Center for Electrochemical Science and Engineering:
Fuel Cell and Sensor Research at the Center
Fuel cells are in transition from being primarily military and space applications to widespread commercialization as an alternative power source for transportation, for stationary electric generation and for portable or mobile applications. This transition has been enhanced by the emergence of proton-conducting polymer electrolytes, such as Nafion™, which make polymer electrolyte methanol fuel cells (PEMFC) possible, and by improvements in hydrocarbon reformers.
PEMFC-type fuel cells for transportation will use hydrogen produced by reforming organic fuels. Reformate hydrogen contains contaminant carbon monoxide, as well as carbon dioxide. Carbon monoxide in particular poisons platinum-based catalysts, thus degrading cell performance. A major objective of the center is the development of carbon-monoxide-tolerant anode catalysts.
In addition to rational strategies for electrocatalyst selection, center researchers have developed combinatorial electrochemistry as a powerful tool for screening ternary and multicomponent alloys as electrocatalysts. The search for more effective reforming catalysts is supported by a fundamental understanding of the catalytic properties of alloy catalysts. For this purpose, center researchers are involved in ab initio quantum-mechanical modeling of such alloys on a scale that enables prediction of adsorption/desorption characteristics.Low-temperature fuel cells of the next generation will directly process organic fuels for power generation (for example, direct methanol fuel cells, DMFCs) or for electro-organic synthesis.
The center has been successful in developing anode catalysts for DMFCs that tolerate carbon monoxide formed by the oxidative adsorption of methanol on catalyst surfaces. Since methanol crosses over from the anode to the cathode side in Nafion™-based polymer electrolyte fuel cells, electric power is lost by chemical oxidation of the fuel at the cathode. Therefore, the center is investigating methanol-insensitive cathodes, helped by such techniques as in-cell or in-situ FTIR spectroscopy of electrode surfaces.
In addition, the center has developed fuel cell hardware and tests stands for both PEMFCs and DMFCs. It has designed separator plates with effective cathode and anode flow fields, and produces membrane electrode assemblies for testing fuels and fuel cell components.
High-temperature fuel cells are of special interest to utilities and industry, for dispersed generation of electric power and cogeneration of heat and power. The center conducts research on materials for these fuel cells and has test stands for fuel cells and fuel cell materials capable of operating at up to 1000°C.
Electro-oxidization of CH3OH produces H+ ions above the catalytic spots on an array electrode. Protonation of the UV-exposed indicator (HIn+) pinpoints regions of high activity by flourescence.
Source: Chemical & Engineering News, June 15, 1998.
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