Highly Efficient Solar Evaporator Based On a Hydrophobic Association Hydrogel

Recently, concerns over water scarcity are on the rise, leading to growing research interest in advanced water purification methods. Solar water purification, which utilizes sustainable energy to separate water impurities and water through evaporation, is emerging as a promising strategy for clean water production. Here, we report a novel solar evaporator based on a carbon nanotube composite polyacrylamide hydrogel (CAH) with a high solar evaporation rate of 4.3 kg·m–2·h–1 under 1 sun irradiation (1 kW·m–2). Such a highly efficient solar evaporator is achieved by introducing solar absorbers (carboxyl multi-walled carbon nanotubes) in the hydrophilic skeleton (polyacrylamide) of hydrophobic association hydrogel. More importantly, the self-healing properties endowed by hydrophobic association also provide a simple fabrication route of double-layer hydrogel-based solar evaporator. By a proper double-layer structure design, the solar evaporation rate of CAH can be further increased to a record high value of 5.1 kg·m–2·h–1. In addition, the CAH can effectively remove salt ions and heavy metal ions in water. The extraordinary performance along with the simple and low-cost fabrication route of CAH offers possibilities for practical ultra-fast solar water purification under natural sunlight.