Improving the visible-light photocatalytic activity of Bi₂O₄ by the combination of the p–n junction and oxygen vacancy strategy for the degradation of organic pollutants

Constructing p–n heterojunction has been recognized as an effective solution to facilitate the separation of photogenerated carriers through the internal electric field. The introduction of oxygen vacancies (OVs) on the surface of photocatalyst can produce an intermediate band (IB) below the conduction band (CB) of photocatalyst and act as electron trap centers. The catalytic activity of photocatalyst can be improved by adopting p–n heterojunction or OVs strategy, respectively. In this paper, a novel high-performance BiOCl-OVs/Bi₂O₄ p–n heterostructure, combining the advantages of the above two strategies, was successfully synthesized via a facile mechanical stirring method. The structure, morphology, and photoelectrochemical properties of the samples were studied in detail. The obtained BiOCl-OVs/Bi₂O₄ catalysts show enhanced visible-light photocatalytic activity compared with pure Bi₂O₄. The apparent rate constant of the optimal BiOCl-OVs/Bi₂O₄-2/5 sample is 1.66 and 2.71 times higher than that of Bi₂O₄ for the degradation of methyl orange (MO) and bisphenol A (BPA), respectively. The improved photocatalytic performance of BiOCl-OVs/Bi₂O₄ catalyst is mainly attributed to the combined p–n heterojunction effect and OVs formed on the surface of BiOCl. Finally, a probable photocatalytic reaction mechanism was proposed.