Hydrothermal preparation of nanostructured manganese oxides (MnO x) and their electrochemical and photocatalytic properties

Abstract

Manganese oxides nanomaterial (MnO x ) with crystalline phases of MnOOH nanorod and Mn 3O 4 octahedron-like were synthesized by hydrothermal method based on the redox reaction between MnO 4 − and CH 2O at 120 °C and 200 °C for 10 h, respectively. The β-MnO 2 nanowires were prepared by calcining MnOOH nanorods at 300 °C for 3 h in air. Particles were characterized by XRD, FE-SEM, TEM, SA-ED, HR-TEM, Brunauer–Emmett–Teller (BET) and UV–vis diffuse reflectance spectroscopy. Their capability of catalytic degradation of alizarin yellow R with air oxygen in aqueous under visible light irradiation and electrochemical properties of as-prepared nanocrystal modified with carbon paste electrode were comparatively studied. The degradation products were determined by GC–MS. In addition, some influences factors, such as pH and temperature on the photocatalytic degradation were also investigated. Among the as-prepared MnO x nanostructures, β-MnO 2 nanowire exhibit higher specific capacitance and better catalytic activity than Mn 3O 4 octahedron-like and MnO(OH) nanorod. The hydroxyl radical mechanism of the photocatalytic degradation of alizarin yellow R was detected and discussed.