Non-faradaic electrochemical modification of catalytic activity: 1. The case of ethylene oxidation on Pt

Abstract

It was found that the catalytic activity of polycrystalline Pt for the oxidation of ethylene to CO 2 and H 2O can be increased by up to a factor of 50 when oxygen anions O 2− are electrochemically pumped onto the Pt catalyst surface. The experiments were conducted using a stabilized zirconia solid electrolyte at temperatures of 550 to 725 K. The steady-state increase in the catalytic reaction rate is typically 10 5 higher than the rate of O 2− transport to the catalyst surface. Over a wide range of conditions the catalytic reaction rate increases exponentially with the catalyst-solid electrolyte overpotential η which is proportional to the change in catalyst work function. The reaction activation energy decreases toward zero with increasing η. The phenomena are completely reversible and show that catalyst work function and catalytic activity can be varied at will by adjusting the catalyst potential. A model which takes into account the change in catalyst work function with changing catalyst activation overpotential and the consequent changes in the bonding strength of chemisorbed species is proposed. The model is in semiquantitative agreement with experiment.