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Book Factors Influencing Electrochemical Properties and Performance of Hydrocarbon Based Ionomer PEMFC Catalyst Layers

Download or read book Factors Influencing Electrochemical Properties and Performance of Hydrocarbon Based Ionomer PEMFC Catalyst Layers written by Toby Duncan Astill and published by . This book was released on 2008 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigated the properties of catalyst layers for proton exchange membrane fuel cells (PEMFC) that contained sulfonated poly(ether ether ketone) (SPEEK). A series of SPEEK polymers were prepared with varying ion exchange capacity (IEC) to test their oxygen mass transport properties, electrochemical kinetic parameters, proton conductivity, and water sorption characteristics. A simple method to fabricate catalyst layers containing SPEEK and polytetrafluoroethylene (PTFE) was developed. Catalyst layers were analyzed using scanning electron microscopy (SEM), mercury porosimetry and contact angle determination. Electrochemical characterization in an operating fuel cell was performed using current-potential polarization, cyclic voltammetry, and electrochemical impedance spectroscopy. Electrochemical oxygen reduction in SPEEK membranes was examined in a solid-state electrochemical cell, which allowed determination of oxygen mass transport properties and kinetic parameters. The oxygen diffusion coefficient and permeability was found to increase with increasing ion exchange capacity (IEC), while the solubility of oxygen correspondingly decreased, these trends are due to an increase in water content with increasing IEC. In comparison to perfluorinated electrolytes, such as Nafion®, SPEEK exhibited a lower permeability of oxygen due to a considerably lower solubility of oxygen. A decrease in fuel cell performance was observed when SPEEK was employed in the cathode catalyst layer as the proton conducting medium. The fuel cell current density showed a strong dependence on the method of fabrication of the catalyst layer and the content of SPEEK. Compared to Nafion®-based catalyst layers, SPEEK catalyst layers were found to suffer from low electrochemically active surface area (ESA) and low ionic conductivity. The weight content of SPEEK electrolyte was found to strongly influence the mass transport limited current density.

Book Polymer Electrolyte Fuel Cells

Download or read book Polymer Electrolyte Fuel Cells written by Michael Eikerling and published by CRC Press. This book was released on 2014-09-23 with total page 567 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides a systematic and profound account of scientific challenges in fuel cell research. The introductory chapters bring readers up to date on the urgency and implications of the global energy challenge, the prospects of electrochemical energy conversion technologies, and the thermodynamic and electrochemical principles underlying the op

Book On the Microstructure of PEM Fuel Cell Catalyst Layers

Download or read book On the Microstructure of PEM Fuel Cell Catalyst Layers written by Tatyana Sobolyeva and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, the microstructure of conventional catalyst layers of PEM fuel cells (PEMFCs) is investigated and correlated to the catalyst layer water sorption and retention properties, electrochemical properties and fuel cell performance. Two types of conventional carbon support were chosen for investigation: Ketjen Black and Vulcan XC-72. The microstructure of carbon supports, Pt/carbon catalyst powders, and 3-component, Pt/carbon/ionomer catalyst layers is studied in order to evaluate the effects of carbon support microstructure and Nafion ionomer loadings on the resultant CL microstructure. The microstructure of the carbon support is found to be a significant factor in the formation of the structure in the 3-component CLs serving as a rigid porous framework for distribution of Pt and ionomer. It is found that deposition of Pt particles on Ketjen Black significantly changes its porosity possibly by forming at the mouth of the support's micropores, thus affecting its effective microporosity, whereas Pt deposited on Vulcan XC-72 does not significantly affect the support's microporosity. The co-deposition of ionomer in the CL strongly influences porosity of the catalyst layer, especially for pore sizes

Book Fully Hydrocarbon Ionomer Catalyst Layers in Proton  and Anion exchange Membrane Fuel Cells

