Next-Gen Electrolysis: Engineering PFAS-Free & Low-Iridium Green Hydrogen Systems

The transition to a global green hydrogen economy is one of the most ambitious engineering challenges of the 21st century. Green hydrogen—produced by splitting water using electricity from renewable sources like wind and solar—holds the key to decarbonizing heavy industry, maritime shipping, and aviation. Yet, as the world races to scale up production to multi-gigawatt levels, the industry faces two silent but monumental bottlenecks hidden deep within the architecture of modern electrolyzers: the reliance on toxic per- and polyfluoroalkyl substances (PFAS) and the severe scarcity of iridium.

For decades, Proton Exchange Membrane (PEM) water electrolysis has been the gold standard for green hydrogen production due to its high efficiency, compact footprint, and ability to handle the fluctuating power loads of renewable energy grids. However, traditional PEM electrolyzers depend heavily on Nafion—a PFAS-based polymer membrane—and rely on iridium, an ultra-rare platinum-group metal, to catalyze the oxygen evolution reaction (OER). With regulatory bodies like the European Union moving rapidly to restrict "forever chemicals" and the global supply of iridium strictly capped by natural geological limits, the hydrogen industry is being forced to innovate or stagnate.

The race is now on to engineer the next generation of electrolyzers. From revolutionary silicon oxide membranes to ultra-low-iridium nanotechnology and entirely iridium-free Anion Exchange Membrane (AEM) architectures, the landscape of water electrolysis is undergoing a radical, rapid transformation.

The PFAS Predicament: Moving Beyond "Forever Chemicals"

Since its development by DuPont in the late 1960s, Nafion has dominated the electrochemical landscape. As a perfluorosulfonic acid polymer, it boasts a unique combination of chemical stability, high proton conductivity, and mechanical durability, making it uniquely capable of surviving the highly corrosive, acidic environment of a PEM electrolyzer. However, Nafion is a PFAS. These synthetic compounds are characterized by strong carbon-fluorine bonds that make them incredibly resistant to degradation. When disposed of or degraded, they leach into the environment, persisting indefinitely and accumulating in the food chain, posing severe risks to ecological and human health.

Driven by these environmental and health concerns, the European Union and other global regulatory bodies are spearheading initiatives to heavily restrict or outright ban the use of PFAS. This impending legislative cliff has catalyzed an industry-wide pivot toward fluorine-free proton exchange membranes. The challenge, however, is monumental: researchers must match or exceed the performance of a material that has enjoyed a 50-year head start.

Hydrocarbon and Polymer Innovations

Several commercial and academic entities are making massive strides in polymer chemistry to replace Nafion. Researchers at the Industrial Technology Research Institute (ITRI) have developed advanced hydrocarbon-based membranes utilizing sulfonated poly(ether ether ketone) (SPEEK). By precisely controlling the sulfonation degree (between 50% and 65%) and utilizing a unique cross-linking strategy with multifunctional agents, these membranes form covalent networks that significantly reduce membrane swelling while maintaining critical ion channels for proton transport.

Similarly, industrial giants like Arkema have introduced PVDF-based alternatives. Their technology incorporates sulfonated side chains to achieve high proton conductivity while maintaining mechanical stability. Through surface modification techniques that enhance hydrophilicity, these fluorine-free or reduced-fluorine membranes are achieving conductivity values of 0.08 to 0.12 S/cm under standard operating conditions, presenting a highly viable drop-in replacement for traditional materials.

Graphene Oxide and Nanomaterial Membranes

At the cutting edge of materials science, researchers are exploring the use of functionalized graphene oxide (GO) to create completely novel electrolytic pathways. Recent laboratory studies have investigated sulfonated graphene oxide (SGO) and graphene oxide-naphthalene sulfonate (GONS) as PFAS-free alternatives. These materials significantly outperform Nafion in terms of Ion Exchange Capacity (IEC). At 80 °C, the proton conductivity of GONS reaches an impressive 1.71 S/cm—more than triple the 0.56 S/cm baseline of commercial Nafion 212. While Life Cycle Assessments (LCA) indicate that the energy-intensive manufacturing of graphene currently presents an environmental hotspot, scaling up production is expected to drastically reduce these impacts, offering a highly sustainable, high-performance membrane for future electrolyzers.

