Study of charge transfer processes in a surface confined redox system by means of differential staircase voltacoulommetry

A new multipotential pulse technique called differential staircase voltacoulommetry (DSVC) is developed to study charge transfer processes which take place in an electroactive monolayer. We have demonstrated that the faradaic capacitances obtained from DSVC ((ΔQ/ΔE)–E   curves) are identical to those obtained in cyclic voltammetry ((I/v)–E(I/v)–E curves) when the pulse amplitude fulfils ΔE ≪ RT/(nF), independently of the reversibility of the electrode process.DSVC presents the advantage of allowing a simpler and more effective correction of the non-faradaic components of the response than does cyclic voltammetry (CV), even considering that the non-faradaic interfacial capacitance changes with the redox state of the adsorbed species.Moreover, DSVC leads to a peak shaped response which is easily characterisable for reversible processes whereas other multipulse techniques lead to null currents in such a way that it is necessary to use short time pulses in order to transform the response to quasi-reversible, which is much more difficult to analyse and which will present a greater distortion, due to non-faradaic effects.Methods for calculating the surface excess and the thermodynamic and kinetic parameters of the electroactive adsorbates are proposed, experimentally tested and compared with those of CV.