Differentiating the Impacts of Cu2O Initial Low‐ and High‐Index Facets on Their Reconstruction and Catalytic Performance in Electrochemical CO2 Reduction Reaction

Abstract Oxide‐derived Cu catalysts from Cu 2 O microcrystals are capable of electrochemically converting CO 2 into various value‐added chemicals. However, their structural transformation and associated preferred products remain unclear, requiring further investigation. Herein, Cu 2 O microcrystals with controllable low‐ and high‐index facets exposure are fabricated to differentiate the effects of initial exposed facets on their structural reconstruction and product selectivity in electrochemical CO 2 reduction reaction. Combined in situ characterizations and theoretical investigation reveal the direct correlations of Cu 2 O reconstruction and product selectivity to its initial facet exposure. The Cu 2 O low‐index facet, being more stable with a high energy barrier on material reduction, tends to partially maintain its original crystalline structure and larger Cu 2 O particle size throughout the transformation. The derived flatter surface and limited Cu 2 O/Cu interfaces result in a favorable selectivity toward 2‐electron transfer products. The chemically active Cu 2 O high‐index facet (311) is energetically favorable to be reduced owing to the feasible protonation process, thus experiencing a drastic reconstruction with rich newly formed Cu nanoparticles and evolved fine Cu 2 O grains; Such a reconstruction creates uncoordinated Cu species and abundant boundaries, benefiting charge transfer and increasing the local pH by confining OH − , thus leading to a high selectivity toward C 2+ products.