, it can be seen that the selection of suction force can affect the alignment of carbon platinum catalyst power and further lead to the difference in performance. However, the establishment of more accurate attraction force and performance relationship, and the optimum alignment of the microstructure of each layer for the exchange membrane resistor array is depending on future experiments. It is also hoped that a faster preparation procedure and a low cost fuel battery can be obtained so that the fuel battery can be more commercialized and become popular.
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Lai, Wen-Jeng, and 賴文政. "Performance Studies and Analysis of Catalyst Coated Membrane Method within Membrane Electrode Assemblies of PEMFC." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/38347415219001583253.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
96
This study focuses on the key part of Membrane Electrode Assembly (MEA) - proton exchange membrane fuel cell, and also includes the component of the MEA; the manufacture method of the MEA and the test results. In this work, MEA were fabricated by catalyst coated membrane (CCM) method, the catalyst (Pt/C) was applied on the surface of membrane directly to improve the continuity of interface between the catalyst film and the membrane. To derive the best performance of MEA, the flow patterm needs to be verified by CFD software-FLUENT, the single serpentine type flow channel (channel width 1.6mm、deeth 1mm, rib width 1.35 mm) was chosen for the following tests. This study started from finding the way to improve the single-cell performance, according to the method of applying catalyst, amount of isopropyl alcohol, drying temperature, the presence of dry Nafion film and the relative humidity of inlet fuel. The results were verified by checking the overpotential curve (I-V curve), scanning electron microscope, cyclic voltammetry. Nafion212 was adopted as the membrane electrode assembly with an active area of 50 mm x 50 mm. The best performance of the home-made MEA was 0.29 W/cm2 at 0.64 V with power density of 450.12 mA/cm2, corresponding to the conditions as: Pt loading at cathode and anode side are both 0.6 mg/cm2, hydrogen and oxygen were at the same gas flow rate of 0.25 SLM, cell temperature at 70℃, and hydrogen andoxygen humidification temperature at 70℃. This study also introduced the design and manufacturing methods of a fuel cell stack. In this work, two cells were used to make a stack. The best output power was 0.53 W/cm2 at 1.2 V and 444.84 mA/cm2. The manufacture procedures in this study were different from others. We can find that some methods would improve the MEA performance. If we can make the procedure more general, or use less amount of material, then can reduce the fuel cell cost dramatically.
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Yang, Tien-Fu, and 楊添福. "The research of high performance proton exchange membrane fuel cell electrode assemblies." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/42451198796449757478.
Full textAbstract:
博士國立中央大學
機械工程學系
102
The conventional 5-layer membrane electrode assembly (MEA) consists of a proton exchange membrane (PEM) locating at its center, two layers of Pt/C-40 (Pt content 40 wt%) locating next on both surfaces of PEM, and two gas diffusion layers (GDL) locating next on the outer surfaces of Pt/C layers (structure-a MEA). In this paper, we report three modified MEAs consisting of Pt/C-40 (Pt content 40 wt%) and Pt/C-80 (Pt content 80 wt%) catalysts. These are: (1) 7-layer structure-b MEA with a thin Pt/C-80 layer locating between Pt/C-40 layer and PEM; (2) 7-layer structure-c MEA with a thin Pt/C-80 layer locating between Pt/C-40 layer and GDL; and (3) 5-layer structure-d MEA with Pt/C-40 and Pt/C-80 mixing homogeneously and locating between PEM and GDL. Under a fixed Pt loading, we find structure-b, -c, and -d MEAs with 20 ~ 40 wt% Pt contributed from Pt/C-80 have better fuel cell performance than structure-a MEA consisting only of Pt/C-40. The reasons are attributed to the better feasibility for H2/O2 gas to reach Pt particles and lower proton transport resistance in catalyst layers of the modified MEAs than structure-a MEA. On the other hand, a two-dimensional, multi-phase, non-isothermal numerical model was used to investigate the effect of the high performance catalyst layer design. Simulation results show that substituting part of the Pt/C 40 wt% with Pt/C 80 wt% increases the cell performance. It was found that factors including proton conductivity, open circuit voltage and sub-layer thickness have a significant impact on overall cell performance. Different water distribution for different MEA designs was also observed in the simulation results. More liquid water accumulation inside the MEA is seen when the Pt/C 80 wt% sub-layer is next to the gas diffusion layer (structure-c MEA).
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Felix, Cecil. "Development of membrane electrode assemblies based on electrophoretic deposition for high temperature polymer electrolyte membrane fuel cell applications." 2013. http://hdl.handle.net/11394/3550.
