Z-scheme bismuth-rich bismuth oxide iodide/bismuth oxide bromide hybrids with novel spatial structure: Efficient photocatalytic degradation of phenolic contaminants accelerated by in situ generated redox mediators

Z-scheme photocatalysts commonly possess both high charge separation efficiency and strong redox ability. In this paper, novel 3-dimensional/2-dimensional (3D/2D) structured bismuth-rich bismuth oxide iodide/bismuth oxide bromide (Bi4O5I2/BiOBr) hybrids with Z-scheme heterojunctions were first prepared. The in situ generated I3-/I- and Bi5+/Bi3+ redox mediators in Bi4O5I2/BiOBr hybrids greatly improve their photocatalytic activity toward phenolic contaminants. Their structure, morphology, optical properties, and electrochemical properties were characterized. Scanning electron microscopy images demonstrated that the 2D BiOBr nanoplates were evenly and tightly anchored on the surface of the 3D Bi4O5I2 microspheres. This novel 3D/2D spatial structure was beneficial for the formation of heterojunctions between BiOBr and Bi4O5I2, which improved the quantum efficiency through interfacial charge transfer. The Bi4O5I2/BiOBr hybrids exhibited excellent photocatalytic activities toward o-phenylphenol (OPP), p-tert-butylphenol, 4-chlorophenol, and p-nitrophenol. Bi4O5I2/BiOBr-5 possessed the best activity in decomposing OPP, which was approximately 3.43 times higher than that of pure Bi4O5I2. The well-matched energy bands of components in the hybrids facilitated the interfacial charge separation through an effective Z-scheme transfer direction guided by I3-/I- and Bi5+/Bi3+ redox mediators. Based on the results of electron spin paramagnetic resonance and trapping experiments, a mechanism was proposed for the degradation of pollutants using the Bi4O5I2/BiOBr hybrids.