PEM electrolyzers: Advancing green hydrogen through materials innovation

Amid mounting consumer and regulatory pressure, industries worldwide are seeking ways to cut their carbon emissions and meet sustainability targets. While adopting renewable energy sources like wind and solar power does help, electrification alone is not enough to offset hard-to-abate sectors including:

• Steel production
• Chemicals
• Refining
• Heavy transport and shipping
• Long-duration energy storage

These industries also need a clean fuel – but most hydrogen produced today still comes from fossil-based sources.

This is where green hydrogen, created by splitting water into hydrogen and oxygen via electrolysis, has emerged as one of the most promising avenues to a lower-carbon future. Global green hydrogen electrolyzer capacity doubled in 2025 to exceed 4 gigawatts, according to the International Energy Agency’s Global Hydrogen Review, with more under construction for 2026.

Proton exchange membrane (PEM) electrolysis has become a leading technology supporting this scale-up. Closing the gap between today’s PEM electrolyzers and the cost, durability, and performance the industry will require in the long term starts with a detailed understanding of the materials inside every stack.

What is a PEM electrolyzer?

PEM electrolysis is a technique that uses electricity to split water into hydrogen and oxygen gas. PEM electrolyzer cells contain an integrated system of critical components, each of which plays a distinct role in getting electricity and water in, and hydrogen and oxygen out. These components are:

• Proton exchange membrane: Lets protons pass from the anode to the cathode, while keeping the hydrogen and oxygen gases from mixing
• Anode catalyst layer: Hosts the oxygen evolution reaction (OER), where water splits into oxygen gas, protons, and electrons – typically using iridium-based catalysts
• Cathode catalyst layer: Hosts the hydrogen evolution reaction (HER), where protons and electrons recombine to form hydrogen gas, usually using platinum-based catalysts
• Porous transport layers: Carry water into the catalyst layers and let the hydrogen and oxygen gases flow back out
• Bipolar plates: Spread electrical current and fluid flow evenly across each cell, and separate one cell from the next in a stack

How does PEM electrolysis work?

Within the cell, the proton exchange membrane sits between two oppositely charged electrodes, and the electrolysis reaction plays out on either side of it:

• At the anode (positively charged): Water is fed in, and an applied voltage splits the H₂O water molecules into oxygen gas, electrons, and hydrogen ions (H⁺, or protons).
• At the cathode (negatively charged): Protons that have passed through the membrane recombine with electrons arriving via an external circuit to form hydrogen gas.

The proton exchange membrane is fundamental to this process. As a solid, proton-conducting material, it lets protons through while acting as a physical barrier that keeps hydrogen and oxygen gases from mixing.

This combination of functions is what allows PEM electrolyzer cells to run at high current density in a compact footprint while still producing very high-purity hydrogen. Each cell only produces a small amount of hydrogen at a low voltage, so to achieve industrial-scale output, manufacturers link dozens or hundreds of these cells together, connected electrically in series, in what is known as a “stack.”

Why materials characterization is critical for PEM electrolyzers

Accelerating innovation in PEM electrolysis relies on rapid and accurate materials characterization. Researchers need precise insight into a wide range of material properties, including:

• Crystal structure
• Composition
• Oxidation state
• Particle size
• Dispersion stability
• Structural evolution during operation

Characterization data connects these properties directly to performance, helping researchers optimize materials faster and make evidence-based development decisions. This represents a broader shift in the field, away from slow trial-and-error development and toward data-driven materials engineering.

Crucially, advanced characterization helps researchers understand why materials perform the way they do and provides essential information about how they can be improved.

Characterizing PEM electrolyzer catalysts

Electrode catalyst development remains one of the most active areas of PEM electrolysis research, and for good reason: catalysts are both the technical bottleneck and the single biggest cost driver in the stack. Much of the current research effort is focused on:

• Reducing the amount of iridium used at the anode
• Increasing catalytic activity
• Improving durability
• Lowering the overall cost of the stack

Achieving these goals requires a detailed understanding of catalyst structure across its life cycle – from freshly synthesized and during active operation to after operation or cycling. Degradation studies in particular can reveal exactly how and why catalyst performance declines over time, pointing researchers toward the specific structural or compositional changes needed to build longer-lasting electrolyzers.

That connection between catalyst chemistry, structure, and real-world durability is what ties materials characterization directly to the industry’s cost-reduction and commercial-scalability goals.

Analytical techniques supporting PEM electrolyzer development

No single analytical technique can tell researchers everything they need to know about their PEM electrolyzer materials. Building a complete picture of how a material performs – and why – takes a range of complementary techniques, each suited to characterizing a different piece of the puzzle.

X-ray diffraction (XRD)

XRD identifies and quantifies the crystalline phases present in a catalyst material and reveals key structural parameters, such as crystallite size, lattice strain, and lattice parameters, from the position, width, and intensity of diffraction peaks.

In PEM electrolyzer catalyst research, XRD is a natural fit for monitoring structural changes as materials are developed and as they age throughout operation, as well as for confirming the crystal phase of new platinum- or iridium-based alloys.

Because XRD data can be collected quickly and repeatably, it’s equally useful in degradation studies, where the same sample is measured before and after cycling, and in day-to-day materials optimization.

Our compact Aeris benchtop x-ray diffractometers handle routine crystallite size and phase measurements, while our modular Empyrean platforms add X-ray scattering and in situ capability for tracking structural changes as catalysts are heated, cycled, or otherwise put under realistic operating conditions.

