Nano-structured cobalt oxide electrodes were prepared by Repetitive Triangular Potential Scans (RTPS) as a simple potentiodaynamic method. The analysis of the experimental data clearly showed that applying various potential windows shows different morphological and electrochemical properties. Electrochemical deposition of cobalt oxide nanostructures onto GC electrode was performed from aqueous Co(NO3)2, (pH 6) solution under three potential windows. The effect of employing potential range on the electrochemical, morphological and electrocatalytic behaviorof cobalt oxide nanoparticles was studied. Different imaging techniques, such as Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM) were used to characterization of fabricated nanostructures. Cyclic Voltametric (CV) and Impedance Spectroscopy (IS) were usedto evaluation of electrochemical properties of deposited films. The imaging and voltammetric studies suggested the existence of at least three shapes of cobalt-oxide, deposited in different deposition conditions. The electrocatalytic activity of the nanostructured cobalt oxides electrodes on hydrogen peroxide and As (III) oxidation shows high dependence to the electrode preparation method. The results shows the variations of potential scanning ranges during deposition process have drastic effects on the geometry, chemical structure, particle size and catalytic properties of nanomaterials.