Kinetic measurements of a surface confined redox reaction

The apparent reversibility of redox reactions between adsorbed reactants and products in square-wave voltammetry (SWV) depends on the kinetic parameter defined as the ratio of the standard rate constant and the frequency. If the experimental ratio of the SWV peak current and the frequency depends parabolically on the inverse frequency, the standard rate constant, ks, can be calculated from the critical frequency fmax, which corresponds to the maximum of this parabola, using the equation ks = Kmax fmax. The theoretically calculated critical kinetic parameter kmax depends on the transfer coefficient, α, and a square-wave amplitude. The values of Kmax are reported. The rate constant and α of the adsorbed azobenzene-hydrazobenzene redox reaction, determined at pH 4.7 in acetate buffer, are 97 ± 11 s−1 and 0.20, respectively.