In a typical photocatalytic reaction, efficient solar light harvesting and charge generation, as well as effective charge transport, are key factors that determine the efficiency of the photocatalytic system for H2 production. Atomically layered heterostructures have attracted significant research interest due to their unique layer-dependent catalysis and electronic properties. Previous studies have reported that the catalytic properties of MoS2 layered materials are highly dependent on the number of layers, and the difficulty of controlling the number of layers over a substrate has been a bottleneck for widespread use. Therefore, developing a simple, facile and environmentally friendly method to fabricate van der Waals heterostructures (vdWHs) with precisely controlled MoS2 layers for achieving highly efficient H2 generation is still a challenge. Here we report for the first time that the H2 bubbles generated by photocatalytic water splitting are effective in the layer-by-layer exfoliation of MoS2 nanocrystals (NCs) into few layers (Figure 1). The as obtained few layers can be in situ assembled with CdS nanosheets (NSs) into vdWHs of few-layered MoS2/CdS NSs which, in turn, are effective in charge separation and transfer, leading to enhanced photocatalytic H2 production activity. The few-layered MoS2/CdS vdWHs exhibited a H2 evolution rate of 140 mmol g(CdS)-1 h-1 and achieved an apparent quantum yield of 66% at 420 nm. This study provides a new strategy for the design of noble-metal-free few-layered MoS2/CdS vdWH systems for photocatalytic H2 generation. We believe that this bubble exfoliation strategy can be extended to a range of other layered transition metal dichalcogenide compounds.
Dr. Shahid Iqbal received his Ph.D. degree at School of Chemistry and Chemical Engineering, National Engineering Laboratory for VOCs Pollution Control Material & Technology, University of Chinese Academy of Sciences, Beijing, China in 2017. Currently, he is a post-doctoral researcher at International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy & Power Engineering, Xi’an Jiaotong University. He has published more than 17 peer-reviewed papers in reputed journals. His research interest is focused on the controlled synthesis and thickness-dependent catalytic properties of few-layered transition metal dichalcogenides (TMDs) for efficient photocatalytic hydrogen evolution and CO2 conversion.