Multi-functional polyelectrolyte materials in photothermal interfacial evaporation for clean water production

Abstract

Freshwater scarcity has become one of the major obstacles threatening human development, while renewable energy technologies represented by solar energy are emerging as promising green methods for producing freshwater. Solar-driven interfacial evaporation technology has garnered widespread attention due to its high water evaporation rate and low operational costs. Among numerous interfacial evaporation materials, polyelectrolyte materials (PEMs) exhibit excellent performance in saline water due to the abundant charged structure on their chains, enabling interactions with water and salt ions. This review highlights the unique ionic benefits of PEMs in interfacial evaporation processes. Firstly, the presence of ionic effects allows PEMs to no longer rely solely on capillary action, but instead leverage significant osmotic pressure advantages to enhance water transport. Secondly, in the long-term enhancement of salt tolerance, PEMs do not only depend on structural design but also utilize the Donnan effect, generated by unique ionic interactions, to slow down the crystallization and accumulation of salt ions during ion diffusion and migration. Moreover, due to the anti-polyelectrolyte effect involving salt ions, the ionic chain structure of PEMs generates more intermediate water with low evaporation enthalpy, significantly boosting the evaporation process. This mechanism plays a crucial role in evaporation operations in real water systems. Finally, the tunable ion types in PEMs further broaden their application prospects in interfacial evaporation processes. By adjusting different charged functional groups, PEMs exhibit excellent antibacterial and anti-fouling properties, along with outstanding mechanical performance. Overall, PEMs hold great potential for future applications in water purification via interfacial evaporation.