Full textAbstract:
Philosophiae Doctor - PhDHigh Temperature Polymer Electrolyte Membrane Fuel Cells (HT-PEMFC) have received renewed interest in recent years due to its inherent advantages associated with the limitations faced by Low Temperature Polymer Electrolyte Membrane Fuel Cells (LT-PEMFC). The high Pt loadings required for PEMFCs have significantly hindered its commercialisation. Electrophoretic Deposition (EPD) is a promising route to reduce the noble metal loading. EPD is a method in which charged colloidal particles are deposited onto a target substrate under the force of an externally applied electric field. To effectively study the EPD method, the methodology of this study was divided into two parts: (i) the EPD method was studied via known empirical methods to fabricate, test and characterise MEAs suitable for HT-PEMFCs. The feasibility of the EPD method was determined by comparing the performance of the fabricated EPD MEAs to MEAs fabricated via spraying methods, and (ii) due to the promising results obtained in part (i) of the methodology, a theoretical model was developed to obtain a deep understanding about nature of the interactions between the Pt/C particles in a colloidal suspension. The theoretical model will serve as a foundation for future studies. In part (i) of the methodology, the Pt/C particles were studied in organic solutions (i.e. Isopropyl Alcohol, IPA) via the Zetasizer Nano ZS instrument under various salt (NaCl) concentrations and pH conditions while introducing polymeric surfactants, i.e. Nafion® ionomer and Polytetrafluoroethylene (PTFE) to the suspension. The optimum catalyst suspensions were selected to fabricate GDEs via the EPD method. Physical characterisations revealed that the EPD GDEs exhibited cracked morphology with high porosity. Electrochemical characterisations revealed that the EPD MEA showed significantly better performance (i.e. 73% higher peak power) compared to the hand vi sprayed MEA due to lower charge transfer and mass transport resistance at high current densities. Compared to the ultrasonically sprayed MEA, the EPD MEA exhibited a peak power increase of ~12% at a slightly lower Pt loading (i.e. ~4 wt%). A comparative study between the Nafion® ionomer and PTFE in the CLs of two EPD MEAs revealed superior performance for the EPD MEA with the PTFE in the CLs. Part (ii) of the methodology deals with the electrical interfacial properties of the aqueous Pt/C suspension. The study consists of two sets of measurements (i.e. electrophoretic and coagulation dynamic studies) conducted for different electrolyte compositions. A theoretical background on determining the interfacial potential and charge from electrophoretic and coagulation dynamic measurements are provided. Detailed statements of the Standard Electrokinetic and Derjaguin, Landau, Vervey and Overbeek Models are given in the forms that are capable of addressing electrophoresis and the interaction of particles for an arbitrary ratio of the particle to Debye radius, interfacial potential and electrolyte composition. The obtained experimental data were processed by using numerical algorithms based on the formulated models for obtaining the interfacial potential and charge. While analysing the dependencies of interfacial potential and charge on the electrolyte compositions charge, conclusions were made regarding the mechanisms of charge formation. It was established that the behaviour of system stability is in qualitative agreement with the results computed from the electrophoretic data. The verification of quantitative applicability of the employed models was conducted by calculating the Hamaker constant from the experimental data. It was proposed how to explain the observed variations of the predicted Hamaker constant and its unusually high value.
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Cheng, Shih-Tse, and 鄭世澤. "Experimental Studies of Dry Layer Preparation in Suction Method of PEMFC Membrane Electrode Assemblies." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/55040995174821793338.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
92
As production cost will be one of the main challenges for commercialization of fuel cells, a new approach to MEA production for PEMFC has been considered. Electrodes are produced by a new dry layer preparation method in a suction procedure and co-operated with a particle diffusion design. All structures in MEA of this process were prepared without any organic solvent; therefore the time of preparation procedures can be drastically reduced. MEA’s sandwiched structures were constituted by many materials- diffusion substrate, carbon powder, PTFE, catalyst, ion conductor, Nafion membrane. A slight difference in the quantity and character of each material will cause a apparent influence on the performance of MEAs. In gas diffusion backing layer the content of PTFE is about 40wt% and with high surface-area Ketjen Black EC600 at an optimized thickness, show better performance compared with Acetylene black and Ketjen Black EC300 carbon in backing layer. In catalyst layer preparation the suction pressure and the flow rate of nitrogen affects directly in the performance of MEA. When the pressure at 12 cm water height and the nitrogen flow rate at 4L/min show an obvious higher power density 0.21 W/cm2. The Pt loading is controlled between 0.4~0.5mg/cm2. This new dry layer preparation method with suction and powder diffusion procedure offers a simple, rapid and reliable method for MEA’s production. A faster and a low cost objective can be achieved.
