Boosting Water Evaporation by Construction of Photothermal Materials with a Biomimetic Black Soil Aggregate Structure

Solar-driveninterfacial evaporation is considered an efficientway to get fresh water from seawater. However, the low evaporationrate, surface salt crystallization, and low energy collection of thephotothermal evaporation layer limit its further application in anoutdoor freshwater field. And the aggregate structure design of thematerial itself is often ignored in solar-driven water evaporation.Black soil (BS), with a unique soil aggregate structure, is rich intubular pores, which can be used for multilevel sunlight utilizationand good capillary water transport. Based on the extraordinary photothermalproperties and pumping capacity of BS, a reasonable unidirectionalsalt-collecting device is designed, which can realize long-term collectionof mineral salts and continuous evaporation of seawater and generateelectric energy in the continuous evaporation. Inspired by the uniqueaggregate structure, the photothermal material doping of halloysiteand nigrosin will simulate the generation of this aggregate structureand retain a good water transport effect while obtaining multistageutilization of sunlight. The solar-driven evaporation rate of a nigrosin-halloysitesolar steam generator is 1.75 kg m(-2) h(-1) under 1 kW m(-2) mimic solar radiation; it can achievestable salt leaching-induced voltage generation of 240 mV. This workdemonstrates not only a solar evaporator that can continuously achievedesalination but also the design strategy of BS-like aggregate photothermalmaterials, which promotes the development of low-cost resource recoveryand energy generation for practical outdoor seawater desalination.

Automated summary

Solar-driven interfacial evaporation for seawater desalination is limited by low evaporation rate, salt crystallization, and energy collection issues. Inspired by the unique aggregate structure of black soil, a salt-collecting device is designed to achieve continuous evaporation and mineral salt collection. Furthermore, the design strategy of BS-like aggregate photothermal materials, using halloysite and nigrosin doping, enables multistage sunlight utilization and efficient water transport. This work demonstrates a practical solution for low-cost seawater desalination and resource recovery.