Effective photocatalytic degradation of organic dyes using ZNC/rGO nanocomposite photocatalyst derived from ZIF-8/rGO thermolysis for water treatment

Abstract

Photocatalytic water treatment using nano-structured semiconductors with in situ generations of electron-hole pairs upon irradiation with light is a very promising oxidation process for environmental remediation. Herein, we report a new synthetic strategy based on coupling semiconductors derived from ZNC (carbonaceous nitrogen-doped zinc oxide) and rGO (reduced graphene oxide) to enhance the electron-hole separation and reduce the recombination of photogenerated charge carriers. ZNC derived from ZIF-8) Zeolitic Imidazolate Framework-8) is a good n-type semiconductor, and rGO is a highly conducting material. The new photocatalytic system, ZNC/rGO, with a bandgap of 2.8 eV, was used to treat wastewater containing methylene blue (MB) dye which is oxidized to environmentally friendly substances (CO2 and H2O). All samples were characterized thoroughly using XRD, FT-IR, XPS, Raman, TGA, SEM, TEM, surface area measurements (SBET), UV–vis spectroscopy, photocurrent response, Mott-Schottky plots, and electrochemical impedance spectroscopy (EIS). The higher photocurrent response intensity of ZNC/rGO compared to that of ZNC reflects the synergistic effect of rGO to enhance the charge separation efficiency. It is worth noting that the loading of a small amount of rGO over ZIF-8 followed by thermolysis results in a great enhancement of MB dye degradation from 51% to 98.9% under simulated solar light irradiation. Finally, we expect the novel photocatalyst, ZNC/rGO, to have important applications in the fields of energy and environmental protection.Synopsis: Thermolysis of ZIF-8/graphene oxide composite affords a highly active photocatalyst for organic pollutant degradation, making water desalination more feasible.