Constructing ultrathin g-C3N4 nanosheets with hierarchical pores by NaClO induced wet etching for efficient photocatalytic Cr(VI) detoxification under visible light irradiation

Abstract

Ultrathin holey graphitic carbon nitride (g-C3N4) nanosheets have caused tremendous concern on highly active photocatalytic elimination of environmental contaminants because of its many interesting physichemical properties. But the photocatalysis ability for the bulk g-C3N4 is always limited by their small specific surface area and the scant number of active sites in the process of photocatalysis. Here, a fast and simple way to prepare ultrathin g-C3N4 nanosheets have rich in-plane pores by sodium hypochlorite etching is reported in water solution at room temperature, whereas the intercalation of Na+ and the synergistic effect of ClO− oxidation enable a fast exfoliation of bulk g-C3N4. Comprehensive structural and morphological of these products were analyzed through transmission electron microscopy, atomic force microscope, N2 adsorption-desorption, X-ray diffractometry, Fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and electron spin resonance measurements at room temperature. The obtained porous ultrathin g-C3N4 nanosheets by N2 adsorption-desorption tests show significantly increased specific surface area (85.7 m2 g−1). In addition, the results of the obtained ultrathin g-C3N4 nanosheets reveal its remarkable hierarchical pore structures composed of abundant mesopores and small micropores (<20 nm) and UV–vis exhibit narrower band gap (2.59 eV), more new exposed edges and improved electron transport capacity. Compared to the bulk g-C3N4, micro-meso of the hierarchical porous ultrathin g-C3N4 show more than 4 times higher activity when tested under visible-light-driven (VLD) Cr(VI) photodetoxification. This can be owed to the enrichment of active sites and the short distance of matter transfers from carrier to reaction sites. The experiment provides a strategy of the clean and scalable preparation the highly reactive and ultrathin g-C3N4 photocatalysts for energy development and environmental treatment.