Large-area manganese oxide nanorod arrays (MnO2 NRAs) have been directly grown vertically on Ti foil with a uniform length and diameter by a simple electrochemical method without any templates. The deposition temperature is one of the most important parameters for formation MnO2 NRAs and at 25 degrees C no MnO2 NRAs can be obtained. The results show that MnO2 has high activity and good stability for oxygen evolution reaction (OER) and the structure of nanorod arrays pronounced enhances MnO2 activity. The onset potential of MnO2 NRAs is lower than that of Pt foil and lower 401 mV than that of MnO2 film, indicating that the structure of MnO2 NRAs shows an easy OER for water split. The MnO2 NRAs may be of great potential in electrochemical water split. Crown Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.