Cu2o@Cu2s Nanocube Heterojunction with a Multitwin Boundary for Electrocatalytic Conversion of Co2 to Ethanol at Low Potential

Copper (I) oxide (Cu2O) is considered a promising catalyst that can effectively reduce the overpotential of the CO2 reduction reaction (CO2 RR) and increase the selectivity for C2+ products. However, developing high performance of CO2-to-ethanol (C2H5OH) based-Cu2O electrocatalysts is still challenging. Herein, Cu2O@Cu2S twin heterojunction catalysts with multigrain boundaries are designed to afford C2H5OH productivity at low potential through the electrocatalytic CO2 RR, and the C2H5OH selectivity is highly dependent on the facet of Cu2O@Cu2S with nanocubes outperforming octahedra. Detailed electrochemical experiments and density functional theory (DFT) calculations reveal that this heterojunction with interface coherent structure and suitable band structure can facilitate electron transfer from Cu2O to Cu2S, leading to a long-term stability (>24 h) of Cu+, the introduction of Cu2S leads to a high coverage of *CO, which can easily spillover to the twin boundaries and generate C2H5OH through *CHOH_*CO coupling reaction pathway. Thus, C2H5OH production in an H-cell begins at an ultralow potential of -0.45 V vs. RHE and reaches 34% of Faradic efficiencies at -0.65 V vs. RHE. This work provides a new avenue to precisely design C2+ production catalysts by regulating the interface configuration.