Nanocomposite cation-exchange membranes based on SPES + S−SiO2 NPs for power generation through reverse electrodialysis

Sustainable power production from salinity gradients can be achieved through reverse electrodialysis (RED). However, although the use of commercial membranes has been extensively reported for this technology, their characteristics constrain overall energy efficiency, constituting the main bottleneck of this technology. For this reason, the present study proposes the fabrication of a nanocomposite cation exchange membrane (CEM), based on a sulfonated polyether sulfone (SPES) polymer matrix and sulfonated silica nanoparticles (S−SiO 2 NPs). Prepared membranes were pretreated with an activation protocol to enhance their conductivity. Their specific resistance ( R SP ) was then analyzed by electrochemical impedance spectroscopy (EIS) to evaluate the influence of S−SiO 2 NPs loading, while their performance was assessed in a lab−scale RED system. The results indicate that the optimal S−SiO 2 NPs loading was 2.5 wt%. The best performance was achieved with the SPES–SS–2.5–AP2 nanocomposite membrane, which yielded a maximum power density ( P d max ) of 1.36 W·m⁻². This value exceeded those obtained for both the activated pristine SPES membrane and the commercial benchmark (FKS−50). Furthermore, the P d max achieved with pure NaCl solutions was maintained when using pretreated seawater (SW) as the high concentration (HC) solution with the SPES–SS–2.5–AP2 nanocomposite membrane, suggesting that membrane performance was not dramatically affected by the presence of divalent ions. The findings of this work highlight nanocomposite CEM development, based on S−SiO 2 NPs additions into a SPES polymer matrix, as a promising approach for enhancing power production in reverse electrodialysis systems.