Hierarchically aligned channels in the distillation membrane enable efficient solar powered desalination

Abstract

Solar-powered interfacial evaporation attracts enormous attention to solve the water crisis as a low-energy consumption, high energy conversion efficiency, and environmental-friendliness technology. Balancing water transport, water content and interfacial temperature is critical to promote evaporation performance. However, fabrication methods and investigation of dedicatedly-designed structures and channel sizes for solar-powered interfacial evaporation have been rarely reported. Herein, we propose to employ vertically aligned channels with hierarchy sizes to modulate water evaporation and energy efficiency. This unique structure is fabricated by a three-step procedure including freeze-drying, ion cross-linking, and hydrogen bond reconstruction in sequence, which achieves a membrane with vertically aligned channels ranging from 1 nm to tons of micrometers. Our solar-powered distillation membrane with finely-modulated hierarchical structure exhibits a high pure water generation rate of 2.37 kg m⁻² h⁻¹ under one sun illumination. Even when treated with seawater, it can achieve a capacity of 2.34 kg m⁻² h⁻¹ (10 wt% seawater) and stabilize a high evaporation rate for at least 50 h, which is superior to most reported solar empowered distillation membranes. Our distillation membrane features a high mechanical strength and low cost, making it an appealing candidate for the actual application in desalination.