Manipulation of Charge-Transfer Kinetics via Ti3C2Tx (T = −O) Quantum Dot and N-Doped Carbon Dot Coloading on CdS for Photocatalytic Hydrogen Production

Photocatalytic water cracking for hydrogen (H2) evolution is a fascinating technology to tackle the energy and environmental crisis. Here, Ti3C2Tx (T = −O) MXene quantum dots (MQDs) and N-doped carbon dots (NCDs) were interspersed on CdS nanoparticles to promote photocatalytic H2 production. When loaded with 1.0 wt % MQDs and NCDs, the composite (1.0% MNC) achieves a high H2-production rate of 5.64 mmol g–1 h–1, which reaches 13.12 and 2.83 times those of bare CdS (0.43 mmol g–1 h–1) and 1.0% Pt/CdS (1.99 mmol g–1 h–1), respectively, and achieved 45.7% apparent quantum efficiency (AQE) at 450 nm. The cycling stability, considered to be the Achilles' heel of the CdS-based photocatalyst, has also been significantly improved. Such an augmentation is mainly ascribed to the electron and hole trapping effect of MQDs and NCDs, respectively, which was demonstrated by systematic characterizations, in association with theoretical calculations. This research paves the way for application of carbon-based quantum dots in photocatalysis and also lays the foundation to develop more MXene-based hybrids for solar energy photocatalysis.