Tailored Nanoscale Architectures for White Light Photoelectrochemistry: Zinc Oxide Nanorod-Based Copper Oxide Heterostructures

This study investigates the morphological evolution, optical properties, and photoelectrochemical (PEC) performance of copper-oxide-coated ZnO nanorods under different annealing conditions. Distinct effects of annealing temperature and atmosphere on Cu2O and CuO growth on ZnO nanorods were observed. SEM images revealed the transformation of Cu2O from silk-like to mushroom-like structures, while CuO formed interconnecting nanomaterials. XRD and XPS analyses showed peak shifts and binding energy changes, highlighting structural and electronic modifications induced by annealing. Moreover, PEC measurements demonstrated the superior photoresponse of CuO-coated ZnO nanorods, especially under negative bias, attributed to favorable band structure, charge carrier separation, and annealing stability compared to Cu2O-coated ones. A noteworthy discovery is that ZnO nanorods coated with CuO nanostructures, prepared under air conditions at 400 °C annealing temperature, exhibit exceptional photocurrents. Applying a 0.4 V voltage increases the photocurrent by approximately 10 mA/cm2. The findings provide valuable insights into tailoring metal oxide semiconductor nanostructures for potential applications in diverse areas, including photoelectrochemistry. This study offers practical guidance on modulating nanostructure growth through annealing to enhance performance. The results hold significance for PEC water splitting and have far-reaching impacts on photocatalysis, environmental remediation, and solar cells.