Oxygen vacancy engineering of Bi₂O₂CO₃ hierarchical microspheres for enhanced adsorption of Cd²⁺ ions and photocatalytic degradation of Rodamine B

Oxygen vacancies (OVs) can adjust surface and electronic structures of materials and behave as active sites, extend spectral responsive range, and promote the transfer and separation of photogenerated carriers. Therefore surface properties and photocatalytic activities of materials can be enhanced via the incorporation of OVs. However, the influences of OV concentration inside a material on its adsorption ability for heavy metal ions associated with surface and photocatalytic activities under different atmospheres are still unexplored. In this work, in order to obtain highly efficient adsorbents and photocatalysts, rose-like Bi₂O₂CO₃ hierarchical microspheres with rich OVs (Bi₂O₂CO₃-ROVs) and deficient OVs (Bi₂O₂CO₃-DOVs) were synthesized through a facile hydrothermal route and H₂O₂ oxidation treatment, respectively. Bi₂O₂CO₃-ROVs hierarchical microspheres showed 2.4-times larger adsorption capacity than Bi₂O₂CO₃-DOVs counterparts. The former also showed significantly enhanced photocatalytic activity for Rodamine B (RhB) degradation in aqueous solution under air, N₂, and Ar atmospheres than the latter, especially under anaerobic conditions. Our work demonstrated that OV engineering could provide a new strategy for enhancing adsorption capability and photocatalytic activity under both aerobic and anaerobic conditions of materials.