Boosting the Atmospheric Water Harvesting of Carbon Xerogels by CO 2 Physical Activation: Effect of Pyrolysis Conditions

Nearly four billion people worldwide face water scarcity, making atmospheric water harvesting (AWH) a pressing need for decentralized water production. Here, we present carbon dioxide (CO 2 )-activated carbon xerogels engineered with a single-step pyrolysis-activation process following the Boudouard reaction instead of complex, brittle, and expensive frameworks. By varying activation temperature (750–830 °C), time (1–3 h), and particle size distributions, hierarchical porous structures were developed with surface areas >2000 m 2 g –1 that maximized water uptake capacity and cycling efficiency at medium and high relative humidities, without altering surface oxygen-containing functionalities. This material demonstrated a high daily water yield of 43.6 L kg –1 day –1 under 95% RH and 30 °C with 50 stable adsorption–desorption cycles. It possesses fast kinetics, hydrolytic stability, with low-cost scalability (