Fabrication and photocatalytic activity enhanced mechanism of direct Z-scheme g-C₃N₄/Ag₂WO₄ photocatalyst

Highlights: • g-C₃N₄ acted as a support for the in situ growth of β-Ag₂WO₄. • g-C₃N₄ nanosheets inhibited the phase transformation of β-Ag₂WO₄ to α-Ag₂WO₄. • g-C₃N₄/Ag₂WO₄ exhibited a superior photocatalytic activity. • A direct Z-scheme photocatalytic mechanism could explain activity enhancement. - Abstract: Herein, a direct Z-scheme graphitic carbon nitride (g-C₃N₄)/silver tungstate (Ag₂WO₄) photocatalyst was prepared by a facile in situ precipitation method using g-C₃N₄ as a support and silver nitrate as a precursor. X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and elemental mapping demonstrated that β-Ag₂WO₄ nanoparticles were evenly distributed on the surface of g-C₃N₄ nanosheets, which acted as a support for the nucleation and growth of β-Ag₂WO₄ and inhibited the phase transformation of metastable β-Ag₂WO₄ to stable α-Ag₂WO₄. Photocatalytic experiments indicated that the g-C₃N₄/Ag₂WO₄ nanocomposite photocatalyst displayed a better photocatalytic activity than pure g-C₃N₄ and Ag₂WO₄ toward the degradation of methyl orange. The enhanced photocatalytic performance of g-C₃N₄/Ag₂WO₄ could be well explained by a direct Z-scheme photocatalytic mechanism. This mechanism was related to the efficient space separation of photogenerated electron–hole pairs and the great oxidation and reduction capabilities of the g-C₃N₄/Ag₂WO₄ system. This work provided new insights into the design and fabrication of g-C₃N₄-based direct Z-scheme photocatalysts.