Flower-like Bi4O5I2/Bi5O7I nanocomposite: facile hydrothermal synthesis and efficient photocatalytic degradation of propylparaben under visible-light irradiation

Abstract

Nonstoichiometric bismuth oxyiodide materials have exhibited high potential for applications in visible-light photocatalytic environmental cleaning and solar energy conversion. Herein, novel Bi₄O₅I₂/Bi₅O₇I nanocomposites, BiOI nanosheets, Bi₄O₅I₂ nanoflowers, and Bi₅O₇I microfibers are synthesized by controlling the alkalinity of reaction solutions in a facile one-pot hydrothermal route. The as-prepared Bi₄O₅I₂/Bi₅O₇I nanocomposite exhibits excellent visible-light photocatalytic performance for the degradation of propylparaben (PPB, a potential environmental contaminant structure that contains a benzene ring, hydroxyl, and carboxyl), which is approximately 32, 33, and 4 times higher than that of pure BiOI, Bi₅O₇I, and Bi₄O₅I₂, respectively. The enhanced photocatalytic activity of the Bi₄O₅I₂/Bi₅O₇I composite can be attributed to enhancement of charge separation by the formation of Bi₄O₅I₂/Bi₅O₇I interfaces, more positive valence band edge potential at +2.18 V, good absorption from UV to visible light, three-dimensional flower-like morphology composed of number nanoflakes, and large specific surface area with mesoporous features. The band structures of Bi₄O₅I₂ and Bi₅O₇I, the electrochemical oxidation behaviors of PPB, and the roles of the primary photogenerated oxidative species are analyzed, then a reasonable photocatalytic mechanism is proposed based on the experimental results. In addition, the as-synthesized Bi₄O₅I₂/Bi₅O₇I heterojunction remains stable throughout photocatalytic process and can be used repeatedly, indicating its potential for practical applications.