Performance of Anion Exchange Membrane Water Electrolysis with High Ionic Strength Electrolyte

Anion exchange membrane water electrolysis (AEMWE) provides the advantages of conventional alkaline water electrolysis and proton exchange membrane water electrolysis for low-temperature hydrogen production. This study investigates the effect of ionic strength in low hydroxide concentration anolyte on AEMWE performance. The anolyte was recirculated at the anode, and the cathode was operated dry. Different alkali cations in the high ionic strength anolyte improved the cathode overpotential by increasing the water transport from the anode to the cathode. Li⁺, Na⁺, K⁺, and Cs⁺ cations were tested with K⁺ providing the lowest electrolysis overpotential among the cations tested. The transference number of the alkali cations was measured by a modified Bruce-Vincent method using a membrane electrode assembly, composed of a hydrogen-evolving cathode and oxygen-evolving anode and anion exchange polymer membrane. The result shows that the cathode overpotential is influenced by the cation mobility, which is related to the hydration shell width. The electrolysis overpotential trend with different alkali cations in the anolyte scaled with the alkali dynamic ionic radius. Durable electrolysis was performed in 1,000 h test at 60 °C and 1 A cm⁻².