Efficient Photocatalytic Degradation of Dyes over Hierarchical BiOBr/β-Co(OH)₂/PVP Multicomponent Photocatalyst under Visible-Light Irradiation

A novel visible-light driven BiOBr/β-Co(OH)₂/PVP (PVP=polyvinylpyrrolidone) hierarchical multicomponent photocatalyst assembled in nanosheets was synthesized by a simple one-pot solvothermal synthesis. The as-prepared photocatalyst was characterized by field-emitting scanning electron microscopy, transmission electron microscopy, N₂ adsorption-desorption analysis, FTIR spectroscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffraction analysis, X-ray photoelectron spectroscopy, UV/Vis diffuse reflectance spectra, and inductively coupled plasma atomic emission spectrometry. This research shows that the formation of the p-n heterojunction would be very conducive to effectively inhibit the recombination of the photoexcited electron-hole pairs and enhance the photoactivity significantly. Owing to its narrow band-gap energy (≈2.49 eV) and fast interfacial charge migration, this novel photocatalyst can efficiently absorb visible light and shows an improved ability for utilizing light energy. Although both β-Co(OH)₂ and BiOBr alone exhibit little photoactivity for the degradation of dyes, the BiOBr/β-Co(OH)₂/PVP hierarchical multicomponent photocatalyst exhibits unexpected, surprisingly high photoactivity and stability in degrading dyes in aqueous solution at moderate Co/Bi molar ratio and moderate PVP addition. The catalyst′s photoactivity is approximately 9.7 times of that of β-Co(OH)₂ and 3.2 times of that of BiOBr. This unusual photoactivity mainly arises from the synergetic chemical coupling effects between BiOBr, β-Co(OH)₂, and PVP. The excellent photoactivity and photostability of this hierarchical multicomponent photocatalyst make it a promising photocatalyst under visible-light response. Beyond that, this novel photocatalyst can be reused many times without significant loss of its activity. Catching light: The synthesis of the hierarchical BiOBr/β-Co(OH)₂/PVP multicomponent photocatalyst by a simple solvothermal method is described. This novel catalyst exhibits enhanced visible-light photoactivity for the degradation of representative dyes such as rhodamine B (RhB).