Abstract: An ITO supported nanostructure manganese dioxide thin film electrode,fabricated by chronoamperometry was evaluated as a potential electrode for electrochemical capacitors.The nucleation mechanism was examined by fitting the experimental data (chronoamperometry) into the Scharifker/Hills nucleation models.SEM images of the electrodeposits show that the microstructure of manganese dioxide is affected by the deposition period.The capacity of the three kinds of manganese dioxide electrode materials formed by different nucleation mechanisms was investigated by cycle voltammetry,constant current chargedischarge method and AC impedance.The results show that the nucleation follows an instantaneous nucleation mechanism in the solution of 0.1 mol/L Mn²⁺ under a 0.365 V step potential,and mixed instantaneous and progressive nucleation mechanism in the solution of 0.01 mol/L Mn²⁺ under a 0.418 V step potential.The nucleation follows a progressive nucleation mechanism in the solution of 0.5 mmol/L Mn²⁺ under a 0.515 V step potential.It is obvious that the instantaneous nucleation is beneficial to preparing deposit sediment which has high specific surface area.Compare with other electrolytic deposit materials,this kind of material displays a better capacitance performance,implying that the capacitance performance can be influenced via different deposit approaches.