Download or read book Fully Hydrocarbon Ionomer Catalyst Layers in Proton and Anion exchange Membrane Fuel Cells written by Benjamin Britton and published by . This book was released on 2018 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure and morphology of fuel cell catalyst layers and concomitant system properties, particularly mass transport, were investigated through electrochemical and physical characterization techniques. Catalyst layers designed for proton-exchange membrane fuel cells (PEMFCs) incorporated a hydrocarbon ionomer (sP4c) soluble in low-boiling solvents. These were used to probe the property alterations effected by increasing ionomer coverage within the catalyst layer, and also to measure the impact an extremely small quantities (0.38 wt%) of a commonly employed high-boiling solvent, DMF, in the catalyst ink. High-boiling solvents are difficult to eliminate during electrode formation, and resultant solvent-annealed catalyst layers lost electrocatalytic surface area, resulting in markedly greater kinetic losses compared to catalyst layers formed without high-boiling solvents. Catalyst layers designed for anion-exchange membrane fuel cells (AEMFCs) incorporating hydrocarbon ionomer in the catalyst layer (FAA-3) requiring high-boiling solvent (NMP, 2.3 wt% of total solvent) were formed over a broad array of conditions. Catalyst layers formed slowly at high temperatures to drive off high-boiling solvent displayed significantly enhanced mesoporosity, relating to enhanced transport characteristics, over solvent-annealed analogues with low mesoporosity, despite comparable total volumes. The impacts of solvent annealing on AEMFC electrode properties and resultant achievable power density and degradation were disproportionate compared to the similar PEMFC study. A new methodology for fuel cell membrane-electrode assembly construction, direct membrane deposition (DMD), enables lower interfacial resistances and enhanced water transport for a given thickness of membrane. These are desired properties for both PEMFCs and AEMFCs. Initially developed with inkjet printers designed for single-cell biological printing applications, this method was adapted to spray-coating systems in order to address issues with fuel and electrical crossover, suitability for hydrocarbon ionomers, and scalability / large-scale reproducibility. A perfluorinated sulfonic acid ionomer reference material (Nafion D520) was employed for direct comparison to initial methods. Highly reproducible DMDs with low fuel and electrical crossover resulted.

Book Polymer Electrolyte Fuel Cell Degradation

Download or read book Polymer Electrolyte Fuel Cell Degradation written by Matthew M. Mench and published by Academic Press. This book was released on 2012 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt: For full market implementation of PEM fuel cells to become a reality, two main limiting technical issues must be overcome- cost and durability. This cutting-edge volume directly addresses the state-of-the-art advances in durability within every fuel cell stack component. [...] chapters on durability in the individual fuel cell components -- membranes, electrodes, diffusion media, and bipolar plates -- highlight specific degradation modes and mitigation strategies. The book also includes chapters which synthesize the component-related failure modes to examine experimental diagnostics, computational modeling, and laboratory protocol"--Back cover.

Book Study of the Microstructure and Properties of a PEMFC Catalyst Layer

Download or read book Study of the Microstructure and Properties of a PEMFC Catalyst Layer written by Nelly Margareth Cantillo Cuello and published by . This book was released on 2018 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the microstructure and performance of Proton Exchange Membrane Fuel Cells (PEMFCs) with platinum (Pt)-metal-group-free and Pt-based electrodes are evaluated to analyze the effect of the catalyst composition and structure on the electrode properties. In PEMFC systems, the thickness, structure and morphology of the catalyst layer (CL) are integral to cell performance and are particularly significant for cathodes using a non-precious metal catalyst due to higher catalyst loadings and thicker catalyst layers that compensate for the relatively low catalytic activity. An iron (III) porphyrin framework material was synthesized, pyrolyzed and its activity for the oxygen reduction reaction evaluated as a function of the catalyst loading (electrode thickness) and oxygen partial pressure. Various polarization losses were decoupled to reveal limiting processes. The kinetic overpotential was the major contributor. Mass transport contributions to voltage loss increased with higher cathode catalyst loading. Observed performance is discussed in the context of CL structure and morphology, analyzed using microscopy and X-Ray Diffraction. For Pt-based electrodes, the effects of the carbon support and the CL composition were experimentally studied. Machine-prepared cathode CLs with different Pt to carbon (Pt:C) ratios on highly graphitized carbon were prepared using a fixed 3M ionomer to carbon ratio. These were characterized and their PEMFC performance was evaluated. The Pt:C ratio had a significant influence on the CL structure and transport properties. The lowest Pt:C ratio (30:70) exhibited a higher volume of secondary pores and higher proton conductivity over the whole relative humidity range, with higher performance in PEMFC. This correlated with a more homogeneous ionomer distribution throughout the CL, caused by a preferential ionomer/carbon affinity. A study of interactions between 3M ionomer adsorption on a series of carbon supports with various Pt:C ratios provided further evidence for higher affinity of ionomer to the carbon surface. The adsorption isotherm for ionomer on carbon was quantified with two methods. Preferential adsorption on amorphous/graphitic carbon structure boundaries was confirmed. Ionomer adsorption occurs mainly on the secondary pores surface, consistent with previous BET results. Pt nanoparticles exhibited a negative effect on the adsorption process, possibly by blocking ionomer adsorption preferential sites.

