Electrosynthesis of CdS/MoS2 Using Electrodeposited MoSx: A Combined Voltammetry–Electrochemical Quartz Crystal Nanogravimetry Study

Here, we describe a strategy for preparing CdS/MoS2 heterostructures using initially electrodeposited MoSx on a polycrystalline gold substrate. The excess sulfur intrinsic to the electrodeposited MoS3 surface was derivatized with Cd to form spherical CdS/MoS2 particles by judicious adjustment of the medium pH and interfacial electrochemistry. The progression of this conversion was monitored by a combination of cyclic/linear sweep voltammetry coupled with electrochemical quartz crystal nanogravimetry. The electrodeposited MoSx and CdS/MoS2 films were further characterized by scanning electron microscopy, energy-dispersive X-ray analysis, laser Raman spectroscopy, and X-ray photoelectron spectroscopy. Heterojunction formation between MoS2 and CdS particles was confirmed by high-resolution transmission electron microscopy as well as via Kelvin probe measurements of the contact potential differences, with and without the presence of CdS on the MoS2 surface. The nonoptimized CdS/MoS2 heterostructures showed improved photoelectrochemical response compared with CdS or MoS2 for oxidation of sulfite species.