Twin Heterostructure Engineering and Facet Effect Boosts Efficient Reduction CO₂-to-Ethanol at Low Potential on Cu₂O@Cu₂S Catalysts

Copper 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 and stable of CO2-to-ethanol (C2H5OH) based-Cu2O electrocatalysts remains challenging. In this work, Cu2O@Cu2S twin heterojunction catalysts with multitwin 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, density functional theory (DFT) calculations and in situ infrared spectroscopy reveals that the introduction of Cu2S boosts the high coverage of *CO, which can easily spillover to the twin boundaries to generate C2H5OH through the *CHOH_*CO coupling reaction pathway. A C2H5OH production begins at an ultralow potential of -0.45 V vs RHE and reaches 34 and 43.9% Faradaic efficiencies (FE) at -0.65 V vs RHE in an H-cell and a flow cell, respectively. Meanwhile, this heterojunction constructed with an interface coherent structure and suitable band structure can facilitate electron transfer from Cu2O to Cu2S, leading to the stability of Cu+ valence states. This work provides an avenue to precisely design C2H5OH production catalysts by regulating the interface configuration.