(509as) Electrochemical Preferential Oxidation: A Novel Approach To Enhance Kinetics And Thermodynamics Of Carbon Monoxide Oxidation

Proton-exchange membrane (PEM) fuel cells are currently limited by CO poisoning of the Pt catalyst. Hence arises the need for an efficient reforming process. The water-gas-shift reaction (WGSR) and preferential oxidation (PrOx) are important aspects of fuel processing, in conjunction with PEM fuel cells.

Due to its moderate exothermicity, the WGSR is thermodynamically favorable but limited by kinetics at lower temperatures. The current PrOx technology is cumbersome with poor hydrogen selectivity. An entirely novel approach involving electrochemical preferential oxidation (ECPrOx) is being developed in our laboratory, where CO electro-oxidation is achieved at the anode by rendering the process electrochemical. In addition, supplemental power is produced with no hydrogen wasted. The ECPrOx can be operated at near room temperature, high anode pressure, atmospheric air breathing and without external humidification. Stable conversions, as high as 95% have been achieved with Ru based catalysts.

The electrochemical enhancement of catalytic WGSR is achieved since the rate of an electrochemical reaction is not only determined by temperature, pressure, and composition, but also by the electrode potential. Moreover, the equilibrium constant of an electrocatalytic reaction is a strong function of potential. Hence both, the thermodynamics and kinetics of WGSR can be improved, if carried out electrochemically.

The electrochemical device has direct application in on-board reforming process for fuel cell applications and the potential to replace both WGSR and PrOx.