X-ray fluorescence (XRF)

Where XRD reveals structure, X-ray fluorescence analyzes elemental composition. XRF verifies catalyst composition and precious metal loadings: confirming that an iridium or platinum loading matches specification, for instance, or checking the ratio of metals in a Pt-alloy catalyst.

This makes it a natural fit for both material quality control and production consistency once a catalyst formulation moves toward manufacturing. Because catalyst cost is so tightly coupled to precious metal content, accurate elemental analysis allows teams to confirm they’re actually hitting the loading and composition targets a new material was designed around.

Our XRF solutions for catalysis include the floor-standing Zetium spectrometer, which delivers the analytical power needed for high-precision composition and loading verification.

The benchtop Epsilon 1 brings standardless, quick-turnaround elemental analysis to routine catalyst screening, while the higher-throughput Epsilon 4 suits production-line QC where sample volumes are much higher.

XANES and EXAFS

XRD and XRF reveal crystal structure and elemental composition, but neither shows what’s happening electronically at the single-atom level.

That’s where X-ray absorption spectroscopy (XAS) comes in. An XAS spectrum is made up of two regions:

1. XANES: X-ray absorption near-edge structure
2. EXAFS: Extended X-ray absorption fine structure

Each reveals something different about the atom being studied. XANES is especially sensitive to oxidation state and coordination geometry, while EXAFS reveals the distances and coordination numbers of neighboring atoms. Together, these measurements provide insight into oxidation states and the local atomic environment around a specific element, even in complex, multi-phase, or amorphous materials where diffraction alone falls short.

For PEM electrolyzers, this is especially valuable for studying iridium-based oxygen evolution catalysts, where subtle changes in iridium’s oxidation state and coordination environment during operation are closely tied to both catalytic activity and long-term degradation. Understanding those atomic-level details is what lets researchers design next-generation catalysts with genuinely improved activity and stability, rather than iterating on bulk composition alone.

Empyrean XAS delivers laboratory-based XANES and EXAFS data onto the same modular Empyrean platform used for XRD and scattering, so PEM electrolyzer researchers can study local atomic environments without competing for scarce synchrotron beamtime.

Particle characterization

Catalyst particle size and dispersion have a direct effect on how well a catalyst layer performs. Smaller, well-dispersed particles expose more active surface area per gram of precious metal, while poorly dispersed or agglomerated particles waste catalytic potential and cost.

Particle characterization data feeds directly into catalyst ink formulation and optimization, with typical applications including:

• Nanoparticle sizing
• Agglomeration assessment
• Dispersion stability studies

The Zetasizer Advance range measures nanoparticle size and zeta potential to assess catalyst ink stability and dispersion. Plus, our Mastersizer 3000+ laser diffraction systems characterize the broader particle and agglomerate size distributions relevant to catalyst powders and supports.

Nanoparticle tracking analysis on the NanoSight Pro and automated static image analysis on the Morphologi range also add a complementary, particle-by-particle view – counting and sizing individual nanoparticles, and assessing agglomerate shape – that helps confirm what the bulk measurements above are showing.

Technique	What it reveals
X-ray diffraction (XRD)	Crystalline phase, crystallite size, lattice strain
X-ray fluorescence (XRF)	Elemental composition, precious metal loading
XANES / EXAFS	Oxidation state, local atomic environment
Particle characterization	Particle size, dispersion stability, zeta potential

Future trends in PEM electrolyzer research

PEM electrolyzer research is continuously advancing, with the future of the field depending on innovations in a combination of materials, manufacturing, and system design. Several converging trends are shaping where the technology goes next, with developers seeking to achieve:

• Lower precious metal usage: Much research effort is aimed at reducing iridium loading at the anode without sacrificing performance, alongside the search for alternative catalyst chemistries and more efficient use of the precious metal that’s still required.
• Improved durability: As the industry pushes to extend operating lifetimes, understanding degradation mechanisms across the entire stack is becoming just as important as raw performance.
• Higher-performance systems: Ongoing work targets higher current densities, improved efficiency, and increased hydrogen output, all while working to bring operating costs down.
• Gigawatt-scale manufacturing: Electrolyzer manufacturing is scaling rapidly to meet rising hydrogen demand, making robust quality control and consistent materials performance across huge production volumes a burgeoning engineering challenge in its own right.
• Renewable energy integration: PEM electrolyzers are taking on a growing role in renewable energy ecosystems, with the potential to contribute to grid balancing, energy storage, and sector coupling as more variable wind and solar capacity comes online.

Advancing PEM electrolyzers through smarter materials characterization

PEM electrolyzers are expected to play a major role in scaling up green hydrogen production over the coming decade, but getting there depends on the performance of the materials they’re made from. Catalysts, membranes, and every other critical component determine a stack’s efficiency, durability, and cost, and improving them starts with detailed materials insight.

Advanced characterization techniques, from XRD and XRF through to XAS and particle analysis, give researchers the key insights they need: enabling teams to understand degradation, validate new materials faster, and reduce development risk on the path to next-generation PEM electrolysis.

Learn more about how Malvern Panalytical’s materials characterization solutions help researchers investigate PEM electrolyzer materials, understand degradation mechanisms, and accelerate the development of more efficient, more durable hydrogen production technologies. Speak with Malvern Panalytical specialists about analytical solutions that bring confidence to hydrogen production.