Effect of heat treatment on material characteristics and pseudo-capacitive properties of manganese oxide prepared by anodic deposition

Hydrous manganese oxide with amorphous structure is prepared by anodic deposition in manganese acetate solution. The effect of heat treatment (100-700 degreesC) on the material characteristics of the oxides is investigated. The thermal property of the deposited oxide is examined by thermogravimetric and differential thermal analyses. Dehydration, organic-matter decomposition, oxidation and crystallization of the manganese oxide as a function of temperature are examined. Glancing angle X-ray diffraction, scanning electron microscope and X-ray photoelectron spectroscopy are carried out to explore, respectively, the crystal structure, surface morphology and chemical state of the oxide electrodes. It is found that the as-deposited manganese oxide, with an amorphous structure and fibrous feature, is further oxidized and tends to tangle with increasing annealing temperature (below 500 degreesC). When the temperature uses above 500 degreesC, the formation of crystalline oxide is confirmed. Cyclic voltammetry is also performed to evaluate the electrochemical performance of the oxide electrodes annealed at various temperatures. Excellent pseudo-capacitive behaviour of the oxide electrodes is revealed at a low annealing temperature (less than or equal to200 degreesC). The cyclic stability of the deposited manganese oxide is significantly improved by introducing proper heat treatment. (C) 2004 Elsevier B.V. All rights reserved.