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

• Single crystal α-MnO2 and β-MnO2 synthesized using microwave hydrothermal synthesis process.
• α-MnO2 structure showed better thermal resistance than that of β-MnO2.
• BET surface area of the α-MnO2 was measured 45.8930 m2 g−1 with average pore size of ∼20 nm.
• BET surface area of the β-MnO2 was found as 4.4388 m2 g−1 with average pore size of ∼15 nm.

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 15 min and 60 min 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 30 min, the single crystal α-MnO2 structure (SSA = 45.8930 m2 g−1 with average pore size of ∼20 nm) was produced without any impurity. When the reaction time and temperature was further increased to 160 °C for 1 h, MnO2 structure completely transformed into β-MnO2 (SSA = 4.4388 m2 g−1 with the average pore size of ∼15 nm).

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