Facile one-pot liquid exfoliation preparation of molybdenum sulfide and graphene heterojunction for photoelectrochemical performance

A MoS2/graphene heterojunction has been prepared via a facile one-pot liquid exfoliation method and proved to have improved photoelectrochemical properties. With a suitable ultrasonic power, small MoS2 nanosheets with dozens of nanometer diameter can be obtained to adhere to graphene layers with tens of micrometer-scale diameter. Atomic force microscopy, transmission electron microscope, Raman spectra and adsorption spectra are used to characterize the structure of these MoS2/graphene heterojunction samples after exfoliation. The characterizations indicate that MoS2/graphene heterojunction in solution is stable and has good crystallinity. Moreover, photoelectrochemical measurements further prove that the obtained MoS2/graphene heterojunction exhibits improved photoresponse activity under the illumination of simulated sunlight compared to MoS2 and graphene. Combined with the first-principle calculation analysis, the improvement can be attributed to the extremely efficient charge separation of the heterojunction. The dynamic mechanism has been revealed through a MoS2/graphene band model, where graphene can serve as a collector for storing and transferring electrons, to promote the separation of photogenerated electron–hole pairs and suppress their recombination. This work verifies the superiority of MoS2/graphene heterojunction through its photoelectrochemical performance, which have referential significance for future MoS2/graphene optoelectronic devices.