Engineering oxygen vacancies by P-doping into BiOBr to enhance photocatalytic activity for Cr(VI) reduction and tetracycline degradation

Oxygen vacancies (Ovs) were introduced on the BiOBr (BOB) surface by P-doping for fine-tailoring the photocatalytic efficiencies toward Cr(VI) reduction and tetracycline (TC) degradation in two individual and coexisting systems. Based on the comprehensive characterization, photocatalytic tests and density functional theory (DFT) calculations, it was confirmed that P-doping promoted the formation of OVs, and the OVs content was mediated through the phosphorus source amount in phosphorization process. OVs modulated the local electronic structure of Bi sites to generate a new donor sub-band within the forbidden band, which narrowed bandgap and increased the charge carrier density to promote the carrier separation/transfer, thus leading to the enhancement in the photoredox properties toward TC and Cr(VI) under visible-light. As a result, the optimal P-doped BOB (PBOB-2) with suitable OVs exhibited superior photo-oxidation/reduction activity in the single-pollutant system, attaining 94.9 % Cr(VI) and 79.0 % TC removal efficiencies for 120 min, and certain synchronous photoredox activity in the coexisting Cr(VI)/TC system. This work offers a facile strategy to design and construct high-performance photocatalysts by rationally tailoring oxygen vacancies for pollutant purification in environmental remediation.