Spray-deposited CuO:In2O3 nanocomposite thin film: Enhancement in electrochemical performance

Abstract

To promote the electrochemical performance of CuO thin films, different weight percentages of indium chloride (0, 5, 10, 15, and 20 wt%) were added to the precursor to spray-deposit the CuO:In2O3 nanocomposite thin film. Grazing incident X-ray diffraction results revealed the simultaneous growth of CuO and In2O3 on the substrate. All the resulting films were fairly thin (less than 240 nm). The film with pure CuO exhibited a morphology with polygon-shaped grains and vivid grain boundaries. In2O3 grew between the CuO polygon-shaped grains with no grain to the extent that the CuO grains in the CuO:In2O3 thin film with the highest value of In salt in the precursor were fully covered by In2O3. As expected, the conductivity of the prepared films considerably improved with In2O3 growth, which enhanced the electrochemical performance. However, the excessive growth of In2O3 itself could limit the faradaic reaction of the CuO with electrolyte and, therefore, reduce the ion storage. Capacitance was calculated from the results of cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy analysis. The calculated capacitance values confirmed ion storage enhancement after adding the In salt to the precursor up to 15 wt%. Moreover, cell resistance was estimated using galvanostatic charge-discharge and electrochemical impedance spectroscopy. The variation of the estimated resistance also denoted the electrochemical performance enhancement of the CuO:In2O3 nanocomposite thin film with 15 wt% of In salt in the precursor.