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

Manganese oxides nanomaterial (MnOx) with crystalline phases of MnOOH nanorod and Mn3O4 octahedron-like were synthesized by hydrothermal method based on the redox reaction between MnO4- and CH2O at 120 degrees C and 200 degrees C for 10 h, respectively. The beta-MnO2 nanowires were prepared by calcining MnOOH nanorods at 300 degrees 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 MnOx nanostructures, beta-MnO2 nanowire exhibit higher specific capacitance and better catalytic activity than Mn3O4 octahedron-like and MnO(OH) nanorod. The hydroxyl radical mechanism of the photocatalytic degradation of alizarin yellow R was detected and discussed. (C) 2011 Elsevier B.V. All rights reserved.