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Chang, Wei-Ming, and 張偉銘. "Perfluorosulfonic acid proton exchange membrane electrode assemblies catalyst layer structure designs and fuel cells performances." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/91972428495761978987.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
97
This thesis used methanol/H2O (4/1 g/g) and ethanol/H2O (4/1 g/g) mixed solutions to dissolve Nafion solid respectively. Nafion membranes were prepared by ” solutions casting ”；and isopropanol/H2O (4/1 g/g) mixed solution, N,N’-dimethylacetamide (DMAc) and N,N’-dimethyl -formamide (DMF) solvent were mixed Nafion solid, Pt catalyst and Pt-C (Pt on carbon powder support) to preparing catalyst ink solution. The above-mentioned Nafion membranes and catalyst ink solution were prepared for membrane electrode assemblies (MEA). Membrane electrode assemblies structures included, (a) convention GDL-Pt/C -membrane-Pt/C-GDL five-layers structure, (b) GDL-Pt-Pt/C-membrane -Pt/C-Pt-GDL seven-layers structure, (c) GDL-Pt/C-Pt-membrane-Pt -Pt/C-GDL seven- layers structure, (d) GDL-Pt-Pt/C-Pt-membrane-Pt- Pt/C-Pt-GDL nine- layers structure. The MEA single cell i-V curve data, and impedance data showed that proton conduction of Nafion membrane which were prepared by methanol/H2O and ethanol/H2O solutions casting was lower than Nafion-212 membrane which were prepared by Du Pont Co..The MEA of structures (c) and (d) had much better fuel cells performances than structures (a) and (b).
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Karimi, Shahram. "A Novel Process for Fabricating Membrane-electrode Assemblies with Low Platinum Loading for Use in Proton Exchange Membrane Fuel Cells." Thesis, 2011. http://hdl.handle.net/1807/29769.
Full textAbstract:
A novel method based on pulse current electrodeposition (PCE) employing four different waveforms was developed and utilized for fabricating membrane-electrode assemblies (MEAs) with low platinum loading for use in low-temperature proton exchange membrane fuel cells. It was found that both peak deposition current density and duty cycle control the nucleation rate and the growth of platinum crystallites. Based on the combination of parameters used in this study, the optimum conditions for PCE were found to be a peak deposition current density of 400 mA cm-2, a duty cycle of 4%, and a pulse generated and delivered in the microsecond range utilizing a ramp-down waveform. MEAs prepared by PCE using the ramp-down waveform show performance comparable with commercial MEAs that employ ten times the loading of platinum catalyst. The thickness of the pulse electrodeposited catalyst layer is about 5-7 µm, which is ten times thinner than that of commercial state-of-the-art electrodes.
MEAs prepared by PCE outperformed commercial MEAs when subjected to a series of steady-state and transient lifetime tests. In steady-state lifetime tests, the average cell voltage over a 3000-h period at a constant current density of 619 mA cm-2 for the in-house and the state-of-the-art MEAs were 564 mV and 505 mV, respectively. In addition, the influence of substrate and carbon powder type, hydrophobic polymer content in the gas diffusion layer, microporous layer loading, and the through-plane gas permeability of different gas diffusion layers on fuel cell performance were investigated and optimized.
Finally, two mathematical models based on the microhardness model developed by Molina et al. [J. Molina, B. A. Hoyos, Electrochim. Acta, 54 (2009) 1784-1790] and Milchev [A. Milchev, “Electrocrystallization: Fundamentals of Nucleation And Growth” 2002, Kluwer Academic Publishers, 189-215] were refined and further developed, one based on pure diffusion control and another based on joint diffusion, ohmic and charge transfer control developed by Milchev [A. Milchev, J. Electroanal. Chem., 312 (1991) 267-275 & A. Milchev, Electrochim. Acta, 37 (12) (1992) 2229-2232]. Experimental results validated the above models and a strong correlation between the microhardness and the particle size of the deposited layer was established.
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Lin, Wan-Sin, and 林婉歆. "Pt-C/PBI/DMAc solutions properties and preparation of membrane electrode assemblies for high temperature PEMFCs." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/22060763981605125791.
