Restructuring of shape-controlled Cu₂O catalysts during CO₂electroreduction

Oxide-derived (OD-Cu) catalysts are well-known catalysts with relatively high activities for the electrochemical reduction of CO₂ (CO₂RR) to C₂₊ products. During CO₂ electrolysis, the strongly reducing conditions lead to a transformation of the morphology and surface sites of copper catalysts. These changes, particularly in the crystallographic orientation of the exposed surfaces, are thought to play an important role in the CO₂RR performance of the catalysts. Herein, we investigated the relation between the restructuring of as-prepared Cu₂O catalysts with different shapes and the catalytic performance for the CO₂RR. The studied electrocatalysts included Cu₂O cubes and Cu₂O octahedra, exposing predominantly (100) and (111) facets, respectively. The difference in catalytic performance could be linked to the exposed metallic facets formed during reduction, which is supported by in situ X-ray diffraction (XRD) and cyclic voltammetry. SEM imaging showed that the bulk morphology was maintained accompanied with the formation of small nanoparticles on the surface of the catalysts, likely caused by Cu dissolution and redeposition. The crystallite size of the Cu phase was significantly smaller than that of the Cu₂O phase, hinting at the substantial restructuring of the catalysts by breaking up of the large particles during the CO₂RR.