Construction of ZnO/C3N4 Composite for Photocatalytic Activity through Charge Transfer

The photocatalyst based on the ZnO/C3N4 composite can harness the high carrier mobility of ZnO along with the visible light absorption characteristics of C3N4. The key to enhance photocatalytic performance through the synergistic effect of these two materials lies in the effective charge transfer. In this work, a combination of ultrasonic dispersion and hydrothermal method was employed to prepare a ZnO/C3N4 composite. The structure of this composite consists of C3N4 thin layers covering ZnO nanoparticles with a size of several tens of nanometers. Theoretical calculations combined with photoluminescence spectroscopy techniques confirmed that charge transfer occurs in ZnO/C3N4 staggered gap heterojunction, which reduces the recombination of photogenerated carriers and enhances the photocatalytic efficiency. The variations of charge-transfer efficiency in different regions of the ZnO/C3N4 composite were observed by spatially and temporally resolved fluorescence imaging measurements. The photocatalytic degradation of pollutants revealed that the optimal amount of C3N4 is 8%. It achieved an impressive 88% degradation efficiency of the pollutant within 100 min and the fastest degradation rate of 0.022 min–1 under the solar simulator. This high efficiency is closely associated with the tight integration between ZnO and C3N4 and their effective charge-transfer rates. Furthermore, the ZnO/C3N4 composite demonstrated a stable photocatalytic performance.