Migration Crystallization Device Based on Biomass Photothermal Materials for Efficient Salt-Rejection Solar Steam Generation

Solar-driven interfacial water evaporation has attracted increasing interest because of its high photothermal conversion efficiency. However, a big challenge still remains as salt crystallization is a bottleneck issue that hinders their practical solar desalination applicability. Herein, we demonstrate a strategy for construction of a salt-rejection solar steam generation system by designing a migration crystallization device (MCD) using superhydrophilic carbonized green algae (SH-CGA) as photothermal materials. By a surface modification, the SH-CGA shows a superhydrophilic wettability which facilitates fast water transportation, in combination with its low thermal conductivity of 0.042 W m–1 K–1, high light absorption (98∼100%), and abundant porosity. The prepared SH-CGA exhibits a high evaporation rate of 1.35 kg m–2 h–1 and conversion efficiency of 83% under 1 kW m–2 illumination. Interestingly, we designed a simple MCD by adding a cotton thread into the margin of SH-CGA for preventing surface crystallization. No obvious salt accumulation was observed after 15 d continuous operation at real sunlight irradiation, and the device realizes the simultaneous collection of salt (24.26 g of NaCl crystallization) and water. This result may provide a novel and versatile way for creation of salt-rejection solar steam generation systems with great potential for practical solar desalination.