Switching CO₂ reduction selectivity in Cu-TiO₂ catalysts: Role of Cu⁺ site location and oxygen vacancy concentration

Efficient conversion of CO₂ into valuable chemicals such as CH₄ under mild conditions is a significant challenge due to the high thermodynamic and kinetic barriers associated with multi-electron transfer reactions. In this study, we present a microwave-assisted strategy for the synthesis of Cu-doped, oxygen vacancy (Ov)-enriched TiO₂ nanotubes (C-CT) that stabilize both bulk and surface Cu⁺ species. These photocatalysts exhibit a remarkable CH₄ production rate of 202.1 μmol g^-1 h^-1 under simulated sunlight, with an outstanding electron selectivity of 99 %. Mechanistic investigations reveal that the synergistic interaction between Cu⁺ sites and oxygen vacancies enhances charge separation, stabilizes critical reaction intermediates, and facilitates the eight-electron reduction pathway for selective CH₄ production. This work offers a sustainable approach to CO₂ utilization, helping to overcome the thermodynamic and kinetic barriers in CO₂ photoreduction. Such efficient photocatalysts have the potential to significantly reduce CO₂ emissions and promote environmental sustainability.