Breath‐Figure Self‐Assembled Low‐Cost Janus Fabrics for Highly Efficient and Stable Solar Desalination

Solar‐driven interfacial evaporation materials for seawater desalination and wastewater treatment have attracted extensive research interest in recent years. Nevertheless, salt accumulation, costly materials, and complex preparation processes greatly hinder the practical application of solar steam generation. Herein, with low‐cost materials such as carbon black (CB), polystyrene‐b‐polybutadiene‐b‐polystyrene (SBS), and commercial cotton fabric, the CB@SBS/cotton fabric Janus evaporator is fabricated via a breath figure template (BFT) method for scalable, long‐term, and stable solar‐driven interfacial desalination. The BFT is a simple yet efficient self‐assembly method that endows the hydrophobic surface of CB@SBS/cotton fabric with a porous structure for high light absorption (≈95.5%) and steam escape. As a result, the CB@SBS/cotton fabric Janus evaporator can achieve a water evaporation rate of 1.37 kg m–2 h–1 and conversion efficiency of 91.3% even in a 3.5 wt% NaCl solution, as well as stably cycling over 15 times without salt accumulation (each cycle: 8 h for illumination and 16 h for rest). The work demonstrates an effective strategy for achieving high‐performance solar steam generation and superior salt rejection capability, which can be potentially utilized in seawater desalination, sterilization, and disinfection. A cost‐effective, high‐efficiency, scalable, and stable Janus evaporator is fabricated via a facile breath figure template method in this work. The breath figure template method is a simple yet efficient self‐assembly strategy that endows the CB@SBS/cotton fabric Janus evaporator with a high water evaporation rate, high conversion efficiency, and excellent long‐term salt‐rejection ability.