Controlled preparation of MnO₂ hierarchical hollow nanostructures and their application in water treatment

A simple controlled preparation of hierarchical hollow microspheres and microcubes of MnO₂ nano-sheets through self-assembly with an intermediate crystal templating process, was demonstrated. Ultrapure water with a resistivity of 18.2 Mω cm, was used in all the experiments. MnCO ₃ microspheres were produced by a simple mixing method. Manganese sulphate and ammonium hydrogen carbonate were separately dissolved in water. Ethanol was then added to the MnSO₄ solution with stirring, and after its complete dispersion, the NH₄HCO₃ solution was added to the mixture. XRD pattern of the remained core after selective removal of the MnO₂ shell by H₂O₂ confirms the MnO ₂-MnCO₃ composite microstructure. MnCo₃obtained were separated from the reaction mixture by centrifugation, and washed several times with ultrapure water and ethanol to remove impurities.