Oxidation reactions in high-temperature fuel cells
The hydrogen oxidation/evolution reaction
Published Online: 15 DEC 2010
Copyright © John Wiley & Sons, Ltd. All rights reserved.
Handbook of Fuel Cells
How to Cite
McEvoy, A. J. 2010. Oxidation reactions in high-temperature fuel cells. Handbook of Fuel Cells. .
- Published Online: 15 DEC 2010
The high temperature fuel cell anode is activated thermally and therefore does not require noble metal catalysts to maintain the oxidation kinetics. Consequently, the high temperature devices are fuel-tolerant, so an important advantage for their commercial future is the adaptability to commercial fuels. At most a simple pre-reforming is all that is required to provide an acceptable fuel stream.
The anode is part of an overall electrochemical system in which the other principal components are the oxygen ion source, either the molten carbonate electrolyte in which the oxygen carrier is the carbonate ion, CO32−, or the solid electroceramic electrolyte in which oxygen ions are mobile, and the gas phase fuel stream. Reactions are generally considered as taking place at a three-phase boundary, which for low polarization must be delocalized to form a volumetrically functioning anode by appropriate materials selection. Concentration overpotential effects are due to diffusion problems for the ingress of the fuel gas, or inhibition of discharge of reaction products.
The functioning of the current state-of-the-art cermet anode is described, as are the considerations motivating the search for new and innovative anode materials, particularly metal oxides and perovskites; in principle these should permit direct oxidation of at least the lower hydrocarbons without restriction by carbon formation and other degradation mechanisms.
Operation of anodes at lower temperatures is also a motivation for current development work, so that the oxidation kinetics are maintained at a lower level of thermal activation of the system.
- carbon deposition (coking);
- carbon monoxide;
- cermet (ceramic/metal composite);
- hydrocarbons (reforming reaction);
- kinetics (reaction;
- methane reforming);
- perovskite (refractory materials);
- solid oxide fuel cells (materials)