Chalcogenide redox couples

In most cases, the iodide-triiodide redox couple has been employed (presumably because of its success in shuttling the photo-oxidized dye in the sensitization experiments) although other redox electrolytes e.g., SCN /(SCN)2 , [342] have also been employed. For the chalcogenide films, sodium selenosulfite was employed [319]. It must be noted that, aside from losses due to the surface recombination and back-reactions, an additional loss component from the increase in film resistance must also be recognized especially as the film thickness is increased. The resistance loss manifests as a deterioration in the photovoltage and fill factor. 

The transition metal chalcogenides such as n-WSe2 are a particular class of electrode materials, and their photoelectrochemical behaviour is of interest from the fundamental point of view. If the basal planar surfaces (perpendicular to the c-axis) with a low density of steps are contacting the electrolyte, these layered materials are relatively stable. Since the corrosion rate is very small, the anodic photocurrent occurs at a high overvoltage with respect to the flatband potential in the dark. As discussed in Section 2.3.1 (Fig. 2.15), the flatband potential t/fb is shifted on illumination because holes accumulate at the surface. On addition of a redox couple such as [Fe(phen)3] ... 

Recently, we demonstrated that the Zintl clusters [Geg]" react with chalcogen atoms (S, Se, and Te) in the presence of surfactant templates to form ordered mesoporous Ge-rich chalcogenides [74]. The mesostructured frameworks grow through a coupling reaction of (Ge9)-clusters with chalcogens in formamide/ethy-lenediamine mixture solution in an unusual reaction that seems to be a redox process (5). 

Ternary chalcogenides, M MoeXs (M = a transition metal, rare earth, etc. and X = S, Se, or Te) a class of ORR active materials, were for the first time synthesized by Chevrel et al. [167] and are referred as Chevrel compounds. These complex chalcogenides have a central octahedral metal cluster wherein the delocalization of the electrons leads to high electronic conductivity and these clusters act as a reservoir for electronic charge carriers. The substitution of Mo atoms by other transition metal atoms causes an alteration in the position of the Fermi level in such a way that it is suitable for the redox potential of the O2/H2O [19] couple. 

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