Solar-driven atmospheric water harvesting with a super-hygroscopic composite modified activated carbon fiber for tropical island ecological farm

Atmospheric water harvesting is a promising strategy to address the water scarcity in islands. In this work, an activated carbon fiber (ACF) templated hybrid water adsorbent ACF-cobalt(Ⅱ)-ethanolamine (ACF-Co-EA) was fabricated and used to build an ecological farm (Eco-farm) for potential application on tropical coral islands. ACF-Co-EA took the advantage of both the pore structure of ACF and the superabsorbent property of the Co-EA complex, thus, exhibiting superior water harvest capacity over ACF or Co-EA. The equilibrium water adsorption of ACF-Co-EA was 763 ​mg ​g⁻¹ ​at 25 ​℃ and 70% RH (typical environment of tropical coral islands). Under 1 ​kW ​m⁻² simulated solar irradiation, the surface temperature of ACF-Co-EA increased rapidly to 50 ​℃ within 12 ​min and stabilized at 54 ​℃ in 30 ​min because of the superior light absorbance of ACF, which made more than 90% of captured water released. ACF-Co-EA-based Eco-farm could harvest 6.9 ​g ​g⁻¹·day⁻¹ of water to ensure plant growth in the tropical coral islands' environment without any additional energy or water supply. The study provided novel ideas to alleviate the problems of freshwater scarcity and food shortage in the tropical coral islands.