bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methanol reformer design considerations
Authors: Hansen J. B. 
Published: December 2010

AbstractThe thermodynamic equilibrium gas compositions have been calculated for typical cases related to the use of methanol reformers in connection with fuel cells. Both steam reforming and partial oxidation with steam, air and methanol are considered. Using these basic considerations as guidelines, different reactor designs are discussed and examples given.The reactor designs based on steam reforming alone mainly differ with respect to the method by which the heat is provided for the endothermal overall reaction. These reactor designs have the overall highest conversion energy efficiency, but reactors based on the simultaneous reactions with steam, air and methanol are faster to start up and more compact. The partial oxidation can either be of the catalytic types (flameless) or with a dedicated burner unit (autothermal) followed by a catalytic zone.Finally the reformers can be integrated with a gas purification unit based on Pd membranes selective for hydrogen permeation.
Performance and durability of bipolar plate materials
Authors: Mepsted G. O. , Moore J. M. 
Published: December 2010

Abstract
The bipolar plate is a multifunctional component of the fuel cell; its primary roles are to evenly distribute reactant gases whilst removing water from the cell. It must also transfer the heat of reaction away from the cell, provide electrical conductivity between adjacent cells and prevent mixing of the fuel and oxidant. An optimized bipolar plate must satisfy a number of materials and construction requirements, have good electrical and thermal conductivity, gas impermeability and corrosion resistance. It should also have minimal volume and weight and be inexpensive. Historically, graphite has been chosen as a compromise between these requirements, it has good electronic conductivity, excellent corrosion resistance and a low density. However, it is expensive, porous in nature, lacks mechanical strength and is not viable for volume production. Two basic types of bipolar plates have emerged as probable replacements for graphite, including composites fabricated from graphite or carbon powder and a polymer resin and metallic. Composite plates are lower cost, lower weight and mechanically stronger than graphite, and they can be fabricated using cost‐effective moulding techniques. Composites are less conductive than graphite, but recent developments have seen conductivities improve to levels approaching that of graphite. Metals, such as stainless steels and titanium, have high mechanical strength and are gas impermeable. Thus, thin bipolar plates can be manufactured using techniques amenable to mass production. The bulk resistivities of most metals are at least an order of magnitude lower than graphite; however, this can be more than offset by contact resistance due to surface oxide layers or corrosion products. The successful utilization of metallic bipolar plates in proton exchange fuel cells depends upon either the identification of metals or alloys with low contact resistance but good corrosion resistance, or the development of low‐cost conductive and protective coatings.
Perfluorinated membranes
Authors: Doyle M. , Rajendran G. 
Published: December 2010

AbstractPerfluorinated ionomer membranes have been the topic of a tremendous amount of research for over three decades due to their use as the predominant membrane system for proton exchange membrane fuel cell (PEMFC) applications. Their excellent physical properties, including high proton conductivity, oxidative and reductive stability, and mechanical properties, have enabled the PEMFC to reach the levels of performance achieved to date. However, the demands on the fuel cell system are increasing as new applications loom with their needs for lower cost, higher performance, and flexibility to accommodate new fuels. System demands are pushing operating temperatures higher, causing the water balance and humidification of the perfluorinated ionomer membrane to become important issues.This section reviews the status of research and development activities around the Nafion®perfluorinated ionomer membrane and Nafion®solutions. The focus of the review is on the measurement of physical property data and new insights into the mechanisms of conduction in these systems. An attempt is made to summarize recent structural studies and characterization techniques that are bringing new insights into the conduction process, as well as recent efforts in mathematical modeling and computer simulations of the conduction process. Finally, membrane‐related issues that arise in the direct methanol PEMFC are reviewed and data on methanol transport in Nafion®membranes are summarized.
Inorganic/organic composite membranes
Authors: Jones D. J. , Rozière J. 
Published: December 2010

