Sustainable Self-Cleaning Evaporators for Highly Efficient Solar Desalination Using a Highly Elastic Sponge-like Hydrogel

Abstract

Interfacial evaporation using light-absorbing hydrogels offers efficient solar evaporation performance under natural sunlight, ensuring an affordable clean water supply. However, achieving light-absorbing hydrogels with durable and efficient utilization is still a challenge due to inevitable salt accumulation, a difficult-to-control surface morphology, and poor mechanical properties on the surfaces of hydrogel-based evaporators. In this work, a photothermal sponge-like hydrogel with a 3D interconnected porous structure was constructed using low-cost activated carbon as a photothermal material, as well as a double-network polymer chain as the basic skeleton using a simple foaming polymerization strategy. The sponge-like hydrogel evaporator showed tailored surface topography, adequate water transport, excellent elasticity and toughness, good salt rejection, and thermal localization properties. Under the irradiation of simulated sunlight (1.0 kW/m2), a high evaporation rate of 2.33 kg·m–2·h–1 was achieved. Furthermore, efficient salt self-cleaning behavior was achieved due to the fast ion diffusion within the 3D interconnected porous structures. Even in highly concentrated brine of 15 wt %, continuous and efficient water evaporation was still achieved. The excellent evaporation and salt rejection properties of this photothermal sponge-like hydrogel indicated its promising long-term sustainable utilization in seawater desalination.

Natural Cellulose Fiber-Derived Photothermal Aerogel for Efficient and Sustainable Solar Desalination

“…Thus, there were main factors that reduced the thermal conductivity of the SBF aerogels. 13,30 The surface morphologies of the SBFAP aerogel were observed as shown in Figure 3d−f. It was observed that the SBFAP material also possessed 3D interconnected porous structures with the similar pore size and pore wall thickness.…”

“…Moreover, Figure S12a presents the water evaporation rate with error bars, indicating that the SSG system’s evaporation rate was also dependent on the indoor conditions during the experiments, such as room humidity and temperature . The increase in the water evaporation performance at a higher thickness of the SBFAP could be attributed to (1) the increased side surface area, leading to the enhanced water evaporation area (steam escape area) and (2) the heat harness from the surrounding environment and bulk water by the side surface. ,, Since the SBFAP material had a low thermal conductivity in the wet conditions (0.137 W m –1 k –1 ), its thermal insulation property could be improved with increasing thickness. As a result, the temperature of SBFAP’s side surface under 1 sun illumination was lower than that of the bulk water and the ambient air.…”

“…Recently, aerogels, as potential substrate materials for the preparation of photothermal materials, have attracted much attention. − This is because aerogels possess many favorable properties, namely (1) 3D interconnected porous structure with a large specific surface area that increases the water transportation ability, (2) high porosity and low density that reduce the thermal conductivity, (3) simple fabrication method, in which freeze drying is a significant step, , and (4) numerous hydroxyl groups that help reduce the enthalpy of water evaporation. , The aerogels used to fabricate photothermal materials were first proposed by combining a bacterial cellulose biomaterial with a graphene oxide layer . Till date, various aerogels have been used as substrates for photothermal material production.…”

“…Besides, the multilayer and 3D interconnected porous structures and the microsized capillary structure of aerogels have been found to improve their light trapping ability. In addition, the aerogel-based photothermal material has low thermal conductivity (0.03–0.1 W m –1 K –1 ), low density (0.06 g/cm 3 ), and high porosity (>90%). ,, Therefore, the photothermal material acts as an insulator foam in the SSG, limiting the heat energy loss to the environment. Since the aerogels were formed by crosslinks of hydrogens, photothermal materials with 3D structures can be easily fabricated.…”

Photothermal–Photocatalytic CSG@ZFG Evaporator for Synergistic Salt Rejection and VOC Removal during Solar-Driven Water Distillation

“…Photothermal hydrogel-based solar evaporators have been emerged as a potential material for proficient clean water production. − Several photothermal materials based on carbon (e.g., carbon nanotubes or graphene), ,, MXenes, , biomass materials, − polymers, , metals, and metal oxides have been incorporated inside the hydrophilic gel to increase the local heat and improve the evaporation performance. However, exploring a low-cost photothermal evaporator with effective thermal management is the need of the hour.…”