Mingrui Wu, Yue Wang, Guojie Xu, Yang Yang, Zhijun Yang, Xinyu Zhao, Huacui Xiang, Guojun Liu, Yen Wei, Jiujiang Ji
ABSTRACT Access to safe water in off‐grid, resource‐limited settings remains a pressing challenge. We report a simple, solvent‐free route for on‐site fabrication of high‐performance solar evaporators that requires no specialized equipment. The resulting quaternary‐ammonium‐modified evaporator (ADCM) exhibits strong salt resistance: fixed positive charges establish a Donnan potential that suppresses ion diffusion and lowers internal salinity. Even in 20 wt.% brine, ADCM achieves an evaporation rate of 3.28 kg m − 2 h − 1 with 91.7% efficiency and operates stably for 12 h without salt accumulation. The quaternary ammonium functionality also affords 99.9% sterilization, enabling concurrent pathogen control. Owing to its solvent‐free, scalable fabrication, environmental compatibility, and low cost, ADCM offers a practical platform for off‐grid water purification and alleviating water scarcity.