A facile template-free hydrothermal approach is developed to synthesize hierarchical flower-like graphene–Bi₂O₂CO₃ microcomposites. The as-prepared samples were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, N₂ adsorption–desorption and UV-visible diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated towards degradation of Rhodamine B (RhB) under visible light. Compared to hierarchical Bi₂O₂CO₃, hierarchical flower-like graphene–Bi₂O₂CO₃ microcomposites show enhanced photocatalytic activity. In addition, our results indicate that both the physico-chemical properties and associated photocatalytic activity of graphene–Bi₂O₂CO₃ composites are shown to be dependent on graphene loadings. The highest photocatalytic performance can be achieved for the graphene–Bi₂O₂CO₃ microcomposites with 1.0 wt% graphene. The underlying mechanism responsible for the formation of graphene–Bi₂O₂CO₃ composites and enhanced photoreactivity was discussed. Results from this study illustrate an entirely new approach to fabricate semiconductor composites containing graphene–bismuth with high visible-responsive photocatalytic performance.

A facile one-step hydrothermal method was developed to synthesize novel hierarchical rose-like Bi₂O₂CO₃ microstructures. The physico-chemical properties of the as-synthesized catalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, N₂ adsorption–desorption and UV-visible diffuse reflectance spectroscopy. A possible formation mechanism of hierarchical Bi₂O₂CO₃ microspheres was proposed. The photocatalytic activity of the as-prepared samples was evaluated toward degradation of rhodamine B, and mixed aqueous solutions containing methylene blue and methyl orange under visible-light. Compared to Bi₂O₂CO₃ and Bi₂WO₆ nanosheets, hierarchical rose-like Bi₂O₂CO₃ microspheres show enhanced photocatalytic activity. The observed photocatalytic performance was attributed to the synergetic effects of particle morphology, average crystallite size, specific surface area, pore structure, and exposed two-dimensional (2D) nanosheets with dominant {001} facets of 3D hierarchical rose-like Bi₂O₂CO₃ microspheres.

Core–shell CdMoO₄@CdS hollow microspheres, fabricated by a simple ion-exchange hydrothermal method, exhibit outstanding photocatalytic activity toward degradation of RhB dye solution.