Electrochemical Promotion of Oxidative Coupling of Methane on Platinum/Polybenzimidazole Catalyst

Abstract

The electrochemical promotion of catalytic methane oxidation was studied using a polybenzimidazole fuel cell at 135°C. It has been found that and water are the main oxidation products. Without polarization the yield of was 0.9% and the yield of was 7.3%. This means that open-circuit selectivity was approximately 11%. Open-circuit voltage was around 0.6 V. It has been shown that the catalytic reaction can be electrochemically promoted at negative polarization and exhibits a clear "volcano-type" promotion behavior, meaning that there was a maximum promotion effect at a polarization of −0.15 V, or 0.45 V catalyst potential vs. a hydrogen electrode (3.8% yield). The catalytic rate enhancement ratio, at this maximum was 4.2. There was no production at polarization ⩾0.1 and ⩽−0.3 V. The yield of decreased with decreasing temperature. Dependence of yield on polarization also showed a "volcano-type" behavior with maximum yield of 8.3% at −0.15 V polarization. The catalytic rate enhancement ratio for production, at this maximum was 1.1, which means that this catalytic reaction is only slightly affected by the electrochemical polarization. This indicates that polarization especially affects the selectivity of the catalyst. The obtained data was explained by the electrochemical production of Pt-H active centers at the electrolyte-catalyst-gaseous reactant interface © 2002 The Electrochemical Society. All rights reserved.