Anion Adsorption on Gold Electrodes Studied by Electrochemical Surface Forces Measurement

Abstract

The adsorption of ions on electrodes determines the surface potential and charge density of the electrode, thus, quantitative evaluation of the ion adsorption on an electrode is necessary and has been one of the central questions in electrochemistry. Electrochemical Surface Forces Apparatus (EC-SFA) can provide an efficient characterization method of these properties. The interactions between two gold electrodes in various electrolyte solutions, that is, 1 mM aqueous KClO 4 , K 2 SO 4 , and KCl, were measured by controlling of the electrochemical potential (E). The longrange, double layer repulsion and the jump-in due to the van der Waals attraction at the surface separation of about 20 nm were observed between the electrodes in all the solutions. We evaluated the ψ 0 and σ values employing DLVO fitting of these interactions. The signs of ψ 0 and σ were determined from the interaction between the electrode and negatively charged mica surfaces. This study demonstrated that the σ values were negative and similar in all the solutions when the applied potential E was lower than the potential of zero charge (pzc). When the potential E was increased to near the pzc, the σ values were negative and low and in the order of KClO 4 ≈ K 2 SO 4 > KCl. When the potential E was further increased to the pzc, the σ value was positive in aqueous KClO 4 because of less anion adsorption on the gold electrode, while those in the K 2 SO 4 and KCl aqueous solutions were negative due to higher adsorption amount of the anions. The method demonstrated in this study enabled us to quantitatively evaluate the influences of the ion adsorption on the effective surface potential and charge density of the electrodes, which should determine the performances of electrochemical devices.

Scrutiny of the LiCoO2 Composite Electrode/Electrolyte Interface by Advanced Electrogravimetry and Implications for Aqueous Li-Ion Batteries

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Anion Layering and Steric Hydration Repulsion on Positively Charged Surfaces in Aqueous Electrolytes

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Kosmotropic anion for improving cycling stability of aqueous lithium-ion batteries in salt-in-water electrolytes

“…The water structure in the bulk solution can be altered at the interfacial region by the local concentration of ions, surface charge of the electrode, material property, and applied electric eld. 50,51 The staircase-potential EIS in the non-faradaic potential region was quanti ed to electric double layer (EDL) capacitance (C dl ) on the LCO electrode (Figure 4a and Figure S13). In addition, the surface charge density (s) was calculated using Eq.…”