Polymer–Carbon Black Composites for Humidity-Driven Water Uptake and Photothermally Induced Rapid Desorption

Water scarcity remains a critical challenge, calling for practical and affordable solutions. This study introduces CB@PAAS, a composite material developed for atmospheric water harvesting. Using a straightforward, solvent-free mechanochemical process, carbon black (CB) and poly(acrylic acid) sodium salt (PAAS) are combined to produce a scalable and low-cost material, with component costs below $2 per kilogram. CB@PAAS exhibits water sorption capacities of up to 1 g g^-1 under typical conditions, outperforming many conventional materials like MOFs, COFs, zeolites, and silica gels, while matching the performance of advanced hydrogels. A key advantage of CB@PAAS, which separates the composite from traditional hydrogels, is its ability to quickly and efficiently release adsorbed water under light exposure, thanks to the photothermal properties of CB. This rapid desorption allows for faster sorption/desorption cycles, addressing a major limitation of conventional atmospheric water harvesting materials. The composite's durability and scalability further enhance its suitability for use in resource-limited regions.