Abstract: Using bismuth oxybromide(BiOBr) and nitrogen-rich carbon nitride(g-C3N5) as raw materials, a Z-scheme g-C3N5/BiOBr heterojunction photocatalyst was constructed via solvothermal method. The crystal phase structure, morphology, specific surface area, optical absorption and photoelectrochemical properties of the materials were characterized by XRD, SEM, BET, UV-Vis DRS and I-t measurements. Through catalytic reduction of Cr(VI) under simulated sunlight, after 45 min of illumination, the reduction efficiency of pure BiOBr for Cr(VI) was 65.85%; the reduction efficiency of 5% g-C3N5/BiOBr heterojunction was 98.58%. By adjusting the acidity and alkalinity of the solution, the reduction efficiency was optimal under weakly acidic conditions of pH=4, reaching 99.6%. The reduction rate of 5% g-C3N5/BiOBr heterojunction remained higher than 97% after five cycles, and it maintained good catalytic activity and stability in tap water and natural sunlight. Free radical capture experiments confirmed that photogenerated electrons (e?) were the main active species. The heterojunction broadens the light absorption range, effectively inhibits carrier recombination, and significantly improves the photocatalytic reduction performance of Cr(VI).

Key words: g-C₃N₅/BiOBr; Z-scheme heterojunction, Photocatalytic reduction, Cr(VI)