Two polymorphs of AgVO 3 , namely the αand βforms, were prepared and their physical, structural, optical, electrochemical, and photoelectrochemical characteristics were compared using a battery of experimental and theoretical tools. A two-step method, previously developed in the our laboratory for the electrodeposition of inorganic semiconductor films, was applied to the electrosynthesis of silver vanadate (AgVO 3 ) films on transparent, conducting oxide surfaces. In the first step, silver was cathodically deposited from a non-aqueous bath containing silver nitrate. In the second step, the silver film was anodically stripped in an aqueous medium containing ammonium metavanadate. The anodically generated silver ions at the interface underwent a precipitation reaction with the vanadate species to generate the desired product in situ. Each of these steps were mechanistically corroborated via the use of electrochemical quartz crystal microgravimetry, used in conjunction with voltammetry and coulometry. As-deposited films were crystalline and showed p-type semiconductor behavior. Theoretical insights are provided for the electronic origin of the α!β phase transformation in AgVO 3 and the disparate optical band gaps of the two polymorphs. Finally, implications for the application of this material in solar cells are provided.

The mechanism of electrodeposition of cobalt selenide (CoSe) thin films was investigated by the combined application of linear sweep voltammetry (LSV) and electrochemical quartz crystal microgravimetry (EQCM) on Pt-coated quartz electrodes. Cobalt selenide films were electrodeposited on the Pt surface from 0.1 M Na 2 SO 4 electrolyte solution containing 5 mM SeO 2 and 5 mM Co(CH 3 COO) 2 by linear sweep voltammetry. Four cathodic waves were observed during the linear scans and the reactions corresponding to these waves were investigated with LSV and EQCM. Combined stripping voltammetry and EQCM showed that CoSe was electrodeposited via two routes: (1) Underpotential deposition of Se followed by deposition of cobalt as CoSe; and (2) Reaction of Co(II) with electrogenerated Se(-II) to result in CoSe. Compositional analyses revealed that the electrodeposited films contained CoSe and free Se, depending on the deposition potential. However, no cobalt was found in these films because of chemical Transition metal chalcogenides, comprised of earth-abundant elements, have served as effective alternatives for expensive, noble metal catalysts for the hydrogen evolution reaction (HER), and the oxygen evolution reaction (OER).1 Especially, cobalt selenides have attracted much attention due to their favorable attributes such as good electrical conductivity, optimal bandgap (∼1.5 eV) in terms of match with the solar spectrum, and a high optical absorption coefficient. [2][3][4]6,7,10,16 Of these variant synthetic options, electrodeposition offers many advantages 17 such as cost-effectiveness, simplicity, easy scale-up, the use of relatively mild conditions, and the fact that (volatile) organometallic chemicals are not needed (as in techniques such as molecular beam epitaxy and atomic layer deposition). In addition, the composition and structure of electrodeposited films can be controlled by controlling pH, electrolyte composition, or deposition potential.In this work, we present a detailed study of the electrodeposition mechanism of cobalt selenide (CoSe) using combined linear sweep voltammetry and electrochemical quartz crystal microgravimetry (EQCM). We are only aware of one prior study on the electrodeposition mechanism for CoSe on fluorine-doped tin oxide (FTO) electrode using cyclic voltammetry. 16 On the other hand, the addition of a complementary mass-change probe such as EQCM to a voltammetrybased study, offers considerable advantage in a mechanistic sense as we demonstrate below. Compositional analysis of the electrodeposited films using combined stripping voltammetry and EQCM, is finally demonstrated. ExperimentalCobalt acetate tetrahydrate, selenium dioxide, and sodium sulfate were from Sigma-Aldrich, and used without further purification. For voltammetry and EQCM, an EG&G Princeton Applied Research * Electrochemical Society Fellow.z E-mail: myung@kku.ac.kr; rajeshwar@uta.edu 263A instrument equipped with Power Suite electrochemistry software, a Seiko EG&G model QCA 922 instrument and an oscillator module (QCA 922-...

Adding a thermolysis step to electrosynthesis (as in "electrothermosynthesis") considerably enhances the scope of electrochemical film deposition and affords multinary compositions previously inaccessible by this otherwise versatile and mild synthetic approach. Copper pyrovanadate (βÀ Cu 2 V 2 O 7 ), a mem-ber of the CuÀ VÀ O family of ternary oxide semiconductors that are of considerable interest to the solar fuel community, is shown herein to be an exemplar of this approach. Finally, the generality of the hybrid approach is discussed for a variety of ternary metal oxides.

Here, we prepared a cobalt–metal organic framework (MOF) by anodic electrodeposition at room temperature and transformed it first to Co3O4 by calcination. The MOF-derived Co3O4 was then employed as a sacrificial template to fabricate CoSe films via anion exchange with a NaHSe medium. Electrodeposited MOF films showed a uniform and well-defined dodecahedral morphology with a particle size in the 3–4 μm range. The MOF-derived Co3O4 retained the original dodecahedral morphology, and these morphological features were essentially preserved in CoSe derived from the Co3O4 template via anion exchange. Both the parent oxide and the chalcogenide were characterized by a variety of spectroscopic and microscopic methods. The MOF-derived CoSe was demonstrated as a nonenzymatic glucose sensor with an analytical sensitivity of 1423.9 μA mM–1 cm–2 and a lower detection limit of 1.53 μM.

Interest in silver-based semiconductors dates to the early years of analog photography. On the other hand, the recent discovery of new silver oxide-based ternary semiconductors has caused a resurgence of interest in these compounds for new technologies. In this vein, the present study provides a counter example to the two perennial issues confronting the electrosynthesis of compound semiconductor films, namely, those of crystallinity and phase purity. It is shown here, for the first time, that a two-step electrosynthesis strategy yields crystalline and phase-pure α-Ag 3 VO 4 films on transparent, conductive oxide substrates under very mild process (ambient temperature and pressure) and time-efficient (minutes synthesis duration) conditions. A complementary suite of experimental methods and thermodynamics/kinetics analyses facilitated a deep understanding of the electrosynthesis mechanism, optoelectronic behavior, semiconductor band structure, thermal and electrochemical stability, and electrochemical/photoelectrochemical attributes.