Daytime air–water harvesting based on super hygroscopic porous gels with simultaneous adsorption–desorption

Abstract

In recent years, solar-powered, passive adsorption-based air–water harvesting has shown tremendous potential in addressing freshwater shortages in arid regions. Although remarkable progress has been witnessed in unlocking the potential of new adsorbents in the laboratory, the productivity of freshwater is still limited by the slow adsorption kinetic, the large latent heat of water evaporation, and the efficiency of condensation. In this work, superhygroscopic porous gels consisting of titanium nitride, hydroxypropyl methylcellulose, and LiCl (THL) were developed and demonstrated to have a unique high water uptake of 1.18–6.43 gwatergsorbent−1 at 25 °C and 15%–90% relative humidity. To validate the feasibility of THL for moisture extraction, reasonable energy management of the water harvester was carried out, and the potential daytime outdoor water collection in summer and winter reached 3.82 and 2.98 lwater kgsorbent−1 day−1, respectively, at relative humidity of ∼60% and ∼30%. The implementation strategy proposed in this paper provides a reliable path for solar-driven AWH, confirming the adaptability and possibility of achieving high yield freshwater production in real scenarios of practical significance.