The Crystal Plane is not the Key Factor for CO2‐to‐Methane Electrosynthesis on Reconstructed Cu2O Microparticles

Abstract Cu 2 O microparticles with controllable crystal planes and relatively high stability have been recognized as a good platform to understand the mechanism of the electrocatalytic CO 2 reduction reaction (CO 2 RR). Herein, we demonstrate that the in situ generated Cu 2 O/Cu interface plays a key role in determining the selectivity of methane formation, rather than the initial crystal plane of the reconstructed Cu 2 O microparticles. Experimental results indicate that the methane evolution is dominated on all three different crystal planes with similar Tafel slopes and long‐term stabilities. Density functional theory (DFT) calculations further reveal that *CO is protonated via a similar bridge configuration at the Cu 2 O/Cu interface, regardless of the initial crystal planes of Cu 2 O. The Gibbs free energy changes (Δ G ) of *CHO on different reconstructed Cu 2 O planes are close and more negative than that of *OCCOH, indicating the methane formation is more favorable than ethylene on all Cu 2 O crystal planes.