Superstructure-Enabled Anti-Fouling Membrane for Efficient Photothermal Distillation

Photothermal membrane distillation (MD) combining solar harvesting and heat localization is a rapidly emerging technology for water purification and desalination. However, state-of-the-art photothermal MD still suffers from several issues in membrane fouling, material instability, poor long-term performance, and complex synthesis. Herein, we demonstrate a multilevel-roughness membrane by immobilizing a nanoparticle-assembled superstructure on a nanofibrous membrane to obtain omniphobic surface wettability. The nanoparticle-assembled superstructure with abundant nano-/microchannels and low surface energy simultaneously captures solar energy, repels chemical/oil-based contaminants, and facilitates vapor flow. The unique mechanism based on the effects of the multilevel-roughness structure allows effective control of surface wettability, leading to a successful photothermal MD application, highlighted by highly efficient solar-thermal conversion, excellent antifouling behavior, and durability. A high clean water yield of 9.01 kg m–2 h–1 is obtained at a solar intensity of 10 kW m–2, corresponding to a solar-water efficiency of 66.8%. More importantly, when operating in complex feed-water conditions, including oil contaminated and high-saline solution, the speed of clean water generation still presents excellent stability over 48 h of consecutive operation, which significantly outperforms the commercial distillation membranes (typically 1 h). Multiple merits of efficient solar-thermal conversion and long-term stability, supported by techno-economic and scalability analyses, make the composite membrane promising for clean water generation from diverse contaminant mixtures in the solar-driven MD system.