Ternary Ag/BiOBr/rGO nanoflower composite as a high-efficiency photocatalyst for formaldehyde and rhodamine B degradation

Abstract

An efficient ternary Ag/BiOBr/rGO nanoflower composite was prepared by applying in situ precipitation and reduction process. The rGO nanosheets and Ag nanoparticles were modified on three-dimensional BiOBr nanoflowers. The structure, morphology, photoelectrochemical properties, etc., of Ag/BiOBr/rGO-4 were characterized and explored. The photocatalytic activity of Ag/BiOBr/rGO was assessed for the degradation of HCHO and RhB. Ag/BiOBr/rGO-4 showed remarkably improved photocatalytic activity than BiOBr and BiOBr/rGO in the degradation of HCHO and RhB under visible light irradiation. The Ag/BiOBr/rGO-4 composite can degrade 69% gaseous HCHO (0.16 mg L⁻¹) in 40 min (λ > 400 nm). The Ag/BiOBr/rGO-4 also has the highest photodegradation performance of RhB, with a 60 minutes degradation rate of 94%. The improved catalytic performance of the Ag/BiOBr/rGO is attributed to the following reasons: (1) rGO and Ag nanoparticles effectively improve the visible light absorption and utilization of BiOBr; (2) the construction of a Schottky junction between Ag nanoparticles and other components promotes charge flow and improves the separation of photo-generated carriers; (3) a three-dimensional nano-flower structure makes each component have good interface contact and fast carrier transfer ability and exposes more catalytic active sites. Furthermore, free-radical capture and ESR display that ˙O₂⁻ and ˙OH play major roles. The degradation process of the RhB is further investigated by LC-MS. The Ag/BiOBr/rGO composite reported in this research has great potential for environmental purification.