Square wave voltcoulometry: a tool for the study of strongly adsorbed redox molecules.

A new multipotential pulse technique called square wave voltcoulometry (SWVC), based on the analysis of the difference of converted charge signals obtained between two successive half-cycles when a square wave potential is applied, is developed to study charge-transfer processes taking place in electroactive monolayers. The use of SWVC presents the advantage of giving rise to a peak-shaped response, which evolves to a charge plateau at high square wave pulse amplitudes, from which the total surface excess and the formal potential can be immediately measured for quasi-reversible and reversible processes. This characteristic represents its main advantage versus other multipotential step techniques, which lead to a negligible current under reversible conditions. The formal potential of the electroactive systems can be measured from the peak potential of the SWVC curves, even for quasi-reversible behavior. Moreover, the non-faradic effects on the response can be easily evaluated and avoided as is demonstrated in this paper. Experimental verification of the theoretical predictions is given for reversible and quasi-reversible systems.