Electrode metal sulfide

To overcome some of the problems associated with aqueous media, non-aqueous systems with cadmium salt and elemental sulfur dissolved in solvents such as DMSO, DMF, and ethylene glycol have been used, following the method of Baranski and Fawcett [48-50], The study of CdS electrodeposition on Hg and Pt electrodes in DMSO solutions using cyclic voltammetry (at stationary electrodes) and pulse polarography (at dropping Hg electrodes) provided evidence that during deposition sulfur is chemisorbed at these electrodes and that formation of at least a monolayer of metal sulfide is probable. Formation of the initial layer of CdS involved reaction of Cd(II) ions with the chemisorbed sulfur or with a pre-existing layer of metal sulfide. 

In their pioneering work on the formation of photoelectrochemically active metal sulfides by oxidation of the parent metal electrode. Miller and Heller [29] reported the anodic formation of polycrystalline Bi2S3 on a bismuth metal electrode in a sodium polysulfide cell, wherein this electrode was used in situ as photoanode. When a Bi metal electrode is anodized in aqueous sulfide solutions a surface film is formed by the reaction... 

Rao, Jayalakshmi and coworkers have prepared NPs of SnO, SnS and ZnS in order to study their capacitance behavior [88-90]. The metal oxide and metal sulfide NPs were prepared using hydrothermal methods. After immobilization in PIGE electrodes, their electrochemical properties were examined. Capacitance values in the 4—15 Fg were reported for SnS. Comparable values were reported for ZnS. 

AgjS can also be used as a matrix for other metal sulfides, notably CuS, PbS, and CdS, giving membranes responsive to the second metal. The electrode can be regarded as responding to the equilibrium activity of Ag" ", which is given by... 

Typical response curves of metal sulfide membrane electrodes in pure aqueous solutions show a linear relation with log C, with the slope expected from the Nemst... 

Souda. N. and Shimizu, Y. (2003) Sensing properties of solid electrolyte SO2 sensor using metal-sulfide electrode. J. Mater. Sci., 38 (21), 4301-5. 

High-performance lithium-sulfur cells are being developed for use in off-peak energy storage batteries in electric utility networks. The cells, which operate at 400°C, consist of a lithium electrode, a sulfur or sulfide electrode, and molten LiCl-KCl electrolyte. The chemistry of the lithium electrode is relatively straightforward. However, the electrochemical reactions at the sulfur electrode involve the formation of several intermediate species that are sufficiently soluble in the electrolyte to limit the lifetime and capacity of the cells. Although this effect can be decreased with soluble additives such as arsenic or selenium in the sulfur, a more promising solution appears to be the use of metal sulfides, rather than sulfur, as the active material in the positive electrode. 

The use of compounds to replace sulfur in the positive electrode necessitates a terminology change with respect to the positive electrode, which can no longer be considered a sulfur electrode. In the case of metal sulfide compounds, the sulfur will not be an electroactive species (except in such compounds as FeS2). The only function of the sulfur is to retain the reactant (i.e., the metal) and the product (i.e., Li2S) within the electrode cavity. 

Metal Sulfide Electrodes for Secondary Lithium Batteries... 

Extensive testing of metal sulfide electrode materials was performed in cells of the type shown in Figure 1. The metal sulfide electrode case and current take-off rod were made of dense graphite to avoid any contact and possible contamination of the active material by metallic constituents. The active material (metal sulfide powder in a porous graphite matrix or a mixture of metal sulfide and graphite powder) was contained in the cavity (2.5 cm in diameter X 0.6 cm deep) of the dense graphite electrode case. A porous ceramic separator was placed over the active material and secured with high purity alumina pins. 

In an entirely similar manner, electrodes responsive to Cu ", Cd , and Pb cations (M "), which form insoluble metal sulfides, can be made by mixing the appropriate metal sulfide with AgjS. In this case, the M + activity controls the sulfide-ion activity in solution, which in turn controls the Ag activity and the electrode response. 

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