Self-floating nanostructured Ni–NiOx/Ni foam for solar thermal water evaporation

Abstract

Solar thermal water evaporation is a clean, sustainable, and energy-saving approach to fresh water generation compared with traditional methods. Electroplated coating, such as nickel black, have been commercialized in solar water heaters. Inspired by this, we developed a nanostructured Ni–NiO_x/Ni foam (NF) composed of Ni metal nanoparticles and NiO_x with defects. The Ni–NiO_x/NF exhibited high solar absorbance due to the plasmonic effect of metal Ni nanoparticles and defects. Ni–NiO_x/NF also showed a low thermal conductivity, which prevented the loss of thermal energy and thermal transfer, which will be beneficial to the generation of localized high temperatures. The as-prepared Ni–NiO_x/NF can self-float on the water surface without any other materials owing to a high contact angle. The average water evaporation rate of the as-prepared Ni–NiO_x/NF reached 1.41 kg m⁻² h⁻¹ and the average solar conversion efficiency was about 94%. The best sample exhibited a water evaporation rate of 1.45 kg m⁻² h⁻¹ and 96% solar conversion efficiency. This report highlights potential semiconductor materials as highly efficient solar water evaporation materials.