Nitrogen vacancy-modulated Z-scheme CTF-based heterojunction for highly efficient and selective photocatalytic CO ₂ reduction

Photocatalytic CO2 reduction into carbonaceous fuels is regarded as a promising strategy to simultaneously alleviate the energy shortage and greenhouse effect. However, rapid charge recombination and sluggish CO2 reduction kinetics still severely restrict the photocatalytic CO2 conversion efficiency. Herein, we fabricated a two-dimensional face-contact TiO2/Ag/CTF-Nv Z-scheme heterojunction featuring abundant N vacancies through a simple electrostatic self-assembly and annealing process for substantially enhancing CO2 photoreduction activity and selectivity. Specifically, in the absence of sacrificial reagent and photosensitizer, the TiO2/Ag/CTF-Nv achieves nearly 100% CO selectivity with a record evolution rate of 74.98 μmol g-1 h-1, surpassing that of TiO2 and CTF-Nv by approximately 12.4 and 4.8 times, respectively. Systematic investigations involving operando experiments and theoretical calculations clearly demonstrate that N vacancies with strong electron-trapping characteristics can accelerate Z-scheme charge transfer by directing electron migration from TiO2 to CTF-Nv, further increasing the charge separation efficiency. Moreover, the N vacancies with high electron density serve as active sites to promote interfacial electrons transfer to CO2, improve CO2 chemisorption/activation capacity, and decrease energy barrier for CO evolution. This work offers novel insight into the construction of defect-modulated Z-scheme heterojunction for significantly improving photocatalytic CO2 reduction performances.