Reduction of KMnO4 to Mn3O4 via hydrothermal process

A simple, inexpensive, low temperature and environmentally benign hydrothermal reduction route has been developed for the synthesis of octahedral Mn₃O₄ nanoparticles by using KMnO₄ and hexamethylenetetramine (HMT). It has been found that, Mn₃O₄ formation during hydrothermal process involves two steps. In the first step, an intermediate MnOOH is formed under the influence of self generated pressure in the autoclave. In the second step, formic acid produced via hydrolysis followed by oxidation of HMT, reduces MnOOH to Mn₃O₄. The powder X-ray diffraction (XRD) data confirms the formation of tetragonal γ-Mn₃O_4. Scanning electron micrograph images exhibit a good octahedral morphology of the product. The formation γ-Mn₃O₄ is further confirmed by Raman and FTIR spectroscopy.