Thermally stable Ni@SiO₂ core-shell nanoparticles for high-temperature solar selective absorber

Improving the thermal stability of solar absorbers persists to be the challenge for solar-thermal technologies operated at high temperatures, such as concentrated solar power trough system. Herein, we report a rationally designed solar selective absorber based on Ni@SiO₂ core–shell nanoparticles with significantly improved thermal stability at temperatures up to 700 °C. Ni nanoparticles were encapsulated into dense ceramic SiO₂ nanoshells, which effectively prevented the formation of Ni-alloys and oxides by inhibiting diffusion of both inclusion Ni and metallic atoms from the substrate at high temperatures. Besides, the spectral absorption properties of the Ni@SiO₂ solar absorber can be optimized by tuning the sizes of Ni cores and absorbing structures. As a result, high solar absorptance (∼0.913) but low thermal emittance (∼0.085) have been achieved for a double-layer Ni@SiO₂ absorber with Ni cores of 40 nm and 80 nm. The excellent thermal stability and high absorption selectivity of the Ni@SiO₂ solar absorber indicate its great potential for high-temperature solar-thermal conversion applications.