Electrochemical enhancement of a catalytic reaction in aqueous solution

THE rates of many heterogeneous catalytic reactions between gaseous adsorbates on metal surfaces supported on solid electrolytes can be increased by applying a potential to the meta^l1-8. This phenomenon, which has been reported previously at temperatures of 250-750°C, has been shown⁹ to be due to the electrochemically induced spillover of ions from the support onto the catalyst surface; the ions then act as promoters for the catalytic reaction. Here we report that a similar effect can be observed in aqueous solution at ambient temperatures. We studied the oxidation of H² on a platinum/graphite electrode immersed in aqueous KOH. Application of a positive potential of 1-2 V to the Pt electrode increased the rate of H² oxidation by up to 500%. We deduce that hydroxide ions are acting as promoters, and find that each ion supplied to the catalyst causes the oxidation of up to 20 hydrogen atoms. This kind of rate enhancement for heterogeneous catalytic reactions in solution may be of considerable technological value, for example in the electrochemical treatment of toxic organics¹⁰ or the generation of useful industrial chemicals⁴.