AbstractThis chapter briefly reviews the state of the art in the preparation and characterization of hybrid inorganic/organic membranes for fuel cells. Examples are drawn from the recent literature to demonstrate the advantages of inorganic/organic membranes compared with polymer‐only systems. Emphasis is placed on the different routes developed over recent years to hybrid fuel cell membranes leading to a high degree of dispersion of inorganic particles or proton‐conductors in a polymer matrix, including dispersion of exfoliated layered proton‐conductors in a polymer solution, in situ local growth of inorganic proton‐conductors in a pre‐formed polymer membrane, polymer in situ sol gel reactions of inorganic alkoxides and alkyl‐ or arylalkoxysilanes, and solvent transfer (aqueous to organic phase) of colloidal inorganic oxides.
Development ofCO‐tolerant catalysts
Authors: Ruth K. , Vogt M. , Zuber R. 
Published: December 2010

AbstractHighly dispersed platinum/ruthenium, supported on carbon black, is today's standard anode catalyst material for polymer electrolyte fuel cells operated by reformate gas (hydrogen containing gases with traces of CO). In order to generate a high rate of hydrogen oxidation in the presence of CO, the catalyst has to be specifically designed for the system operation conditions. This includes the total precious metal loading of the catalyst, the ratio of platinum to ruthenium, the distribution of platinum and ruthenium on a nanoscopic scale as well as the oxidation state of the metal surface.The current level of CO tolerance is in the range of a few hundred ppm dependent on the airbleed level used. Investigations on lifetime of Pt/Ru electrocatalysts demonstrate that these catalyst systems are principally suited to achieve the desired lifetime targets of polymer electrolyte fuel cells systems for mobile and residential application.Besides the principal technical suitability of Pt/Ru catalysts, further requirements regarding to production and catalyst costs have to be fulfilled. The cost of precious metal precursor formation and catalyst production are important factors for the total production costs. However, enhancement of precious metal utilization and simplification of fuel cell systems are a must for the future mass application of fuel cells. These will generate further progress in catalyst development.
Precious metal supply requirements
Authors: Jaffray C. , Hards G. 
Published: December 2010

Abstract
Two scenarios for the growth of the transportation market for proton exchange membrane (PEM) fuel cell engines have been developed. A continuing growth in the global vehicle population and a continuing technological development to reduce platinum loadings employed in the fuel cells form the basis of this study. At current projected levels for fuel cell vehicles in 2010, the precious metal requirements will have a minor impact on precious metal supply and demand forecasts. Wholesale introduction of fuel cell vehicles to over 50% of the total market from beyond 2025, will require a significant increase in platinum supply. However, there are proven resources of platinum at current economical extraction depths to support a major fuel cell market such as this, provided the precious metal producers have sufficient demand visibility.
Diffusion media materials and characterisation
Authors: Mathias M. F. , Roth J. , Fleming J. , Lehnert W. 
Published: December 2010

AbstractGas‐diffusion media (also known as gas diffusers and gas‐diffusion backings) are required in most polymer electrolyte fuel cell (PEFC) designs. Their function is to provide uniform reactant (H2, O2, and electrons) access to and product (H2O) removal from the electrodes, efficient heat removal from the membrane electrode assembly (MEA), and mechanical support to the MEA. The vast majority of gas‐diffusion media are based on carbon‐fiber materials; a variety of forms are used, with carbon‐fiber paper and carbon cloth receiving widest application. This chapter describes the production and properties of currently available and emerging materials. Commonly employed treatments and coatings used to tailor the wicking and hydrophobic properties of diffusion media for efficient water removal are discussed. Finally, ex‐situ and in‐situ methods for characterizing diffusion media are described.
Catalyst coated composite membranes
Authors: Cleghorn S. , Kolde J. , Liu W. 
Published: December 2010

Abstract

The introduction of expanding polytetrafluoroethylene (ePTFE) micro‐reinforced composite perfluorosulfonic acid membranes by Gore (Gore‐Select
®
membrane) provides numerous benefits for polymer electrolyte membrane fuel cells (PEMFCs). This chapter reviews some of the important physical properties of the membranes such as tear strength, dimensional stability, hydrogen permeability, and resistance as a function of RH, comparing a commercially available nonreinforced membrane and the Gore‐Select
®
membrane.

