Facile synthesis of g-C3N4/ZnO composite with enhanced visible light photooxidation and photoreduction properties

The composite photocatalyst g-C3N4/ZnO was synthesized by heat treatment of the precursor obtained via the deposition–precipitation method. The photocatalyst was characterized by XRD, SEM, TEM, DRS, and TA-PL. The photocatalytic properties of the photocatalyst were evaluated by photooxidation of RhB and photoreduction of Cr6+ under visible light irradiation. The results showed that the photocatalytic properties of the photocatalyst were much better than that of single C3N4 or ZnO. The optimal g-C3N4 content in the composite is 5.0 wt.%. Both photooxidation and photoreduction processes follow first-order kinetics. The photooxidation rate constant of RhB for g-C3N4(5.0 wt.%)/ZnO is 0.0367 min−1, while it is only 0.0112 min−1 for pure C3N4. The photoreduction rate constant of Cr6+ for g-C3N4(5.0 wt.%)/ZnO is more than five times that observed for pure C3N4. The stability of the prepared photocatalyst in the photocatalytic process was also investigated. The enhanced visible photocatalytic properties originate from the injection of excited electrons from the CB of C3N4 to that of ZnO.