Acceleration of Ethanol Electro-Oxidation on a Carbon-Supported Platinum Catalyst at Intermediate Temperatures

Abstract

The performance of a direct ethanol fuel cell is expected to improve at relatively high temperatures. In this study, the electro-oxidation of ethanol on a carbon-supported platinum catalyst (Pt/C) at intermediate temperatures (235–260°C) was investigated using a single cell fabricated with the CsH2PO4 proton conducting solid electrolyte. The main products of ethanol electro-oxidation at intermediate temperatures were H2, CO2, and CH4 while the formation of C2 compounds was much small in comparison with the gaseous products even at a high ethanol concentration (i.e., water/ethanol molar ratio = 3). An analysis of the reaction products revealed that the C–C bond dissociation ratio of ethanol is higher than 90% at intermediate temperatures. In addition, a high current efficiency for the total oxidation of ethanol (ca. 80%) was observed. The apparent activation energy for this ethanol oxidation suggests reaction paths for the formation of CO2: the C–C bond dissociation or the subsequent oxidation of the adsorbed CHx species is thought to be rate-determining at intermediate temperatures. These observations clearly demonstrate the advantages of the efficient and direct use of ethanol at intermediate temperatures.