Anion Exchange Membrane Water Electrolysis

Anion exchange membrane water electrolysis (AEMWE) is an emerging technology for sustainable hydrogen generation that combines the low-cost catalyst benefits of alkaline electrolysis with the compact, zero-gap design of proton-exchange systems. In AEMWE, a hydroxide-conducting polymer separates the anode and cathode compartments, enabling the use of non-precious metal catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) under moderate operating conditions (50–80 °C, near-neutral pH at the membrane interface). Advances in polymer chemistry have increased ionic conductivity and chemical stability, while electrode engineering has focused on optimising catalyst layers, gas-liquid transport and interfacial contact resistances. The result is steadily improving energy efficiency, long-term durability and potential for integration with intermittent renewable electricity. Remaining challenges include membrane alkaline stability at elevated temperature, mass transport limitations in thick catalyst layers and standardisation of performance metrics to enable scale-up toward megawatt-scale green hydrogen production.

Research from Nature Portfolio

Recent studies have deployed electrochemical impedance spectroscopy to dissect performance losses in AEMWE cells, quantifying ohmic and charge-transfer resistances under varied voltages, flow rates and electrolyte concentrations. These investigations reveal that the anodic side (OER) often contributes more to total overpotential than the cathode and that higher temperature and flow can mitigate this effect. In parallel, the design of an all-in-one membrane electrode assembly with oriented intergrowth of catalyst layers has demonstrated a marked increase in energy efficiency. By engineering a porous membrane that guides solvothermal growth of aligned catalysts and creates integrated hydroxide pathways, researchers achieved current densities of 1 A cm⁻² at 1.57 V in concentrated KOH, corresponding to energy efficiencies above 90 %.

Anion Exchange Membrane Water Electrolysis publication trend

The graph below shows the total number of articles in anion exchange membrane water electrolysis across all publications each year (not limited to Nature Index journals).

Technical terms

Anion Exchange Membrane (AEM): a polymer film that selectively conducts hydroxide ions (OH⁻) while separating anode and cathode chambers.

Membrane Electrode Assembly (MEA): the integrated unit combining membrane, catalyst layers and porous transport layers in a zero-gap configuration.

Overpotential: the extra voltage required beyond the thermodynamic potential to drive an electrochemical reaction at a given rate.

Anion Exchange Ionomer (AEI): a polymeric binder within catalyst layers that provides pathways for hydroxide ion conduction.

Oxygen Evolution Reaction (OER): the anodic half-reaction in electrolysis where hydroxide ions are oxidised to molecular oxygen.

References

1. Anion-Exchange Membrane Water Electrolyzers. Chemical Reviews (2022).
2. Comprehensive impedance investigation of low-cost anion exchange membrane electrolysis for large-scale hydrogen production. Scientific Reports (2021).
3. Oriented intergrowth of the catalyst layer in membrane electrode assembly for alkaline water electrolysis. Nature Communications (2022).
4. Recent Advances in Alkaline Exchange Membrane Water Electrolysis and Electrode Manufacturing. Molecules (2021).
5. What is Next in Anion‐Exchange Membrane Water Electrolyzers? Bottlenecks, Benefits, and Future. ChemSusChem (2022).
6. Advanced membrane‐based electrode engineering toward efficient and durable water electrolysis and cost‐effective seawater electrolysis in membrane electrolyzers. Exploration (2023).