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Thermodynamic evidence for K+–SO42? ion pair formation on Pt(111). New insight into cation specific adsorption

Thermodynamic evidence for K+–SO42? ion pair formation on Pt(111). New insight into cation specific adsorption
Thermodynamic evidence for K+–SO42? ion pair formation on Pt(111). New insight into cation specific adsorption
This work contributes to the understanding of cation specific effects on platinum electrochemistry by means of a thorough thermodynamic analysis of potassium adsorption on Pt(111) in sulfuric acid solutions. It is concluded that potassium specific adsorption is better described as the adsorption of the K+–SO2?4 ion pair. From the evaluation of the potassium sulfate concentration, it is found that potassium specific adsorption only takes place in the presence of coadsorbed sulfate species. Within the main sulfate adsorption state, for [similar]0.3 V < E < [similar]0.4 V (vs. SHE), the extent of potassium specific adsorption is small, reaching [similar]0.1 × 1014 species per cm2 for cK+ > 0.1 M. Then, at higher potentials, E > 0.55 V (vs. SHE), a second potassium adsorption process takes place, concomitant with the second sulfate adsorption process (associated to the small voltammetric feature called “the hump”). This last process involves the adsorption of an equal amount of potassium and sulfate species, leading to the adsorption of [similar]0.5 × 1014 ion pair species per cm2 ([similar]0.03 ion pair species per platinum surface atom). Furthermore, the results of the formal partial charge numbers corroborate that potassium adsorption involves sulfate cooperative coadsorption, in such a way that the effective adsorbing species is anionic, rather than cationic. In conclusion, this work evidences that cation specific effects may originate from the formation of surface ion pairs, which is probably related to the presence of ion pairs in solution
1463-9076
12146-12152
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37
Climent, Victor
c3ecab58-edb5-4055-8fa0-c0aef0fc60a4
Rodriguez, Paramaconi
5a751a4e-490e-42bb-9c22-7b0fc72e9a09
Feliu, Juan M.
f2a5301a-2886-4f27-b614-99a74a0a9a28
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37
Climent, Victor
c3ecab58-edb5-4055-8fa0-c0aef0fc60a4
Rodriguez, Paramaconi
5a751a4e-490e-42bb-9c22-7b0fc72e9a09
Feliu, Juan M.
f2a5301a-2886-4f27-b614-99a74a0a9a28

Garcia-Araez, Nuria, Climent, Victor, Rodriguez, Paramaconi and Feliu, Juan M. (2010) Thermodynamic evidence for K+–SO42? ion pair formation on Pt(111). New insight into cation specific adsorption. Physical Chemistry Chemical Physics, 12 (38), 12146-12152. (doi:10.1039/C0CP00247J).

Record type: Article

Abstract

This work contributes to the understanding of cation specific effects on platinum electrochemistry by means of a thorough thermodynamic analysis of potassium adsorption on Pt(111) in sulfuric acid solutions. It is concluded that potassium specific adsorption is better described as the adsorption of the K+–SO2?4 ion pair. From the evaluation of the potassium sulfate concentration, it is found that potassium specific adsorption only takes place in the presence of coadsorbed sulfate species. Within the main sulfate adsorption state, for [similar]0.3 V < E < [similar]0.4 V (vs. SHE), the extent of potassium specific adsorption is small, reaching [similar]0.1 × 1014 species per cm2 for cK+ > 0.1 M. Then, at higher potentials, E > 0.55 V (vs. SHE), a second potassium adsorption process takes place, concomitant with the second sulfate adsorption process (associated to the small voltammetric feature called “the hump”). This last process involves the adsorption of an equal amount of potassium and sulfate species, leading to the adsorption of [similar]0.5 × 1014 ion pair species per cm2 ([similar]0.03 ion pair species per platinum surface atom). Furthermore, the results of the formal partial charge numbers corroborate that potassium adsorption involves sulfate cooperative coadsorption, in such a way that the effective adsorbing species is anionic, rather than cationic. In conclusion, this work evidences that cation specific effects may originate from the formation of surface ion pairs, which is probably related to the presence of ion pairs in solution

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Published date: 9 August 2010
Organisations: Electrochemistry

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Local EPrints ID: 345750
URI: https://eprints.soton.ac.uk/id/eprint/345750
ISSN: 1463-9076
PURE UUID: 22fc01b8-6376-4aac-9275-e4103c84f337
ORCID for Nuria Garcia-Araez: ORCID iD orcid.org/0000-0001-9095-2379

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Date deposited: 29 Nov 2012 14:48
Last modified: 26 Nov 2019 01:36

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Author: Victor Climent
Author: Paramaconi Rodriguez
Author: Juan M. Feliu

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