Scalable Multifunctional Fabrics with Boosted Intrinsic Photothermal Efficiency for Salt‐Resistant Solar‐Driven Janus Evaporators

Abstract Global population growth and climate change are causing freshwater scarcity, which necessitates creative solutions like solar‐driven desalination. This technology's widespread adoption is hampered by cost and efficiency issues. Intrinsic photothermal conversion efficiency has gotten less attention than light trapping and thermal management, which have been the main focuses of efforts to increase photo‐to‐vapor efficiencies. Here, a commercial padding and vapor polymerization method are used to develop scalable nylon fabrics that act as solar absorbers. This is achieved by anchoring iron catalysts with hydrolyzed perfluorooctyltriethoxysilane chains, which cause confined polymerization of pyrrole to generate polypyrrole. By narrowing the bandgap and generating bioinspired light‐trapping nanostructures, this technique achieves a superior intrinsic photothermal conversion efficiency of 84.6%, which is 4.94 times higher than that of unconfined polymerization. These fabrics are used to create a Janus evaporator, which operates steadily in prolonged seawater testing and shows an evaporation rate of 3.84 kg m −2 h −1 . The low manufacturing cost of ≈28 RMB m −2 emphasizes its scalability and economic potential. This work offers insights into the design of high‐performance, scalable, and cost‐effective solar absorbers by prioritizing increases in light absorption and intrinsic photothermal conversion efficiencies for developing solar desalination technology.