Cyclic voltammetry of a TCNQ(0/-1) solid-state redox couple role of nucleation and nonideality for a square scheme surface redox reaction

The cyclic voltammetry of a persistent TCNQ(0/-1) couple generated from thin polycrystalline films of 9-aminoacridinium(TCNQ)(2) in contact with 1.0 M potassium acetate does not correspond to simple electron-transfer reactions of surface-confined species. The voltammograms are characterized by narrow peak widths much less than 3.52 RT/F for a one-electron process, wide hysteresis (>200 mV) between the anodic and cathodic peaks, and significant apparent double-layer capacities. This voltammetric response has been modeled in the context of a square scheme on the basis of two different assumptions: (i) nonideality in terms of interaction parameters and (ii) nucleation phenomena. While calculated voltammograms based on either assumption predict the experimental hysteresis, the assumption of activation-controlled nucleation gave better agreement with the wave shapes. Chronoamperometric experiments gave further support for the role of a three-dimensional nucleation phenomenon.