Macroporous Hydrogel for High-Performance Atmospheric Water Harvesting

Abstract

Simple, low-cost, and high-performance atmospheric water harvesting (AWH) still remains challenging in the context of global water shortage. Here, we present a simple and low-cost macroporous hydrogel for high-performance AWH to address this challenge. We employed an innovative strategy of pore foaming and vacuum drying to rationally fabricate a macroporous hydrogel. The hydrogel is endowed with a macroporous structure and a high specific surface area, enabling sufficient contact of the inner sorbent with outside air and high-performance AWH. The experiments demonstrate that macroporous hydrogels can achieve high-performance AWH with a broad range of sorption humidity [relative humidity (RH) from 100% to even lower than 20%], high water sorption capacity (highest 433.72% of hydrogel’s own weight at ∼98% RH, 25 °C within 60 h), rapid vapor capturing (the sorption efficiency is as high as 0.32 g g–1 h–1 in the first 3 h at 90% RH, 25 °C), unique durability, low desorption temperature (∼50 °C, lowest), and high water-releasing rate (release 99.38% of the sorbed water under 500 W m–2 light for 6 h). The results show that this macroporous hydrogel can sorb water more than 193.46% of its own weight overnight (13 h) at a RH of ∼90%, 25 °C and release as high as 99.38% of the sorbed water via the photothermal effect. It is estimated that the daily water yield can reach up to approximately 2.56 kg kg–1 day–1 in real outdoor conditions, enabling daily minimum water consumption of an adult. Our simple, affordable, and easy-to-scale-up macroporous hydrogel can not only unleash the unlimited possibilities for large-scale and high-performance AWH but also offer promising opportunities for functional materials, soft matter, flexible electronics, tissue engineering, and biomedical applications.

Advances in harvesting water and energy from ubiquitous atmospheric moisture

“…Nanostructured photothermal materials like CNTs are also infused into the hydrogel network to form a hybrid hydrogel network to exploit solar energy for AWH. 129,131,140 Fig. 4b shows one of the typical examples to illustrate the release of the collected water under solar irradiation from a CNT-infused hybrid hydrogel.…”

Recent advances in porous adsorbent assisted atmospheric water harvesting: a review of adsorbent materials

“…It also enables rapid water separation from the adsorbent surface to accelerate the release of internal water [Figure 23A]. In addition, adsorbent films offer an increased contact area with the atmosphere and heater, resulting in a rapid kinetic process [152,165] . Guo et al prepared super hygroscopic polymer films (SHPFs), which can undergo a transition from hydrophilic to hydrophobic after being heated.…”

Hygroscopic and Photothermal All-Polymer Foams for Efficient Atmospheric Water Harvesting, Passive Humidity Management, and Protective Packaging

“…Although some powder and liquid desiccants (i.e., hygroscopic salts, silica gel, zeolite, and glycerin) have been used for conventional sorption-based dehumidification, there are significant challenges in developing bulk desiccants with tailorable structures, stable water adsorption/desorption, and low energy input for regeneration. − The incorporation of organic/inorganic hybrid desiccants within porous three-dimensional (3D) scaffolds is of particular interest, enabling the development of hybrid desiccants with multidimensional shapes (i.e., fabrics, gels, membranes, aerogels, hydrogels, and foams). − Emerging desiccants based on metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) have shown rapid water vapor adsorption and desorption. − It is noted that 3D hybrid desiccants can release water and become regenerated via low-grade thermal energy intake (i.e., waste heat and solar energy) with the help of photothermal or radiative cooling materials, minimizing the carbon footprints of air conditioning. − The reversible water uptake/release and good long-term stability provide a potential avenue for using 3D hybrid desiccants as indoor humidity regulators compared to conventional humidifiers (i.e., based on evaporation and steam) and dehumidifiers (i.e., based on air conditioning and refrigeration). − …”