Book Polymer Electrolyte Fuel Cell Durability

Download or read book Polymer Electrolyte Fuel Cell Durability written by Felix N. Büchi and published by Springer Science & Business Media. This book was released on 2009-02-08 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers a significant number of R&D projects, performed mostly after 2000, devoted to the understanding and prevention of performance degradation processes in polymer electrolyte fuel cells (PEFCs). The extent and severity of performance degradation processes in PEFCs were recognized rather gradually. Indeed, the recognition overlapped with a significant number of industrial dem- strations of fuel cell powered vehicles, which would suggest a degree of technology maturity beyond the resaolution of fundamental failure mechanisms. An intriguing question, therefore, is why has there been this apparent delay in addressing fun- mental performance stability requirements. The apparent answer is that testing of the power system under fully realistic operation conditions was one prerequisite for revealing the nature and extent of some key modes of PEFC stack failure. Such modes of failure were not exposed to a similar degree, or not at all, in earlier tests of PEFC stacks which were not performed under fully relevant conditions, parti- larly such tests which did not include multiple on–off and/or high power–low power cycles typical for transportation and mobile power applications of PEFCs. Long-term testing of PEFCs reported in the early 1990s by both Los Alamos National Laboratory and Ballard Power was performed under conditions of c- stant cell voltage, typically near the maximum power point of the PEFC.

Book Advanced water splitting technologies development  Best practices and protocols

Download or read book Advanced water splitting technologies development Best practices and protocols written by Ellen B. Stechel and published by Frontiers Media SA. This book was released on 2023-04-04 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Influence of Coating Method on the Performance of Roll to Roll Coated PEM Fuel Cell Catalyst Layers

Download or read book Influence of Coating Method on the Performance of Roll to Roll Coated PEM Fuel Cell Catalyst Layers written by and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As production of fuel cell vehicles and power systems increases there is a need to understand the process science of fuel cell manufacturing. Industrial production of polymer electrolyte membrane fuel cell (PEMFC) electrodes will rely on continuous roll-to-roll (R2R) coating methods to meet the rates needed for mass production. There are a variety of coating methods that could be used to coat catalyst layers. The different physics of each method may result in different morphologies and performance. Here we present the results of a study comparing fuel cell catalyst layers coated using two R2R coating methods: slot-die and gravure. These two methods were selected because the physics of applying the liquid to the substrate is very different between the two cases. Pt/C catalysts layers were coated directly onto carbon-fiber gas diffusion media to create gas diffusion electrodes (GDEs), without the use of a decal transfer process. These GDEs were assembled into membrane electrode assemblies (MEAs) by hot pressing to Nafion membranes. In situ performance and other electrochemical diagnostics were used to determine the influence of coating method on catalyst layer electrochemical properties. Electron microscopy was utilized to understand the influence of coating method on electrode morphology and its influence on electrochemical properties. We also explored the influence of solvent ratio to understand the potential coupling between ink formulation and coating methodology.

Book Rotating Electrode Methods and Oxygen Reduction Electrocatalysts

Download or read book Rotating Electrode Methods and Oxygen Reduction Electrocatalysts written by Wei Xing and published by Elsevier. This book was released on 2014-03-26 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rotating Electrode Methods and Oxygen Reduction Electrocatalysts provides the latest information and methodologies of rotating disk electrode and rotating ring-disk electrode (RDE/RRDE) and oxygen reduction reaction (ORR). It is an ideal reference for undergraduate and graduate students, scientists, and engineers who work in the areas of energy, electrochemistry science and technology, fuel cells, and other electrochemical systems. Presents a comprehensive description, from fundamentals to applications, of catalyzed oxygen reduction reaction and its mechanisms Portrays a complete description of the RDE (Rotating Disc Electrode)/RRDE (Rotating Ring-Disc Electrode) techniques and their use in evaluating ORR (Oxygen Reduction Reaction) catalysts Provides working examples along with figures, tables, photos and a comprehensive list of references to help understanding of the principles involved

