Effect of synthesis conditions on the morphology of MnO2 (α-, β-, γ-) synthesized by the hydrothermal-electrochemical method

The morphology and particle size of various MnO2 compounds synthesized by the hydrothermal-electrochemical method is presented. Individual crystals as well as bundles of fibers were obtained, with diameters ranging from several tens of nanometers to several microns. The effects of the solution pH, synthesis temperature and the applied current density are discussed. Two very different morphologies were found for α-MnO2 synthesized under different conditions. Various morphologies were also found for γ-MnO2 and γ/β-MnO2 compounds. The relationship between the synthesis parameters, γ-MnO2 structural parameters and the morphology is discussed.