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Measurements of the double layer capacitance for electrodes in supercritical CO2/acetonitrile electrolytes

Measurements of the double layer capacitance for electrodes in supercritical CO2/acetonitrile electrolytes
Measurements of the double layer capacitance for electrodes in supercritical CO2/acetonitrile electrolytes
Electrochemical impedance measurements were made in the single supercritical phase of CO2 with 11 wt% acetonitrile as the co-solvent at temperatures and pressures between 306 and 316 K and 15.5 and 20.2 MPa over the potential range from ?0.45 to +0.75 V vs. Pt. Gold, platinum and glassy carbon electrodes were studied together with the effects of electrolyte concentration for [NBu4n][BF4]. Two other electrolytes, [NBu4n][B{3,5-C6H3(CF3)2}4] and [NMe4][BF4], were also studied. We find that the impedance data can be described by a simple RC equivalent circuit where the uncompensated solution resistance is independent of the electrode potential and is consistent with earlier measurements for the electrolyte conductivity. The results for the double layer capacitance can be described by a simple Helmholtz layer model and are very similar to those found for similar electrolytes in non-aqueous solvents such as propylene carbonate. For glassy carbon the double layer capacitances show a parabolic like potential dependence which we attribute to the lower density of states near the Fermi level.
supercritical fluid, double layer capacitance, carbon dioxide, electrochemical impedance
1572-6657
18-24
Bartlett, P.N.
d99446db-a59d-4f89-96eb-f64b5d8bb075
Cook, D.A.
0fca0ffb-eef4-422f-b513-ce9a1f7de7cc
Bartlett, P.N.
d99446db-a59d-4f89-96eb-f64b5d8bb075
Cook, D.A.
0fca0ffb-eef4-422f-b513-ce9a1f7de7cc

Bartlett, P.N. and Cook, D.A. (2015) Measurements of the double layer capacitance for electrodes in supercritical CO2/acetonitrile electrolytes. Journal of Electroanalytical Chemistry, 746, 18-24. (doi:10.1016/j.jelechem.2015.03.022).

Record type: Article

Abstract

Electrochemical impedance measurements were made in the single supercritical phase of CO2 with 11 wt% acetonitrile as the co-solvent at temperatures and pressures between 306 and 316 K and 15.5 and 20.2 MPa over the potential range from ?0.45 to +0.75 V vs. Pt. Gold, platinum and glassy carbon electrodes were studied together with the effects of electrolyte concentration for [NBu4n][BF4]. Two other electrolytes, [NBu4n][B{3,5-C6H3(CF3)2}4] and [NMe4][BF4], were also studied. We find that the impedance data can be described by a simple RC equivalent circuit where the uncompensated solution resistance is independent of the electrode potential and is consistent with earlier measurements for the electrolyte conductivity. The results for the double layer capacitance can be described by a simple Helmholtz layer model and are very similar to those found for similar electrolytes in non-aqueous solvents such as propylene carbonate. For glassy carbon the double layer capacitances show a parabolic like potential dependence which we attribute to the lower density of states near the Fermi level.

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Accepted/In Press date: 19 March 2015
e-pub ahead of print date: 20 March 2015
Published date: 1 June 2015
Keywords: supercritical fluid, double layer capacitance, carbon dioxide, electrochemical impedance
Organisations: Electrochemistry

Identifiers

Local EPrints ID: 376463
URI: http://eprints.soton.ac.uk/id/eprint/376463
ISSN: 1572-6657
PURE UUID: 3bb690a5-e002-4c89-ad68-06de2a6ee06d
ORCID for P.N. Bartlett: ORCID iD orcid.org/0000-0002-7300-6900

Catalogue record

Date deposited: 28 Apr 2015 15:40
Last modified: 20 Jul 2019 01:22

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