Voltammetry of multi-electron electrode processes of organic species

Classically the analysis of the voltammetric response of multi-electron transfer processes is achieved through the use of the Randles–Sevcik equations based on analytical theory. In such it is assumed that the after the ‘rate determining step’ all electron transfers are highly driven. Conversely, it is commonly found experimentally that the formal potentials for different electrochemical steps (1, 2, 3 … ) are found to be at comparable potentials (i.e. E f , 1 θ ∼ E f , 2 θ ∼ E f , 3 θ ); this leads to significant deviations from the Randles–Sevcik analysis. This article highlights various ‘simple’ electrochemical mechanisms (EE, EC, EEC) and discusses how the voltammetric peak height resulting from linear sweep voltammetry is expected to vary with scan rate and other parameters, with the aim of providing a general theoretical basis upon which analysis of complex voltammetric systems may be approached and understood.