Construction of Z-scheme heterojunction 1D/2D g-C3N5/g-C3N4 and visible photocatalytic degradation of methyl orange

1D/2D g-C3N5/g-C3N4 heterojunction photocatalysts were prepared by a direct thermal polymerization method using melamine and 3-amino-1，2，4-triazole as raw materials. The crystal form， chemical composition， morphology and photoelectric chemical properties of the photocatalytic materials were characterized by XRD， XPS， SEM. Photocatalytic activity of 1D/2D g-C3N5/g-C3N4 heterojunction photocatalyst was studied using methyl orange（MO）as target pollutant and 500 W xenon lamp as visible light source. The active substances of the system were studied by active substance capture experiment and ESR characterization. The results show that the disordered stacking of one-dimensional g-C3N5 nanorods and two-dimensional g-C3N4 nanosheets increases the number of active sites. The formation of Z-scheme heterojunction between g-C3N5 and g-C3N4 improves the absorption intensity and spectral range of visible light， and inhibits the recombination of photoelectrons and holes. The superposition of π-π * conjugated systems similar to g-C3N5 and g-C3N4 reduces the mass transfer resistance of charge transfer and improves its photocatalytic activity. Under visible light irradiation for 30 min， 20 mg of 1D/2D g-C3N5/g-C3N4 photocatalytic material almost completely degraded 50 mL of 10 mg/L MO solution， and the apparent rate constant is 0.14836 min-1. After 5 cycles， the photocatalytic degradation rate of 1D/2D g-C3N5/g-C3N4 photocatalytic material for MO is 92.2%， indicating its good stability. The capture experiment of active substances and ESR characterization show that the main active substances in the photocatalytic degradation of MO system by g-C3N5/g-C3N4 photocatalyst are •O2- and h+， and the photocatalytic degradation of MO was a complex bond breaking and oxidation process.