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.

Polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) technology are promising forms of low-temperature electrochemical power conversion technologies that operate on hydrogen and methanol respectively. Featuring high electrical efficiency and low operational emissions, they have attracted intense worldwide commercialization research and development efforts. These R&D efforts include a major drive towards improving materials performance, fuel cell operation and durability. In situ characterization is essential to improving performance and extending operational lifetime through providing information necessary to understand how fuel cell materials perform under operational loads.Polymer Electrolyte Membrane and Direct Methanol Fuel Cell Technology, Volume 2 details in situ characterization, including experimental and innovative techniques, used to understand fuel cell operational issues and materials performance. Part I reviews enhanced techniques for characterization of catalyst activities and processes, such as X-ray absorption and scattering, advanced microscopy and electrochemical mass spectrometry. Part II reviews characterization techniques for water and fuel management, including neutron radiography and tomography, magnetic resonance imaging and Raman spectroscopy. Finally, Part III focuses on locally resolved characterization methods, from transient techniques and electrochemical microscopy, to laser-optical methods and synchrotron radiography.With its international team of expert contributors, Polymer electrolyte membrane and direct methanol fuel cell technology will be an invaluable reference for low temperature fuel cell designers and manufacturers, as well as materials science and electrochemistry researchers and academics. Polymer electrolyte membrane and direct methanol fuel cell technology is an invaluable reference for low temperature fuel cell designers and manufacturers, as well as materials science and electrochemistry researchers and academics. - Details in situ characterisation of polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs), including the experimental and innovative techniques used to understand fuel cell operational issues and materials performance - Examines enhanced techniques for characterisation of catalyst activities and processes, such as X-ray absorption and scattering, advanced microscopy and electrochemical mass spectrometry - Reviews characterisation techniques for water and fuel management, including neutron radiography and tomography, and comprehensively covers locally resolved characterisation methods, from transient techniques to laser-optical methods

Alkaline Anion Exchange Membranes for Fuel Cells Build the fuel cells of the future with this cutting-edge material Alkaline anion exchange membranes (AAEMs) are cutting-edge polyelectrolyte materials with growing renewable energy applications including fuel cells, batteries, hydrogen electrolyzers and electrodialysis technologies. Their use in relatively new alkaline exchange membrane fuel cells (AEMFCs) is designed to produce cost-effective clean energy (electricity) produced by a chemical reaction. Rigorous studies are being conducted to meet the requirements of AAEMs precisely tailored for high anion conductivity and durability for future high energy efficient devices. Hence, over the past few years the academic and industrial scientific communities have explored various polymeric, composite and inorganic materials and studied their properties as a potential AAEM. The accumulated literature in this area of investigation is vast and in order to provide the community with the tools needed to strive forward, there is a clear need to condense this information in a single volume. Alkaline Anion Exchange Membranes for Fuel Cells meets this need with a comprehensive overview of the properties of these membranes and their applications. The book considers recent developments, common challenges, and the long-term prospects for this field of research and engineering. It constitutes a one-stop resource for the development and production of AAEM fuel cells and related electrochemical applications. Alkaline Anion Exchange Membranes for Fuel Cells readers will find: Discussion of electrochemical applications like redox flow batteries, water electrolysis, and many more Detailed treatment of specially tailored cationic groups such as quaternary ammonium and guanidinium Expert advice on efficient fabrication and electrode assembly Alkaline Anion Exchange Membranes for Fuel Cells is ideal for electrochemists, materials scientists, polymer chemists, electrical engineers, and anyone working in power technology or related fields.

Water management has a major impact on the performance of the polymer electrolyte membrane fuel cells. An understanding of water permeation through polymer electrolyte membranes is crucial to offset the unbalanced water activity within fuel cells. The work presented in this thesis includes contributions that provide insight into internal and interfacial water permeation behavior of membranes, as well as insight into how membranes could be designed to enhance water management. Three types of ex-situ water permeation techniques are used in this thesis work. These are: liquid-liquid water permeation (LLP) in which both sides of the membrane are in contact with liquid water; liquid-vapor permeation (LVP) where one side of the membrane is exposed to liquid, and the other is exposed to vapor; and vapor-vapor permeation (VVP) where both sides of the membrane are exposed to water vapor. Three polymer electrolyte membrane systems were investigated under varied experimental conditions: degraded Nafion®, short side chain (SSC) perfluorosulfonic acid ionomer membrane, and an emerging class of anion exchange membrane, poly(benzimidazolium). Correlations between membrane series were drawn and compared to the commercially-available materials. It was found that membranes of smaller thickness, greater water volume fraction (Xv), and higher ion exchange capacity (IEC) result in a higher overall water permeability. However, the membrane thickness, Xv, and IEC do not dominate the rate of water permeation through the membrane interface. In contrast, the side chain length of the polymer is found to influence the interfacial water permeation, wherein membranes with longer side chain length are more water permeable at the interface.