Book Fuel Cells and Hydrogen Production

Download or read book Fuel Cells and Hydrogen Production written by Timothy E. Lipman and published by Springer. This book was released on 2018-10-05 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The expected end of the “oil age” will lead to increasing focus and reliance on alternative energy conversion devices, among which fuel cells have the potential to play an important role. Not only can phosphoric acid and solid oxide fuel cells already efficiently convert today’s fossil fuels, including methane, into electricity, but other types of fuel cells, such as polymer electrolyte membrane fuel cells, have the potential to become the cornerstones of a possible future hydrogen economy. This handbook offers concise yet comprehensive coverage of the current state of fuel cell research and identifies key areas for future investigation. Internationally renowned specialists provide authoritative introductions to a wide variety of fuel cell types and hydrogen production technologies, and discuss materials and components for these systems. Sustainability and marketing considerations are also covered, including comparisons of fuel cells with alternative technologies.

Book Control of Ionomer Distribution in Roll to Roll Coated Fuel Cell Catalyst Layers

Download or read book Control of Ionomer Distribution in Roll to Roll Coated Fuel Cell Catalyst Layers written by and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fuel cell catalyst layers are a complex mixture of catalyst particles and ion-conducting polymers. The performance of catalyst layers is highly dependent on microstructure, which must balance proton and electron conduction with gas transport. As fuel cells transition from the laboratory to industrial production for vehicles and other applications, there is a need to understand how manufacturing processes impact the microstructure and, ultimately, the performance of catalyst layers. In this work, we have focused on the roll-to-roll coating of catalyst layers for proton exchange membrane fuel cells. The catalyst layers are responsible for the electrochemical reactions that enable power production. In these devices the catalyst is commonly a Pt nanoparticle supported on porous carbon blacks. The ion conducting polymer, or ionomer, is typically a perfluorosulfonic acid. The most common being Nafion. To fabricate the catalyst layer, the catalyst particles are dispersed in an ink with the ionomer and cast to form the catalyst layer. Commonly, laboratory samples are prepared using spray coating or hand painting, which effectively coat many thin layers to achieve the desired catalyst layer thickness. This creates catalyst layers with uniform distributions of materials throughout the thickness of the full catalyst layer. In contrast, roll-to-roll methods, like slot die, gravure or screen printing, coat the catalyst layer as a single wet film. As the film dries, ink constituents are able to segregate, leading to a heterogeneous distribution of materials through the thickness of the layer. It is also known that the choice of solvent and drying rate can affect the morphology of the catalyst layer. Thus, there is a need to understand how ink formulation and the drying process influence the distribution of materials and catalyst layer morphology. Here, we have explored the influence of solvent and drying rate on morphology of roll-to-roll coated catalyst layers. We show the development of the Kelvin probe method as a rapid screening technique for qualitative analysis of ionomer distribution. We also utilize nano X-ray computed tomography to visualize electrode structure and to quantify particle-size and pore-size distributions, thickness-dependent ionomer distribution, tortuosity, and effective transport properties. We find that solvent has a strong influence on ionomer distribution, with less of an effect on porosity. Conversely, drying temperature has a strong influence on porosity, but less influence on ionomer distribution. Finally, we utilize in situ fuel cell performance testing and other advanced diagnostics to quantify the impact of catalyst layer properties on fuel cell performance and demonstrate that roll-to-roll coating is capable of coating high performance catalyst layers in multi-meter lengths.

Book Fuel Cells

    Book Details:
  • Author : Klaus-Dieter Kreuer
  • Publisher : Springer Science & Business Media
  • Release : 2012-12-14
  • ISBN : 1461457858
  • Pages : 795 pages

Download or read book Fuel Cells written by Klaus-Dieter Kreuer and published by Springer Science & Business Media. This book was released on 2012-12-14 with total page 795 pages. Available in PDF, EPUB and Kindle. Book excerpt: The expected end of the “oil age” will lead to increasing focus and reliance on alternative energy conversion devices, among which fuel cells have the potential to play an important role. Not only can phosphoric acid and solid oxide fuel cells already efficiently convert today’s fossil fuels, including methane, into electricity, but other types of fuel cells, such as polymer electrolyte membrane fuel cells, have the potential to become the cornerstones of a possible future hydrogen economy. Featuring 21 peer-reviewed entries from the Encyclopedia of Sustainability Science and Technology, Fuel Cells offers concise yet comprehensive coverage of the current state of research and identifies key areas for future investigation. Internationally renowned specialists provide authoritative introductions to a wide variety of fuel cell types, and discuss materials, components, and systems for these technologies. The entries also cover sustainability and marketing considerations, including comparisons of fuel cells with alternative technologies.

