Non-faradaic electrochemical modification of catalytic activity III. The case of methanol oxidation on Pt

Abstract

It was found that the catalytic activity and selectivity of polycrystalline Pt for the oxidation of methanol to formaldehyde and Co 2 can be dramatically and reversibly affected when oxygen anions O 2− are electrochemically pumped to or from the Pt catalyst surface. The experiments were conducted using a stabilized zirconia solid electrolyte at temperatures 600 to 900 K. The steady state increases in the catalytic rates of H 2CO and CO 2 formation, are typically 10 3–10 4 higher than the rate of O 2− transport to or from the catalyst surface. Over a wide range of experimental conditions the catalytic rates depend exponentially on the catalyst-solid electrolyte overpotential, which is proportional to the induced change in catalyst work function. The product selectivity to H 2CO can be varied between 35 and 60% by controlling the catalyst potential. The phenomena are reversible and show that catalyst work function and catalytic activity and selectivity can be varied at will by adjusting the catalyst potential. As in previous studies of non-Faradaic electrochemical modification of catalytic activity one can interpret the observed behaviour by taking the change in catalyst work function with changing catalyst potential and the concomitant changes in the strength of chemisorptive bonds into account.