Characteristics of pyridine adsorption on Au(111) and Au(210) by EIS parameters fitting procedure

Resumo

Some aspects of the application of electrochemical impedance spectroscopy to studies of
solid electrode / solution interface, in the absence of faradaic processes, are analysed. In order to perform
this analysis, gold electrodes with (111) and (210) crystallographic orientations in an aqueous solution
containing 10 mmol dm -3 KF, as supporting electrolyte, and a pyridine concentration varying from 0.01
to 4.6 mmol dm -3 , were used. The experimental data was analysed by using EQUIVCRT software, which
utilises non-linear least squares routines, attributing to the solid electrode / solution interface behaviour
described by an equivalent circuit with a resistance in series with a constant phase element. The results
of this fitting procedure were analysed by the dependence on the electrode potential on two parameters:
the pre-exponential factor, Y 0 , and the exponent n f , related with the phase angle shift. By this analysis it
was possible to observe that the pyridine adsorption is strongly affected by the crystallographic orientation
of the electrode surface and that the extent of deviation from ideal capacitive behaviour is mainly of
interfacial origin.