Water splitting catalyzed by low cost and earth abundant material is critically important issue in mass production of hydrogen from water using electrical energy. In this study, we developed highly efficient manganese oxide (MnOx) electrocatalytic films by a simple chemical solution deposition (CSD) method for oxygen evolution reaction (OER). Specifically, the MnOx electrocatalytic films were synthesized at different annealing temperatures at 350, 450, and 550 degrees C after the precursor solution coating on fluorine-doped tin oxide (FTO) glass substrates. The MnOx electrocatalytic film prepared at 450 degrees C has exhibited the most catalytic activity for OER with the overpotential of 387 mV at 10 mA/cm(2) in 1 M NaOH alkaline solution. We suggested that this high OER activity of MnOx electrocatalytic film arise from the higher surface area, richer Mn3+ state on the catalysts surface, and low charge transfer resistance between electrocatalytic film and electrolyte based on electrochemical surface area (ECSA), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) analysis. (C) 2016 The Electrochemical Society. All rights reserved.