Nickel modified NiOOH electrodes were used for the electrocatalytic oxidation of ethanol in alkaline so lutions. The electro-oxidation of ethanol in a 1 mol/L NaOH solution at different concentrations of ethanol was stu died by ac impedance spectroscopy. Electrooxidation of ethanol on Ni shows negative resistance on impedance plots. The impedance shows different patterns at different applied anodic potential. The influence of the electrode potential on impedance was studied and a quantitative explanation for the impedance of ethanol oxidation was given by means of a proposed mathematical model. At potentials higher than 0.52 V(vs. Ag/AgCl), a pseudoinductive behavior was observed, but at those higher than 0.57 V, impedance patterns were reversed to the second and third quadrants. The conditions required for the reversing of impedance pattern were delineated with the impedance model. Nickel modified NiOOH electrodes were used for the electrocatalytic oxidation of ethanol in alkaline so lutions. The electro-oxidation of ethanol in a 1 mol / L NaOH solution at different concentrations of ethanol was stu died by ac impedance spectroscopy. Electrooxidation of ethanol on Ni shows The influence of the electrode potential on impedance was studied and a quantitative explanation for the impedance of ethanol impedance was given by means of a proposed mathematical model. The impedance shows different patterns at different applied anodic potential. than 0.52 V (vs. Ag / AgCl), a pseudoinductive behavior was observed, but at at those higher than 0.57 V, and those patterns required for the reversing of impedance pattern were delineated with the impedance model.