Superhydrophilic hydrogel with adjustable vertical channels and low water evaporation enthalpy for efficient solar evaporation

The technology of solar-driven interfacial water evaporation (SDWE) is a promising approach for producing freshwater, which addresses the challenges of water scarcity and aims for sustainable desalination. However, the low rate of evaporation poses a major obstacle to the broader implementation of SDWE technology. In the present research, drawing inspiration from the porous structure of natural wood, we developed hydrogel evaporators with vertically aligned channels adjusting pore sizes, composed of polyacrylamide/hydroxypropyl cellulose, through directional freeze casting techniques. In view of excellent superhydrophilic properties and adjustable aperture, the transport of water was improved to meet the requirement of thermal management preferably, effectively reducing heat loss. Furthermore, by optimizing hydratable polymeric network within the polyacrylamide/hydroxypropyl cellulose evaporator, the enthalpy of water evaporation could was reduced, resulting in a higher evaporation rate. The hydrogel evaporator prepared achieved a remarkable rate of 2.68 kg m −2  h −1 and an efficiency of 90.0 % under irradiation of 1 sun. In addition, this hydrogel evaporator displayed excellent resistance to salt and maintained stability during evaporation, making it a viable option for purifying various non-potable water types. Thus, this research provides an innovative perspective for improving the efficacy of solar-driven interfaces in processes such as seawater desalination and wastewater treatment by managing water transport and decreasing evaporation enthalpy.