Dependence of catalytic rates on catalyst work function

Abstract

THE catalytic activity and selectivity of metals can be altered dramatically and reversibly by supplying or removing oxide anions, O^2–, at the metal catalyst surface by interfacing the catalyst with an O^2– conductor such as zirconia^1–6. This effect, termed non-faradaic electrochemical modification of catalytic activity (NEMCA), leads to a steady-state catalytic reaction rate increase up to 3 × 10⁵ times higher than the rate of supply or removal of O^2– at the catalyst surface^1,3,4. Here we report that β"-Al₂O₃, which is a Na⁺ conductor, can also induce the NEMCA effect. Furthermore we show that the origin of the NEMCA effect lies in the controlled variation of catalyst work function on polarization of the metal-solid-electrolyte interface, and demonstrate that the rates of metal-catalysed reactions depend exponentially on the average catalyst work function. Thus the influence of catalyst electronic structure, rather than surface geometry, is here the key factor in catalytic activity.