The crystalline α-MnO2 and β-MnO2 nanorods have been successfully prepared via a facile hydrothermal method from γ-MnOOH nanorods precursor, respectively. The samples were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscope (FESEM) and Fourier transformed infrared spectra (FTIR). The morphology and structure of γ-MnOOH nanorods precursors have a great influence on the crystal structure of the obtained products. The α-MnO2 nanorods are prepared from the 100°C γ-MnOOH precursor, while the β-MnO2 nanorods are obtained from the 150°C γ-MnOOH precursor, respectively. Besides, the catalytic activity of the prepared α-MnO2 and β-MnO2 nanorods for the H2O2 decomposition has been investigated comparatively, and the latter shows better catalytic activity.

The relationship among the β-MnO2 nanorod preparation conditions, morphology and catalytic performance on H2O2 decomposition has been investigated in the work. β-MnO2 nanorod catalysts were prepared by heating different γ-MnOOH nanorod precursors at 250–450°C. They were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen adsorption. The experimental results indicate that γ-MnOOH nanorod precursors prepared at higher hydrothermal temperature make final β-MnO2 nanorods uniform. The catalytic performance on H2O2 decomposition shows that β-MnO2 nanorod catalysts have excellent catalytic activity on the decomposition of H2O2, which has not been reported to our knowledge. β-MnO2 nanorods which were prepared by calcining γ-MnOOH precursors at 250°C have higher catalytic activity than those at higher calcination temperatures. The reaction of H2O2 decomposition over β-MnO2 nanorod catalysts was found to follow first-order kinetics.