Book Control of Ionomer Distribution and Porosity in Roll to Roll Coated Fuel Cell Catalyst Layers

Download or read book Control of Ionomer Distribution and Porosity in Roll to Roll Coated Fuel Cell Catalyst Layers written by and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As fuel cells transition from the laboratory to industrial production for vehicles and other applications there is a need to understand how manufacturing processes impact the properties and, ultimately, the performance of materials. Roll-to-roll coating enables processing at meters per second speeds with physics that can be quite different from common laboratory coating methods. In this work, we have focused on the coating of catalyst layers for proton exchange membrane fuel cells. Commonly, laboratory samples are prepared using spray coating or hand painting, which effectively coat many thin layers to achieve the desired catalyst layer thickness. This creates catalyst layers with uniform distributions of materials throughout the thickness of the full catalyst layer. In contrast, roll-to-roll methods, like slot die and gravure, coat the catalyst layer as a single wet film. As the film dries, ink constituents are able to segregate, leading to a heterogeneous distribution of materials through the thickness of the layer. It is also known that solvent and drying rate can affect the morphology of the catalyst layer. Thus, there is a need to understand how ink formulation and the drying process influence the distribution of materials and catalyst layer morphology. Here, we have explored the influence of solvent and drying rate on morphology of roll-to-roll coated catalyst layers. We show the development of the Kelvin probe method as a rapid screening technique for qualitative analysis of ionomer distribution. We also utilize nano X-ray computed tomography to visualize electrode structure and to quantify particle-size and pore-size distributions, thickness-dependent ionomer distribution, tortuosity, and effective transport properties. We find that solvent has a strong influence on ionomer distribution, with less of an effect on porosity. Conversely, drying temperature has a strong influence on porosity, but less influence on ionomer distribution. Finally, we utilize in situ fuel cell performance testing and other advanced diagnostics to quantify the impact of catalyst layer properties on fuel cell performance and demonstrate that roll-to-roll coating is capable of coating high performance catalyst layers in multi-meter lengths. have focused on the coating of catalyst layers for proton exchange membrane fuel cells. Commonly, laboratory samples are prepared using spray coating or hand painting, which effectively coat many thin layers to achieve the desired catalyst layer thickness. This creates catalyst layers with uniform distributions of materials throughout the thickness of the full catalyst layer. In contrast, roll-to-roll methods, like slot die and gravure, coat the catalyst layer as a single wet film. As the film dries, ink constituents are able to segregate, leading to a heterogeneous distribution of materials through the thickness of the layer. It is also known that solvent and drying rate can affect the morphology of the catalyst layer. Thus, there is a need to understand how ink formulation and the drying process influence the distribution of materials and catalyst layer morphology. Here, we have explored the influence of solvent and drying rate on morphology of roll-to-roll coated catalyst layers. We show the development of the Kelvin probe method as a rapid screening technique for qualitative analysis of ionomer distribution. We also utilize nano X-ray computed tomography to visualize electrode structure and to quantify particle-size and pore-size distributions, thickness-dependent ionomer distribution, tortuosity, and effective transport properties. We find that solvent has a strong influence on ionomer distribution, with less of an effect on porosity. Conversely, drying temperature has a strong influence on porosity, but less influence on ionomer distribution. Finally, we utilize in situ fuel cell performance testing and other advanced diagnostics to quantify the impact of catalyst layer properties on fuel cell performance and demonstrate that roll-to-roll coating is capable of coating high performance catalyst layers in multi-meter lengths.

Book PEM Water Electrolysis

    Book Details:
  • Author : Dmitri Bessarabov
  • Publisher : Academic Press
  • Release : 2018-08-04
  • ISBN : 0081028318
  • Pages : 140 pages

Download or read book PEM Water Electrolysis written by Dmitri Bessarabov and published by Academic Press. This book was released on 2018-08-04 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: PEM Water Electrolysis, a volume in the Hydrogen Energy and Fuel Cell Primers series presents the most recent advances in the field. It brings together information that has thus far been scattered in many different sources under one single title, making it a useful reference for industry professionals, researchers and graduate students. Volumes One and Two allow readers to identify technology gaps for commercially viable PEM electrolysis systems for energy applications and examine the fundamentals of PEM electrolysis and selected research topics that are top of mind for the academic and industry community, such as gas cross-over and AST protocols. The book lays the foundation for the exploration of the current industrial trends for PEM electrolysis, such as power to gas application and a strong focus on the current trends in the application of PEM electrolysis associated with energy storage. Presents the fundamentals and most current knowledge in proton exchange membrane water electrolyzers Explores the technology gaps and challenges for commercial deployment of PEM water electrolysis technologies Includes unconventional systems, such as ozone generators Brings together information from many different sources under one single title, making it a useful reference for industry professionals, researchers and graduate students alike

