Synergy mechanism of confined effect and Z-scheme electron transfer in core–shell structure photocatalyst for boosting photoreduction CO2 activity

Core-shell structure photocatalysts are favored due to their confinement effect that enhances photoreaction efficiency, but their synergistic effect with heterojunctions is frequently overlooked. Herein, we synthesized a porous core–shell photocatalyst TiO2 nanoparticles@graphitic carbon nitride (labeled as TNPs@CN) from self-assembled supramolecular precursors for high-efficient photocatalytic CO2 reduction. The porosity facilitates CO2 transport and adsorption, while Z-scheme on the core–shell interface enhances electron transfer. Both in situ experimental and theoretical calculations have proved the Z-scheme heterojunction of TNPs@CN with a high photoreduction CO2 rate of 26.89 and 8.91 μmol g−1h−1 for CO and CH4, respectively, which are far higher than those of amorphous TNPs-CN. A 13CO2 labeled isotopic experiment and in situ FT-IR results laid the foundation for the mechanism of CO2 photoreduction, which was then investigated in-depth by calculating free energy profile. This work provides valuable insights for designing high-performance photocatalysts that leverage the synergistic effect of core–shell structure and Z-scheme electron transfer for artificial photosynthesis.