The methanol-air fuel cell: A selective review of methanol oxidation mechanisms at platinum electrodes in acid electrolytes

Abstract

Over the past few years there has been a resurgence of interest in methanol oxidation in acid electrolytes, where platinum group metals are the only practical catalysts. The recent literature concerning the adsorption and oxidation processes occurring at platinum in acid solutions is reviewed. The overall model based on contemporary data assumes that methanol adsorption follows Langmuir kinetics at low surface coverages and Elovich kinetics at higher values. The ‘poisoning’ intermediate (probably COH) is susceptible to an ageing process, rendering it less active, and its ultimate removal is achieved via a chemical reaction with an electrosorbed water molecule. Bimetallic catalysts which adsorb both water and methanol at low potentials are much more active than platinum alone. Modern, highly-dispersed catalysts on carbon supports have been reported with high specific activities. However, for commercial viability (particularly with regard to automotive applications) considerable improvements are still required.