The performance of the Primea
®
membrane electrode assembly (MEA) Series based on the Gore‐Select
®
membrane is discussed and compared to thicker nonreinforced membranes. The reduced thickness of the electrolyte results in an obvious reduction in membrane resistance in the cell, but also provides increased membrane hydration uniformity as a result of the rapid water back diffusion. The combination of these factors provides improved power density, as well as the ability to operate fuel cell systems with sub‐saturated reactant streams and at higher temperatures.

Fuel cell test results for a series of reinforced and nonreinforced membranes, along with ex‐situ analysis, provides insight into predominant membrane failure mechanisms in PEMFCs. Thin reinforced membranes have been found to have significantly longer life than much thicker nonreinforced membranes, supporting the conclusion that mechanical properties of membranes maybe more important than their intrinsic chemical properties in dictating membrane life.

This chapter discusses the economic aspects of Gore‐Select
®
composite membranes compared to commercially available pure‐film membranes, including the combined benefits of increased performance and decreased ionomer content.
Durability
Authors: Wilkinson D. P. , St‐Pierre J. 
Published: December 2010

Abstract
Durability and reliability are necessary requirements for fuel cells to be introduced into the market place. However, activities necessary to meet these requirements are costly and time‐consuming. As a result, past experience and information is valuable and emphasis should be placed on ex situ and accelerated testing to minimize resource investment. In this contribution, gaps in knowledge are identified which could form the basis of further studies. The key components of performance degradation (kinetic, ohmic, mass transport) are briefly defined and provide a basis for the discussion on the sources of degradation (water management, impurities, reformate, materials, operating conditions, uniformity). Understanding of the factors affecting degradation leads to a discussion of possible mitigation strategies. Since the current state of the art is fragmentary and far from being comprehensive, further research efforts are required to clearly understand root causes, secondary effects and interactions in order to develop appropriate mitigation strategies for performance degradation.
System design for stationary power generation
Authors: Barbir F. 
Published: December 2010

AbstractThe stationary fuel cell system components, function and various design options with respect to application, grid connection, nominal power output, load following, choice of fuel, installation and cogeneration capabilities are discussed. Fuel processor, fuel cell stack design and operation requirements are treated only to an extent they that affect the system design and operation. Efficiency and economics of stationary fuel cell systems are also addressed.
System design for vehicle applications: Daimler Chrysler
Authors: Konrad G. , Sommer M. , Loschko B. , Schell A. , Docter A. 
Published: December 2010

AbstractThis article describes the fundamental procedure for designing fuel cell systems for vehicle applications, especially propulsion systems. It starts with the definition of the target specifications concerning vehicle performance, derived from the driving requirements of the customer. The design process of a fuel cell vehicle is repetitive and starts with a first vehicle concept, followed by the layout of drive train, where the requirements concerning fuel consumption, emissions, acceleration, top speed and climbing ability must be considered. The design procedure of the fuel cell system consists of the concept phase, the modeling phase as well as the simulation phase. The results, which include efficiency, emissions, turn‐down ratio, weight, volume, costs, cold start‐up time and heat rejection, are then compared with the original specifications. For a detailed simulation, input data and boundary conditions are necessary at the start, which can only result from the total design process — so these data have to be estimated before starting the layout process. The data found in the simulation of the fuel cell system are re‐used within the vehicle simulation. Analysis shows the sensitivity of the system concerning changes of a given technology and leads to the final definition of the design of all components of the drive system.
System design for transport applications
Authors: Lamm A. , Müller J. 
Published: December 2010

