Enhanced photocatalytic performance of BiOBr/CQDs hierarchical nanostructures mixed with SiO2 nanospheres

Reinforcing light harvesting is an effective means to improve photocatalytic efficiency of semiconductors. In this study, carbon-quantum-dot-modified BiOBr mixed with SiO2 nanospheres (BiOBr/CQDs+SiO2) were prepared via stepwise chemical precipitation route. The characterizations of X-ray diffraction, field-emission scanning electron microscopy and energy-dispersive X-ray apparatus demonstrated that the as-prepared BiOBr/CQDs+SiO2 displayed nanosheets-building spherelike hierarchical nanostructures mixing with dispersive SiO2 nanospheres. Control photocatalytic degradation of orange II under natural sunlight illumination indicated that the presence of SiO2 nanospheres could further promote the photocatalytic behaviors of BiOBr/CQDs apart from CQDs. Diffuse reflection spectrum demonstrated that SiO2 nanospheres were capable of reflecting UV-Vis light near to 100%. The possible mechanism for the enhanced light-absorption surface of suspending hierarchical photocatalyst in presence of SiO2 nanospheres was proposed via light propagation over suspending SiO2 nanospheres under vertical light illumination. Our method for enhancing photocatalytic efficiency provided a general method to enhance light harvesting of every suspending two- or three-dimensional photocatalysts.