Synergetic Exfoliation and Lateral Size Engineering of MoS2 for Enhanced Photocatalytic Hydrogen Generation.

Generally, exfoliation is an efficient strategy to create more edge site so as to expose more active sites on molybdenum disulphide (MoS2 ). However, the lateral sizes of the resultant MoS2 monolayers are relatively large (≈50-500 nm), which retain great potential to release more active sites. To further enhance the catalytic performance of MoS2 , a facile cascade centrifugation-assisted liquid phase exfoliation method is introduced here to fabricate monolayer enriched MoS2 nanosheets with nanoscale lateral sizes. The as-prepared MoS2 revealed a high monolayer yield of 36% and small average lateral sizes ranging from 42 to 9 nm under gradient centrifugations, all exhibiting superior catalytic performances toward photocatalytic H2 generation. Particularly, the optimized monolayer MoS2 with an average lateral size of 9 nm achieves an apparent quantum efficiency as high as 77.2% on cadmium sulphide at 420 nm. This work demonstrates that the catalytic performances of MoS2 could be dramatically enhanced by synergistic exfoliation and lateral size engineering as a result of increased density of active sites and shortened charge diffusion distance, paving a new way for design and fabrication of transition-metal dichalcogenides-based materials in the application of hydrogen generation.