Chemical composition and discharge characteristics of gamma-MnO2 prepared using manganese ore

gamma-MnO2, synthesized chemically from local manganese ore, was subjected to physicochemical studies. X-ray diffraction, Fourier transform infrared spectroscopy, surface area measurement, thermogravimetry/differential thermal analysis, scanning electron microscopy, and chemical analyses were used to determine the structural and chemical disorder present in the samples. The electrochemical activity in alkaline medium was evaluated by recording discharge profile at constant current and constant load condition. The charge-discharge profile in 9 M KOH was studied by cyclic voltammetry. The samples were found to be type III gamma-MnO2 with high degree of microtwinning defect (T (w)). The De Wolff disorder was in the range 0.21 < P (r) < 0.32. Thermal studies showed weight loss due to the loss of structural water and formation of lower manganese oxides. Mn4+ vacancy, calculated on the basis of cation vacancy model, was in range 0.06 < x < 0.1. The discharge in alkaline medium was accompanied by homogeneous solid-state proton diffusion in MnO2 lattice. The energy density is explained as a function of proton transfer rate (P (t)) during the discharge.