Efficient organic pollutant photodegradation driven by sulfur-doped carbon nitride/bismuth oxybromide heterojunctions featuring enhanced interfacial charge separation.

The rational design of visible-light-responsive photocatalysts is of great significance for addressing environmental pollution. In this study, sulfur (S) was introduced into graphitic carbon nitride (g-C3N4) through calcination using thiourea as the S source, resulting in the formation of two-dimensional, sulfur-doped g-C3N4 (SCN) with a hollow tubular structure. Utilizing a microwave hydrothermal method, SCN was grown on the surface of flower-like bismuth oxybromide (BiOBr) frameworks containing oxygen vacancies, leading to the fabrication of a unique two-dimensional/two-dimensional BiOBr/SCN heterojunction photocatalyst (SCNB-x). The optimized SCNB-5 achieved a degradation efficiency of 93.3% for norfloxacin (NOR, 20 mg L-1 within 72 min) and 95% for Acid Orange 7 (AO7, 20 mg L-1 within 60 min). The apparent reaction rate constants (k = 0.03651 min-1 for NOR, k = 0.04456 min-1 for AO7) were 6.81 and 3.06 times higher than those of the pristine SCN, respectively. Experimental and theoretical analyses confirmed that the enhanced catalytic performance originated from the synergistic effects of an extended solar absorption range, increased oxygen vacancy content in the composite catalyst, and the formation of an S-type heterojunction that strengthened the interfacial electric field. This work provides a novel strategy and theoretical foundation for the design and preparation of high-performance BiOBr-based photocatalysts.