Photocatalytically reactive surfaces for simultaneous water harvesting and treatment

Atmospheric water harvesting provides decentralized and sustainable supplies of fresh water in areas away from natural water resources. However, an important challenge is that water sources such as fog are subject to contamination from airborne pollutants, especially near population centres. Here we demonstrate a rationally designed system that can capture fog at high efficiency while simultaneously degrading organic pollutants. At the heart of our design is a wire mesh coated with anatase titanium dioxide nanoparticles embedded in a polymer matrix. Once activated by sunlight, the photoactive titanium dioxide layer decomposes organic molecules such as diesel, even in the absence of sunlight; moreover, the wettability of the mesh surface is engineered to enhance water extraction. In outdoor tests, the device can maintain a good fog harvesting performance as well as a water treatment efficiency of >85%. The continuous production of water with passive purification demonstrated in our study provides an energy-free solution to address water scarcity.