Abstract
Salinity gradient (blue) energy has been identified as a promising power source and many technologies have been proposed for its recovery, one of which is nanopore power generators. The single-pore/channel membranes selectively transport ions to achieve efficient salinity gradient power generation. However, porous membranes fail due to concentration polarization. Here, we constructed a heterogeneous membrane by covering ion-selective hydrogel on a polyethylene terephthalate (PET) cylindrical nanochannel porous membrane for the first time to eliminate concentration polarization. The gel layer enhances the ion selectivity of cylindrical nanochannels, making heterogeneous membrane present the ion current rectification effect. The gel layer also avoids the negative impact of concentration polarization on the power generation of porous membranes. The results show that PET porous membrane can hardly generate electricity, but the power density of PET-hydrogel heterogeneous membrane can reach 1.92 W/m2 under 50 times salinity gradient, which is superior to commercial ion exchange membranes. Our work provides a strategy (ion-selective hydrogel covering) to eliminate concentration polarization of porous membranes, and shows the prospect of cylindrical nanochannels for salinity gradient power generation.