Photoelectrochemical properties of Cu₂O/CuO microstructure grown on cu foil using dielectric barrier discharge plasmas

This research presents a non-traditional method for surface modification. a Cu₂O/CuO heterostructure was prepared on Cu foil by a dielectric barrier discharge (DBD) plasma and used as a photocathode for photoelectrochemical (PEC) water splitting. Cu₂O/CuO heterostructure was prepared at 1 min, 3 min, and 6 min exposures of the Ar/O₂ gas mixture using DBD plasma, followed by the calcination process at 200 °C for 2 hours. The samples were applied toward PEC water splitting. The samples' X-ray diffraction (XRD) pattern confirmed the cubic phase of Cu₂O and the monoclinic phase of CuO. The field emission scanning electron microscope (FE-SEM) images show that the sample after 1 min of plasma exposure consists of a broccoli-like microstructure, and by increasing the duration time to 3 min and 6 min, the microwire structure was prepared. The presence of minuscule nanoparticles on the surface of all microstructures leads to an elevation in aspect ratio and charge carrier density, resulting in improved performance in photoelectrochemical (PEC) properties. The highest photocurrent of 6.53 mA/cm² at 1.23 V vs. reversible hydrogen electrode (RHE) was recorded for Cu₂O/CuO heterostructure prepared at 3 min exposure plasma under AM 1.5G irradiation. A longer exposure time of DBD plasma causes more thickness and increases the recombination of charge carriers, which decreases the photocurrent density to 4.32 mA/cm² at 1.23 V_RHE. This study demonstrates the development of a Cu₂O/CuO heterostructure on Cu foil with a high aspect ratio as a promising method for enhancing the photoresponse of the Cu₂O/CuO photocathode in the context of photoelectrochemical (PEC) water splitting.