g-C3N4 modified flower-like WO3–Bi2WO6 microspheres with enhanced photoelectrocatalytic activity

Abstract

Graphitic carbon nitride (g-C₃N₄) modified flower-like WO₃–Bi₂WO₆ microspheres were prepared by hydrothermal and thermo polymerization methods. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The photoelectrocatalytic activity of all samples was evaluated by decomposition of methyl orange (MO) and phenol under visible light illumination. The photoelectrochemical test and analysis of energy-band theory showed that the photogenerated electrons (e⁻) and holes (h⁺) had strong reducing capability and oxidation capability, respectively, compared with WO₃–Bi₂WO₆ heterojunction energy-band theory. The photoelectrocatalytic activity of g-C₃N₄ modified WO₃–Bi₂WO₆ was higher than that of pure g-C₃N₄ and WO₃–Bi₂WO₆, which attributed to the efficient visible-light and electricity utilization efficiency and the construction of the double Z-scheme. The g-C₃N₄ served as a charge transmission bridge between the WO₃ and the Bi₂WO₆, and the Z-scheme kept the electrons with high reducing capability in the conduction band (CB) of Bi₂WO₆ and the holes with high oxidation capability in the valence band (VB) of WO₃. Meanwhile, the influence of the g-C₃N₄ amount on photoelectrocatalytic activity was discussed in detail. It was found that the optimal amount of g-C₃N₄ was 5 wt% in the double Z-scheme system, which demonstrated excellent photoelectrocatalytic activity.