Electrochemical preparation of nanosized manganese dioxides from manganese chloride solutions

Manganese dioxides were fabricated by electrodeposition from MnCl2, MgCl2/MnCl2, and HCl/MnCl2 aqueous solutions at 100 °C, respectively. Oxidation behaviors of Mn(II) on titanium plate were studied by cyclic voltammetry. X-ray diffractometer, scanning electron microscopy, and BET measurements were used to characterize manganese dioxide crystal structures, micromorphologies, and specific surface area. The effects of electrolyte composition and potential on manganese dioxide crystal structure and micromorphology were investigated. Manganese dioxide structure type and micromorphology were controlled by adjusting electrolyte composition. γ-MnO2 aggregates consisting of nanosheets were electrodeposited from 0.05 mol L−1 MnCl2 aqueous solution. Crystallinity and the size of γ-MnO2 nanosheet were increased by adding Mg(II) into electrolyte. Nanosized rod-like α-MnO2 with higher specific surface area was prepared by adding 2.0 mol L−1 hydrochloric acid into manganese chloride solution.