Constructing Cu defect band within TiO 2 and supporting NiO x nanoparticles for efficient CO 2 photoreduction.

Effectively harnessing solar energy for the conversion of CO 2 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 2 . In this study, we employed a facile sol-gel method combined with wetness impregnation to synthesize Cu-doped TiO 2 coated with NiO x nanoparticles. Various characterizations verified the successful incorporation of Cu ions into the TiO 2 crystal lattice and the formation of NiO x co-catalysts within the composites. The optimal performance attained with CTN-0.5 demonstrates an output of 11.85 μmol h -1 g -1 for CO and 9.51 μmol h -1 g -1 for CH 4 , which represent a 4.4-fold and 15.6-fold increase, respectively, compared to those achieved with pure TiO 2 . The induced Cu defect band broadens the light absorption by decreasing the conduction band edge of TiO 2 , while NiO x upshifts the valence band of TiO 2 because of the interaction of valence orbitals. Light irradiation EPR and FTIR tests suggest that the collaboration of CuO x and NiO x promotes the formation of oxygen vacancies/defects and a rapid charge transfer pathway, thereby provides numerous active sites and electrons to enhance CO 2 photoreduction performance.