Adjustable Selectivity for CO₂ Electroreduction to Ethylene or Ethanol by Regulating Interphases Between Copper and Tin Oxides

Abstract Enhancing the selectivity of C₂ products and revealing the reaction mechanisms in CO₂ electroreduction reaction (CO₂RR) remain challenging. Regulating the interphases in catalysts is one of the most promising pathways. Herein, the interphases between copper (Cu) and tin (Sn) oxides are regulated by controlling the degree of reduction during the self‐assembly process, which exhibits obvious different selectivity to ethylene and ethanol, respectively. The interphase in Cu‐SnO₂ exhibits selectivity to ethanol as high as 74.6%, while the interphase in Cu₂O‐SnO₂ shows selectivity to ethylene as high as 71.4% at –0.6 V versus RHE. In situ Fourier‐transform infrared spectroscopy measurements and density functional theory calculations demonstrate that the interphase in Cu‐SnO₂ shows strong electron interaction, preferentially forming the key *COH intermediates for asymmetrical C─C coupling to produce ethanol. In contrast, Cu₂O‐SnO₂ possesses oxygen vacancies at both sites, thus enriching *CO intermediates for symmetrical C─C coupling to produce ethylene at the interphase. The findings in this work offer an advanced strategy by regulating the interphases to adjust C₂ selectivity in CO₂RR.