Chalcogenide cathodes

The most attractive candidates for electrodes are thus a combination of an alkali metal (possibly an alkaline earth metal) anode with a halogen or chalcogenide cathode. These might well be immersed in a eutectic alkali metal halide melt electrolyte. 

The electrochemical preparation of metal chalcogenide compounds has been demonstrated by numerous research groups and reviewed in a number of publications [ 1-3]. For the most part, the methods that have been used comprise (a) cathodic co-reduction of the metal ion and a chalcogen oxoanion in aqueous solution onto an inert substrate (b) cathodic deposition from a solvent containing metal ions and the chalcogen in elemental form (the chalcogens are not soluble in water under normal conditions, so these reactions are carried out in non-aqueous solvents) (c) anodic oxidation of the parent metal in a chalconide-containing aqueous electrolyte. 

This complex may be reduced either directly to the metal chalcogenide or to the zero-valent metal, which then reacts chemically with selenosulfate adsorbed at the cathode to form MSe. 

On account of the fact that the electrode potential of molybdenum is more negative than the discharge potential of hydrogen, principle difficulties arise to cathodically electrodeposit molybdenum chalcogenide films from aqueous solutions. Theoretically, the deposition of pure molybdenum by electrolytic reduction of molybdates in acidic aqueous solutions is possible according to the reaction... 

An early attempt for ordered growth of a chalcogenide simple compound has been the cathodic deposition of thin (3 p,m) CdTe films on n-type (100) GaAs single crystals from an acidic aqueous electrolyte at 95 °C, which contained Cd(II) and Te traces generated electrolytically in situ by using a pure Te anode [4]. The... 

Binary systems of ruthenium sulfide or selenide nanoparticles (RujcSy, RujcSey) are considered as the state-of-the-art ORR electrocatalysts in the class of non-Chevrel amorphous transition metal chalcogenides. Notably, in contrast to pyrite-type MS2 varieties (typically RUS2) utilized in industrial catalysis as effective cathodes for the molecular oxygen reduction in acid medium, these Ru-based cluster materials exhibit a fairly robust activity even in high methanol content environments of fuel cells. 

Schbllhom R, Meyer H (1974) Cathodic reduction of layered transition metal chalcogenides. Mater Res Bull 9 1237-1245... 

Two earlier reviews were published on high temperature cells and batteries based on molten salt and solid electrolytes. The first one (69) describes the Li/Cl2 cells, particularly the LiA.l/LiCl-KCl/Cl2 cell with gaseous CI2. Li cells with chalcogenides as cathode materials are mentioned, as well as some details of construction. This review, and the 26 references attached to it, reflects the state of the Li molten salt batteries to the end of 1970 (69). The second review (70), prepared two years later is more comprehensive. It discusses in detail some theoretical problems, the thermodynamics and rate processes in electrochemical cells, and presents tables and... 

As with the n-TiCte and n-SrTiCh counterparts discussed earlier in Section 6.2 of this Chapter (see also Ref. 407), luminescence probes have proven to be very useful for unraveling the mechanistic details of the cathodic processes both at n-type (e.g., n-GaAs)556 and p type (e.g., p InP)557,558 Group III V semiconductor surfaces. Finally, these semiconductors share another trend with those discussed earlier (metal chalcogenides) in that the majority of the studies since 1990 have been directed at solid solutions (alloys of GaP and InP, GaAs and InAs etc.). These newer studies will be addressed in Section 12 of this Chapter. 

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