Assisting Bi2Sn2O7 nanoparticles with nitrogen-doped porous carbon spheres as bifunctional support for highly-efficient photocatalytic CO2 reduction

It is rather important to increase CO₂ adsorption capacity and improve separation efficiency of photo-induced carriers for solar-driven photocatalytic CO₂ reduction. Herein, millimeter-sized nitrogen-doped porous carbon spheres (NPCS-F6) with metal-like activity, as bifunctional support to immobilize and tailor Bi₂Sn₂O₇ nanoparticles (Bi₂Sn₂O₇/NPCS-F6) for enhancing CO₂ photoreduction activity, have been constructed by suspension polymerization assisted with carbonization and impregnation method. Bi₂Sn₂O₇/NPCS-F6 composite photocatalyst realized the photocatalytic CO₂ reduction activity to CO of 203.25 μmol·g⁻¹ under 8 h simulated sunlight irradiation, approximately 1.34 times and 11.53 times higher than that of pure Bi₂Sn₂O₇ (152.03 μmol·g⁻¹) and NPCs-F6 (17.61 μmol·g⁻¹), respectively. The excellent CO₂ reduction activity should be attributed to the synergistic effect of Bi₂Sn₂O₇ and NPCS-F6, in which Bi₂Sn₂O₇ loaded on the surface of NPCS-F6 improved the hydrophobic property, promoted the oxidation reaction of H₂O and provided more effective electrons for photocatalytic CO₂ reduction. On the other hand, large specific surface area and alkaline nitrogen species (N-6, N-5) of NPCS-F6 provided more reaction sites, while hierarchical pore structure and N-Q as electron transfer channels favored the separation of photogenerated electron-hole pairs. Finally, the possible photocatalytic CO₂ reduction mechanism for Bi₂Sn₂O₇/NPCS-F6 was proposed. Our findings should provide a favorable and feasible strategy to immobilize powder photocatalyst on millimeter-sized bifunctional carbon spheres for efficient photocatalytic CO₂ reduction.