Hierarchical core-shell SiO₂@PDA@BiOBr microspheres with enhanced visible-light-driven photocatalytic performance

To explore catalysts combining highly accessible specific surface areas with low recombination of the photo-induced electron-hole pairs, a novel SiO₂@PDA@BiOBr composite photocatalyst with a hierarchical core-shell structure was prepared by a facile solvothermal method. The catalyst shows a superior performance on photodegradation of Rhodamine B under visible light irradiation, especially for SiO₂@PDA-2@BiOBr with the reactant kinetics constant (k = 0.0487 min^-1). The enhanced photocatalytic performance of SiO₂@PDA-2@BiOBr was ascribed to the decreased band-gap, higher surface area, and effectively photo-generated electron-hole pairs by the introduction of polydopamine (PDA). In addition, the photocatalytic degradation is initiated by ˙O₂^- derived from dye photosensitization and h⁺ from the BiOBr. Cyclic experiments also indicate that the SiO₂@PDA-2@BiOBr is reusable during the photodegradation process. The hierarchical core-shell SiO₂@PDA@BiOBr photocatalyst will provide a theoretical model for the development of physical chemistry and structural properties of BiOBr-based composites to enhance the photocatalytic performances.