Influence of Copper Valence in CuOx/TiO2 Catalysts on the Selectivity of Carbon Dioxide Photocatalytic Reduction Products

The Cu cocatalyst supported on the surface of TiO₂ photocatalysts has demonstrated unique activity and selectivity in photocatalytic CO₂ reduction. The valence state of copper significantly influences the catalytic process; however, due to the inherent instability of copper's valence states, the precise role of different valence states in CO₂ reduction remains inadequately understood. In this study, CuO_x/TiO₂ catalysts were synthesized using an in situ growth reduction method, and we investigated the impact of various valence copper species on CO₂ photocatalytic reduction. Our results indicate that Cu⁺ and Cu⁰ serve as primary active sites, with the selectivity for CH₄ and CO products during CO₂ photoreduction being closely related to their respective ratios on the catalyst surface. The adsorption and activation mechanisms of CO on both Cu⁺ and Cu⁰ surfaces are identified as critical factors determining product selectivity in photocatalytic processes. Furthermore, it is confirmed that Cu⁺ primarily facilitates CH₄ production while Cu⁰ is responsible for generating CO. This study provides valuable insights into developing highly selective photocatalysts.