Graphene quantum dots-assisted exfoliation of graphitic carbon nitride to prepare metal-free zero-dimensional/two-dimensional composite photocatalysts

Abstract

The high aspect-ratio morphology of two-dimensional (2D) nanostructures endues them with distinct advantages for photocatalytic or photoelectrical applications. Although various attempts have been devoted to the liquid exfoliation of graphitic carbon nitride (g-C3N4) to obtain ultrathin nanosheets (CNNSs), the high exfoliation efficiency, well preservation of in-planar structure and facile operation cannot be simultaneously realized. Furthermore, functionalization of CNNSs is highly desired to promote the capability of photoabsorption, charge separation and transfer. Herein, we one-step prepared well-dispersed graphene quantum dots (GQDs)-modified CNNSs (GQDs/CNNSs) colloids via a facile and efficient GQDs-assisted exfoliation approach in a normal ultrasonic water bath. The exfoliation procedure was optimized by tuning the dopant in GQDs, ultrasonic time and GQDs dosage. The obtained colloidal GQDs/CNNSs show a typical 2D morphology with lateral size of several 100 nm and ultrathin thickness of 1.5–1.8 nm. What is more, we can tailor the semiconductive behavior of GQDs by heteroatom doping and achieve a p–n-type P-doped GQDs-modified CNNSs colloids. This p–n GQDs/CNNSs material presents the enhanced separation efficiency of photoexcited carriers and photocatalytic activity in comparison with bulky g-C3N4 (CN) and other CNNSs materials from acid or alkali exfoliation.