Abstract
We used a simple, cost effective and scalable chemical method to deposit mixed oxides of copper and cobalt on indium tin oxide (ITO) and stainless steel (ss) substrates. The deposited mixed oxides of Cu-Co and Co-Cu exhibit uniform surface morphology with nanoporous structure as obtained from scanning electron microscopy (SEM). The electrochemical properties were characterized by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The Cu-Co oxide film on ITO yielded very high specific and volumetric capacitances of 919Fg−1 and 616.1Fcm−3 respectively with high energy (28.78Whkg−1) and power (51.8Wkg−1) densities. The same oxide on ss yields 195Fg−1 and 236.8Fcm−3 respectively for the specific and volumetric capacitances. In addition, the Cu-Co oxide electrode shows superior rate capability and excellent long-term cyclability. While the ss offers less internal resistance, the stability of the films is higher on ITO substrates. The bundles of rod-like Cu-Co mixed oxide embedded with nanoporous structure exposed more active surfaces with minimal ion diffusion length thereby enhancing the redox behavior and the binary oxides are synergistically responsible for superior rate capability and excellent durability. Our results indicate that these nanoporous electrodes are promising for use in pseudocapacitive applications.
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•Mixed oxide thin films of Cu and Co were deposited on ITO and stainless steel substrates.•The Cu-Co oxide film on ITO showed superior rate capability and excellent long-term cyclability•Has high specific capacitance of 919Fg−1 and volumetric capacitance of 616Fcm−3 at a scan rate of 5mV/s•The ss offers less internal and series resistances, the stability of the films is better on ITO.•The electrode films have strong potential for pseudocapacitive applications.