Enhanced performance of a Reverse Electrodialysis stack for hydrogen and electricity cogeneration with tailored low-resistance ion-conductive spacers

Reverse electrodialysis (RED) is a promising technology for harnessing salinity gradient energy (SGE) to generate electricity and hydrogen. This study presents a performance-enhancing approach for RED stacks via the integration of tailored ion-conductive wire mesh spacers. Experimental results demonstrated that these customized spacers reduced the stack’s ohmic resistance by up to 49.9% compared to conventional non-conductive spacers. The internal resistance was found to be dependent on the concentration of the dilute solution, following the order of 0.02 mol·L−1 > 0.04 mol·L−1 > 0.06 mol·L−1. Furthermore, expanding the membrane area significantly improved power generation, increasing the open-circuit voltage (OCV) by up to 152.16% and the output power density (Pdd) by 26.0%. We systematically evaluated the hydrogen production rate (JH2) and total power density (Ptotal) under the influence of three key factors: spacer material, dilute solution concentration, and working solutions type. The use of ion-conductive spacers markedly boosted Ptotal, with the enhancement rate accelerating at higher currents, leading to a maximum increase of 37.46%. The hydrogen production power (PH2) was strongly influenced by the ionic species of the working solutions, exhibiting a hierarchy of Na+ > K+ for cations and Cl− < Ac− for anions.