In-situ designed Bi metal @ defective Bi₂O₂SO₄ to enhance photocatalytic NO removal via boosted directional interfacial charge transfer

Photocatalytic technology provides a new approach for the harmless treatment of low concentration NO_x in the atmosphere. The development of high-performance semiconductor materials to improve the light absorption efficiency and the separation efficiency of photogenerated carriers is the focus of the research. Bismuth oxybismuth sulfate (Bi₂O₂SO₄) shows significant potential for photocatalytic NO_x purification due to its unique electronic and layered structure. However, its wide bandgap limits light absorption efficiency in the visible region, resulting in an undesirable photocatalytic activity. The surface plasmon resonance effect presents an effective strategy to enhance the catalytic activity of wide bandgap semiconductors under visible light. In this study, metal Bi loaded Bi₂O₂SO₄ photocatalysts with abundant oxygen vacancies (OVs) were prepared by in-situ reduction with NaBH₄, which exhibited a significantly enhanced visible-light catalytic purification of NO. The OVs not only induced the formation of intermediate energy levels and reduced the bandgap, but also enhanced the visible-light absorption ability of Bi₂O₂SO₄ and promoted carrier separation. The Bi metal also promoted the carrier separation and provided more hot electrons for the activation of small molecules to generate reactive radicals, which facilitated the photocatalytic reaction. The photocatalytic NO purification pathway and its performance enhancement mechanism were investigated by combining theoretical calculations and in-situ infrared characterization. This work provides new insights for the development and design of novel Bi-based semiconductors and new materials for the application of low concentration NO_x photocatalytic purification process.