Top-down synthesis of sponge-like Mn₃O₄ at low temperature

A top-down synthetic method was developed for the fabrication of sponge-like Mn₃O₄ composed of Mn₃O₄ nanocrystals by decomposition of manganese formate at 200 °C. The samples were characterized in terms of their structural and morphological properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) studies. TEM and SEM images showed that the morphology of sponge-like Mn₃O₄ structures was mostly retained from the morphology of the manganese formate precursor, which was controlled by the solvothermal process. Large sponge-like Mn₃O₄ structures exhibiting crystallographic symmetry were prepared under solvothermal treatment for a long time. The XRD pattern showed that the Mn₃O₄ exhibit a tetragonal hausmannite structure. The results of N₂ adsorption analysis indicated that the sponge-like Mn₃O₄ nanostructures possess high surface area. The possible formation mechanism of Mn₃O₄ nanostructures has been discussed.