AbstractThe following contribution concerns direct methanol fuel cells (DMFC) and their ability to use the new technology as an electrochemical device in an electric propulsion system in the future. First, a brief introduction is given regarding alternative fuels and the attractiveness of methanol as one alternative fuel in comparison with hydrogen (CHG) and synthetic fuels. In addition, the properties of the DMFC propulsion system are compared with those of systems based on CHG and synthetic fuels from a technical point of view. Second, the design of the liquid‐feed DMFC system is discussed on the basis of comparison between a gaseous and a liquid‐feed DMFC system. Third, the CO2separation process is simulated, and hardware presented. The thermal management of a DMFC stack is also modeled. A brief description of system management concludes the chapter.
Seawater aluminum/air cells
Authors: Iudice de Souza J. P. , Vielstich W. 
Published: December 2010

Abstract

Aluminum/air cells have a theoretical energy density of 8.1 kWh kg
−1
. Using an alkaline electrolyte and aluminum alloys as the anodes, discharge currents of 200 mA cm
2
are obtained with a power density of 0.6 W cm
2
. Saline systems show a much lower power, but with a reasonable energy density of more than 2 kWh kg
−1
and stationary discharge conditions. It has to be considered that closed battery systems need an exchange of electrolyte due to the formation of insoluble aluminum hydroxides. Practical applications for the saline electrolyte version are, therefore, suggested via the use of seawater as the electrolyte in battery systems open to the sea.
Hy.Power — a technology platform combining a fuel cell system and a supercapacitor
Authors: Dietrich P. , Büchi F. , Tsukada A. , Bärtschi M. , Kötz R. , Scherer G. G. , Rodatz P. , Garcia O. , Ruge M. , Wollenberg M. , Lück P. , Wiartalla A. , Schönfelder C. , Schneuwly A. , Barrade P. 
Published: December 2010

AbstractIn a joint project, the Paul Scherrer Institut PSI, ETH Zurich, FEV Motorentechnik and Volkswagen have developed the fuel cell hybrid vehicle “Hy.Power”. Hy.Power is a technology platform for the demonstration of a powertrain combining a hydrogen fuel cell system designed for 40 kW peak net power output and a double‐layer capacitor arrangement with a peak power of 60 kW net. The gaseous hydrogen is stored in pressurized tanks of up to 350 bar. The potential of innovative technologies, such as newly designed bipolar plates and double‐layer capacitors as well as new air supply and humidification concepts, are tested under real conditions. The fuel cell system consists of six fuel cell stacks into which the media are fed in parallel. The performance of the Hy.Power technology demonstrator was successfully tested under extreme boundary conditions by crossing the Simplon Pass in the wintry Alps in January 2002.
Automotive development
Authors: Hacker V. , Kordesch K. 
Published: December 2010

AbstractAlkaline fuel cells were the best performers in the initial decades of fuel cell development. In the past two decades a rapid change has taken place and many groups have stopped developing alkaline fuel cell systems. From the few remaining groups ZeTek was the only one to produce small series of stacks and prototypes of hybrid vehicles. The prototypes demonstrated that, in practice the alkaline fuel cell is well developed, simple to operate and is inexpensive to manufacture. The uses of alkaline fuel cells are still uncertain. The article gives an overview of the system packaging and operation of alkaline fuel cells when installed as on‐board chargers for mobile applications. The main driving force for application of alkaline fuel cells for electric vehicles in future will be the cost issue.
Potential economic impact of fuel cell technologies
Authors: Jochem E. , Schirrmeister E. 
Published: December 2010

Abstract
This section analyses the possible impacts on regional economies and employment from the introduction of the fuel cell into cars and as stationary small co‐generation plants into buildings and homes. For this purpose, the components of the new propulsion system or co‐generation plant are analyzed and assumed to substitute the components of the traditional components by using input/output analysis. The results demonstrate that there are substantial changes within the car and boiler industries and also in the outfitter and supplier industries. Depending on the car manufacturer's decision of what, where and by whom production will take place, the technological change may substantially influence a regional economy. The effect on employment of an annual production of half a million fuel cell‐driven cars ranges from an additional 40 000 jobs to job losses of 10 000. The chances and risks of this new energy‐converting technology require a sensitive and forward‐looking attitude of many players in a country or region producing cars or boilers, power and co‐generation plants today.
Enzyme catalysis in biological fuel cells
Authors: Barton S. C. 
Published: December 2010