Inorganic Oxide Membranes

Perhaps the most radical departure from traditional polymer membranes is the development of solid-state proton-conducting oxide membranes. Using advanced manufacturing techniques like Atomic Layer Deposition (ALD), researchers are engineering ultra-thin silicon dioxide (SiO2) membranes. In recent proof-of-principle demonstrations, a chip-scale water electrolyzer based on a 100-nanometer-thick POx-SiO2 membrane achieved a current density of 2 A/cm² at a potential of 2.5 V. Because these membranes are entirely inorganic, they represent an absolute elimination of PFAS. If successfully scaled from micro-chip dimensions to industrial multi-cell stacks, these oxide membranes could redefine the thermal and chemical boundaries of low-temperature water electrolysis.

The Iridium Bottleneck: A Crisis of Scarcity

Solving the membrane issue is only half the battle; the catalytic bottleneck presents an even more rigid barrier to scale. The Oxygen Evolution Reaction (OER) at the anode of a PEM electrolyzer is kinetically sluggish and requires a highly active, robust catalyst to operate efficiently. In the harsh, highly acidic conditions of a PEM cell, almost all metals instantly dissolve or corrode. Iridium—and specifically its oxidized form, IrO2—is the only element that has historically demonstrated the necessary electrocatalytic activity and stability.

The problem is that iridium is one of the rarest elements on Earth. Found in the Earth's crust at an abundance of only about 0.001 parts per million, it is roughly 40 times rarer than gold. Because there are no direct iridium mines, it is almost exclusively extracted as a minor byproduct of platinum and palladium mining, primarily in Southern Africa. Consequently, global annual production hovers at a mere 8 to 9 tons.

Currently, conventional PEM electrolyzers require massive catalyst loadings—between 2 and 4 milligrams of iridium per square centimeter (mg/cm²)—to ensure efficient electron, proton, and mass transport. On a macro scale, this translates to roughly 300 to 400 kilograms of iridium required for every 1 Gigawatt (GW) of hydrogen production capacity. A simple mathematical calculation reveals a devastating reality: even if the entire global supply of iridium were diverted exclusively to green hydrogen production, it could only support the manufacturing of roughly 30 GW of capacity per year. To meet global decarbonization targets, the world will need hundreds, if not thousands, of gigawatts of capacity. The U.S. Department of Energy’s “Hydrogen Shot” initiative, which aims to reduce the cost of green hydrogen to $1 per kilogram, explicitly recognizes that current iridium loadings make large-scale deployment economically and physically impossible.

Slashing Iridium: Breakthroughs in Ultra-Low Loading Catalysts

To bridge the gap between global energy demands and geological reality, scientists and engineers are employing aggressive structure engineering, oxidation state modulation, and advanced deposition techniques to drastically reduce the amount of iridium required per cell. The U.S. Department of Energy has set an aggressive target to reduce iridium loading to at least 0.125 mg/cm². Recent breakthroughs indicate that the industry is not only meeting this target but surpassing it.

Porous Transport Electrodes and Dry Coating

Traditionally, electrolyzers utilize Catalyst-Coated Membranes (CCMs), where a thick slurry of catalyst is applied directly to the Nafion membrane. This method results in poor catalyst utilization, often dropping below 20%, as much of the precious metal gets buried and isolated from the electrochemical reaction pathways.

The industry is now pivoting toward Porous Transport Electrodes (PTEs) and advanced nanotechnology coating. Companies like VSParticle are utilizing single-step dry coating technology to create highly uniform nanoporous layers (NPLs) that slash iridium requirements by a factor of four. By applying ultra-thin catalyst layers directly onto Porous Transport Layers (PTLs), the efficiency of the three-phase boundary (where gas, liquid, and solid meet) is maximized, ensuring that almost every atom of iridium is actively participating in water splitting.