Book Ionomer Degradation in Electrodes of PEM Fuel Cell

Download or read book Ionomer Degradation in Electrodes of PEM Fuel Cell written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Although PEMFC Membrane Electrode Assembly (MEA) durability related studies have increased dramatically since 2004, studies on ionomer degradation of the composite electrodes has received far less attention than that of the proton exchange membranes, electrocatalysts, and catalyst supports. The catalyst layer ionomer unavoidably gets involved in other components degradation processes since it is subjected to exposure to different operating effects, including the presence of the catalyst, catalyst support, and the porous nature of the electrode layer which includes 2-phase flow. PEMFC durability issues cannot be fully resolved without understanding the contribution of ionomer degradation in electrode to the performance decay in life time. However, addressing the impact of changes to the catalyst layer ionomer during durability tests is experimentally difficult mainly because of the need to separate the ionomer in the electrode from other components during chemical, electrical and materials characterization. The catalyst layer ionomer is essentially chemically identical to the membrane ionomeric material, and is composed of low atomic number elements, making characterization difficult. In the present work, MEAs with different Nafion ionomer types: stabilized and non-stablized ionomer in the electrode layer (Type I) and mixed membrane/ionomer MEAs (Type II) were designed to separate ionomer degradation from membrane degradation, as shown in Figure (1a) and (b) respectively. Stabilized and non stabilized ionomers were 5% Nafion{reg_sign} solutions (Ion Power, New Castle, Delaware). The non-stabilized version is the typical Nafion chemical structure with carboxylic acid ( -COOH) end groups; these end groups are thought to be a susceptible point of degradative peroxide attack. The stabilized version replaces the -COOH end groups with -CF3 end groups to prevent peroxide attack at the end groups. Type I MEAs were designed to compare ionomer degradation and its effect on performance decay. Since F− ions are released only from PFSA based membranes, and not from non-PFSA based membranes, Type II MEAs use a hydrocarbon membrane with no fluorine with a PFSA (Nafion{reg_sign}) ionomer in the catalyst layer for FER measurements. Any F− ions measured will then have come only for the catalyst layer ionomer during degradation experiments. Type II MEAs allow more detailed chemical characterization exclusively of the catalyst layer ionomer to better understand its degradation.

Book Improving the Efficiency of Fully Hydrocarbon based Proton exchange Membrane Fuel Cells by Ionomer Content Gradients in Cathode Catalyst Layers

Download or read book Improving the Efficiency of Fully Hydrocarbon based Proton exchange Membrane Fuel Cells by Ionomer Content Gradients in Cathode Catalyst Layers written by Hien Nguyen and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Recently, the cell performances of fully hydrocarbon-based fuel cells approached those of cells with perfluorinated ionomers. Most studies used a low catalyst layer ionomer content (∼10 wt%) to enable the highest performance. However, such low ionomer contents can cause a lower cell performance, especially under application-relevant, i.e. reduced humidities (≤50% relative humidity). This work systematically investigates ionomer content gradients in cathode catalyst layers based on hydrocarbon ionomer. A graded ionomer content in the catalyst layer with a higher ionomer content in the vicinity of the membrane (I/C = 0.4, 25% of total layer) and a lower ionomer content (I/C = 0.2, 75% of entire layer) near the gas diffusion layer was found to ensure sufficient proton conductivity without compromising reactant transport. In single-cell tests at hot and dry operation conditions (H2/air, 95 °C and 50% RH), the graded layer enabled both significantly improved current density at relevant cell potentials vs. a monolithic catalyst layer (496 mA cm−2vs. 367 mA cm−[email protected] V) and slightly increased peak performance (0.76 W cm−2vs. 0.71 W cm−2). Under the given conditions, the performance of the graded layer is similar to that of a Nafion catalyst layer. At 80% RH, the hydrocarbon-graded catalyst layer outperforms the Nafion catalyst layer at high current densities