BiO x Cl y /BiO m Br n /BiO p I q /GO quaternary composites: Syntheses and application of visible-light-driven photocatalytic activities.

Herein, the preparation of numerous bismuth oxychloride/bismuth oxybromide/bismuth oxyiodide/graphene oxide (BiOx Cly /BiOm Brn /BiOp Iq /GO) composites is reported. A facile hydrothermal method was employed to synthesize these photocatalysts, which had various GO contents. A total of 10 bismuth-oxyhalide composites were isolated and characterized using FE-SEM, XRD, FE-TEM, UV-Vis-DRS, FT-IR, EPR, HR-XPS, PL, and BET. The photocatalytic efficiencies of these 10 bismuth-oxyhalide composites were measured under visible-light irradiation by estimating the concentration of 2-hydroxybenzoic acid (HBA) degradation. The findings indicated that the rate constant order of the HBA degradations was BiOCl/BiOBr/BiOI/GO > Bi3 O4 Cl/Bi3 O4 Br/Bi4 O5 I2 /GO > Bi12 O17 Cl2 /Bi3 O4 Cl/Bi12 O17 Br2 / Bi7 O9 I3 /GO > Bi12 O17 Cl2 /BiOBr/BiOI/GO > Bi12 O17 Cl2 /Bi12 O17 Br2 /Bi7 O9 I3 /Bi5 O7 I/GO > Bi3 O4 Cl/BiOBr/Bi3 O4 Br/Bi4 O5 I2  > Bi3 O4 Cl/BiOBr/BiOI > BiOCl/BiOBr/BiOI > Bi12 O17 Cl2 /Bi5 O7 Br/Bi5 O7 I > GO. A maximum rate constant of 0.191 h-1 was reached for BiOCl/BiOBr/BiOI/GO, providing photocatalytic efficiency that was eight times higher than that of composite BiOCl/BiOBr/BiOI. We also proposed a photocatalytic mechanism demonstrating that O2 - , h± , OH, and 1 O2 are all essential for HBA degradation.