Synergy between ionic thermoelectric conversion and nanofluidic reverse electrodialysis for high power density generation

Nanofluidic reverse electrodialysis (NERD) is a promising method for the collections of salinity gradient energy. However, further improving the performance is necessary for the commercial applications, while only optimizing the nanopore structure and concentration ratio is hard to achieve the propose due to the tradeoff between high selectivity and low resistance in NERD systems. Based on ionic thermoelectric (i-TE) materials, which possessing huge Seebeck coefficient and natural ion channels, using the i-TE membrane and low-grade heat energy to introduce an additional driving force of temperature difference is proposed for the acceleration of ionic migrations. Results show that the effect of temperature difference is equivalent to overlaying an additional voltage difference, and then the synergy between i-TE conversion and NERD significantly enhances both the power density and efficiency. For the temperature differences of 10 K and Seebeck coefficient of 10 mV K-1, the power densities can be enhanced from 11.72 W/m2 to 23.4-93.8 W/m2, and the efficiencies can also be increased to nearly the upper limit of 0.5. Our study provides new roadmap for improving the NERD performance and the utilizing the low-grade heat energy.