Ultrafast hot electron transfer and trap-state mediated charge separation for boosted photothermal-assisted photocatalytic H2 evolution

Comprehensive interpretation of photo-generated carrier dynamics in photocatalytic systems will strengthen its position as a candidate for future utilization and development of solar energy resources. As exploratory models, aggregated carbon dots (A-CDs) and dispersed carbon dots (D-CDs) were coated on the surface of g-C3N4 nanovesicles (CNNVS) to form A-CDs/CNNVS and D-CDs/CNNVS composite systems. Among of them, A-CDs/CNNVS exhibits a superior photothermal-assisted photocatalytic H2 evolution of up to 24.8 mmol/g, which was about 2.03 and 1.23 times higher than that of CNNVS and D-CDs/CNNVS, respectively. Ultrafast transient absorption spectroscopy (TAS) demonstrates that the improved thermalization of photo-generated electrons and trapping behavior of cooled electrons via the introduction of A-CDs in A-CDs/CNNVS to complement the hot electrons of intrinsic excitation and electrons trapping of CNNVS at a higher extent in comparison of D-CDs/CNNVS. This work presents an in-depth insight to investigate CDs-based photothermal-assisted photocatalytic H2 evolution system for realizing solar energy conversion.