Molecularly Engineered Rigid Ultra-Micropore Membranes for Ultrahigh-Power Osmotic Energy Harvesting from High-Temperature Hypersaline Brine

Abstract

Osmotic energy is a promising renewable energy source for its giant reserves and can be easily harvested with ion selective membranes. However, the output power density in membrane-scale applications is always below 10 W m⁻² due to the high resistance from low salinity solution and the serious concentration polarization phenomenon. Here, this study shows that rigid ultra-micropores can greatly improve the output power density of the osmotic energy conversion process with high-temperature hypersaline brine. The membrane with rigid ultra-micropores is constructed by confining the high-content semi-rigid sulfonated poly(ether ether ketone) molecules in graphene oxide nanochannels and fixing them with amphiphilic molecules. The output power density of the membrane can be as high as 175.1 W m⁻² with an energy conversion efficiency of 44.5% at the salinity gradient of 5 M/0.5 M, which can further increase to 371.65 W m⁻² when the solution temperature is up to 60 °C. This study also demonstrates that the high-temperature hypersaline brine can be obtained from a passive solar stiller. The molecular engineering of ion selective membranes and the optimization strategy of the reverse electrodialysis process will inspire the development of a next-generation osmotic energy harvesting system.