Impedance studies of reconstructed and non-reconstructed gold single crystal surfaces

The (100), (111) and (210) surfaces of single crystal gold electrodes were investigated by impedance spectroscopy over the frequency range from I Hz to 10 kHz. In solutions containing weakly adsorbed anions, such as ClO4-, F- and PF6-, the data could be fitted to a simple equivalent circuit consisting of the double layer capacitance and the electrolyte resistance connected in series. Probably, the adsorption of these anions is so fast that it cannot be detected in the frequency range employed. In contrast, the anions Cl- and Br- adsorb more strongly and with a measurable rate; in this case an adsorption branch had to be added to the equivalent circuit. On Au(100) and Au(III) the well-known reconstruction phenomena were observed. Both the potentials at which they occur and the rate depend on the type and the concentration of the anion. The double layer capacity was measured on the reconstructed and on the ideal surfaces, and for a series of concentrations. In all cases considered, Parsons-Zobel plots are linear, but the slopes are much smaller than unity.