Electronic State Coupling for Cu ⁺ Stabilization to Boost Highly Efficient Transformation of CO ₂ to C2 Products

ABSTRACT Cu‐based nanomaterials are attracting great attention for the electroreduction of CO 2 to valuable C2 products. However, the optimization of physicochemical properties of Cu‐based active species, especially the electronic valence and orbital states, remains one of the greatest challenges in achieving desirable C2 products synthesis performance under harsh reductive electrolysis conditions. To tackle this obstacle, we propose a pulse‐enabled Cu valence‐state regulation strategy by integrating carbon quantum dots (CQDs). Under pulsed electrolysis, Cu 2‐x Se/CQDs delivers a Faradaic efficiency (FE) of up to 85.3% for C2 products and maintains FE C2 >70% over an ultra‐wide potential window of 1.6 V. Multiple in situ spectroscopic characterizations and theoretical simulations clarify that the strong electronic state coupling between Cu 2‐x Se and CQDs, together with pulsed electrolysis, maintains monovalent Cu species (Cu + ), guaranteeing the outstanding C2 products synthesis efficiency. This work presents an innovative and universal protocol to guide the rational design of catalysts requiring precise oxidation‐state control.