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Double layer structure of ionic liquids at the Au(111) electrode interface : an atomic force microscopy investigation
journal contribution
posted on 2011-01-01, 00:00 authored by R Hayes, N Borisenko, M Tam, Patrick HowlettPatrick Howlett, F Endres, R AtkinThe double layer structure of two ionic liquids (ILs), 1-butyl-1- methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([Py 1,4]FAP) and 1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate ([EMIm]FAP) at the polarized Au(111) electrode interface is probed using Atomic Force Microscopy force measurements. The force-separation profiles suggest a multilayered morphology is present at the electrified Au(111)-IL interface, with more near surface layers detected at higher potentials. At the (slightly negative) open circuit potential, multiple ion layers are present, and the innermost layer, in contact with the Au(111) surface, is enriched in the cation due to electrostatic adsorption. Upon applying negative electrode potentials (-1.0 V, -2.0 V), stronger IL near surface structure is detected: both the number of ion layers and the force required to rupture these layers increases. Positive electrode potentials (+1.0 V, +2.0 V) also enhance IL near surface structure, but not as much as negative potentials, because surface-adsorbed anions are less effective at templating structure in subsequent layers than cations. This interfacial structure is not consistent with a double layer in the Stern-Gouy-Chapman sense, as there is no diffuse layer. The structure is consistent with a capicitative double-layer model, with a very small separation distance between the planes of charge.
History
Journal
Journal of physical chemistry cVolume
115Issue
14Pagination
6855 - 6863Publisher
American Chemical SocietyLocation
Washington, D. C.Publisher DOI
ISSN
1932-7447eISSN
1932-7455Language
engPublication classification
C1 Refereed article in a scholarly journalCopyright notice
2011, American Chemical Society.Usage metrics
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No categories selectedKeywords
Science & TechnologyPhysical SciencesTechnologyChemistry, PhysicalNanoscience & NanotechnologyMaterials Science, MultidisciplinaryChemistryScience & Technology - Other TopicsMaterials ScienceELECTRICAL DOUBLE-LAYERPOTENTIAL-DEPENDENT STRUCTUREDIFFERENTIAL CAPACITANCEGOLD ELECTRODESOLVATION FORCESWATER-MOLECULESGLASSY-CARBONMOLTEN SALTSTEMPERATURESURFACE
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