The synthesis of a BiOCl_xBr_1−x nanostructure photocatalyst with high surface area for the enhanced visible-light photocatalytic reduction of Cr(<scp>vi</scp>)

Abstract

The photocatalytic reduction of poisonous Cr(vi) to environmentally friendly Cr(iii) driven by visible-light is highly foreseen. The construction of heterojunctions is a promising and solid strategy to tune the photocatalytic performance of BiOCl in the visible region. Herein, for the first time, we report Cr(vi) reduction by a BiOCl_0.8Br_0.2 composite produced <i>via</i> a facile <i>in situ</i> synthetic process at room temperature while making use of PVP (MW = 10 000). In this study, a series of BiOCl _<i>x</i> Br_1-<i>x</i> nanocomposites with different concentrations of chlorine and bromine have been prepared. The results show that BiOCl_0.8Br_0.2 has crystalline lattice, a large surface area (147 m² g^-1), a microporous structure (0.377 cm³ g^-1), and very high chemical stability. It is revealed that the BiOCl_0.8Br_0.2 composite is much more active than those synthesized using different molar concentrations of chlorine and bromine. The DRS analysis and high photocurrent suggested that BiOCl_0.8Br_0.2 possessed absorption properties under visible light, which is beneficial for the efficient generation and separation of electron-hole pairs. In addition, we evaluated the photocatalytic activity of BiOCl_0.8Br_0.2 on the reduction of Cr(vi) under visible light irradiation and found that the obtained composite material exhibited a higher photocatalytic activity than single BiOCl or BiOBr without any decline in the activity after five cycles and is the best performing photocatalyst among those tested.