(532ax) Dynamic Promotion of Heterogeneous Catalysis By Oscillating Electric Potentials

Heterogeneous catalysis is usually restrained by the Sabatier limit – the compromise between binding energies of different reactants, intermediates, and products. Although this inevitably holds true for time-invariant catalysts, dynamic changes of catalyst surfaces can overcome this restriction. Among other possible methods, we envisioned applying oscillating electric potentials to electrodes to be a suitable approach for the enhancement of catalytic activity. We found this to be the case for the Faradaic formic acid electrooxidation, cycling between potentials favoring the initial dehydration of formic acid to carbon monoxide and potentials allowing the subsequent oxidative stripping of CO allow us to determine coverage-dependent reaction kinetics. With this fractional CO coverage quantitative information on reaction rates of different electrode surfaces (Rh, Pd, and Pt) can be obtained. Besides enhancing Faradaic reactions, oscillating potentials can also promote non-Faradaic reactions (without stoichiometric electron transfer between the electrode and adsorbates). As a demonstration, we report the ethylene hydrogenation reaction which can be enhanced by a factor of ~5 when oscillating potentials are applied to the catalyst surface. Kinetic studies shed light on the effect of electric potentials on the catalyst surface coverage with substrates and intermediates.