Hydrothermal synthesis of a Ba and Mg co-doped Bi12GeO20 photocatalyst with enhanced visible light catalytic activity

Abstract

Visible-light-activated (Ba,Mg)-codoped Bi₁₂GeO₂₀ has been successfully synthesized through a one-step hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS) and photoluminescence spectroscopy (PL). XPS study suggests that barium and magnesium were introduced into the Bi₁₂GeO₂₀ crystal successfully. The band gap of (Ba,Mg)-codoped Bi₁₂GeO₂₀ was greatly reduced in comparison with the pure and single-doped Bi₁₂GeO₂₀. (Ba,Mg)-codoped Bi₁₂GeO₂₀ showed higher photocatalytic activity than pure Bi₁₂GeO₂₀ and single-doped Bi₁₂GeO₂₀ in the photodegradation of Rhodamine B (RhB) aqueous solution under visible light irradiation. Photogenerated holes were the dominating active species, with the secondary and minor factors of hydroxyl radical and superoxide radical in the photodegradation process of (Ba,Mg)-codoped Bi₁₂GeO₂₀. For three cycles, the co-doped Bi₁₂GeO₂₀ exhibited high stability.