Rational design of efficient boron-doped and nitrogen-deficient g-C₃N₄/lead-free Cs₃Bi₂Br₉ perovskite nanocrystals Z-scheme heterojunction by optimised surface-active site and interfacial charge transfer

The major limitation for the photodegradation of pollutants by g-C₃N₄-based and lead-free halide perovskite photocatalysts are the moderate adsorption-photocatalytic ability and interfacial charge transfer rates. Herein, we have synthesized boron doped and nitrogen deficient g-C₃N₄ (BNCN_x/y) and fabricated the BNCN_x/y/Cs₃Bi₂Br₉ heterojunctions by anti-solvent method to regulate bandgap and improve photoabsorption. The optimal ratios BNCN_0.6/450/Cs₃Bi₂Br₉ (BNCN-CBB-30) exhibited the highest degradation efficiency of 98.62 % for chloroquine phosphate (CQ) within 60 min, which possessed not only high oxidation ability (>82.19 %) for a variety of antibiotics but excellent structural stability and reusability. DFT calculations revealed that BNCN_x/y/Cs₃Bi₂Br₉ had the shortest bond distance and greater adsorption energy with CQ. Under visible light irradiation, the rapid electron transfer from Cs₃Bi₂Br₉ to BNCN_450/0.6 driven by the built-in electric field enhanced generation of •O₂^–, ¹O₂, and •OH. This work provides new insights into the internal structure design of heterojunction photocatalysts.