Photocatalytic degradation of phenol using Au/Bi2WO6 composite microspheres under visible-light irradiation

Gold loaded Bi₂WO₆ (Au/Bi₂WO₆) nanosheet-based microspheres were prepared via a hydrothermal method combined with an in-situ reduction approach. The products were characterised by scanning electron microscopy, a high-resolution transmission electron microscope, X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance. The characterisation results revealed that it was the Au nanoparticles deposited on Bi₂WO₆ microspheres. A photocatalytic test for the degradation of phenol proved that Au loading was an effective means to enhance the photocatalytic activity of Bi₂WO₆ nanosheet-based microspheres under visible-light irradiation (λ > 420 nm). The photocatalytic mechanism over the Au/Bi₂WO₆ was analysed by active species trapping experiments. The main active species ·OH for the photocatalytic test was produced by two pathways, that is, photogenerated holes oxidised water molecules to form ·OH (oxidative pathway), and O₂ captured the photogenerated electron to generate ·O^{2 -} and subsequently produce ·OH (reductive pathway).