Accelerated CO electrooxidation through a formate pathway in intermediate-temperature alkaline media

Abstract

To explore strategies for addressing the process of CO poisoning on Pt-based catalysts, CO electrooxidation on Pt-based electrodes in alkaline media has been studied by cyclic voltammetry in the intermediate temperature range of 80 to 130°C. In this temperature range, CO spontaneously reacts with bulk hydroxide anion to generate soluble formate, which electrooxidation is apparently more facile than the CO electrooxidation. A pathway involving the formate intermediate therefore results in accelerated CO electrooxidation. The corresponding voltammetric behaviors are characteristic of: (i) low onset potentials falling within the hydrogen zone, (ii) maximized oxidation currents in the double-layer zone and (iii) the oxidation inhibition in the oxide zone. These observations are quite different from the literature results for the CO electrooxidation in low temperature alkaline media. This fact provides fundamentals for the development of novel fuel cell and hydrogen purification technologies since CO can be oxidized at very low potentials in the intermediate temperature alkaline media.