Electro-oxidation of hydrazine shows marcusian electron transfer kinetics

Although hydrazine (N2H4) oxidation in an electrochemical environment has been of great interest for years, its intrinsic electron transfer kinetics remain uncertain. We report that the phenomenological Butler-Volmer (BV) theory is not appropriate for interpreting the process of hydrazine oxidation for which an astonishingly wide range of transfer coefficients, Tafel slopes and diffusion coefficient have been previously reported. Rather Tafel analysis for voltammetry recorded at Glassy Carbon (GC) electrodes reveals a strong potential dependence of the anodic transfer coefficient, consistent with the symmetric Marcus-Hush (sMH) theory. According to the relationship $$\beta = {{\lambda + FE_f^0} \over {2\lambda }} - {F \over {2\lambda }}E$$ , the reorganization energy (0.35±0.07 eV) and an approximate formal potential of the rate-determining first electron transfer were successfully extracted from the voltammetric responses.