Janus Polypyrrole Nanobelt@Polyvinyl Alcohol Hydrogel Evaporator for Robust Solar-Thermal Seawater Desalination and Sewage Purification
Xi Zhao, Yingying Chen, Yingying Chen, Yue Yin, Liqing Zou, Qiyang Chen, Kai Liu, Pengcheng Lin, Hua Su, Ying Chen, Ying Chen
Abstract
The state-of-the-art solar-thermal evaporators demonstrating high energy utilization efficiency, a high evaporation rate, and salt rejection are highly desirable in solar-driven low-energy water purification/harvesting. Herein, a novel Janus solar evaporator is constructed by loading polypyrrole (PPy) nanobelts on the polyvinyl alcohol (PVA) hydrogel. The PPy nanobelts present a high solar absorption of 98.3%, leading to a localized solar-thermal efficiency of 82.5% when insulated from bulk water by the PVA hydrogel. The porous PVA hydrogel and the hydrophilic PPy nanobelts enable the efficient three-dimensional water transport. Taking advantages of the synergistic effect in the water-energy nexus, the Janus PPy nanobelt@PVA hydrogel evaporator evaporates water with a high rate of 2.26 kg m–2 h–1 via 80.1% solar energy from 1 sun irradiance with a low PPy loading of ∼3 mg cm–2 even at a rate of 2.64 kg m–2 h–1 via 96.3% solar energy for a biomimetic conical evaporator. The Janus evaporator presents superior salt-resistant desalination and contaminant purification performance in seawater and sewage. Furthermore, a portable solar-thermal purifier equipped with the Janus evaporator desalts real seawater far above the drinking water standard with over a 99.9% salt rejection rate and eliminates 95.8% of chemical oxygen demand in real sewage, highlighting its potential for advanced clean water harvesting.