BiOBr/g-C₃N₄ Planar Heterostructures toward Enhanced Tetracycline Hydrochloride Removal

The redox ability of photocatalysts is a key to the degradation of tetracycline hydrochloride (TCH) which resulted in serious environmental problems. In this paper, narrow band gap BiOBr nanoplates were grown on superior thin graphitic carbon nitride (g-C₃N₄) nanosheets to increase light absorption and enhance redox ability for TCH removal. Meanwhile, g-C₃N₄ nanosheets were created by a two-step thermal polymerization at 600 and 700 °C, respectively. The deposition of layered BiOBr was finished along the surface of g-C₃N₄ nanosheets by a direct wet-chemical precipitation. BiOBr nanoplates were in situ grown on g-C₃N₄ nanosheets to create a well-developed interface and form S-scheme BiOBr/g-C₃N₄ heterostructures with enhanced photocatalytic performance. Visible light-derived photocatalytic tests indicated that the heterostructure sample created using optimized conditions revealed excellent performance, in which Rhodamine B of 10 mg/L was completely degraded within 9 min (10 mg catalyst added). TCH (50 mg/L) of 80% was degraded within 60 min with a degradation rate of 2.4 × 10^-2 min^-1, which was 6 and 3.4 times of those of pristine g-C₃N₄ nanosheets and BiOBr, respectively. The free radical capture test suggested that superoxide radicals dominated TCH degradation, and cyclic stability test indicated the degradation rate was kept 72% after 6 cycles. The S-scheme pathway in the heterostructure-enhanced charge separation and retained high redox ability for photocatalytic degradation of pollutants. These results supplied useful approaches for the photocatalysts with a high redox ability.