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Published October 23, 2019 | Version Published
Journal article Open

On the non-ideal behaviour of polarised liquid-liquid interfaces

  • 1. Departamento De Química, Facultad De Ciencias, Universidad Nacional De Colombia, Cra 30 # 45-03, Edificio 451, Bogotá, Colombia
  • 2. The Bernal Institute and Department of Chemical Sciences, School of Natural Sciences, University of Limerick (UL), Limerick V94 T9PX, Ireland

Description

Interpretation of electrochemical data generated at the interface between two immiscible electrolyte solutions (ITIES), and realisation of the ITIES for technological applications, requires comprehensive knowledge of the origin of the observed currents (i.e., capacitive, ion or electron transfer currents) and the factors influencing the electrical double layer. Upon formation, the ITIES is away from equilibrium and therefore is a close approximation, but not a perfect realisation, of an ideally polarisable interface. Nevertheless, the formalism of equilibrium thermodynamics, e.g., the Nernst equation, are universally applied to interpret electrochemical processes at the ITIES. In this study, electrochemical impedance spectroscopy (EIS), cyclic and AC voltammetry were applied to probe electrochemical processes at an ITIES formed between aqueous and α,α,α-trifluorotoluene electrolyte solutions. A significant contribution from faradaic currents is observed across the whole polarisable potential window and the electrolyte solution is not an ideal resistor (especially at high electric field frequencies). The electrical double-layer at the interface is influenced by the nature of the ions adsorbed. Small inorganic ions, such as sulfate anions and aluminium cations, are shown to absorb at the interface, with methanesulfonic acid absorbing strongly. The nature of ions adsorbed at the interface shifts the potential of zero charge (PZC) at the ITIES, which we propose in turn influences the kinetics of ion transfer.

Notes

M.F.S.-H. acknowledges the "Universidad Nacional de Colombia" for allowing his sabbatical leave.

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Additional details

Funding

Designing Reactive Functionalised Soft Interfaces _ Self-healing soft materials for solar energy conversion, energy storage, and sustainable low cost hydrogen production 13/SIRG/2137
Science Foundation Ireland
SOFT-PHOTOCONVERSION – Solar Energy Conversion without Solid State Architectures: Pushing the Boundaries of Photoconversion Efficiencies at Self-healing Photosensitiser Functionalised Soft Interfaces 716792
European Commission