Full textAbstract:
碩士元智大學
先進能源研究所
98
In this study, using static light scattering (SLS), gel permeation chromatography (GPC) and cyclic voltammetry(CV), we reported the dilute solutions properties of polybenzimidazole (PBI) in N,N’-dimethylacetamide (DMAc) solutions blended with LiCl and preparation of Pt-C/PBI membrane electrodes assemblies for high temperature fuel cells. Our GPC experimental results showed weight-average molecular weight (Mw) is 1.13×105 g/mol (PBI-113) and 2.53×105 g/mol (PBI-253) of PBIs synthesiszed in our lab. An ultrasonic coating made of electrode catalyst slurry solution, a cyclic voltammetry (CV) was used to study the electrochemical properties of electrodes prepared form various Pt-C/PBI/DMAc/LiCl solutions. We found the ekectrode prepated from Pt-C/PBI/DMAc/LiCl solution with a [LiCl]/[PBI] wt ratio of 1/1 and a [PBI] / [Pt-C + PBI] wt ratio of 10 wt% had a higher Pt surface activity area. The 160℃PEMFC unit cell test showed the membrane electrode assembly (MEA) prepared from a PBI with catalyst layes prepared a solution consisting of [PBI]/[Pt-C+PBI] = 5 wt% and [LiCl]/[PBI] = 1/1 by wt had a best fuel cell performance. The 228 hr long time continuous PEMFC unit cell test had been carried out at 160℃ and I = 200 mA/cm2. The experimental result showed a voltage decay rated of ~1.34×10-4 V/hr.
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Hoek, Henry Howell. "MEA and GDE manufacture for electrolytic membrane characterisation / Henry Howell Hoek." Thesis, 2013. http://hdl.handle.net/10394/11723.
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In recent years an emphasis has been placed on the development of alternative and clean energy sources to reduce the global use of fossil fuels. One of these alternatives entails the use of H2 as an energy carrier, which can be obtained amongst others using thermochemical processes, for example the hybrid sulphur process (HyS). The HyS process is based on the thermal decomposition of sulphuric acid into water, sulphur dioxide and oxygen. The subsequent chemical conversion of the sulphur dioxide saturated water back to sulphuric acid and hydrogen is achieved in an electrolyser using a platinum coated proton exchange membrane. This depolarised electrolysis requires a theoretical voltage of only 0.158 V compared to water electrolysis requiring approximately 1.23 V. One of the steps in the development of this technology at the North-West University, entailed the establishment of the platinum coating technology which entailed two steps; firstly using newly obtained equipment to manufacture the membrane electro catalyst assemblies (MEA’s) and gas diffusion electrodes (GDE’s) and secondly to test these MEA’s and GDE’s using sulphur dioxide depolarized electrolysis by comparing the manufactured MEA’s and GDE’s to commercially available MEA’s and GDE’s.
Different MEA’s and GDE’s were manufactured using both a screen printing (for the microporous layer deposition) and a spraying technique. The catalyst loadings were varied as well as the type and thickness of the proton exchange membranes used. The proton exchange membranes that were included in this study were Nafion 117®, sPSU-PBIOO and SfS-PBIOO membranes whereas the gas diffusion layer consisted of carbon paper with varying thicknesses (EC-TP01-030 – 0.11 mm and EC-TP01-060 – 0.19mm). MEA and GDE were prepared by first preparing an ink that was used both for MEA and GDE spraying. The MEA’s were prepared by spraying various catalyst coatings onto the proton exchange membranes containing 0.3, 0.6 and 0.9 mg/cm2 platinum respectively. The GDE’s were first coated by a micro porous carbon layer using the screen printing technique in order to attain a suitable surface for catalyst deposition. Using the spraying technique GDE’s containing 0.3, 0.6, 0.9 mg/cm2 platinum were prepared. After SEM analysis, the MEA’s and GDE’s performance was measured using SO2 depolarized electrolysis. From the electrolysis experiments, the voltage vs. current density generated during operation, the hydrogen production, the sulphuric acid generation and the hydrogen production efficiency was obtained.
