Here, we describe a strategy for preparing CdS/MoS 2 heterostructures using initially electrodeposited MoS x on a polycrystalline gold substrate. The excess sulfur intrinsic to the electrodeposited MoS 3 surface was derivatized with Cd to form spherical CdS/MoS 2 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 MoS x and CdS/MoS 2 films were further characterized by scanning electron microscopy, energy-dispersive Xray analysis, laser Raman spectroscopy, and X-ray photoelectron spectroscopy. Heterojunction formation between MoS 2 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 MoS 2 surface. The nonoptimized CdS/MoS 2 heterostructures showed improved photoelectrochemical response compared with CdS or MoS 2 for oxidation of sulfite species.

Molybdenum telluride (MoTe2) belongs to the family of layered transition metal dichalcogenides (TMDs) with unique optical, optoelectronic, structural properties and potential applications in a wide array of technologies related to solar energy conversion, optoelectronics, lubrication, and hydrogen production. Here, electrodeposition is shown to be a facile method for the synthesis of MoTe2 in bulk (i.e., not exfoliated) form. The electrosynthesis of MoTe2 films and the underlying compound formation mechanism were investigated for the first time using linear sweep voltammetry (LSV) combined with electrochemical quartz crystal microgravimetry (EQCM). A Te-modified electrode in an electrolyte containing molybdenum precursor species, a MoO x -modified electrode in tellurium precursor-containing electrolyte and a variety of control experiments were employed to elucidate the electrodeposition mechanism of MoTe2 films. Electrogeneration of HTe− was the key step in MoTe2 film formation which occurred by the reaction of electrodeposited MoO x with HTe− generated by electroreduction of Te or HTeO2 +. Thermodynamic aspects of this reaction are finally presented.

Here, we demonstrate a two-step electrochemical approach for the synthesis of cobalt chalcogenides, CoQ (Q = S or Se) based on the prior modification of a substrate with S or Se, followed by electrochemical reduction in a Co2+-complexing electrolyte to afford CoS or CoSe in film form. The two-step strategy circumvents a common problem with the electrodeposition of metal chalcogenides, namely admixture of the target material with undesired phases such as excess metal or the chalcogen. The strategy was combined with complexation to shift the free metal deposition regime to more negative potentials. Compositional analysis showed that as-synthesized films retain a stoichiometric ratio of Co and S or Se and XPS analysis confirmed the formation of CoS and CoSe. The electrodeposited films were successfully used as electrocatalysts for the triiodide/iodide redox system and showed comparable (or even, superior) performance to a Pt electrode. As also demonstrated both by the present work and by companion studies in our laboratories, the two-step strategy is generally applicable to a variety of other metal chalcogenides.