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

Cu2O microparticles with controllable crystal planes and relatively high stability have been recognized as a good platform to understand the mechanism of the electrocatalytic CO2 reduction reaction (CO2RR). Herein, we demonstrate that the in situ generated Cu2O/Cu interface plays a key role in determining the selectivity of methane formation, rather than the initial crystal plane of the reconstructed Cu2O 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 Cu2O/Cu interface, regardless of the initial crystal planes of Cu2O. The Gibbs free energy changes (ΔG) of *CHO on different reconstructed Cu2O planes are close and more negative than that of *OCCOH, indicating the methane formation is more favorable than ethylene on all Cu2O crystal planes. The in‐depth mechanism of electrocatalytic CO2 reduction on in situ reconstructed Cu2O microparticles is still ambiguous. Now strong evidence shows that the Cu2O/Cu interface plays a key role in determining the selectivity of methane production rather than the initial crystal planes of the Cu2O microparticles.