Tellurium electrodeposition from tellurium(II) and (IV) chloride salts in dichloromethane
Tellurium electrodeposition from tellurium(II) and (IV) chloride salts in dichloromethane
Electrodeposition of elemental Te from [NnBu4]2[TeCl6] in a weakly coordinating solvent, dichloromethane, has been investigated. The reduction of the Te(IV) complex to deposit Te shows a very large (> 1 V) overpotential on clean Pt macrodisc electrodes and microelectrodes that is significantly reduced once Te has been deposited on the electrode. Corresponding studies show that there is no significant overpotential for the deposition of Te from the Te(II) complex, [NEt4]2[TeI4], under the same conditions, suggesting that the barrier for electrodeposition from [TeCl6]2− arises because of the instability of the intermediate Te(III) species. Density functional theory (DFT) calculations with the M06–2X density functional and treatment of solvation using the polarizable continuum model confirm that the possible Te(III) complexes, [TeCl5]2−, [TeCl4]− and [TeCl3], are all unstable with respect to disproportionation, confirming that the Te(III) intermediate is a thermodynamic barrier to the electrodeposition of Te(0) from [TeCl6]2−. We propose that this thermodynamic barrier is overcome for the reaction at the Te electrode surface by a catalytic mechanism in which the transient Lewis acidic [TeCl5]− complex forms a Lewis acid/base adduct ([TeCl5]− —Tesurface) through p-orbital overlap with the Te on the electrode surface. This mechanism is shown to be consistent with the results of DFT calculations for the speciation equilibria for the Te(IV) chloride complexes and with the results of experiments at different chloride concentration. Our results suggest that Lewis acid/base adduct formation at the electrode surface may also play a role in electrodeposition of other p-block elements.
Chlorometallate, Electrodeposition, Lewis acid, Non-aqueous, Tellurium
Cook, D. A.
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Reeves, S. J.
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Zhang, W.
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Reid, G.
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Levason, W.
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Bartlett, P.N.
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Dyke, J.M.
46393b45-6694-46f3-af20-d7369d26199f
Greenacre, V.K.
c665a38b-0b1a-4671-ac75-bf0679dd1c57
10 July 2023
Cook, D. A.
bee684eb-8b88-4617-a2b0-b8b15d641fed
Reeves, S. J.
121fe250-d3b8-4fd7-830b-deaa06385b9c
Zhang, W.
1f80ac5e-d4c2-4720-b19e-be700cd411e7
Reid, G.
37d35b11-40ce-48c5-a68e-f6ce04cd4037
Levason, W.
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Bartlett, P.N.
d99446db-a59d-4f89-96eb-f64b5d8bb075
Dyke, J.M.
46393b45-6694-46f3-af20-d7369d26199f
Greenacre, V.K.
c665a38b-0b1a-4671-ac75-bf0679dd1c57
Cook, D. A., Reeves, S. J., Zhang, W., Reid, G., Levason, W., Bartlett, P.N., Dyke, J.M. and Greenacre, V.K.
(2023)
Tellurium electrodeposition from tellurium(II) and (IV) chloride salts in dichloromethane.
Electrochimica Acta, 456, [142456].
(doi:10.1016/j.electacta.2023.142456).
Abstract
Electrodeposition of elemental Te from [NnBu4]2[TeCl6] in a weakly coordinating solvent, dichloromethane, has been investigated. The reduction of the Te(IV) complex to deposit Te shows a very large (> 1 V) overpotential on clean Pt macrodisc electrodes and microelectrodes that is significantly reduced once Te has been deposited on the electrode. Corresponding studies show that there is no significant overpotential for the deposition of Te from the Te(II) complex, [NEt4]2[TeI4], under the same conditions, suggesting that the barrier for electrodeposition from [TeCl6]2− arises because of the instability of the intermediate Te(III) species. Density functional theory (DFT) calculations with the M06–2X density functional and treatment of solvation using the polarizable continuum model confirm that the possible Te(III) complexes, [TeCl5]2−, [TeCl4]− and [TeCl3], are all unstable with respect to disproportionation, confirming that the Te(III) intermediate is a thermodynamic barrier to the electrodeposition of Te(0) from [TeCl6]2−. We propose that this thermodynamic barrier is overcome for the reaction at the Te electrode surface by a catalytic mechanism in which the transient Lewis acidic [TeCl5]− complex forms a Lewis acid/base adduct ([TeCl5]− —Tesurface) through p-orbital overlap with the Te on the electrode surface. This mechanism is shown to be consistent with the results of DFT calculations for the speciation equilibria for the Te(IV) chloride complexes and with the results of experiments at different chloride concentration. Our results suggest that Lewis acid/base adduct formation at the electrode surface may also play a role in electrodeposition of other p-block elements.
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Accepted/In Press date: 19 April 2023
e-pub ahead of print date: 20 April 2023
Published date: 10 July 2023
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Funding Information:
This work was supported by the EPSRC through the Advanced Devices by ElectroPlaTing program grant (ADEPT; EP/N035437/1 ).
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© 2023 The Author(s)
Keywords:
Chlorometallate, Electrodeposition, Lewis acid, Non-aqueous, Tellurium
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Local EPrints ID: 477178
URI: http://eprints.soton.ac.uk/id/eprint/477178
ISSN: 0013-4686
PURE UUID: 01771d0b-1ee6-4f0f-9104-4621657db59a
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Date deposited: 31 May 2023 16:57
Last modified: 18 Mar 2024 03:47
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Author:
V.K. Greenacre
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