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Biochemical
fuel cells (Volume 1, Chapter 21) |
Eugenii
Katz, Andrew N. Shipway and Itamar Willner
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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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