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

It is rather important to increase CO 2 adsorption capacity and improve separation efficiency of photo-induced carriers for solar-driven photocatalytic CO 2 reduction. Herein, millimeter-sized nitrogen-doped porous carbon spheres (NPCS-F6) with metal-like activity, as bifunctional support to immobilize and tailor Bi 2 Sn 2 O 7 nanoparticles (Bi 2 Sn 2 O 7 /NPCS-F6) for enhancing CO 2 photoreduction activity, have been constructed by suspension polymerization assisted with carbonization and impregnation method. Bi 2 Sn 2 O 7 /NPCS-F6 composite photocatalyst realized the photocatalytic CO 2 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 Bi 2 Sn 2 O 7 (152.03 μmol·g −1 ) and NPCs-F6 (17.61 μmol·g −1 ), respectively. The excellent CO 2 reduction activity should be attributed to the synergistic effect of Bi 2 Sn 2 O 7 and NPCS-F6, in which Bi 2 Sn 2 O 7 loaded on the surface of NPCS-F6 improved the hydrophobic property, promoted the oxidation reaction of H 2 O and provided more effective electrons for photocatalytic CO 2 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 CO 2 reduction mechanism for Bi 2 Sn 2 O 7 /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 CO 2 reduction.