One-pot hydrothermal synthesis of BiPO4/BiVO4 with enhanced visible-light photocatalytic activities for methylene blue degradation

Abstract

Novel composite BiPO₄/BiVO₄ photocatalysts with different amounts of BiPO₄ were synthesized by a simple one-pot hydrothermal method at pH = 0.5. The obtained photocatalysts were systematically characterized using X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activities of BiPO₄/BiVO₄ were evaluated by the degradation of methylene blue (MB), methyl orange (MO) and rhodamine B (RhB) under visible light (λ > 400 nm). The results showed that all of the BiPO₄/BiVO₄ composites exhibited much higher photocatalytic activities than pure BiVO₄ and BiPO₄. Among the composites, 10% BiPO₄/BiVO₄ could degrade 92.1% MB after 5 h illumination and possessed the best photocatalytic activity. Meanwhile, the k value of 10% BiPO₄/BiVO₄ was 0.503 h⁻¹, which was twice that of pure BiVO₄. The enhanced photocatalytic activity could be mainly ascribed to the suitable BiPO₄/BiVO₄ heterojunction interface which could effectively promote the separation of photoinduced electron–hole pairs. Moreover, the radical scavengers experiments demonstrated that ˙O₂⁻ and h⁺ were the main reactive species for MB degradation under visible light.