Differential Capacity of Bromide Anions Adsorption onto Ag(100) in the Absence, and onto Ag(poly) in the Presence of NaClO4

V. D. Jović

Abstract
In this work, the adsorption of bromide anions onto Ag(100) and Ag(poly) in the absence and presence of NaClO4 was investigated. The cyclic voltammetry, EIS and Cdiff vs. E measurement results were analyzed. For the determination of the adsorption parameters, the equivalent circuit containing constant phase element (CPE) instead of the double layer capacity (Cdl) and new equations for the analysis of the anion adsorption, based on a different definition of the CPE, have been developed and used. It was shown that the proposed equivalent circuit and corresponding equations for the differential capacity (Cdiff) as a function of frequency (ω) can successfully be applied in the investigated systems. Excellent agreement between the cyclic voltammograms (CVs) and the Cdiff vs. E curves recorded at frequencies lower than 10 Hz has been detected. The homogeneity of the charge distribution over the real single crystal surfaces, as well as other parameters of the adsorption process were found to change with the potential. In the presence of the supporting (“non-adsorbing”) electrolyte (0.1 M NaClO4) diffusion-like phenomenon was detected and ascribed to the slow step in exchanging anions adsorbed in the inner Helmholtz plane.

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Keywords
Bromide anions adsorption, differential capacity, CPE, surface homogeneity