All-in-One Hydrogel Achieves Highly Efficient Solar Desalination, Water Purification and Waste Heat Power Generation

Recently, theresearch team of Shanghai Institute of Applied Physics, Chinese Academy of Sciences, has made significant progress in developing a multifunctional hydrogel using high-energy γ-ray irradiation technology. This work establishes a ternary coupled system integrating Solar Steam Generation, Photocatalytic Degradation, and Thermoelectric Conversion (SSG-PCD-TE). The related findings have been published in the top-tier international chemical engineering journal Chemical Engineering Journal, under the title "All-in-one photothermal hydrogel: Graphene@CuS with microchannels for fast evaporation, water purification, and heat reuse." The first author of the paper is Dr. Lin Lin, a Ph.D. candidate at the institute, and the corresponding authors are Associate Researcher Jihao Li and Researcher Linfan Li from the Department of Applied Chemistry.

Against the backdrop of increasing global freshwater scarcity, solar steam generation (SSG) technology has emerged as a promising solution due to its green and low-energy characteristics. However, conventional photothermal evaporation materials are prone to structural degradation and performance decline in high-temperature, high-salinity, or polluted water environments. Moreover, they struggle to simultaneously achieve efficient evaporation, pollutant degradation, and waste heat utilization, limiting their practical application.

Building on the team’s previous work on graphene/Ag composite hydrogels (Chemical Engineering Journal, 2023, 147249) and graphene/MXene composite hydrogels (Desalination, 2025, 118657), this study further developed an integrated multifunctional photothermal composite hydrogel named PG@CuSₓ. The material uses hydrophilic polyacrylamide (PAM) as a 3D network framework, incorporating reduced graphene oxide (rGO) for broad-spectrum light absorption and narrow-bandgap copper sulfide (CuS) as a semiconductor. Through γ-ray irradiation and freeze-drying techniques, a 3D structure with vertically aligned porous microchannels was constructed under ambient temperature and pressure.

Key features of this multifunctional photothermal hydrogel include:

1. High-Efficiency Photothermal Evaporation: Under one-sun illumination, PG@CuS_2.5 achieved an evaporation rate of 8.1 kg·m⁻²·h⁻¹. By adjusting the evaporation area index, the rate could be increased to 28.7 kg·m⁻²·h⁻¹, realizing "full-cold evaporation" where the evaporation temperature is lower than the ambient temperature.

2. Excellent Salt Tolerance and Purification Capability: In a high-salinity environment (25 wt% NaCl), no salt crystallization was observed after 16 hours of continuous illumination. The removal rate of salt ions in simulated and real seawater reached 99.9%, meeting the drinking water standards of the WHO and the U.S. EPA.

3. Photocatalytic Degradation of Pollutants: The hydrogel demonstrated a removal efficiency of 90% for typical organic pollutants such as methylene blue (MB), showcasing sustained purification capability.

4. Thermoelectric Cogeneration: When integrated with a thermoelectric generator (TEG), an output voltage of 883 mV was achieved under a 0°C cold source condition, enabling multi-level utilization of solar-thermal-electric energy.

This research successfully realizes a ternary coupled SSG-PCD-TE system, offering a novel strategy to address both freshwater and energy challenges in sun-rich but water-scarce regions.

Link: https://doi.org/10.1016/j.cej.2025.167997

Figure 1. Multifunctional PG@CuS_x composite hydrogels prepared by γ-ray irradiation for efficient desalination and pollutant degradation.