Z. Shi et al., INVESTIGATIONS OF SO4(2-) ADSORPTION AT THE AU(111) ELECTRODE BY CHRONOCOULOMETRY AND RADIOCHEMISTRY, Journal of electroanalytical chemistry [1992], 366(1-2), 1994, pp. 317-326
Chronocoulometry was employed to measure charge density at the Au(111)
electrode surface. Thermodynamic analysis of the charge density data
for ionic adsorption from a solution with an excess of a supporting el
ectrolyte is described and used to study SO42- adsorption at the Au(11
1) electrode from a 0.1 M HClO4 solution. The Gibbs excesses determine
d from the charge density data are compared with the Gibbs excesses de
termined from radiochemical measurements using S-35-labelled sulphate
solutions. Very good agreement between the Gibbs excesses determined b
y the two techniques is observed. Essin-Markov coefficients for SO42-
adsorption from two series of solutions were determined: (i) at consta
nt pH and variable K2SO4 concentration; (ii) at constant K2SO4 concent
ration and variable pH. The Essin-Markov coefficients were used to ide
ntify the nature of the adsorbed species (HSO4- or SO42-). Our results
indicate that SO42- ion is the adsorbed species even if HSO4- predomi
nates in the bulk of the solution.