Facile Synthesis of gamma-MnOOH Nanorods via a Redox Precipitation Route Using Oxygen and Their Thermal Conversion

A green chemistry approach was successfully fabricated in this work to synthesize gamma-MnOOH nanorods under mild conditions, in which oxygen was used as the green oxidizer and no surfactants or templates were involved. Only the oxygen was bubbled through the solutions of divalent manganese in the presence of NaOH. The morpholgy and structure of gamma-MnOOH were dependent on several cruicial factors, i. e. the amount of glacial acetic acid (HAc), the kind of anions, reaction time, and reaction temperature. To gain mechanistic information on the dependence, the gamma-MnOOH nanorods were characterized by TEM, SEM and XRD. Results showed that gamma-MnOOH nanorods were evolved from Mn3O4 by a redox process. Furthermore, the corresponding beta-MnO2, alpha-Mn2O3, Mn3O4 were prepared by calcining gamma-MnOOH nanorods under different temperature and atmosphere. Among them, beta-MnO2 nanorods were most efficient for the catalytic decomposition of O-3