Charge-Mediated Stable Low-Valence Cu on TiO₂ for Photocatalytic CO₂-to-Ethylene Production

Cu is a key element for many photo- and electro-driven catalyst systems, but it readily undergoes natural oxidation in air and electron-mediated support interactions when in contact with reducible oxides. The production of value-added hydrocarbons via photocatalytic CO2 reduction is promising, but it remains an unresolved challenge due to the hurdles associated with controlling the valence state of the Cu cocatalyst within a heterogeneous composite formed as a result of oxidative stabilization during nucleation process. Herein, we report a local-charge-mediated strategy to synthesize Cu nanoparticles on a TiO2 photocatalyst, thus inducing a stable intermediate Cu valence state favorable for spontaneous C–C dimerization. Distinctive to fast-driven Cu2+-dominant valence state generation upon photoreduction, the negatively charged local electrons within the oxygen-deficient TiO2–x environment facilitates anoxic stabilization toward the Cu+-dominant valence state under dark conditions. Supported by combined structural analysis and theoretical calculations, the optimized Cu/TiO2–x exhibited a significant photocatalytic ethylene production rate of 1.85 μmol/g·h, making this a potential strategy to utilize interfacial coordination chemistry.