Fabrication of nitrogen-deficient g-C3N4 nanosheets via an acetaldehyde-assisted hydrothermal route and their high photocatalytic performance for H2O2 production and Cr(vi) reduction

Abstract

A highly nitrogen-deficient g-C₃N₄ (AH-CN) nanosheet material was successfully prepared via an acetaldehyde-assisted hydrothermal route. The as-prepared AH-CN material was analyzed by X-ray powder diffraction (XRD), N₂ physical adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), Fourier transform infrared (FT-IR) spectroscopy, UV–vis diffuse reflectance spectroscopy (UV-Vis DRS), elemental analysis (EA), electron paramagnetic resonance (EPR) and photoelectric tests. Compared with H-CN (g-C₃N₄ treated hydrothermally without acetaldehyde), a large number of nitrogen vacancies were produced over AH-CN (g-C₃N₄ treated under acetaldehyde-assisted hydrothermal conditions). The bandgap of AH-CN decreases and its light absorption was largely improved in UV and visible light regions. Moreover, the as-prepared material possesses a low recombination rate of photogenerated carriers and a relatively negative conduction band potential over AH-CN, which contributes to its strong photocatalytic reduction ability. Under simulated sunlight illumination, the photocatalytic performance for H₂O₂ production and Cr(VI) reduction of the AH-CN material was evaluated. The highest H₂O₂ yield of 670 μM was obtained over 50AH-CN, which was 2.6 times that of g-CN. In the removal of Cr(VI) via reduction, the removal rate of Cr(VI) over 50AH-CN reaches 56% which is about 5.6 times that of g-CN.