Facile solvothermal synthesis of porous Bi2O3 microsphere and their photocatalytic performance under visible light

A facile template-free method has been developed for the controllable fabrication of novel hierarchical flower-like Bi₂O₃ microspheres via a solvothermal process in the presence of ethylene glycol. The products were characterised by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflection spectroscopy and nitrogen adsorption. The formation mechanism was proposed based on the evolution of morphology as a function of solvothermal time, which involves the initial formation of nanoparticles followed by their self-aggregation to microspheres and transformation into hierarchical flower-like microspheres by Ostwald ripening. The photocatalytic activities of as-prepared Bi₂O₃ hierarchitectures were six to nine times higher than that of the commercial sample, which was evaluated by the degradation of rhodamine B dye under visible light irradiation (λ>;420 nm). The improved photocatalytic performance could be ascribed to the special hierarchical microsphere structure, good permeability, large surface area (58.2 m²g^-1) and large bandgap (2.89 eV). The as-obtained products may have potential applications in water treatment and other related microscale or nano-scale devices.