The development of fuel cells is indispensable to enable the hydrogen society. Anion exchange membrane fuel cells (AEMFCs) have triggered great interest over the past few years. In this dissertation, electrocatalysis in alkaline media and polymer electrolytes for AEMFCs have been explored from fundamental aspects to practical applications. For the oxygen reduction reaction (ORR) in alkaline media, electrochemically dealloyed Pd-M (M = Ni, Mn) nanoparticle catalysts were developed to enhance electrocatalytic activity. The electrochemical dealloying process was demonstrated to be effective in selectively leaching out the less noble metal and metal oxides on the surface. The higher atomic concentration of electrochemically active Pd exposed on the surface of the nanoparticles was found to be the reason for the enhanced ORR activity in alkaline media. These findings provide insights for the rational design of the composition and structure of electrocatalysts with enhanced electrocatalytic activity, based on post-synthesis modification methods. From a fundamental perspective, to explain and predict the electrocatalytic activity of heterogenous reactions, the energy of intermediates is usually used as an activity descriptor. However, this was recently called into questions. We developed a novel method, based on fast scan rate cyclic voltammetry, to directly measure the kinetics of the electro-adsorption processes. The Had adsorption reaction, the elementary step of the hydrogen evolution reaction (HER), on Pt(111) in acid was found to be >100x faster than in alkaline media, although the Had binding energy was the same. Together, with cation effects and isotope effects found in alkaline media, we demonstrated that the slow kinetics of the HER at high pH are not due to an unfavorable Had binding energy but to the high barrier of interfacial water reorganization. Polymer electrolytes in AEMFCs, namely anion exchange membranes and ionomers, play important roles in the transport of anions and water molecules. In situ characterization of these materials in their electrochemical environment is critical for understanding the anion transport mechanism and improving the design of them. The anion exchange and water dynamics in a perspective phosphonium-based AEM during the methanol oxidation process were studied with the electrochemical quartz crystal microbalance (EQCM). The results provide insights of the anion exchange process in the membranes during the reaction and emphasize the importance of characterizing the membranes in a hydrated electrochemical environment. The influence of ion exchange capacity (IEC) on the solubility, the ionomer viscoelasticity in water and the transport of charged and uncharged species, of a promising polyethylene piperidinium methyl (PEPM) ionomer were also investigated. The design of ionomers and membranes, with suitable IEC for their different functions in AEMFCs from the aspect of solubility, mechanical properties and mass transport, can be guided via this work.

In this book the authors focus on the ion and water transport characteristics in Nafion and other perfluorinated ionomer membranes that are recently attracting attention in various fields such as water electrolysis, mineral recovery, electrochemical devises and energy conversion. Methodology of measurements and data analysis is first presented that enables basic characterisation of transport parameters in the perfluorinated ionomer membranes. Cation exchange isotherm data are collected in binary cation systems, with the aim to see the behaviours of cationic species that exist with H+ in the membrane. Water transference coefficients, ionic transference numbers, ionic mobilities and other membrane transport parameters are measured in single and mixed counter cation systems using electrochemical methods. Diffusion coefficients of water and cations are also measured by pulsed-field-gradient spin-echo NMR (PGSE-NMR) at various temperatures in different kinds of perfluorinated ionomer membranes. The results are discussed in two perspectives. One is to predict the hydration state in perfluorosulfonated ionomer membranes in relation to the possible degradation of performances in fuel cells under contaminated conditions with foreign cations. An analytical formulation of membrane transport equations with proper boundary conditions is proposed, and using various parameters of membrane transport, a simple diagnosis of water dehydration problem is carried out. This analysis leads one to an effective control of fuel cell operation conditions, especially from viewpoint of proper water management. The others are to elucidate the ion and water transport mechanisms in the membrane in relation to polymer structures (e.g., different ion exchange capacity), and to propose a new design concept of polymer electrolyte membranes for fuel cell applications. Additionally for this purpose methanol and other alcohols are penetrated into the membrane, and alcohol permeability, membrane swelling, ionic conductivity and diffusion coefficients of water and CH3 are measured systematically for various kinds of membranes to cope with the problem of methanol crossover in direct methanol fuel cells (DMFCs).It is found that in order to realise a high ionic conductivity in the membrane, one should aim at a polymer structure through molecular design that takes into account the relative size of ions with a hydration shell against the size and atmosphere of ionic channels. For DMFC, a partially cross-linked polymer chain with high degree of hydrophilic ion transport paths based on phase-separated structures is recommended. Various possibilities of such polymer electrolytes are discussed.

