Franco-Swiss project tests corrosion-resistant coatings to reduce costs and critical materials in PEM electrolyzers for clean H2

Reducing the cost of green hydrogen doesn't just depend on more renewable energy or larger electrolyzers. It also depends on less expensive materials, more stable coatings, and components capable of withstanding extreme chemical environments for years. This is the goal of the project. PROTIS, a Franco-Swiss initiative dedicated to protective titanium suboxide coatings for polymer membrane electrolyzer components. The project involves theInstitute of Corrosion of Brest, the LEMTA of the University of Lorraine and theEMPA, the Swiss Federal Laboratories for Materials Science and Technology.

The starting point is industrial rather than scientific. According to material released by EMPA, over 90 percent of the hydrogen produced today still comes from fossil fuels, primarily natural gas. The electrolytic process powered by renewable electricity remains more sustainable, but is estimated to be approximately twice as expensive as conventional production. This gap lies in one of the most concrete issues of the future. sustainability energy: making a technology competitive without reducing its reliability, durability, and compatibility with industrial use.

The correct picture, however, is not that of a Swiss research project with ancillary partners. The Agence Nationale de la Recherche (National Research Agency) profile identifies PROTIS as a project coordinated by Michel Prestat of the Institut de la Corrosion (Institute of Corrosion). LEMTA presents it as a project born from the PRCI call, the Projets de recherche collaborative internationale (International Collaborative Research Projects), between France e Switzerland, funded by the ANR and the Swiss National Science Foundation. The project is expected to last 42 months, from 2023 to 2026, with a total funding of €828, of which €271 will be allocated to LEMTA. This institutional architecture changes the way we interpret innovation: at its core, it is not a single laboratory, but a network of complementary skills.

Franco-Swiss governance to reduce CAPEX

PROTIS addresses a specific obstacle to the widespread use of PEM electrolyzers: their dependence on titanium components and noble metal-based coatings. Proton exchange membrane electrolyzers, or PEMWEThey are efficient and well-suited to adapting to fluctuations in electricity generated by wind and photovoltaic energy. This very characteristic makes them attractive for an energy system with a growing share of intermittent renewables. The problem is that the internal environment, especially on the anode side, combines acidity, high potential, and oxidizing conditions: a context in which many metals rapidly degrade.

The state of the art often employs porous transport layer and other titanium components, protected by platinum or other noble metal coatings. This choice guarantees strength and conductivity, but increases the capital cost of the stack. The project's ANR datasheet clearly describes the goal: to replace expensive titanium PTLs with 316L stainless steel, cheaper, but protected with thin titanium suboxide coatings. The innovation therefore lies not only in the change in material, but also in the ability to maintain performance and durability while reducing the cost of the components.

The division of expertise helps understand the project's design. The Institut de la Corrosion (Institute of Corrosion) contributes its expertise in corrosion, aggressive environments, and material degradation assessment. EMPA contributes materials science and coatings development. LEMTA, through its hydrogen and electrochemical systems group, participates in the in-operando characterization to assess how microstructural properties influence the performance and durability of polymer membrane electrolyzers. This division of roles makes PROTIS more like a technology transfer platform than a single laboratory experiment.

Titanium suboxides and stainless steel against corrosion

Corrosion is the physical crux of the project. In PEMWEs, unprotected steel is not a realistic alternative because the internal environment can dissolve it and contaminate the ultrapure water that feeds the device. Even small amounts of dissolved metals can degrade the catalyst-coated membrane, increase contact resistance, or compromise stack stability. Therefore, replacing titanium requires a coating capable of acting as a barrier, without becoming an electrical obstacle.

“In the core of the electrolyzer, the steel simply dissolves like sugar in a cup of tea,”

observes Konstantin Egorov, researcher at EMPA.

The solution studied by PROTIS concerns the titanium suboxides, oxygen-poor compounds that combine chemical stability and good electrical conductivity. In the formulation described by EMPA, researcher Konstantin Egorov is working on a highly crystalline, oxygen-deficient form of titanium oxide, capable of offering corrosion resistance and charge transport. In the ANR formulation, these materials are referred to as TinO2n-1, substoichiometric titanium suboxides suitable for protecting metal components in PEM electrolyzers, particularly PTLs and bipolar plates.

The transition to stainless steel is also relevant for mechanical design. Steel is less expensive than titanium and easier to machine, allowing for more advanced geometries for water distribution and gas evacuation. Cost reduction is therefore not just a question of raw materials: it also concerns manufacturability, design freedom, and the ability to integrate more complex components into industrial stacks.

“In addition to being more cost-effective, steel components are much easier to manufacture, which allows engineers to create more advanced designs that improve cell performance,”

explains Egorov.

