Ellipsometry of silver electrodes in base solutions under different potential controlled perturbation conditions

Abstract

The ellipsometric and reflectance response at 5461 A of silver in 0.1 M NaOH at 25°C, is studied in the Ag(O)/Ag(I) potential range when the electrode has been subjected to different complex potentiodynamic perturbations. The optical response depends remarkably on the potential sweep rate, on the accumulated anodic charge and on the number of potential cycles. The data of the complex anodic film can he interpreted in terms of a single film model in two limiting cases defined, in,terms of the ancdic charge involved as thin and thick films, respectively: (i)for thin anodic films (Q_a < 50 mCcm^-2) n_f = 1.50 -0.12 i and (ii) for thick anodic films (Q_a < 50 mCcm^-2) n_f = 1.50 - 0.22 i. Time dependence of the optical parameters of both reformed silver and anodic film are shown. Optical results correlates with electrochemical data recently reported and arc discussed in terms of different degree of hydrations For each type of anodic film