Self-cleaning Si/CrN nano-absorber with broadband absorption and excellent corrosion resistance for photothermal application

• The Si/CrN nano-absorber exhibits an impressive light absorption of up to 95 %. • The nano-absorber shows excellent photothermal conversion and corrosion resistance properties. • The self-cleaning evaporation system achieves a brine steam generation rate of 30 mg/min and 72 % solar to evaporation efficiency. We present a stable and efficient broadband Si/CrN nano-absorber using the techniques of magnetron sputtering and inductively coupled plasma (ICP) etching. By combining the advantages of CrN nanoparticles and Si nanopores (Si NPs), the obtained nano-absorber exhibits an impressive average light absorption of up to 95 % across the spectrum range of 220 to 2500 nm. The results obtained from the FDTD method reveal the cavity mode resonance effect, wherein the distribution of the electromagnetic field is predominantly localized on the inner walls of the Si NPs. The surface temperature of the Si NP/CrN absorber increases to 500 K within 250 s and maintains more than 30 min, showing pronounced photothermal conversion stability. The Si/CrN absorber can operate stably in an air atmosphere of 400 °C and maintain efficient broadband absorption characteristics. The Si/CrN nano-absorber also shows the excellent corrosion resistance properties with the corrosion current density of 3.05 × 10 −8 A/cm 2 and the polarization resistance value of 1.55 × 10 6 Ω·cm 2 . Consequently, we explore a thermally stable self-cleaning evaporation cycle system which can provide a brine steam generation rate of about 30 mg/min and achieve about 72 % solar to evaporation efficiency with no salt precipitation left on the sample surface.