Stoichiometry, Morphology, and Size-Controlled Electrochemical Fabrication of Cu_xO (x = 1, 2) at Underpotential

A new one-step electrochemical approach has been developed for the morphology, size, and stoichiometry-controlled synthesis of Cu₂O, CuO, and Cu₂O/CuO composite structures at room temperature without using surfactants, capping agents, or any other additives. The electrochemical deposition of a Cu monolayer using underpotential deposition (UPD) and the flow rate of oxygen gas bubbled through the deposition solution used for oxidation of the Cu layer are the key parameters for controlling the stoichiometry of the Cu_xO (x = 1, 2) structures. The morphologies, crystallinity, stoichiometries, optical properties, and photoelectrochemical properties of the as-electrodeposited Cu₂O and CuO materials were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), UV-vis absorption, and photoelectrochemical (PEC) techniques. The results indicated that the Cu₂O and CuO materials electrodeposited on both indium tin oxide coated (ITO) quartz and gold electrodes using this new electrochemical technique exhibit high-quality single crystalline structures and high photoactivity with rapid photoelectrical response to light irradiation.