PFAS-Free Membranes for Electrolysis: The EU Restriction and the AEM Answer

If you build or buy electrolysers for the European market, PFAS has moved from a chemistry footnote to a procurement question. The EU is evaluating one of the broadest chemical restrictions ever proposed, covering per- and polyfluoroalkyl substances across almost all uses. The membranes and ionomers at the heart of conventional PEM electrolysers belong to that group. This page explains what PFAS are, where the EU process stands today, what it means for electrolyser buyers and OEMs, and why a PFAS-free membrane in an AEM electrolyser avoids the problem rather than managing it.

What PFAS are, and why electrochemistry uses them

PFAS (per- and polyfluoroalkyl substances) are a family of many thousands of synthetic chemicals. The restriction proposal submitted to the European Chemicals Agency (ECHA) covers around 10,000 of them. What they share is an extremely stable chemical backbone. That stability is why industry likes them: they resist heat, strong acids, oxidising conditions and wear.

The same property is why regulators worry about them. According to ECHA, all PFAS in the scope of the proposal are very persistent in the environment. Once released, they do not break down on any human timescale. The five national authorities that prepared the proposal estimated that around 4.4 million tonnes of PFAS would end up in the environment over 30 years without action.

The restriction proposal does not only target small, mobile molecules. It also covers fluoropolymers, the large, solid materials used in seals, coatings, cables and membranes. These polymers are not very mobile on their own. The concern is their whole life cycle: emissions during manufacture, the use of smaller PFAS as processing aids, and what happens at end of life.

Why PEM membranes are affected

A proton exchange membrane (PEM) electrolyser splits water in a strongly acidic environment. Its membrane must conduct protons, keep hydrogen and oxygen apart, and survive years of oxidising conditions at the anode. For decades, the standard answer has been perfluorosulfonic acid (PFSA) polymers. They are fully fluorinated, which makes them chemically robust and highly conductive when hydrated.

PFSA polymers fall within the PFAS definition used in the EU proposal. And the membrane is not the only place they appear in a PEM stack:

• The membrane itself is typically PFSA-based.
• The ionomer that binds the catalyst layers and carries ions to the active sites is normally the same family of polymer.
• Auxiliary parts such as gaskets, seals, coatings and tubing may also contain fluoropolymers, in PEM and in other technologies.

In other words, PFAS are not an additive in conventional PEM. They are the core functional material. That is why the restriction matters so much more to PEM than to most other industrial users of fluoropolymers.

Status of the EU universal PFAS restriction (as of October 2026)

The EU process runs under REACH, the EU chemicals regulation. Here is the timeline from ECHA's official publications:

On 26 March 2026, ECHA summarised the position of both committees: they support an EU-wide restriction, subject to specific derogations, on the manufacture, placing on the market and use of PFAS. SEAC considers that targeted derogations are needed where the evidence shows that alternatives are not available and where costs and benefits justify them.

Three points are important for anyone reading headlines about the restriction:

• Nothing is law yet. After ECHA's committees finish, the Commission prepares a draft amendment to REACH Annex XVII, and EU Member States vote on it in the REACH Committee. Final scope, derogations and transition periods are only fixed in that legal text.
• Energy is one of the assessed sectors. ECHA's committees evaluated energy applications as a separate sector. The outcome for any specific electrolyser use depends on the final text.
• Derogations are tied to the lack of alternatives. SEAC's draft opinion links derogations to evidence that alternatives are not available. Where PFAS-free alternatives exist and work, the case for a long derogation gets weaker.

We do not predict the final outcome. We do note the direction of travel. In its Chemicals Industry Action Plan of 8 July 2025, the Commission said it is committed to presenting a proposal as soon as possible after receiving ECHA's opinion, with the overall objective of minimising PFAS emissions.

What it means for electrolyser buyers

An electrolyser bought in 2027 should run well into the 2040s. The stacks will need refurbishment, replacement membranes and spare parts throughout that time. That makes PFAS a lifetime question, not only a purchase question.

• Spare-part and refurbishment risk. Even if a derogation covers today's stacks, it may be time-limited. Ask your supplier how replacement stacks and membranes will be supplied if the rules change mid-project.
• Supply-chain risk. Regulation affects the makers of fluorinated materials as well as their users. Availability and price of PFSA membranes and ionomers can change for reasons that have nothing to do with electrolyser demand.
• Reporting and ESG. Many industrial buyers already track substances of concern in their supply chains. A PFAS-free stack is easier to document and defend to investors, offtakers and permit authorities.
• Component-level clarity. "PFAS-free membrane" does not automatically mean "PFAS-free electrolyser". Ask for a component-by-component declaration covering membrane, ionomer, seals, gaskets and balance of plant. We explain why in PFAS-free electrolysers: it's not only the membrane.

