Enhancement of power density and hydrogen productivity of the reverse electrodialysis process by optimizing the temperature gradient between the working solutions

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-10, Vol.498, p.155385, Article 155385
• Main Authors: Wu, Xi, Zhang, Youwen, Sun, Dexin, Lv, Yibo, Liu, Mingjun, Zhu, Xiaojing
• Format: Article
• Language: English
• Subjects: Electrolyte solution; Hydrogen production; Ion exchange membrane; Reverse electrodialysis; Temperature difference
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.155385

•Temperature difference of solutions has a crucial effect on the reverse electrodialysis process.•The enhancement effect is more pronounced under negative temperature difference (NTD) mode.•The highest H2 production of 1.128 ± 0.019 mol∙m−2∙h−1 is achieved under NTD mode at 25℃.•Performances of the system using three kinds of solutions with different thermal effects are studied.•Effects of cations and anions on the power density and hydrogen productivity were tested out. Reverse electrodialysis (RED) is an emerging technology that converts the salinity gradient energy (SGE) embedded in two solutions of different concentrations into electricity or hydrogen productivity. Given that two solutions containing SGE in nature are often at different temperatures, this study experimentally investigated the effects of the temperature and salinity ratio of the working solutions on the performance of RED systems. The results show that the power density and hydrogen productivity of RED systems could be markedly improved by adjusting the imposed temperature difference on the basis of the salinity gradient. The degree of improvement mainly depends on the magnitude and direction of the temperature difference between the high- and low-concentration solutions. The enhancement effect was more pronounced under a negative temperature difference (NTD) than under a positive temperature difference (PTD). Additionally, the improvement in system performance owing to the temperature difference was not affected by the endothermic or exothermic effects of different solutes in the water. At a NTD of 25℃ and a concentration of 0.1 M aqueous NaOH as the electrode solution, a RED system based on LiBr solution with a salinity ratio of 4.5 M/0.02 M as the working solution achieved a maximum power density of 0.754 ± 0.006 W∙m−2 and the highest hydrogen productivity of 1.128 ± 0.019 mol∙m−2∙h−1, which was 15.1% and 5.5% higher than the hydrogen productivity under LiCl and NaCl solution conditions, respectively. These results show the great potential of LiBr solution in the field of RED hydrogen productivity.