Construction and synthesis of ternary rGO/COF–C4N/NH2–Bi2O3 heterojunctions for efficient photocatalytic degradation of chlorophenol

Abstract

A new type of highly efficient ternary rGO/COF–C₄N/NH₂–Bi₂O₃ heterojunction was designed and synthesized by solvothermal and ultrasonic methods, and was applied to photocatalytic degradation of chlorophenol in water. The results show that the photocatalytic activity and stability of rGO/COF–C₄N/NH₂–Bi₂O₃ for the degradation of o-chlorophenol (2-cp) were significantly increased compared with those of pure Bi₂O₃, COF–C₄N, and COF–C₄N/NH₂–Bi₂O₃. The photocatalytic degradation rates of 2-cp by rGO/COF–C₄N/NH₂–Bi₂O₃-5% reached 83.7% and 97.4%, and the highest degradation rate constants were 0.0072 min⁻¹ and 0.0158 min⁻¹ under visible light and full light, respectively. The ternary photocatalyst rGO/COF–C₄N/NH₂–Bi₂O₃-5% maintained its performance even after four consecutive cycles, with only a 5% decrease in its degradation rate. The degradation experiments for other chlorophenol pollutants under visible light demonstrated that this ternary heterojunction is mainly applicable to the degradation of 2-cp and 2,4-dcp, but inefficient for cp, 3-cp, and 4-cp. The degradation rate of 2,4-dcp could reach 85.1% under visible light. Based on the analysis of band structure, free radical trapping experiments and the analysis of photoelectrochemical properties, the photocatalytic degradation mechanism of chlorophenols by a type II rGO/COF–C₄N/NH₂–Bi₂O₃ heterojunction was proposed, in which h⁺ and ˙OH⁻ have a primary influence on the degradation activity, and rGO plays an important role in improving charge transfer and separation. This work provides an effective strategy for the effective removal of chlorophenols from wastewater by photocatalysis.