ChemInform Abstract: PHOTOELECTROCHEMICAL STUDY OF TIN DISULFIDE IN AQUEOUS SOLUTION

Katty, A.; Fotouhi, B.; Gorochov, O.

doi:10.1002/chin.198514008

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“…The negative shift depends on the concentration of I3-. The shift has been considered to be due to I3-adsorption (2)(3)(4)(5). Photopotentials (Table I) are small and do not vary with redox couples' potential as theoretically predicted.…”

Section: Resultsmentioning

confidence: 92%

“…The corrosion product which stays back on the surface was also dissolved in KOH and the analysis indicated that it was constituted of a mixture of selenium, sulfur, and tin. It seems that .in alkaline medium, hydroxide ions react with the semiconductor in such a way that selenium and sulfur are substituted by these ions in a reaction such as SnSSe + 4 OH---~ Sn(OH)4 + S = + S~ [1] From the fact that the corrosion reaction is accompanied with an anodic current, it is reasonable to assume that a part of S = and Se = formed according to reaction [1] whose energies are sufficiently high can inject electrons into the conduction band and a part diffuse out into the solution according to the following reactions S = ---, S -+ 2e-S-+ H20 ---> SH-+ OH- [2] Se-~Se+ 2e-Se = +H20~SeH-+ OHOn the other hand, thermodynamic consideration indicates that Sn(OH)~ dissolves partly to SnO:~ = in alkaline medium (8) 2Sn(OH)4 ~ SnO3-+ SnO2 + 3H~O + 2H ~ [3] The presence of sulfur, selenium, and tin, both in the solution and in the layer which deposits on the surface, and the fact that the total charge consumed during the electrolysis is six times smaller than the concentration of dissolved tin, would support this interpretation. The addition of Fe(CN)63-to the alkaline solution increases the anodic current and the corrosion rate.…”

Section: Discussionmentioning

confidence: 99%

“…A deviation from linearity is observed between SnS1.sSe0.5 and SnS~ (2.22 eV). Photoelectrochemical properties of SnS2 have already been studied (2), and it seems interesting to consider the ternary compound.…”

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Photoelectrochemical and Corrosion Study of n‐Type SnSSe

Fotouhi

Katty

Gorochov

1985

J. Electrochem. Soc.

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Single crystals of n-type SnS~Se2_x (x = 1.04) obtained both by transport and Bridgman methods exhibit an energy gap of 1.53 eV. The flatband potential is pH dependent, and its values in acidic and alkaline solutions are, respectively, 0.06 and -0.6V (SCE). In the dark, SnSSe is stable in acidic medium, but the stability decreases as pH increases. It is also unstable in acidic solutions containing the oxidizing form of a redox reagent with a sufficiently positive redox potential (ca. more positive than 0.8V/SCE). The presence of an oxidizing form of a redox couple in alkaline medium enhances the already existing corrosion reaction. The corrosion reaction is accompanied with an anodic current. The corrosion rate as well as the magnitude of the anodic current depends on pH and the concentration of the oxidizing state of the couple. Light-driven reactions in both acidic and alkaline media are corrosion reactions. However, decomposition may be avoided in acidic solution containing potassium iodide.The solid solution SnSxSe2_x can be prepared over the entire composition range from SnS2 to SnSe2. Compounds obtained are layered semiconductor with CdI.,-type structure. Optical properties of the mixed series SnSxSe2 x (where 0 < x < 2) have already been studied (1). Indirect energy gaps obtained vary linearly between SnSe2 (1.09 eV) and SnS,.sSe0.5 (1.75 eV). A deviation from linearity is observed between SnS1.sSe0.5 and SnS~ (2.22 eV). Photoelectrochemical properties of SnS2 have already been studied (2), and it seems interesting to consider the ternary compound.Although this ternary compound could present a particular interest in solar energy conversion because of its adjustable energy gap, it has not yet received attention in photoelectrochemistry. SnSSe, whose reported energy gap is 1.52 eV (1), which is an optimum value for solar spectrum, could be an interesting candidate for solar energy conversion into electrical or chemical energy. ExperimentalSnSxSe2_x single crystals were obtained both by transport and Bridgman methods. In both cases, stoichiometric amounts of purified tin sulfur and selenium were used. In the transport method, iodine and bromine were the transporting agents. The charge zone was at 630~ and the transport zone at 580~ Single crystals of SnS~Se2 x (3 • 3 • 0.1 ram) were obtained within a week. In the Bridgman method, the transport zone was fixed at 780~ and the temperature gradient was 70~ Ingots of 10 cm length with 1 cm diam were obtained. Microprobe analysis indicated that the composition of the samples prepared by tranport was x = 1.04. For those prepared by Bridgman technique, the same composition was found for the higher part of the tube (x = 1.05). The composition for the lower and the central parts of the tube was approximately x = 1.2. Hall measurements gave a carrier concentration of 6 • 10 '7 cm -~3 and a resistivity of 0.36 ~-cm at room temperature for samples prepared by transport method, and a carrier concentration of 2 • 10 '" cm -:~ and a resistivity of 200 ~-cm for those prepared...

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Section: Resultsmentioning

confidence: 92%