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

Abstract

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.