BiO_xCl_y/BiO_mBr_n/BiO_pI_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 (BiO_xCl_y/BiO_mBr_n/BiO_pI_q/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 > Bi₃O₄Cl/Bi₃O₄Br/Bi₄O₅I₂/GO > Bi₁₂O₁₇Cl₂/Bi₃O₄Cl/Bi₁₂O₁₇Br₂/ Bi₇O₉I₃/GO > Bi₁₂O₁₇Cl₂/BiOBr/BiOI/GO > Bi₁₂O₁₇Cl₂/Bi₁₂O₁₇Br₂/Bi₇O₉I₃/Bi₅O₇I/GO > Bi₃O₄Cl/BiOBr/Bi₃O₄Br/Bi₄O₅I₂ > Bi₃O₄Cl/BiOBr/BiOI > BiOCl/BiOBr/BiOI > Bi₁₂O₁₇Cl₂/Bi₅O₇Br/Bi₅O₇I > 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 ¹O₂ are all essential for HBA degradation.