Thermoenhanced osmotic power generator via lithium bromide and asymmetric sulfonated poly(ether ether ketone)/poly(ether sulfone) nanofluidic membrane

Congcong Zhu,Hao Guo,Yue Sun,Xiang-Yu Kong,Ercang Luo,Yadong Wu,Lei Jiang,Liping Wen,Yuhao Hu

doi:10.1038/s41427-021-00317-9

Abstract

Osmotic energy, existing between solutions with different concentrations, is a sustainable and ecofriendly resource for solving energy issues. However, current membrane-based osmotic energy conversion technologies focus on electricity generation from an “open” system by directly mixing salt (NaCl) solutions at room temperature. For the integrated utilization of thermal energy and higher power output performance, we demonstrate thermoenhanced osmotic energy conversion by employing highly soluble lithium bromide (LiBr) solutions, asymmetric sulfonated poly(ether ether ketone)/poly(ether sulfone) (SPEEK/PES) membranes, and LiMn2O4/carbon nanotube (LMO/CNT) electrodes. The thin top layer of this heat-resistant membrane contains hydrophilic groups (i.e., the sulfonated groups in SPEEK) that are beneficial for ion-selective transport. The thermal effect on each solution is investigated, and osmotic energy conversion can be improved by regulating the heat gradient. The power density is ~16.50 W/m2 by coupling with a temperature gradient (30 °C). This work is a step forward for promoting the performance of osmotic energy conversion with thermal energy assistance and provides the basis for a closed-loop system with regenerated osmotic energy from other energy forms. Moreover, the external field-osmotic hybrid energy conversion system shows powerful potential in the energy harvesting field.

Highlights

Salinity gradient energy is identified as a promising and abundant source of sustainable energy, which is obtained from the ionic gradient between sea water and fresh water[1,2]
SPEEK was prepared by sulfonating PEEK with concentrated sulfuric acid, and the degree of sulfonation (DS) of SPEEK was 94.6% according to the 1H NMR technique (Supplementary Fig. S2)
Some additives increase the viscosity of a casting solution, inhibiting the mutual diffusion process of the solvent and nonsolvent owing to the reduced fluidity of a mixed solution[18]

Summary

Introduction

Salinity gradient energy is identified as a promising and abundant source of sustainable energy, which is obtained from the ionic gradient between sea water and fresh water[1,2]. Membrane characterization and ionic transport properties Asymmetric SPEEK/PES blend membranes were fabricated by utilizing nonsolvent-induced phase inversion with the assistance of trace water as the nonsolvent additive (Supplementary Fig. S1). To obtain an asymmetric finger-like membrane, trace Milli-Q water was added to the SPEEK/PES casting solution as a nonsolvent additive.

Results

Conclusion