Sample Articles
 
 
Biochemical fuel cells (Volume 1, Chapter 21)
Eugenii Katz, Andrew N. Shipway and Itamar Willner
Institute of Chemistry and The Farkas Center for Light-Induced Processes, The Hebrew University of Jerusalem, Jerusalem, 91904 Israel
Biofuel cells transform abundant raw materials into electrical power in the presence of biocatalysts, enzymes, or whole cell organisms. Biomaterials may participate in the biofuel cell activity by either producing fuel substrates or by catalyzing the electron transfer chain between the fuel substrates and oxidizers and the electrodes. Two types of biofuel cell elements are discussed in this review article: microbial-based biofuel cells and enzyme-based biofuel cells.

Microorganisms may act as microreactors in fuel cells for the generation of the fuel products such as H2 or H2S. These fuel products may be generated apart from the biofuel cell and transported to its anodic compartment or, alternatively, may be directly generated in the anodic compartment of the biofuel cell. Different microbial-based biofuel cells are reviewed in the account.

Enzymes are employed as catalysts for the activation of electron transfer chains between the fuel substrate and the anode in the anodic compartment, and between the oxidizer and the electrode in the cathodic compartment. In order to activate the electron transfer cascades between the enzymes and the electrodes, native electron carriers (co-factors) and artificial electron transfer mediators must be coupled to the biocatalytic transformations. By the nanoengineering of the electrode surfaces with co-factor/electron-relay/enzyme assemblies, integrated, electrically contacted, bioelectrocatalytic anodes and cathodes are tailored. Different enzyme-based biofuel cell configurations are described. The different parameters controlling biofuel cells efficiencies are discussed. The efficiencies of the different biofuel cell configurations are evaluated in terms of the limiting factors and kinetic features of the systems.
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Methanol and CO electrooxidation (Volume 2, Chapter 41)
Teresa Iwasita Instituto de Quimica de Säo Carlos, USP, Säo Carlos-SP, Brasil
Present knowledge of methanol and CO electrooxidation reactions is given in the light of electrochemical, spectroscopic and microscopic data. Strong catalytic effects on CO electrooxidation by nonmetallic adatoms (S, Se, Te) are presented and discussed. For methanol oxidation, several authors have shown, besides CO2, nonnegligible yields of formaldehyde and formic acid, depending among other factors on concentration, potential, electrode roughness and temperature. Infrared spectra assist mechanistic interpretations. Promotion of methanol oxidation by ruthenium presents a maximum effect on alloy materials at room temperature for a surface concentration of Ru between 15% and 45%.
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Diffusion media materials and characterisation (Volume 3, Chapter 46)
Mark Mathias General Motors – Global Alternative Propulsion Center, Honeoye Falls, NY, USA
Joerg Roth Adam Opel AG – Global Alternative Propulsion Center, Rüsselsheim, Germany
Jerry Fleming Spectracorp, Inc., Lawrence, MA, USA
Werner Lehnert Center for Solar Energy and Hydrogen Research Baden-W¨urttemberg, Ulm, Germany
Gas-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.
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System design for vehicle applications: Daimler Chrysler (Volume 4, Chapter 58)
Gerhard Konrad, Marc Sommera DaimlerChrysler AG, Ulm, Germany
Birgit Loschko, Andreas Schell and Andreas Docter DaimlerChrysler AG, Stuttgart, Germany
This 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.
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