Nitrogen vacancy-modulated Z-scheme CTF-based heterojunction for highly efficient and selective photocatalytic CO₂ 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.