The crystal phase transformation of Ag₂WO₄ through loading onto g-C₃N₄ sheets with enhanced visible-light photocatalytic activity

A g-C₃N₄/Ag₂WO₄ composite photocatalyst was synthesized via a simple co-precipitation method at room temperature and was thoroughly characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, UV-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. The characterization results indicated that upon depositing Ag₂WO₄ onto the surface of g-C₃N₄ its morphology changed from primary rod-like particles to globular nanoparticles and its phase changed from α-type to β-type Ag₂WO₄. When the composite was used as the catalyst in the photodegradation of Rhodamine B, 40%-g-C₃N₄/Ag₂WO₄ exhibited the highest photocatalytic activity with its rate constant was about 10.8 times larger than that of pure g-C₃N₄ and 3.12 times larger than that of bare Ag₂WO₄. The enhanced photocatalytic activity can be attributed to the complementary potentials of the conduction bands and valence bands of g-C₃N₄ and Ag₂WO₄, which could not only realize the effective separation of photoinduced electron and hole pairs, but also retained the catalysts high stability and photocatalytic performance even after five recycles. Furthermore, a possible photocatalytic mechanism for the degradation of RhB over the g-C₃N₄/Ag₂WO₄ composite was proposed according to the results of active species quenching experiments.