In early 2025, Swedish nanotechnology firm Smoltek achieved a massive milestone by successfully demonstrating a hydrogen-producing cell with a catalyst loading of just 0.1 mg of iridium per square centimeter. Over a 250-hour continuous durability test operating at high current densities (2 A/cm²), Smoltek’s advanced nanostructure showed zero degradation. By re-engineering the nanostructure to survive the harsh electrochemical environment, they achieved a 95% reduction in iridium usage compared to conventional technology without compromising cell performance—proving that ultra-low-iridium PEM electrolysis is commercially viable.

Transition Metal Doping and Support Engineering

Beyond physical restructuring, chemists are actively tuning the electronic properties of iridium to make it work harder. Doping iridium oxides with transition metals such as Niobium (Nb) and Titanium (Ti) modulates the electronic structure of the catalyst. This doping stabilizes the intermediate oxidation states of iridium during the OER process, resulting in remarkable improvements in both intrinsic activity and long-term durability.

Furthermore, by anchoring these doped iridium nanoparticles onto highly conductive, corrosion-resistant support materials, the catalyst particles are prevented from agglomerating. Advanced architectures, such as Ruthenium-Iridium-Tantalum oxide (RuIrTaOx) nanosheets, have demonstrated the ability to operate stably for over 500 hours at 1 A/cm² with a negligible degradation rate of just 27 microvolts per hour.

The Holy Grail: Engineering Iridium-Free Electrolysis

While reducing iridium loading to 0.1 mg/cm² represents a massive triumph of modern engineering, the ultimate "holy grail" of green hydrogen production is eliminating the need for platinum-group metals entirely. This is being aggressively pursued through two distinct pathways: the discovery of novel acid-stable non-noble catalysts for PEM systems, and a fundamental architectural shift to Anion Exchange Membrane (AEM) electrolysis.

Breakthroughs in Acid-Stable Non-Noble Catalysts

For decades, finding an abundant material that survives the highly corrosive acidic anode environment of a PEM cell seemed impossible. However, researchers have recently identified incredibly promising eco-friendly methods to generate hydrogen without rare elements. A landmark development involves an anode catalyst made from cobalt-tungsten oxide (CoWO4).

Through a novel delamination process, scientists were able to substitute a portion of the tungsten oxide in the crystalline lattice structure with water molecules. This substitution resulted in a highly robust catalyst designed to actively involve water and its molecular fragments in its own structural stabilization. In testing, this CoWO4 catalyst demonstrated unprecedented stability for over 600 hours at a high energy density of 1 A/cm². This record-breaking stability for an iridium-free catalyst in a PEM environment represents a pivotal leap forward, suggesting that scalable, fully non-noble PEM electrolysis may soon become a reality.

The Rise of Anion Exchange Membrane (AEM) Electrolysis

While researchers labor to make non-noble metals survive in acidic PEM environments, a rapidly maturing alternative bypasses the acid problem entirely: Anion Exchange Membrane (AEM) electrolysis.

AEM technology combines the best of both worlds: it utilizes an alkaline operating environment (similar to traditional alkaline electrolyzers) which allows the use of cheap, earth-abundant transition metal catalysts like iron, nickel, and cobalt, while employing a solid polymer membrane that permits the rapid response times, high pressure, and compact design characteristic of PEM systems. Crucially, AEM electrolyzers do not use Nafion, inherently making them a PFAS-free technology, and they operate completely without iridium.

Commercialization of AEM technology is accelerating rapidly. Companies like Dioxide Materials are pioneering the production of large-scale PFAS-free anion exchange membranes (such as their Sustainion line) tailored specifically for high-efficiency hydrogen generation. Meanwhile, electrolyzer manufacturers like Enapter have commercialized fully iridium-free AEM stacks. Their highly modular systems range from 2.4 kW single-core units up to the 1 Megawatt (MW) "AEM Nexus," which combines up to 420 individual stacks to produce 450 kilograms of hydrogen every 24 hours. Because they are not tethered to the volatile pricing and supply chain constraints of rare earth metals, AEM electrolyzers possess the potential to drastically decrease the levelized cost of hydrogen (LCOH), with recent studies projecting costs falling to €1.29 per kilogram, closely tracking the DOE's ambitious cost targets.

