Synthesis of Nanostructured Mesoporous Manganese Oxides with Three-Dimensional Frameworks and Their Application in Supercapacitors

Abstract

Nanostructured mesoporous manganese oxides were easily prepared by mixing KMnO 4 with ascorbic acid in an aqueous solution under ambient conditions. The obtained manganese oxides were identified as having an R-MnO 2 tunnel structure composed of an edge-shared network of [MnO 6 ] octahedra. TEM observations revealed that the obtained MnO 2 materials had three-dimensional frameworks which consisted of homogeneous nanoparticles with sizes of ca. 5 nm. Nitrogen sorption analyses showed that these MnO 2 nanoparticles exhibited a type IV isotherm, indicating a mesoporous character. Large surface areas up to 284 m 2 g À1 were recorded. The electrochemical performances of the synthesized R-MnO 2 nanoparticles as supercapacitor electrode materials were studied using cyclic voltammetry and galvanostatic chargeÀdischarge cycling in a threeelectrode system at a potential range from 0 to 1.0 V vs a saturated calomel electrode in 0.5 M sodium sulfate solution. The result showed that mesoporous MnO 2 with three-dimensional frameworks exhibit a high capacitance up to ∼200 F g À1 . Furthermore, a hybrid supercapacitor was assembled by using MnO 2 mixed with a small amount of activated carbon as the positive electrode and activated carbon as the negative electrode in a 0.5 M Na 2 SO 4 electrolyte. By balancing the mass of MnO 2 and activated carbon, a practical cell voltage of 1.8 V could be obtained in aqueous medium with a capacitance of 23.1 F g À1 . After 1200 cycles, the maximum energy density is 10.4 Wh kg À1 and power density is 14.7 kW kg À1 . Thus, the obtained R-MnO 2 nanoparticles are suitable for use as supercapacitor electrode materials.

Effect of reduced graphene oxide–silica composite in polyaniline: electrode material for high-performance supercapacitor

“…1 a Cyclic voltammograms of the rGOSP composites (i) rGOSP20, (ii) rGOSP40, (iii) rGOSP60, (iv) rGOSP80, and (v) rGOSP100 in 1 M H 2 SO 4 electrolyte measured at a sweep rate of 10 mV s −1 and b comparison of the specific capacitance of rGOS, PANI, and rGOSP composites measured at various sweep rates Scheme 1 Schematic representation for the preparation of rGOSP composite up to 250°C. In fact, a considerable amount of water is essential for an electrode material as it is conducive for ionic transportation in an electrolyte, thus enhancing electrochemical performance [21][22][23]. However, weight loss at 250°C is found to be lower in the case of rGOSP20 (14 %) compared to that of PANI (18 %).…”

Review of Electrochemical Capacitors Based on Carbon Nanotubes and Graphene

“…There are two mechanisms proposed for the charge storage in MnO 2 electrodes. The first one is based on intercalation of alkali metal cations (C+) such as Li+, Na+, K+ or protons (H+) during reduction, and as well extraction of cations upon oxidation [33,34]. …”

A three-dimensional nanostructured PANI/MnO x porous microsphere and its capacitive performance

“…4, the initial weight loss corresponding to a broad endothermic peak is observed around 50-300°C for PM4. It can be attributed to dehydration of water molecules physically adsorbed on surface (around 100°C) [45] and the loss of chemically bonded water in the samples (around 200°C) [46][47][48]. The endothermic DTA peak around 200°C is quite large, indicating that the content of chemically bonded water in the sample is high.…”