A parametric study on the rapid synthesis of one dimensional (1D) α-MnO2 nanowires

Abstract

In this study, a parametric study was carried out to synthesize 1D α-MnO2 nanowires by microwave hydrothermal synthesis. Mixed manganese oxides such as α-MnO2/Mn2O3 and α-MnO2/β-MnO2 and β-MnO2 structures were also synthesized with applying different microwave hydrothermal synthesis conditions such as reaction dwell time, altered between 15min and 60min and reaction temperature, altered between 120°C and 160°C. Growth mechanism of α-MnO2 and phase transformation to β-MnO2 was studied by changing such microwave hydrothermal synthesis conditions. The products were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. In order to investigate thermal resistance of the products, TG-DTA analyses were performed under dry air medium. Furthermore, the specific surface area (SSA) and the porosity of the α-MnO2 and β-MnO2 were measured. As a result, when the reaction maintain at 140°C for 30min, the single crystal α-MnO2 structure (SSA=45.8930m2g−1 with average pore size of ∼20nm) was produced without any impurity. When the reaction time and temperature was further increased to 160°C for 1h, MnO2 structure completely transformed into β-MnO2 (SSA=4.4388m2g−1 with the average pore size of ∼15nm).