In situ synthesis of PPy-FexOy-CTS nanostructured gel membrane for highly efficient solar steam generation

Abstract Solar steam generation through sunlight capturing and energy conversion by photothermal membrane is a promising green and energy-saving method to tackle the current situation of water scarcity. The present work developed a simple approach for fabricating novel PPy-Fe x O y -CTS gel membranes via synthesizing polypyrrole (PPy) in chitosan (CTS) sol in situ , in which PPy as the photothermal conversion material was evenly dispersed in CTS gel network, the swelling properties of CTS result in a hierarchically (micro/nano) porous structure to provide water transmission channel. The optimized evaporation rate reached to 1.93 kg m −2  h −1 under one-sun irradiation (1 kW m −2 ) at room temperature (25 °C) and humidity (30%), more than the reported vacuum filtration membranes. The excellent property was attributed to PPy that synthesis in situ is more beneficial to light absorption and heat utilization while cross-linking CTS gel nanostructure reduces the enthalpy of water evaporation. Furthermore, the large area gel film was prepared by coating technology, when purified domestic sewage under natural sunlight, 13.68 L of water per square meter from PPy-Fe x O y -CTS gel membrane could be delivered daily and the TDS value of evaporated water decreased significantly. Note that the environmental-friendly membrane materials, excellent evaporation performance, as well as the easy construction of the solar steam generator, this work may contribute practical applications for alleviating clean water scarcity.