Alkaline membrane water electrolysis performance improvement from high ionic strength anolyte

Abstract

Low-temperature hydrogen generation using anion exchange membranes electrolysis (AEMEL) uses the advantages of liquid water alkaline electrolysis and proton exchange membrane electrolysis. In this study, liquid water was fed to the anode and the cathode was operated dry. During electrolysis, water diffuses to the hydrogen cathode through the AEM. It was found that the supporting electrolyte in the water-fed anode (i.e., anolyte) plays an important role in the performance of the dry cathode. Alkali cations from the hydroxide-containing anolyte permeate into the membrane and migrate to the cathode during electrolysis delivering water and significantly improving cathode conductivity and kinetics. The alkali ions in the anolyte can be from an inert salt, not hydroxide, which lessen the potential degradation of cell components because the pH is not as high. There is an optimum concentration of neutral alkali salt in the anolyte because the non-electroactive anions in the anolyte lower the concentration of the hydroxide reactant in the anode ionomer.