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

Abstract

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.