Constructing Cu defect band within TiO and supporting NiO nanoparticles for efficient CO photoreduction.

Effectively harnessing solar energy for the conversion of CO into valuable chemical energy presents a viable solution to address energy scarcity and climate change concerns. Nonetheless, the limited light absorption and sluggish charge kinetics significantly hinder the photoreduction of CO. In this study, we employed a facile sol-gel method combined with wetness impregnation to synthesize Cu-doped TiO coated with NiO nanoparticles. Various characterizations verified the successful incorporation of Cu ions into the TiO crystal lattice and the formation of NiO co-catalysts within the composites. The optimal performance attained with CTN-0.5 demonstrates an output of 11.85 μmol h g for CO and 9.51 μmol h g for CH, which represent a 4.4-fold and 15.6-fold increase, respectively, compared to those achieved with pure TiO. The induced Cu defect band broadens the light absorption by decreasing the conduction band edge of TiO, while NiO upshifts the valence band of TiO because of the interaction of valence orbitals. Light irradiation EPR and FTIR tests suggest that the collaboration of CuO and NiO promotes the formation of oxygen vacancies/defects and a rapid charge transfer pathway, thereby provides numerous active sites and electrons to enhance CO photoreduction performance.