Cyclic versus staircase voltammetry in electrocatalysis: Theoretical aspects

The transient response of a series RC equivalent circuit to a staircase potential perturbation, where R represents the resistance due to the electrolyte and C a voltage dependent interfacial capacitance, has been examined theoretically using, as a model system, capacitance data believed to be characteristic of the Pt (111) 0.1 M HCl O₄ interface. Solutions to the governing algebraic differential equation were obtained by numerical techniques, which were then used to generate current versus potential curves assuming various data sampling protocols. In general, the resulting curves were not only found to be sensitive to the time at which the current was sampled within each step, but, also, quite different than those obtained by scanning the potential at a constant rate, as in conventional linear scan voltammetry (LSV). Excellent agreement between the staircase voltammetry (SCV) and LSV results could be achieved, however, based on values of the average step currents, Q _step /T, where Q_step represents the total charge injected during the step and T the length of the step, as well as by the postfiltering technique introduced by He [Anal. Chem., 67, 986 (1995)]. Implications of these results for studies involving electrocatalytic systems are discussed.