S-scheme P-doped g-C3N4/BiOBr heterojunction with oxygen vacancy for efficient photocatalytic degradation of phenanthrene: Enhance molecular oxygen activation and mechanism insights

S-scheme heterojunction photocatalysts, renowned for their efficient charge separation and strong redox properties, have gained considerable attention in pollutant remediation. Hence, a dual-active site S-scheme P-doped g-C3N4/BiOBr with oxygen vacancy (PCN/BiOBr-OV) was synthesized. The optimized PCN/BiOBr-OV(2:1) exhibited an impressive degradation rate of 99.2% (kobs = 0.04048 min−1) and superior efficiency for various water conditions. Synergistic effects resulting from P-doping and oxygen vacancy (OV) enhanced charge transfer and promoted S-scheme heterojunction generation. The S-scheme charge transfer pathway in PCN/BiOBr-OV was validated using in-situ irradiation X-ray photoelectron spectroscopy (in-situ irradiation XPS). Experimental results and density functional theory (DFT) calculations provided direct evidence supporting the role of P-doping and OV in facilitating water and oxygen adsorption and activation at dual-active sites, leading to the generation of active species (h+, OH, and O2▪−). Quantum mechanical theory and intermediate product analysis effectively elucidated the ring-opening process of PHE. The highly efficient PCN/BiOBr-OV photocatalyst represents a promising strategy for the environmental remediation of PHE.