Localized Electrochemical Deposition of Cu2O and CuO Films as Supercapacitor Electrodes

The process of forming Cu2O and CuO microstructures using localized electrochemical deposition was investigated. These materials were studied for the first time as potential supercapacitor electrodes. X-ray powder diffraction demonstrated that heat treatment of the obtained material at 100°C in air produces a copper(I) oxide film, while treatment at 400°C leads to oxidation of the material and the formation of CuO. According to scanning electron microscopy data, the formed oxide pixels have a diameter of approximately 350 µm. It was determined that the film formed at the longest contact duration between the substrate and the meniscus of the reaction system under applied voltage exhibits a dendrite-like, hierarchically organized microstructure. The primary particles assemble into elongated structures, which in turn form two-dimensional fractal-like Cu2O agglomerates. Atomic force microscopy was used to determine the maximum height variation of the oxide structures, and Kelvin probe force microscopy was employed to assess the electron work function values of the film surfaces. Electrochemical measurements of the formed materials were performed in an aqueous potassium hydroxide electrolyte. It was shown that the Cu2O film exhibits a 1.6 times higher specific capacitance value compared to the CuO film at a current density of 1 mA/cm2. Impedance spectroscopy also revealed that the Cu2O film is characterized by lower resistance.