Clean Water from Air Utilizing Black TiO₂-Based Photothermal Nanocomposite Sheets

Abstract

Herein, we demonstrate a simple, highly efficient, and cost-effective clean water generation strategy that can be implemented in the geographical locations deprived of freshwater resources. We captured and purified the atmospheric water utilizing CaCl2 as a deliquescent material followed by solar thermal desalination with an engineered-photothermal nanocomposite sheet (E-PNS). The E-PNS was prepared using Mn2+ ion promoted oxygen vacancy (VO) rich black anatase TiO2 nanoparticles as filler and poly(vinylidene fluoride) as the polymer matrix. The developed E-PNS exhibits an excellent radiation absorption of ∼98.5% covering the entire solar spectrum (250–2500 nm) and has interconnected micropores that facilitate efficient solar–thermal heat and mass transfer. Hence, the reported clean water generation strategy achieves a high solar to thermal conversion efficiency of 90% under light irradiation (solar simulator, intensity 1.13 kW m–2), which is 2.2 times higher when compared to water itself. Further, real-time analysis of an E-PNS integrated all-in-one water from air generator prototype showed a clean water generation rate of 0.365 kg m–2 h–1, i.e., ∼2.2 L m–2 day–1, under direct solar irradiation (∼1.06 kW m–2), thereby offering a very promising technological solution for the production of clean water in water-scarce regions.