Exfoliated Molybdenum Disulfide-Wrapped CdS Nanoparticles as a Nano-Heterojunction for Photo-Electrochemical Water Splitting.

We developed a heterojunction photocathode, MoS2@CdS, based on the wrapping of CdS nanoparticles by the MoS2 nanocrystals. The liquid-phase exfoliation method was adopted for preparing few-layer MoS2 nanocrystals of a layer thickness of ∼7.9 nm, whereas CdS nanoparticles of an average diameter of ∼17 nm were synthesized by the one-step hydrothermal process. The synthesized nanocrystals and nanoparticles were characterized by AFM, FESEM, HRTEM, STEM, XRD, GIXRD, UV-vis absorption, fluorescence emission, and Raman spectroscopy. The difference between two modes in the Raman spectrum of MoS2 indicates the formation of few-layer MoS2. The photoelectrochemical performance of the heterojunction photocathode was excellent. The MoS2@CdS heterostructure photocathode increased the photocurrent density (JPh) under 100 mW/cm2 illumination. We obtained the maximum applied biased photoconversion efficiency (ABPE) of ∼1.2% of the MoS2@CdS heterojunction photocathode in optimum device configuration. The production of H2 was measured as ∼72 μmol/h for the MoS2@CdS heterostructure with a cyclic stability of up to 7500 s.