"Fuel cells have received an increasing amount of attention over the past decade for their power production capabilities. Polymer electrolyte membrane (PEM) fuel cells in particular are researched because of their high power density, large range of operating conditions, green products, and ease of scalability. PEM fuel cells do have a number of issues that reduce their overall performance. These issues include variations in reactant distribution, materials issues for the bipolar plate, and flooding caused by poor water management. Variations in the reactant distribution causes lower overall power output due to regions of low reactant density. This means that optimizing the flow field to increase reactant density increases performance. One optimization method is to mimic natural structures that have similar functions. Leaves, lungs, and vein structures all have similar purposes to those in PEM fuel cells. Imitating their structure has been shown to improve power. It is also important to determine their water management properties. The membrane in the fuel cell must be hydrated to operate at optimally; however excess water causes mass transport issues by either blocking the channels or filling pores in the gas diffusion layer (GDL). This means that the water content in a PEM fuel cell must be delicately balanced to ensure that the membrane stays hydrated without causing flooding issues. Therefore, it is important to determine the water management capabilities of various bipolar plate designs. Clear bipolar plates are used to directly observe the water management capabilities of different flow field designs, which will be verified by the finite element model. These tests have shown that bio-inspired designs perform well in comparison with their conventional counterparts"--Abstract, page iii.

Increasing global demand and dependence on fossil fuels, coupled with environmental concerns arising from their use, have sparked interest in alternative energy sources. Hydrogen-powered fuel cells are a promising solution, offering a clean, scalable method for energy production. The most prominent low-temperature fuel cell devices today operate under an acidic environment, using a semi-permeable proton exchange membrane (PEM) to separate the two electrodes. However, their caustic operating conditions present unique stability and activity issues for the metal catalysts and ultimately necessitates the use of platinum-group materials, severely limiting commercial viability. A potential solution is to operate the fuel cell device under an alkaline environment using an anion exchange membrane (AEM), transporting hydroxide ions in lieu of protons. The basic environment opens the door for cheaper catalysts based on nickel and molybdenum, eliminating the cost barrier associated with PEM fuel cells. Unfortunately, typical AEMs exhibit poorer ionic conductivity and stability compared to traditional acidic membranes (e.g. Nafion), offsetting any potential cost advantage they may afford. This dissertation discusses design rationales towards enhancing the macroscopic properties of AEMs. Specifically, I present two experimental design motifs for improving the device viability of AEMs. In the first case, I present a semi-interpenetrating network design where a linear AEM ionomer is stabilized by a crosslinked poly(styrene-co-divinylbenzene) matrix. The crosslinked network acts as a reinforcing scaffold, dramatically increasing dimensional stability while maintaining excellent anion conductivity. Prototypical single-stack fuel cells with enhanced performance and stability have been fabricated from these materials, validating the design choices. In the second approach, I demonstrate the ability to increase hydroxide conductivity by tuning the nanostructure of the polymer electrolyte. Specifically, I show that tethering hydrophilic poly(ethylene glycol) grafts onto a benzyltrimethylammonium polysulfone benchmark AEM results in phase-separated, water-rich domains on the order of 5 to 10 nm. These domains serve as an ion transport pathway, facilitating the diffusion of hydroxide anions and consequently enhancing the efficiency of hydroxide conduction. Finally, in order to better understand the phase behavior and structure-property relationships of typical AEM materials, we have developed coarse-grained simulations and fundamental polymer theory to elucidate the thermodynamic behavior of random copolymers. We find that both the stochastic distribution of monomers along the polymer backbone as well as the overall stiffness of the polymer chain heavily influences its phase behavior (i.e., morphology and critical point). The ultimate objective is to provide not only a theoretical basis for understanding and explaining structure-property relationships in existing AEM materials, but to provide a set of general design guidelines moving forward.