The enhanced photocatalytic and photothermal effects of Ti3C2 Mxene quantum dot/macroscopic porous graphitic carbon nitride heterojunction for Hydrogen Production

A new heterostructure between Ti3C2 MXene quantum dot and 3D macroscopic porous graphitic carbon nitride (PGCN) was successfully obtained by integrating Ti3C2 quantum dots onto porous graphitized carbon nitride (Ti3C2QDs/PGCN) using in situ electrostatic self-assembly techniques. The photocatalytic H2 evolution rate of optimized 5.5 wt% Ti3C2 QD/PGCN composites is nearly 15.24 and 3.53 times higher than pristine CN, and PGCN, respectively. Ti3C2 quantum dots can significantly enhance the hydrogen production activity of PGCN. In addition, their good photothermal conversion ability accelerates the overall reaction process and enhances the light absorption and carrier density. Furthermore, to elucidate the photocatalytic mechanism, a series of tests involving electron spin resonance (ESR) and density functional theory (DFT) calculations were performed. The results confirmed that the Schottky barrier between PGCN and Ti3C2 QD can effectively promote spatial charge separation and significantly improve the photocatalytic performance. This work provides a new approach for the construction of photocatalytic systems and the application of MXene QD.