Cobalt telluride (CoTe) thin films were electrodeposited for the first time using alkaline solutions containing nitrilotriacetic acid (NTA), CoCl 2 , and K 2 TeO 3 . NTA was employed in order to shift the reduction potential of cobalt in the negative direction and to stabilize Co 2+ ions in alkaline electrolytes via the formation of Co-NTA complexes. The electrodeposition mechanism was investigated by linear sweep voltammetry (LSV) combined with electrochemical quartz crystal microgravimetry (EQCM). The formation of CoTe is proposed to occur through the reaction of Co 2+ with HTe − , which is generated by the reduction of TeO 3 2− via a 6-electron reduction pathway. A concurrent pathway consists of the stepwise reduction of TeO 3 2− to Te by a 4-electron process, followed by the 2-electron process reduction of Te to HTe − . The electrodeposited CoTe films were characterized by a variety of physical methods including scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, and X-ray photoelectron spectroscopy. An optical energy bandgap of ∼1.86 eV was obtained by diffuse reflectance spectroscopy.

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.

We report a facile strategy for the synthesis of cadmium and cobalt metal-organic frameworks (MOFs), and their subsequent conversion to the corresponding oxide. Thus, Cd-MOF and Co-MOF were prepared by successive ionic layer adsorption and reaction (SILAR) using Cd2+ or Co2+ cation precursors and a p-phenylenediamine anion precursor. As-synthesized particles with unique morphology were converted into CdO or Co3O4 after heat treatment under air. The resultant CdO and Co3O4 retained the original morphology of the MOF precursors. The optical and photoelectrochemical behavior of thus-prepared CdO was studied by diffuse reflectance spectroscopy and photovoltammetry. Finally, the capacitive behavior of the cobalt oxide electrode was assessed by cyclic voltammetry.

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.