Remarkable Capacity Retention of Nanostructured Manganese Oxide upon Cycling as an Electrode Material for Supercapacitor

Abstract

Electrochemical capacity retention of nearly X-ray amorphous nanostructured manganese oxide (nanoMnO(2)) synthesized by mixing directly KMnO(4) with ethylene glycol under ambient conditions for supercapacitor studies is enhanced significantly. Although X-ray diffraction (XRD) pattern of nanoMnO(2) shows poor crystallinity, it is found that by Mn K-edge X-ray absorption near edge structure (XANES) measurement that the nanoMnO(2) obtained is locally arranged in a delta-MnO(2)-type layered structure composed of edge-shared network of MnO(6) octahedra. Field emission scanning electron microscopy and XANES measurements show that nanoMnO(2) contains nearly spherical shaped morphology with delta-MnO(2) structure, and ID nanorods of alpha-MnO(2) type structure (powder XRD) in the annealed (600 degrees C) sample. Volumetric nitrogen adsorption-desorption isotherms, inductively coupled plasma analysis, and thermal analysis are carried out to obtain physicochemical properties such as surface area (230 m(2) g(-1)), porosity of nanoMnO(2) (secondary mesopores of diameter 14.5 nm), water content, composition, etc., which lead to the promising electrochemical properties as an electrode for supercapacitor. The nanoMnO(2) shows a very high stability even after 1200 cycles with capacity retention of about 250 F g(-1).