Boosted charge transfer and photocatalytic CO2 reduction over sulfur-doped C3N4 porous nanosheets with embedded SnS2-SnO2 nanojunctions

Two-dimensional porous nanosheet heterostructure materials, which combine the advantages of both architecture and components, are expected to feature a significant photocatalytic performance toward CO2 conversion into useful fuels. Herein, we provide a facile strategy for fabricating sulfur-doped C3N4 porous nanosheets with embedded SnO2-SnS2 nanojunctions (S-C3N4/SnO2-SnS2) via liquid impregnation-pyrolysis and subsequent sulfidation treatment using a layered supramolecular structure as the precursor of C3N4. A hexagonal layered supramolecular structure was first prepared as the precursor of C3N4. Then Sn4+ ions were intercalated into the supramolecular interlayers through the liquid impregnation method. The subsequent annealing treatment in air simultaneously realized the fabrication and efficient exfoliation of layered C3N4 porous nanosheets. Moreover, SnO2 nanoparticles were formed and embedded in situ in the porous C3N4 nanosheets. In the following sulfidation process under a nitrogen atmosphere, sulfur powder can react with SnO2 nanoparticles to form SnO2-SnS2 nanojunctions. As expected, the exfoliation of sulfur-doped C3N4 porous nanosheets and ternary heterostructure construction could be simultaneously achieved in this work. Sulfur-doped C3N4 porous nanosheets with embedded SnO2-SnS2 nanojunctions featured abundant active sites, enhanced visible light absorption, and efficient interfacial charge transfer. As expected, the optimized S-C3N4/SnO2-SnS2 achieved a much higher gas-phase photocatalytic CO2 reduction performance with high yields of CO (21.68 mu molg(-1) h(-1)) and CH4 (22.09 mu molg(-1) h(-1)) compared with the control C3N4, C3N4/SnO2, and S-C3N4/SnS2 photocatalysts. The selectivity of CH4 reached 80.30%. Such a promising synthetic strategy can be expected to inspire the design of other robust C3N4-based porous nanosheet heterostructures for a broad range of applications.