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A MnO 2 @BP nanocomposite was synthesized by simultaneously reduction of KMnO 4 with Mn(CH 3 COO) 2 .4H 2 O and highly porous Black Pearls 2000 at room temperature. The specific surface area, porosity, crystalline form and conductivity of MnO 2 @BP nanocomposite were characterized by nitrogen gas adsorption measurements, scanning electron microscopy, X-ray diffraction and 4-point probe measurements, respectively. The content of MnO 2 and BP in the composite was determined by thermogravimetric analysis. Chemical mapping using Raman spectroscopy was performed to investigate the distribution of MnO 2 and BP in a composite electrode film prepared with polytetrafluoroethylene (PTFE) as binder. This composite electrode exhibits more homogeneously distributed MnO 2 particles when compared to an electrode made by physical mixing of MnO 2 , BP and PTFE (MnO 2 /BP-PTFE). Also, Raman spectroscopy data of both composite electrodes indicates a loss of electrical conductivity of BP in the case of MnO 2 @BP-PTFE. The electrochemical properties were characterized by cyclic voltammetry in aqueous 0.65 M K 2 SO 4 . The specific capacitance of MnO 2 @BP-PTFE composite electrode was 122 ± 5 F/g, which is statistically equivalent to the capacitance of MnO 2 /BP-PTFE composite electrode (129 ± 6 F/g Owing to its large theoretical capacitance, low cost, environmental friendliness and high density, manganese dioxide (MnO 2 ) is an ideal candidate for positive electrode in asymmetric electrochemical capacitor.1-4 However the performance of MnO 2 -based electrodes is limited by the low electrical and ionic conductivities of MnO 2 . Approaches to increase the low specific capacitance of MnO 2 -based electrode include the addition of a conductive additive such as carbons [5][6][7][8][9] or conductive polymers 10-14 to MnO 2 for the fabrication of a composite electrode. On the other hand, the deposition of a thin MnO 2 layer on carbon with various (nano)architectures 7,15-24 yielded high capacitance (∼700 F/g) when only the mass of MnO 2 was taking into account. 1,8,9,16 Such composite electrodes show typical specific capacitance in the range of 150-250 F/g. Thus, the reported specific capacitance per mass of manganese dioxide is more dependent on the quantity of MnO 2 than the nature of the conductive carbon. 5,8,9,16,[21][22][23][25][26][27][28][29][30][31][32][33] Obtaining good electrochemical performance for MnO 2 -based composite electrodes requires that the electrical contact between MnO 2 and the carbon to be as intimate as possible. 21,34 An attractive approach to achieve it, involves the deposition of MnO 2 onto carbon. 15,22,31,[34][35][36][37][38] By this mean, the effective interfacial area between manganese oxide and the solution is greatly increased. Moreover the contact between MnO 2 and carbon will lead to a high electronic conductivity. MnO 2 has been deposited onto a carbon support by various methods such as sol-gel route, thermal decomposition, electrodeposition, sonochemical synthesis, and redox reaction. 18,31,[34][35]...

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Composite electrodes based on manganese dioxide, a binder (poly(tetrafluoroethylene, PTFE) and a carbon additive (Acetylene black or high surface area Black Pearls 2000) were characterized by nitrogen gas adsorption. The electrochemical performances of the MnO2/Carbon/PTFE composite electrodes were evaluated by cyclic voltammetry. Brunauer–Emmett–Teller (BET) surface area measurements indicated only a minor effect of acetylene black (AB) on the mesoporous surface of composite electrode, presumably because of its larger particle size compared to Black Pearls 2000 (BP). The electrochemical utilization of MnO2 is similar whether AB or BP is used as carbon additive. This suggests that the porosity of Black Pearls, which could perhaps act as a reservoir of ionic species, does not appear to play a significant role. Finally, using a high surface carbon support with MnO2 can cancel the effect of the larger potential window of electroactivity of MnO2 because of its smaller electrochemical potential stability range.