Structurally regulated hydrogel evaporator with excellent salt-resistance for efficient solar interfacial water evaporation

Hydrogel-based solar interfacial evaporator has been a promising tool for energy-efficient fresh water production. However, the slow water transportation and dissatisfactory performance in strong brain were a common suffering for hydrogel evaporator. Herein, with the aid of direct ink writing (DIW) printing technology, we propose a novel strategy of structural control for accelerating the water transportation of polyvinyl alcohol (PVA) / sodium alginate (SA) hydrogel evaporator by fabricating vertically ordered microchannels. The capillary pressure insides microchannels would be a strong power of fast water transportation. Resultingly, the structural evaporator demonstrated an evaporation rate of 3.23 kg m- 2 h-1 with the energy conversion efficiency of 92% under 1 sun irradiation. The weight change of structural hydrogel was only 6.12%, presenting largely enhanced structure stability. Simultaneously, through morphological optimization of evaporation surface, the DIW-printed hydrogel evaporator reached a remarkable evaporation rate of 4.07 kg m- 2 h-1. Based on the sufficient water pathway, the competitive evaporation performance could be maintained in sewage rich in dyes and salts. There is no visible contaminants accretion on the evaporation surface after sunlight exposure in 20 wt% brine for 30 days. With the versatile solar evaporation strategy, various hydrogel evaporators could be developed for fresh water production application.