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.