Hidden Mechanism Under Roughness-enhanced Selectivity of Carbon Monoxide Electrocatalytic Reduction.

High roughness has been proved to be an effective design strategy for electrocatalyst in many systems. Especially, high selectivity of carbon monoxide reduction (CORR) in competition with the hydrogen evolution reaction has been observed with the use of high roughness electrocatalyst. However, the two well-known mechanisms, i.e., decreasing the energy barrier of CORR and increasing local pH, were demonstrated to be failed by recent experiments. Here we unravel the hidden mechanism by establishing a comprehensive kinetic model for CORR on catalysts with different roughness factors. We conclude that the roughness-induced high CORR selectivity is actually kinetic controlled by local-electric-field-directed mass transfer of adsorbed species on the electrode surface. Several ways to optimize CORR selectivity are predicted. Our work highlights the kinetics in electrocatalysis on nanocatalysts, and provides a conceptually new principle for future catalyst design.