Effects of electrode rinse solution on performance of hydrogen and electricity cogeneration system by reverse electrodialysis

Abstract

A harvestable salinity gradient energy exists between the concentrated and diluted electrolyte solutions, which can be converted to the electromotive force of a reverse electrodialysis (RED) stack to drive the power generation and hydrogen production. The performance of a hydrogen and electricity (H&E) cogeneration system by RED method is significantly influenced by the characteristics of the electrode rinse solution (ERS). The study experimentally investigated the effects of ERS concentration, flow rate, electrolyte composition, and active additive on the system's output voltage, power density, and hydrogen and oxygen production. Besides, a surface-active substance with catalytic activity was applied for the first time to the H&E cogeneration system, aiming to decrease the overpotentials of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The results showed that the output voltage increased with an increase in ERS flow rate, but hydrogen production declined. Increasing the concentration of the ERS was beneficial to promoting the output voltage and power density, but an extremely high pH of the ERS was not conducive to hydrogen production. The electrical output performance of the H&E cogeneration system using NaOH solution as the ERS was generally better than that of the corresponding KOH solution. The addition of trioctylmethylammonium chloride (Aliquat-336) was detrimental to the electrical output performance but promoted evolution of hydrogen and oxygen. At a current of 0.3 A and an Aliquat-336 concentration of 0.4 mM, the system achieved a hydrogen production rate of 0.71 ± 0.002 mol·m−2·h−1.