From the results it became clear that while the catalyst loading had little effect on performance there were a number of factors that did have a significant influence. These included the type of proton exchange membrane, the membrane thickness and whether the catalyst coating was applied to the proton exchange membrane (MEA) or to the gas diffusion layer (GDE). During SO2 depolarized electrolysis VI curves were generated which gave an indication of the performance of the GDE’s and MEA’s. The best preforming GDE was GDE-3 (0.46V @ 320 mA/cm2), which included a GDE EC-TP01-060, while the best preforming MEA’s were NAF-4 (0.69V @ 320mA/cm2) consisting of a Nafion117 based MEA and PBI-1 (0.43V @ 320mA/cm2) made from a sPSU-PBIOO blended membrane. During hydrogen production it became clear that the GDE’s produced the most hydrogen (best was GDE-02 a in house manufactured GDE yielding 67.3 mL/min @ 0.8V), followed by the Nafion® MEA’s (best was NAF-4 a commercial MEA yielding 57.61 mL/min @ 0.74V) and the PBI based MEA’s. , (best was PBI-2 with 67.11 mL/min @ 0.88V). Due to the small amounts of acid produced and the SO2 crossover, a significant error margin was observed when measuring the amount of sulphuric acid produced. Nonetheless, a direct correlation could still be seen between the acid and the hydrogen production as had been expected from literature. The highest sulphuric acid concentrations produced using the tested GDE’s and MEA’s from this study were the in-house manufactured GDE-01 (3.572mol/L @ 0.8V), the commercial NAF-4 (4.456mol/L @ 0.64V) and the in-house manufactured PBI-2 (3.344mol/L @ 0.8V). The overall efficiency of the GDE’s were similar, ranging from less than 10% at low voltages (± 0.6V) increasing to approximately 60% at ± 0.8V. For the MEA’s larger variation was observed with NAF-4 reaching efficiencies of nearly 80% at 0.7V.
In terms of consistency of performance it was shown that the Nafion MEA’s preformed most consistently followed by the GDE’s and lastly the PBI based MEA’s which for the PBI based membranes can probably be ascribed to the significant difference in thickness of the thin PBI vs. the Nafion based membranes. In summary the study has shown the results between the commercially obtained and the in-house manufactured GDE’s and MEA’s were comparable confirming the suitability of the coating techniques evaluated in this study.MSc (Chemistry), North-West University, Potchefstroom Campus, 2014
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Chen, Po-Chung, and 陳柏仲. "Electrochemical Assessment of the Degradation of Membrane Electrode Assemblies Prepared with Electrodes made by Filter-Transfer Method." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/11144110933873318668.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
95
Fuel cell is an electrochemical device that transforms chemical energy of the fuel used to electricity at high efficiency. The durability of polymer electrolyte membrane fuel cells (PEMFCs) is a major barrier to the commercialization of these systems. This work deals with fundamental electrochemical aspects of polymer electrolyte fuel cell research. Various electrochemical analyses were applied to assess and understand the degradation mechanisms for MEA samples prepared with electrodes made by filter-transfer methods. This study focuses on degradation rate versus transfer ratio or filtration time used in electrode preparation. At an operating condition of 50% humidity and a cell temperature of 70℃, polarization curve, electrochemical impedance spectroscopy (EIS), and Cyclic Voltammetry (CV) measurements were performed before and after a 100-hour continuous operation. The results showed that the MEA with the highest transfer ratio or a 95-minute filtration time has the highest Pt utilization, and decay or degradation rate, but not the highest resistances overall. In other words, a higher transfer ratio or Pt utilization does not necessarily mean lower decay rate or better durability. Distinctly different oscillatory behaviors were observed for all the four MEA samples made with electrodes of different transfer ratio studied here.
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Lin, Yi Cheng, and 林怡成. "The Effect of Gas Diffusion Layers and Membrane Electrode Assemblies Made In-House on the Performance of Proton Exchange Membrane Fuel Cells." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/30080852450996902584.
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Jao, Ting-Chu, and 饒庭竹. "The accelerated degradation test evaluation and degradation mechanism study of the membrane electrode assemblies with PTFE/Nafion and Nafion membranes for proton exchange membrane fuel cell cell." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/04693466809864083813.
Full textAbstract:
博士元智大學
機械工程學系
99
Nafion was used in the commercial membrane electrode assemblies (MEAs) for proton exchange fuel cells (PEMFCs). Gore invented the PTFE/Nafion composition membrane. The PTFE/Nafion composition membrane has the advantages of low cost, high mechanical strength, low swelling and high durability in high temperature. This study fabricated the PTFE/Nafion MEA from the composition of the PTFE/Nafion membrane. The character of PTFE/Nafion MEA and the accelerated degradation test were analyzed using in-situ electrochemical methods. This study used spray coating and ink drop coating to compare the effect of different fabrication methods on MEAs. During the test of operation parameters, the water content of the membrane was found to affect the hydrogen crossover and consequently affect the open circuit voltage of PTFE/Nafion MEA. This study proposed the mechanism of unique character for PTFE/Nafion MEA. Experiments were conducted on the Nafion MEA and PTFE/Nafion MEA using the accelerated degradation test (ADT). Only the PTFE/Nafion MEA showed increased internal resistance under ADT.