Abstract
Biocatalysts represent a compelling alternative to precious metals as catalysts for low‐temperature fuel cell power systems. Enzymatic catalysts capable of reducing oxygen or oxidizing small organic molecules can be less expensive and manufacturable, and have favorable reaction selectivity as compared to precious metals. The key barriers to realization of practical biocatalyzed fuel cells are the insufficient current, power, and lifetime achievable with current devices. Recently, significant progress has been made in addressing these issues, from the standpoint of fundamental studies of electron transfer to enzymes, mediation of enzyme‐catalyzed reactions, and immobilization of enzymes in materials that confer stability and high surface area for heterogeneous reactions. In this article, we introduce concepts in enzyme catalysis for energy applications and describe important recent progress.
Catalysts for the electro‐oxidation of small molecules
Authors: Watanabe M. , Uchida H. 
Published: December 2010

AbstractDirect oxidation‐type fuel cells (DOFCs) have attracted great interest as a primary power source for portable electronic devices, wheelchairs, vehicles, and robots because of their simple system (no additional equipment such as a fuel reformer) and ease of maintenance. The direct methanol fuel cell (DMFC) is a typical example of DOFC. Development of highly active anode catalysts for them is one of the most important issues in achieving high‐energy conversion efficiency in DOFCs. To design such new electrocatalysts, we discuss the mechanism of methanol oxidation reaction (MOR) as well as CO oxidation reaction at several electrodes, based onin situFTIR spectroscopy and X‐ray photoelectron spectroscopy combined with an electrochemical cell (EC‐XPS). We also show changes in the MOR activities at various Pt alloy electrodes over the wide temperature range from 20 to 120 °C, obtained by using a thin‐layer flow cell under pressurized operation. The electrooxidation of methoxy fuels is briefly discussed.
Density functional theory applied to electrocatalysis
Authors: Venkatachalam S. , Jacob T. 
Published: December 2010

AbstractA combination of density functional theory (DFT) and thermodynamic considerations is used to evaluate the electrochemical (a,T, Δϕ) phase diagram for Pt(111) in contact with an aqueous electrolyte, which is then compared with experimental data. After specifying the electrode potential region at which no surface oxidation or oxide formation occurs, DFT calculations on the reaction of H2 + 1/2O2→ H2O over a Pt catalyst via direct oxygen reduction are discussed. Within these studies we first examine the binding characteristics and energetics for each likely intermediate chemisorbed on the Pt(111) surface, modeled by a 35‐atom cluster: O, H, O2, H2, OH, OOH, H2O2, and H2O. Then, the pathways for the dissociation processes of the various intermediates were calculated. Using binding energies and dissociation barriers, two main reaction mechanisms could be distinguished: O2dissociation and OOH/H2O2formation. While the latter one is the only mechanism to be expected when neglecting the surrounding water, both pathways have almost comparable reaction barriers when taking water into account.
Platinum dissolution models and voltage cycling effects: platinum dissolution in polymer electrolyte fuel cell (PEFC) and low‐temperature fuel cells
Authors: Ota K. , Koizumi Y. 
Published: December 2010

AbstractAll the metals except gold form a metal oxide on the surface in the presence of oxygen at room temperature. Once an oxide layer is formed on a metal surface, it dissolves into a solution to some extent. This is the dissolution. Even platinum makes an oxide layer and has solubility. Platinum islands in an electrolyte membrane in polymer electrolyte fuel cells (PEFCs) were reported in many papers. These islands are closely related to the dissolution of Pt from cathode. Platinum dissolves in an acidic media in the presence of oxygen although the solubility is very low. The solubility is proportional to pH of sulfuric acid solution and increases at higher temperatures. The dissolution reaction follows the acid dissolution mechanism. The dissolution reaction is enhanced by the potential cyclings. Considering the characteristics of fuel cell vehicles, there are voltage changes and the dissolution of Pt should be reduced.