Global Consortia Driving the Transition

The sheer magnitude of the technical challenges surrounding PFAS elimination and iridium reduction has spurred unprecedented international collaboration. Fragmented research is no longer sufficient; instead, large-scale, multi-national consortia are pooling resources, data, and manufacturing capabilities to push next-generation systems out of the lab and onto the grid.

The SUPREME Project

Funded under the EU Clean Energy Transition Partnership, the SUPREME initiative (SUstainable, low-cost, high PerfoRmance, novel water Electrolysis Material, production & system) is a flagship three-year project dedicated to reinventing green hydrogen. Steered by the University of Southern Denmark (SDU) alongside partners such as Graz University of Technology (TU Graz), TÜBITAK (Turkey's Scientific and Technological Research Council), Fraunhofer, and Ames Goldsmith, SUPREME's core mission is to industrialize PEM electrolysis systems that are 100% free of fluorinated polymers and operate on drastically reduced quantities of critical raw materials.

By vertically integrating innovations—from TÜBITAK developing the underlying PFAS-free microporous membranes, to SDU engineering ultra-low-iridium and highly recyclable catalysts, to Fraunhofer producing the finalized electrolyzer materials—the project is de-risking the supply chain and ensuring these novel components can endure the harsh realities of industrial application.

The HYScale Initiative

Running parallel to SUPREME is the HYScale project, an industry-driven, interdisciplinary EU-funded mission focused specifically on upscaling AEM technology. HYScale's primary objective is to leap from modular small-scale units to the construction of the first single-stack 100 kW AEM electrolyzer prototype that fully implements Critical Raw Material-free (CRM-free) and PFAS-free components at the cell level. By focusing on cost-effective mass production designs and highly efficient Balance of Plant (BoP) integrations, HYScale aims to validate this technology in industrially relevant environments (TRL 5), proving that AEM technology can be scaled to multi-gigawatt levels in Europe before 2030.

VoltaChem and TNO Validation

In the Netherlands, the collaborative VoltaChem program, co-initiated by the independent research organization TNO, is heavily focused on testing and validating commercially supplied fluorine-free membranes at its Faraday Lab. Recognizing that the EU's impending PFAS restrictions threaten to temporarily halt electrolyzer deployments if alternatives are not ready, TNO is providing vital, independent benchmarking of next-generation membranes. Their ongoing testing has shown highly promising results, providing the electrochemical industry with the data confidence required to pivot away from Nafion-based standards.

The Future of the Hydrogen Economy

The next generation of water electrolysis is arriving exactly when the world needs it most. The initial wave of green hydrogen technology proved that deep industrial decarbonization was possible, but it relied on an unsustainable material foundation. The heavy dependence on toxic "forever chemicals" and the mathematically impossible reliance on an element as rare as iridium threatened to throttle the green energy transition before it could truly begin.

However, the rapid convergence of nanomaterial engineering, advanced polymer chemistry, and global institutional support is actively dismantling these bottlenecks. Whether it is through Swedish breakthroughs utilizing mere fractions of a milligram of iridium, the invention of cobalt-tungsten oxide catalysts that eliminate noble metals entirely, or the explosive scaling of PFAS-free AEM architectures capable of megawatt-scale production, the technological leap occurring right now is staggering.

As we look toward 2030 and beyond, the architecture of green hydrogen will be fundamentally redefined. The electrolyzers that will power the shipping fleets, steel mills, and electrical grids of the future will not be constrained by the legacy of toxic fluorine compounds or the scarcity of precious metals. By engineering PFAS-free and low-iridium systems, the global scientific community is not just making hydrogen cleaner; they are making the scalable, sustainable, and affordable energy transition a physical reality.