Ionic Liquid Structure Dependent Electrical Double Layer at the Mercury Interface

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• 作者：Muhammad Tanzirul Alam ; Md. Mominul Islam ; Takeyoshi Okajima ; Takeo Ohsaka
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：February 21, 2008
• 年：2008
• 卷：112
• 期：7
• 页码：2601 - 2606
• 全文大小：94K
• 年卷期：v.112,no.7(February 21, 2008)
• ISSN：1932-7455

文摘

Structures of the electrical double layer at Hgroom-temperature ionic liquid (RTIL) interfaces were studiedby measuring the differential capacitance and electrocapillary curves as a function of potential. Maxima ofthe electrocapillary curves measured at the Hg1-hexyl-3-methylimidazolium tetrafluoroborate (HMIBF₄) and1-octyl-3-methylimidazolium tetrafluoroborate (OMIBF₄) interfaces demonstrate an unusual broadness onthe anodic side of the potential of zero charge (PZC), which is significantly different from those obtained atHg in RTILs containing shorter alkyl chains or in conventional molecular solvents containing electrolytes.This broadness of the electrocapillary curve was found to depend on the crystal structure and spatialheterogeneity of the RTILs containing larger alkyl groups, which impede the charged moieties from being incontact with the electrode surface within a certain potential range. Cleaving of the liquid crystal structure bythe dilution of OMIBF₄ with dimethyl sulfoxide, which is reflected on the electrocapillary and surface chargedensity versus potential curves, supports the above reasoning. This is the first report on the dependence ofthe interfacial structure at the Hg electrode on the structure of the RTIL itself. A schematic model of thestructure of the electrical double layer is also given.