Tuning the Capacitance Properties of Nanocrystalline MnCO3 by the Effect of a Carbonizing Agent

Nanocrystalline MnCO3 is synthesized by hydrothermal reduction of KMnO4 using different amounts of pyrrole. The effect of molar ratio of KMnO4 :pyrrole on the phase purity, size of the particle, textural and capacitance properties of MnCO3 is studied systematically using various physico-chemical and electrochemical techniques. While X-ray diffraction studies confirm decline in the phase purity of MnCO3, FTIR, Raman spectroscopic and thermogravimetric studies reveal an increase in the amount of adsorbed water and residual carbon content on increasing the pyrrole concentration during the synthesis. An increase in the size of the particles and reduction in the number of mesopores are observed from the morphological and sorption studies on increasing the pyrrole concentration during the synthesis. A highest specific capacitance value of 296 F g(-1) is obtained at a current density of 0.16 A g(-1) for the nanocrystalline MnCO3, and this capacitance value found to decrease on increasing the concentration of pyrrole during the synthesis of nanocrystalline MnCO3 (166 and 140 F g(-1) for the KMn04:pyrrole ratio of 1:1 and 1:2, respectively). (C) 2018 The Electrochemical Society.