Abstract

In this paper studies of overvoltage and capacitance measurements at
silver cathodes in aqueous perchloric acid at room temperature are
described. Capacitances were deduced from open-circuit potential decay
measurements. The increase of overvoltage and the growth of the measured
capacitances in the course of electrolysis are attributed to a growing
pseudocapacitance component. This is analysed in terms of an increasing
coverage, ? ,of the cathode by adsorbed hydrogn atoms. The increase in
surface coverage from the beginning up to several days of cathodisation
ranged up to 2% of a monolayer for silver in 0.1 mol HC1 ,and up toO.9%
of a monolayer in 1 mol 1-' HCIO,. The increase in overvoltage at constant
current density and the increase in electrode capacitance at constant
overvoltage with the logarithm of the cathodic charge (-Q) were linear up to
Q values of about -60° C . This increase in overvoltage and
pseudocapacitance might be attributed to the adsorption and absorption of
hydrogen atoms by silver cathodes