B-derived charge carrier transfer in SnO2/g-C3N4 heterostructures towards enhanced photocatalytic H2O2 production and tetracycline removal

Abstract

To improve photocatalytic hydrogen peroxide (H₂O₂) generation and antibiotic degradation, SnO₂ nanocrystals were embedded in boron-doped graphitic carbon nitride (g-C₃N₄) nanosheets. Superior thin B-g-C₃N₄ nanosheets were created via two-step thermal polymerization at 550 and 700 °C in Ar atmosphere. SnO₂ nanocrystals less than 5 nm were homogeneously embedded in nanosheets by mechano-chemical pre-reaction and heat-treatment at 400 °C in air condition to form SnO₂/B-g-C₃N₄ composites. The mechano-chemical pre-treatment and B doping were crucial for the homogeneous distribution of SnO₂ nanocrystals. The formation of heterostructure, well-developed interfaces, introduced B components, and decent conductivity of SnO₂ components resulted in efficient charge separation/transfer during photocatalysis. B-doping played key role in enhancing photoinduced charge separation/transfer to enhance H₂O₂ generation and tetracycline degradation. After embedding SnO₂ nanocrystals in B-g-C₃N₄, the photocatalytic activity was drastically enhanced. A SnO₂/B-g-C₃N₄ sample prepared using optimized conditions revealed a H₂O₂ production rate of 9287.0 μM g^-1 h^-1 which was 3.8 times of that of g-C₃N₄ (2449.8 μM g^-1 h^-1). The photocatalytic tetracycline degradation rate constant of the SnO₂/B-g-C₃N₄ composites was 0.018 min^-1 using first-order kinetic fitting, which was 6 times of that of g-C₃N₄ (0.003 min^-1). These results provide novel insight for the application of photocatalytic technology in environmental field.