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.