PVD and ALD address two different levels of protection

One of the most interesting parts of the project concerns the comparison between two deposition techniques. physical vapor deposition, or PVD, is already widespread in industry and is used to protect the outermost surface of the component, the one directly exposed to the acidic conditions of the catalyst-coated membrane. EMPA has announced that it has successfully developed a method for coating the bipolar plate, a component that has already passed corrosion tests and checks in a functioning electrolyzer.

The second approach is theatomic layer deposition, or ALD. The ANR specification assigns it a different task: to conformally cover the entire internal surface of porous transport layers, including the pore walls. The distinction is crucial. PVD can offer interfacial protection on the most exposed areas, while ALD aims for integral protection even within porous structures. If demonstrated on stainless steel PTLs, this coating could address one of the most complex problems of titanium replacement: preventing corrosion without closing the pores through which water and gas must pass.

“We have succeeded in developing a method to successfully coat the first component of the PEMWE electrolyzer, the so-called bipolar plate, with titanium oxide,”

he still states Konstantin Egorov.

“It’s important for us to develop something that industry can actually use.”

The transfer from the bipolar plate to the porous transport layer, however, is more delicate. A flat or relatively accessible surface can be coated and controlled with established methods; a porous structure, however, requires uniformity in depth. The protection must be continuous, because an exposed area becomes a point of corrosion. At the same time, the coating must not obstruct the channels, otherwise the electrochemical function of the PTL is compromised. This highlights the value of the cooperation between materials, corrosion, and on-site diagnostics.

“Coating porous materials poses many challenges,”

observes Egorov.

“The pores must be evenly coated so that the underlying material does not corrode, but at the same time they must not be blocked.”

From accelerated testing to industry-required durability

The work program described by the ANR shows a progression from microstructural inspection to testing under operational conditions. The coatings are studied with high-resolution electron microscopy and analytical techniques such as Raman spectroscopy, X-ray diffraction, photoelectron spectroscopy, and compositional analysis. The goal is to correlate coverage, nanostructure, porosity, and thickness with protective properties in environments simulating the anodic side of PEMWE.

Ex situ corrosion tests are performed in dilute sulfuric acid solutions containing fluoride anions, a choice designed to reproduce conditions representative of the anodic environment. Coated PTLs with promising properties are then subjected to in-operando tests to evaluate the coating's impact on electrolysis performance and durability. The ANR datasheet also mentions accelerated aging tests of up to two months, to be compared with an expected industrial operating life exceeding 50 hours for PEMWE systems.

This step is important for companies because it separates material innovation from simple initial performance. A coating may appear effective in initial measurements, but fail when exposed to prolonged cycling, voltage differences, gases, acidity, and thermal stress. The post-mortem evaluation after disassembly of the electrolyzer serves precisely to verify whether the nanostructure remains stable, whether corrosion products remain trapped, or whether metallic elements from the stainless steel contaminate the membrane.

From this perspective, the role of LEMTA is not marginal. In-operando characterizations allow us to link the coating's microstructure to the actual behavior of the cell. EMPA's expertise in materials preparation and that of the Institut de la Corrosion in evaluating corrosion mechanisms are thus complemented by diagnostics that focus on electrochemical performance during operation. The expected result is not only a more resistant material, but a more robust understanding of the relationship between deposition process, coating structure, and industrial performance.

A European piece in the green hydrogen supply chain

PROTIS doesn't solve the green hydrogen economy by itself, but it addresses a very specific point in the value chain. If PTLs and protected stainless steel bipolar plates can replace titanium components without losing durability, PEMWE stacks could reduce some of their CAPEX and move closer to more competitive production. This benefit would be particularly significant in a market where electrolysis must compete with mature and still cost-effective processes based on fossil fuels.

The story is also an example of distributed innovation. France contributes with the scientific coordination of the Institut de la Corrosion and with the electrochemical expertise of LEMTA; Switzerland brings EMPA's expertise in materials science and the development of industrializable coatings. The collaboration stems from a bilateral ANR-SNSF framework, not a generic European framework. This is an important detail because it demonstrates how applied hydrogen research often proceeds through targeted cross-border networks, built around specific technical problems.

For the sector, the lesson is clear. The competitiveness of green hydrogen will depend on large-scale infrastructure, the availability of renewable energy, and industrial policies, but also on seemingly invisible components. Lining a pore without closing it, protecting steel without reducing its conductivity, replacing expensive metals without introducing new fragilities: these are small but crucial steps. These details measure the distance between a promising technology and a supply chain capable of scaled production.

The project is expected to conclude in 2026. After that phase, according to EMPA, the researchers aim to involve industrial partners to bring the technology closer to commercialization. Caution remains necessary: ​​the path from laboratory testing to a marketable stack is long and requires validation of durability, cost, repeatability, and production integration. But PROTIS points to a concrete direction: making PEM electrolysis less dependent on expensive materials, more compatible with industrial processes, and closer to the goals of the future. sustainability energy.

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