BACKGROUND: The commonly used RhB dye is a carcinogen that is widely found in environmental matrices and poses a threat to aquatic biota and human health. However, conventional wastewater treatment processes do not effectively remove low concentrations of these pollutants. Herein, the P-Bi 4 O 5 Br 2 /AgI (PBA) heterojunction was synthesized via a polyvinylpyrrolidone (PVP)-assisted solvothermal and precipitation method in this work. RESULTS:The photocatalytic efficiency of the PBA heterojunction was evaluated by degrading rhodamine B (RhB) with the irradiation of simulated sunlight. P-Bi 4 O 5 Br 2 /AgI-50 (PBA-50, the mass fraction of AgI in the composite was 50%) composite could degrade 98% RhB under 90 min irradiation of 500 W Xenon lamp, and its pseudo first-order reaction rate constant was 0.04265 min −1 , which was 17.1, 2.16, and 2.94 times higher than that of Bi 4 O 5 Br 2 , P-Bi 4 O 5 Br 2 , and AgI, respectively. Besides, the effects of the dosage of photocatalyst and the anion on the photocatalytic degradation of RhB over PBA-50 were analyzed. CONCLUSION:The enhanced photocatalytic activity of PBA was attributed to its better visible light capture ability, larger specific surface area, and faster photogenerated carrier separation efficiency, all of which were confirmed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), UV-Vis diffues reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and photoelectrochemical analysis. In addition, the free radical trapping experiments confirmed that •O 2 − and h + were the main active species for degradation of RhB. Additionally, the smaller bandgap and the more negative conduction band position of Bi 4 O 5 Br 2 were reached after the introduction of PVP. Accordingly, a possible type-II heterojunction photocatalytic mechanism of P-Bi 4 O 5 Br 2 /AgI was proposed.