Nanostructured g-C3N4/AgI composites assembled by AgI nanoparticles-decorated g-C3N4 nanosheets for effective and mild photooxidation reaction

Abstract

Graphitic carbon nitride (g-C₃N₄) and its composites have attracted considerable interest in the last decade for their use as photocatalysts. However, most of the modifications have imparted a strong oxidization ability to g-C₃N₄, which has restricted its applications in mild and selective oxidation requirements in organic syntheses. In this study, we prepared g-C₃N₄/AgI composites by the decoration of g-C₃N₄ nanosheets (NSs) with AgI nanoparticles (NPs), and we characterized them via XRD, SEM, TEM, EDS, XPS, and DRS. The photocatalytic activities of the g-C₃N₄/AgI composites were evaluated by the photocatalytic oxidation of 1,4-dihydro-2,6-dimethyl-3,5-dicarboxylate (1,4-DHP) under visible-light irradiation (λ > 400 nm). 1,4-DHP was nearly converted into its dehydrogenation product without deep oxidation and degradation, as determined by the UV-visible and mass spectroscopic studies. All the g-C₃N₄/AgI composites were found to exhibit improved photocatalytic activity when compared with that of pure g-C₃N₄; the g-C₃N₄/AgI-30% sample showed the best photocatalytic activity. The mechanism studied using active species trapping technique indicated that superoxide radicals (˙O₂⁻) and photoinduced holes (h⁺) were the main active species in the photocatalytic reaction. Based on these observations, plausible mechanisms for photoexcited charge carrier separation and photocatalytic oxidation were proposed.