Facile fabrication of heterostructured g-C₃N₄/Bi₂MoO₆ microspheres with highly efficient activity under visible light irradiation.

A facile and template-free solvothermal method was developed for the synthesis of microspheric g-C3N4/Bi2MoO6 photocatalysts. The obtained g-C3N4/Bi2MoO6 composites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photo-electron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and ultraviolet-visible diffuse reflection spectroscopy (DRS). The XRD, FTIR, and HRTEM characterization results confirmed the formation of heterojunction structures at the interfaces of g-C3N4 and Bi2MoO6. The DRS results showed that the absorption edges of g-C3N4/Bi2MoO6 composites were red shifted in the visible light region with the increase of g-C3N4 content. The SEM and TEM images revealed that the composites exhibited a microsphere-like morphology and were composed of smaller nanoplates. The elemental mapping images revealed that g-C3N4 and Bi2MoO6 nanoflakes uniformly assembled together to form hierarchical flowers. Compared with pure g-C3N4 and Bi2MoO6, the as-prepared samples exhibited superior photocatalytic activity towards the degradation of dyes (Rhodamine B and Methyl blue) under visible light irradiation. The enhanced photocatalytic activity of g-C3N4/Bi2MoO6 composites could be attributed to their strong visible light absorption, the high migration efficiency of photo-induced carriers, and the interfacial electronic interaction. The electrochemical impedance spectroscopy (EIS) confirmed that the interface charge separation efficiency was greatly improved by coupling g-C3N4 with Bi2MoO6. It was also confirmed that the photo-degradation of dye molecules is mainly attributed to the oxidizing ability of the generated holes (h(+)) and partly to the oxidizing ability of ·O2(-) and ·OH radicals.