Charge–potential and capacitance–potential curves corresponding to reversible redox monolayers

General expressions for the charge–potential (Q/E) and capacitance–potential (C/E) curves corresponding to reversible redox monolayers are deduced. These responses present time-independent and universal behaviour, which does not depend on the voltammetric or chronopotentiometric technique employed to obtain them. This holds even in the more complex case in which non-faradaic effects are taken into account. The simultaneous availability of both Q/E and C/E curves allows the total characterisation of the reversible electroactive monolayer. The initial presence of both species in the monolayer can be detected only from the Q/E curves which present a cross potential from which the ratio of initial excesses can be obtained. Experimental C/E data are easily available from chronopotentiometric or voltammetric measurements. Nevertheless, to obtain the experimental Q/E curve, chronopotentiometric data results are more suitable.