Strategies to Modulate the Copper Oxidation State Toward Selective C₂₊ Production in the Electrochemical CO₂ Reduction Reaction

Abstract The electrochemical reduction of CO₂ to form value‐added chemicals receives considerable attention in recent years. Copper (Cu) is recognized as the only element capable of electro‐reducing CO₂ into hydrocarbons with two or more carbon atoms (C₂₊), but the low product selectivity of the Cu‐based catalyst remains a major technological challenge to overcome. Therefore, identification of the structural features of Cu‐based catalysts is of great importance for the highly selective production of C₂₊ products (ethylene, ethanol, n‐propanol, etc.), and the oxidation state of Cu species in the catalysts is found critical to the catalyst performance. This review introduces recent efforts to fine‐tune the oxidation state of Cu to increase carbon capture and produce specific C₂₊ compounds, with the intention of greatly expediting the advance in the catalyst designs. It also points to the remaining challenges and fruitful research directions for the development of Cu‐based catalysts that can shape the practical CO₂ reduction technology.