Effect of Pore Structure on the Electrochemical Capacitive Performance of MnO[sub 2]

Abstract

Three types of porous MnO 2 : ordered mesoporous β - MnO 2 ( OMMnO 2 ) , disordered mesoporous γ - MnO 2 ( DMMnO 2 ) , and disordered porous α - MnO 2 ( DPMnO 2 ) were synthesized using hard template, self-assembly, co-precipitation methods, respectively. The electrochemical capacitance profiles have been evaluated in 1 M Na 2 SO 4 aqueous solution by means of cyclic voltammetry and impedance measurements. The capacitance profile of the three types of 1D tunnel structure MnO 2 is clearly dependent upon its pore structure despite its crystalline structure. The three porous MnO 2 deliver a capacitance of 70 – 90 μ F ∕ cm 2 . Compared to the disordered porous MnO 2 , the ordered mesoporous and disordered mesoporous MnO 2 , especially for the ordered mesoporous MnO 2 , shows better rate capability due to the unique structure of their well ordered mesoporous network, which is more favorable for fast ionic transport than in the disordered porous MnO 2 .