Nanopore Functionalized by Highly Charged Hydrogels for Osmotic Energy Harvesting

The salinity gradient between brine and fresh water is an abundant source of power which can be harvested by two major membrane methods: pressure-retarded osmosis and reversed electrodialysis. Nowadays, the latter technology is close to real application, but it still suffers from low power yield. Low membrane selectivity and complex membrane fabrication are the main limiting factors. To improve that, we design a couple of ion-selective membranes based on the track-etched polymer nanopore functionalized by highly charged hydrogels. Two nanopore geometries are compared (cylindrical and conical shape) to generate osmotic energy with gel functions and more importantly can be scaled up. Experiments from the single nanopore and multipore membrane to stacked membranes show complete characterization from ionic transportation to energy generation and a clear relationship from the single pore to stacked membranes. In the actual experiment conditions, a power density of 0.37 W m^-2 at pH 7 was achieved. By improving ionic tracks and reducing intermembrane distances, it can be a good candidate for industrial applications.