Anion Exchange Membranes in Electrochemical Energy Systems

Anion exchange membranes (AEMs) are polymeric separators that conduct negatively charged ions—most commonly hydroxide—within alkaline electrochemical devices. By replacing liquid electrolytes or protonic membranes, AEMs enable the use of non-precious metal catalysts, reduce corrosive handling and facilitate device simplification. Key performance metrics include ionic conductivity, chemical and mechanical stability in high-pH environments, dimensional control under hydration and compatibility with electrode architectures. Advances in polymer backbone design, cationic head-group chemistry and microphase separation have yielded membranes with improved transport channels and robustness. These developments underpin growing interest in AEM fuel cells (AEMFCs) and AEM water electrolysers, which together promise lower system costs and enhanced sustainability for hydrogen production and utilisation in a decarbonised energy landscape.

Research from Nature Portfolio

Recent studies have introduced poly(fluorenyl aryl piperidinium) membranes exhibiting hydroxide conductivities exceeding 200 mS cm−1 at 80 °C, paired with low gas permeability and tensile strengths above 80 MPa. These materials sustain over 200 h of continuous fuel cell operation at practical current densities under alkaline conditions, demonstrating stable membrane–electrode integration. Complementary work on sterically protected bis-arylimidazolium polymers has delivered hydroxide exchange capacities above 1 mmol g−1 alongside exceptional chemical endurance in caustic media. The tailored arylimidazolium architectures resist degradation through strategic shielding of cationic sites, offering a route to durable, high-pH electrolyte layers for solid polymer systems.

Anion Exchange Membranes in Electrochemical Energy Systems publication trend

The graph below shows the total number of articles in anion exchange membranes in electrochemical energy systems across all publications each year (not limited to Nature Index journals).

Technical terms

Anion exchange membrane (AEM): a polymeric film that conducts anions, typically hydroxide ions, while blocking gases and liquids in electrochemical cells.

Hydroxide conductivity: a measure of an AEM’s ability to transport OH− ions, expressed in millisiemens per centimetre (mS cm−1).

Ion exchange capacity (IEC): the number of exchangeable ions per unit mass of dry membrane, indicating the density of charged sites.

Dimensional stability: the ability of a membrane to resist swelling or shrinkage under varying hydration and temperature conditions.

Ionomer: a polymer containing ionic groups used to bind catalysts and facilitate ion transport in electrode layers.

References

1. Poly(fluorenyl aryl piperidinium) membranes and ionomers for anion exchange membrane fuel cells. Nature Communications (2021).
2. Poly(bis-arylimidazoliums) possessing high hydroxide ion exchange capacity and high alkaline stability. Nature Communications (2019).
3. Separators and Membranes for Advanced Alkaline Water Electrolysis. Chemical Reviews (2024).
4. Fluorinated Poly(aryl piperidinium) Membranes for Anion Exchange Membrane Fuel Cells. Advanced Materials (2023).
5. Quaternary Ammonium‐Free Membranes for Water Electrolysis with 1 m KOH. Advanced Energy Materials (2023).