High photothermal conversion deep eutectic solvent nanofluids combined with high reflectivity film for atmospheric water gathering

Solar photothermal utilization of nanofluid has huge potential, but there are still some problems such as low-temperature rise and low efficiency of photothermal conversion. In the present work, stable zirconium carbide (ZrC) based deep eutectic solvent (DES) nanofluids are synthesized and its photothermal conversion properties are studied. The results show that the maximum photothermal conversion efficiency of 0.07 wt% ZrC-based DES nanofluids reaches 85.8 %, and the maximum temperature can reach 69 °C. In addition, not many studies have been conducted to apply nanofluids to atmospheric water harvesting, and this work proposes for the first time to combine ZrC-based DES nanofluids with a high-reflectivity film for atmospheric water harvesting. The high reflectivity film can increase the light path and improve the evaporation rate of nanofluids, while the ZrC-based DES nanofluid is hygroscopic and can enable the integration of adsorption and desorption, which provides a new option for nanofluid applications. The findings indicate that ZrC-based DES nanofluids at a low concentration of 0.07 wt% under the irradiation of 1000 W•m−2 have 53.7 % water absorption at RH 70 % and evaporation rate is 0.49 kg/m2•h compared the conventional solar heating method, improved by 69 % on the original basis, reflective film/DES nanofluids evaporation rate is up to 0.77 kg/m2•h, which is improved by 166 % on the conventional solar heating method. These results demonstrate that ZrC-based DES nanofluids have great promise for solar-driven atmospheric water generators.