Effect of g-C₃N₄ on structural, optical, and photocatalytic properties of hexagonal cylinder-like twinned ZnO microcrystals prepared by the hydrothermal method

The effect of g-C₃N₄ on the structural, optical, and photocatalytic properties of ZnO microcrystals under hydrothermal conditions was investigated in this research. The addition of g-C₃N₄ changed not only the phase composition, but also affect the growth of ZnO crystals, changing the lattice parameter and the transformation of hexagonal cylinder-like twinned ZnO microcrystals (1–2 μm length and 0.5–1 μm diameter) to g-C₃N₄ amalgamated rice-like ZnO nanostructure (500 nm length and 100 diameter) with type II heterojunction. The optical bandgap was found to be 3.27 and 3.21 eV for pristine ZnO and g-C₃N₄@ZnO, respectively. Owing to the narrow bandgap (2.7 eV) of g-C₃N₄, a red shift towards the visible region in optical absorption and a substantial reduction in the optical bandgap was observed for g-C₃N₄@ZnO heterostructure. Besides, it is also found that g-C₃N₄@ZnO has significantly higher photocatalytic effect (93 %) on RhB dye degradation than pristine ZnO (70 %) and g-C₃N₄ (68 %), because it produce a large number of reactive species (^·OH and O₂^•− radicals) by hold-up the recombination of charge carriers via type II heterojunction. This research may be one of the most realistic approaches to developing effective photocatalysts for environmental remediation.