Full-exposed Cu site of Cu2O-(1 0 0) driven high ethylene selectivity of carbon dioxide reduction

Cu2O shows great potential as a catalyst for the electrochemical CO2 reduction reaction (ECO2RR). However, the mechanism behind the formation of different final products from Cu2O nanostructures remains a challenge. In this study, we combine theoretical and experimental approaches to demonstrate that the full-exposed Cu sites in Cu2O (1 0 0) microcubes contribute to superior C2H4 selectivity compared to other microstructures such as Cu2O (1 1 1), (1 1 0), and (3 1 1) facets. Density functional theoretical (DFT) calculations reveal that the stronger orbital splitting between Cu 3d and O 2p orbital of Cu2O (1 0 0) facet facilitates the formation of neighboring and low valence state Cu active site, thereby enhancing *CO adsorption and C2H4 formation. These DFT results are supported by the synthesis of four kinds of Cu2O microparticles (MPs) with different exposed facets, where cubic-Cu2O with the (1 0 0) facet exhibits the highest Faradaic efficiency (61.3 %). This study has significant implications for the structural design and mechanism analysis of innovative catalysts used in ECO2RR.