Аннотация:We report the comparison of the electrochemical performances of α-MnO2 and δ-MnO2 produced by hydrothermal treatment.The structure and morphology of these materials were analyzed by SEM, HRTEM, XRD, and XPS, while their electrochemicalproperties were tested in the 1 M Na2SO4aqueous electrolyte by cyclic voltammetry, galvanostatic charge–dischargemeasurements, and electrochemical impedance spectroscopy. The specific capacitance of δ-MnO2 at 1 mV·s−1 was 4.8 timeshigher than that of α-MnO2 (211 vs. 44 F·g−1) because of the layered structure of δ-MnO2 that provided better availabilityof the electrode surface for electrolyte ions during charge–discharge cycles and pseudocapacitance behavior attributed tofaradaic redox reactions. Moreover, δ-MnO2 revealed high electrochemical stability (more than 98% of the initial capacitanceafter 5000 charge/discharge cycles) confirming its good performance as an electrode material for pseudocapacitors. Thecontributions of surface and diffusion capacitances were analyzed by the differentiation method.
