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 alpha-type to beta-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.