In AEM water electrolysis, lifetime claims are cheap. Hours on a test station are not. When engineers ask us about an anion exchange membrane, the first question is rarely peak current density. It is: how long does it last, and under what conditions? Here is our most direct answer yet.
The result
Our composite membrane, AionFLX™ Plus, has passed 8,000 hours of continuous operation, and the test is still running. It has been held at constant current the whole time, under conditions that are hard on any AEM:
- 1 M KOH electrolyte
- 50 °C
- 1 A/cm², galvanostatic
- 4 cm² single cell
- PGM-free electrodes on both sides: our OXYGN™ anode and H2GN™ cathode
At 1 A/cm² the cell started at about 1.82 V and read about 1.97 V after roughly 7,000 hours. After the usual break-in period, the degradation rate has stayed below 10 µV/h since hour 2,300.
For scale: 8,000 hours is almost eleven months without a break. It is a long, clean data set at a concentration where many AEMs lose their ionic groups quickly, and it points in the right direction.
Why 1 M KOH is the harder test
AEM electrolysers can run on anything from pure water to fairly concentrated lye. More KOH lowers ohmic losses and improves performance at a given voltage, but it also puts much more chemical stress on the membrane. Hydroxide attack is the classic AEM failure mode, which is why many published AEM durability runs use 0.1 M KOH or less.
Running at 1 M KOH is deliberately the tougher route. A membrane that holds up there gives system designers a real choice: dilute electrolyte for a simpler, less corrosive balance of plant, or higher concentration for efficiency.
AionFLX™ and AionFLX™ Plus: which does what
AionFLX™ Plus builds on our standard AionFLX™ membrane, which has its own track record under different conditions. Keep the two apart when you compare numbers:
| Membrane and test | Result |
|---|---|
| AionFLX™ Plus, 1 M KOH, 50 °C, 1 A/cm², 4 cm² | > 8,000 h and running; < 10 µV/h after hour 2,300 |
| AionFLX™, 0.1 M KOH, 50 °C, 4 cm² | ≈ 5,000 h at ≈ 20 µV/h (commercial reference membrane in the same cell: ≈ 170 µV/h) |
| AionFLX™, 2 M KOH | 18 µV/h over ≈ 2,100 h |
| AionFLX™, independent test at DLR, 0.1 M KOH, 50 °C, EU harmonised protocol | 2.01 A/cm² at 2.01 V; < 5 µV/h over 330 h |
| AionFLX™ membrane properties | 1.1 meq/g ion-exchange capacity; 82.7 mS/cm OH⁻ conductivity (50 °C, 1 M KOH); 20 % swelling |
| AionFLX™, H₂ in O₂ at 1.3 A/cm² (0.1 M KOH, 50 °C) | ≈ 0.2 vol % |
Three points matter for anyone qualifying an AEM supplier.
The degradation rate beats the hour count. A membrane that runs 5,000 hours at 170 µV/h and one that runs 5,000 hours at 20 µV/h are not in the same class. The first crosses your end-of-life voltage long before the second. Always ask for the rate, the conditions, and whether the test is still running.
Low swelling and low crossover make stacks easier to build. At 20 % swelling, the membrane keeps its dimensions during wet assembly and start-up. About 0.2 vol % hydrogen in oxygen at 1.3 A/cm² keeps the anode gas well below the lower explosive limit in normal operation. Crossover rises at low load, so check it against your turndown range.
Everything is PFAS-free. AionFLX™ membranes and ionomers come from the same fluorine-free polymer family. With a broad EU PFAS restriction under discussion, that matters for supply security as much as for the environmental footprint.
Working with CENmat as your AEM membrane supplier
We make the membrane, the matching ionomer and the PGM-free electrodes in-house, so when a cell misbehaves we look at the whole membrane electrode assembly, not one component in isolation. You can get:
- AionFLX™ and AionFLX™ Plus membrane sheets, validated up to 900 cm²
- Matched AionFLX™ ionomer for catalyst layers
- Ready-to-assemble OXYGN™ and H2GN™ electrodes, or complete MEAs
- Test data under your conditions, including the protocol used
Screening AEM membranes for a stack or a research programme? Request samples or download the AEM qualification pack. The AionFLX™ product page has the current specification. Tell us your electrolyte concentration, temperature and target current density, and we will share the data set that matches them best.
Test status: September 2026. We will update this article as the run continues.