CuO-based solar absorber layers with aluminum selective coatings as corrosion-resistant barriers for low-temperature applications

The increasing demand for sustainable energy requires the development of cost-effective solar energy materials as a desired source of power generation. This work presents the fabrication and evaluation of selective solar absorber coatings comprising copper oxide (CuO) layers on copper substrates, with or without protective aluminum top coatings. The CuO layers were synthesized via anodic oxidation in an alkaline medium of 1 M NaOH at 60 °C, with a current density of 4 mA/cm 2 for 30 min. A nanometric aluminum layer was deposited by physical vapor deposition (PVD) to enhance corrosion resistance while maintaining solar absorptance. Surface morphology, crystallinity, and elemental composition were characterized by SEM, EDS, XRD, and GD-OES. Optical performance was assessed using diffuse reflectance spectroscopy across the UV-Vis-NIR-SWIR-MWIR spectral range (200–2500 nm), while corrosion behavior was evaluated using Tafel polarization. The Cu/CuO/Al system achieved solar absorptance values of 94-98% (200–1000 nm) and reduced corrosion rates by 82% compared to uncoated CuO. The nanostructured morphology, featuring a nanoflake-like surface, promotes light trapping and adhesion, while the aluminum overlayer enhances electrochemical stability. Cu/CuO-based systems with aluminum are alternatives for flat-plate solar collectors operating below 100 °C in harsh environments.