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

Abstract

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 (<i>J</i>_Ph) 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.