What it means for electrolyser OEMs and stack developers

For OEMs, PFAS is a design-cycle problem. A new stack platform takes years to develop and qualify. Starting that work on a material that may face restrictions, or that depends on a time-limited derogation, builds regulatory risk into the product roadmap.

• Qualification takes time. Switching the membrane and ionomer later means repeating cell, short-stack and durability testing. It is cheaper to qualify a PFAS-free set now than to re-qualify under deadline pressure.
• Matched materials matter. A PFAS-free membrane paired with a PFAS-based ionomer still leaves PFAS in the stack. Membrane, ionomer and electrodes should be qualified as a set.
• Customers will ask. Project developers and public funding programmes increasingly look at materials risk. A credible PFAS-free answer is a sales argument.

How AEM electrolysis avoids the PFAS issue

Anion exchange membrane (AEM) electrolysis uses a solid polymer membrane like PEM, but the membrane conducts hydroxide ions instead of protons. The chemistry is alkaline, not acidic. That difference changes what the materials have to survive.

• No fully fluorinated backbone needed. In alkaline conditions, the membrane and ionomer can be made from PFAS-free polymers. The design is PFAS-free by construction, not by substitution after the fact.
• The same compact cell design. AEM keeps the advantages of a thin, dense membrane: compact stacks, high current density and lower gas crossover than a porous diaphragm.
• No scarce precious metals needed. Alkaline conditions also allow electrodes free of critical raw materials, which removes the other main materials risk of PEM.
• Dilute electrolyte. AEM systems run on pure water to dilute alkaline electrolyte, far gentler than the concentrated lye of classic alkaline electrolysis.

For a side-by-side comparison of the three technologies, read alkaline vs PEM vs AEM electrolysis: the materials question, or our full guide to AEM electrolysis.

The historical objection to AEM was durability. PFAS-free polymers had to prove they could last in a working cell. That is exactly where the data have moved.

The solution: AionFLX™ and AionFLX™ Plus PFAS-free AEM membranes

AionFLX™ is CENmat's family of PFAS-free anion exchange membranes for AEM water electrolysis. It is developed together with the matching AionFLX™ ionomer from the same material family, so the catalyst-layer binder is PFAS-free too.

• AionFLX™ Plus, the composite version, has run for more than 8,000 hours with a degradation rate below 15 µV/h in a long-term test (50 °C, 1 M KOH). See AEM membrane durability: AionFLX™ Plus passes 8,000 h.
• Validated for wet assembly and supplied in pilot-relevant sheet sizes, validated up to 900 cm².
• Proven at stack scale. The same membrane chemistry runs in CENmat's HYScale AEM electrolyser stack: a 6 kW short stack with 400 cm² cells is validated, and the 100 kW system with 900 cm² cells has completed production and is in commissioning.

AionFLX™ is qualified together with CENmat's CRM-free OXYGN anodes and H2GN cathodes. That gives OEMs a matched, PFAS-free materials set for cells and stacks instead of a single component to fit around existing materials. The background on membrane production is in scaling AEM membrane manufacturing.

CENmat also works on PEM. There, our focus is ultra-low iridium catalysts. For PFAS-free electrolysis, AEM is our main route.

FAQ: PFAS-free membranes

Is the EU PFAS restriction already in force?

No. As of October 2026, ECHA's Risk Assessment Committee has adopted its final opinion (2 March 2026) and the Socio-Economic Analysis Committee is expected to adopt its final opinion by the end of 2026. The European Commission then drafts the restriction, and Member States vote on it. Scope, derogations and transition periods are only fixed in the final legal text.

Are PEM membranes PFAS?

Conventional PEM membranes and ionomers are made from perfluorosulfonic acid (PFSA) polymers, which fall within the PFAS group covered by the EU proposal.

What is a PFAS-free AEM membrane?

It is an anion exchange membrane made from polymers that are not PFAS. Because AEM electrolysis runs in alkaline rather than acidic conditions, it does not need a fully fluorinated membrane to survive.

Is a PFAS-free membrane enough to make an electrolyser PFAS-free?

Not on its own. The ionomer, seals, gaskets, coatings and balance-of-plant parts must be checked too. Pairing AionFLX™ membrane with AionFLX™ ionomer covers the two largest PFAS uses inside the cell.

How durable is AionFLX™?

AionFLX™ Plus has run for more than 8,000 h at a degradation rate below 15 µV/h in a long-term test (50 °C, 1 M KOH).

How do I get samples?

Samples are paid and prices are on request. Use the sample form; we reply with price, available sizes and lead time.