Electrodeposition and Characterization of Selective Coatings Based on Black Cobalt for Solar-to-Thermal Energy Conversion

Abstract

The desired optical properties of selective coatings for solar-to-thermal energy conversion include a high absorbance in the wavelength region of the solar spectrum, coupled with a low thermal emittance in the infrared upon heating of the substrate and coating. Selective coatings consisting of a metallic nickel interlayer and black cobalt top layer have been deposited onto a copper substrate using electrodeposition. The coatings have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The total reflectance spectra in the UV-visible and IR were evaluated before and after a thermal treatment at 300 ºC, and it was observed that the optical properties were not affected, suggesting a good thermal stability of the selective coatings. The solar absorbance of around 90% and thermal emissivity of 15-20% indicate that the optical properties of these selective coatings are suitable for low to medium temperature solar-to-thermal energy conversion applications.