Why Electrolyser Degradation Needs Managing

No electrolyser can last forever. But how long they can last is critical to hydrogen costs. A 5MW stack degrading at just one microvolt per hour could translate into an additional $565,000 in electricity costs over its operating life, according to modelling from advanced materials maker James Cropper. Losses of that scale underline why researchers and manufacturers are racing to understand degradation. While electricity remains the biggest driver of the levelised cost of hydrogen, manufacturers can influence performance. That comes down to two key areas: efficiency and lifetime. With power prices a fixed external challenge, technology innovation is where developers can directly extend lifetimes, improve efficiency, and ultimately lower hydrogen costs.

Understanding electrolyser degradation

No electrolyser stack is immune to wear, and even under ideal conditions, components inside a PEM electrolyser will begin to deteriorate over time. This leads to small but significant efficiency losses.

Dr David Hodgson, Strategic Advisor at James Cropper Advanced Materials, even joked during an H2 View webinar last year that the best way to avoid electrolyser degradation is to “not use it.”

The company’s Head of Innovation, Dr Srijita Nundy, told H2 View degradation occurs across every layer of a PEM electrolyser – from the ion-exchange membrane to the catalyst-coated layer and the bipolar plate – with each component contributing to overall performance loss.

“The crucial one is Nafion degradation,” Nundy said, which lies in the membrane itself. Nafion, the perfluorinated polymer used as the proton exchange membrane, gradually fatigues under electrochemical stress.

As it breaks down, it releases degraded fluorine-based fragments into the cell, which attack adjacent layers and reduce proton conductivity.

“Those degraded fragments that are produced by the Nafion start corroding the nearby environment around it, which is the porous transport layers (PTLs),” she added.

“Immediately, the titanium PTLs have corrosive pits formed in them, hot spots created on them, and then your electrical resistivity shoots up, leading to entire electrolyser failures.”

The PTLs and titanium bipolar plates provide conductivity and distribute reactants; however, they’re susceptible to corrosion and passivation.

In oxidative environments of high oxygen, voltage, and acidity, titanium forms a resistive oxide layer that can progress to hydrogen embrittlement and microscopic cracks, driving localised damage.

Hodgson explained that “electrochemical systems don’t like to be interrupted too often. So, keep the system operation as steady a state as possible, or ensure the materials used are robust.”

Water is also another underestimated pathway towards degradation, according to the James Cropper representatives. Electrolysers require ultra-pure water, but even trace cations or anions can poison the system.

“You can even see an S-shaped polarisation curve when contamination occurs,” Nundy explained. “Then, there will be
issues with mass transportation limitations, which is why water purity is so critical.”

While the chemical mechanisms of degradation are complex, the consequences are ultimately financial.

The cost of degradation

The Low-Carbon Resources Initiative (LCRI) noted in a whitepaper that the future deployment of electrolysis production will rely heavily on total hydrogen production cost, with other processes, such as steam methane reforming, being much cheaper.

While some degradation losses on a single project can be absorbed, at scale, when developers are aiming to build gigawatts of capacity, marginal degradation translates into millions in additional costs.

The LCRI highlighted the mismatch: stacks last just 7–10 years, compared with 20–40 years for plants. That means multiple replacements are planned into every project, with stack swaps alone accounting for 35%–45% of system capital costs.

PEM electrolyser stacks typically degrade by 1%–1.5% per year under steady baseload operation. As stacks account for almost half of the total system capex, swapping them out isn’t just an operational inconvenience but a capital-intensive event.

Therefore, the industry is doubling down on durability, exploring new coatings, catalysts, and materials to extend stack lifetimes.

Balancing cost and lifetime

According to Nundy, the challenge comes down to cost-benefit. “The cost of platinum coating on a titanium electrode can be prohibitive, but is it more expensive than this? That’s the debate that is going on,” she said.

“So yes, the coating is expensive, but is it actually more expensive than the millions lost over 80,000 operating hours if you don’t use it?”

With lifetime modelling, including accelerated stress tests and cost simulations, you can quantify whether coatings reduce costs over the full lifetime.

Because long-term field data is still scarce, these models are essential for predicting trade-offs today rather than waiting a decade for operating evidence.

Nundy said that early results suggest coatings do pay off. She added that platinum remains the main focus, but James Cropper is also exploring alternatives.

“We are also looking into gold, which some studies suggest can reduce hydrogen embrittlement on the cathode side,” Nundy said.

“It’s still very early-stage research, but hybrid coatings, such as platinum on the anode and gold on the cathode, are areas we’re beginning to explore.”

Hodgson also underlined that iridium, the key catalyst in PEM electrolysers, is one of the scarcest elements in the Earth’s crust, with only a few tonnes available across the globe each year.

Iridium is stable under acidic, high-potential conditions, making it ideal for the oxygen evolution reaction, but its relative scarcity and high cost present some concerns.

“We’ve seen iridium loadings come down by about an order of magnitude in the last ten years,” Hodgson said. “So, the progress has been quite dramatic, but we’re still in a place where supply is a challenge.”

To meet the challenge, Hodgson argued that developers need to make “every atom work harder.” He explained that the challenge comes down to optimisation and balancing material costs against stack lifetime.

Room for development

As highlighted by Nundy, Nafion fatigue is another critical pathway for performance loss. Therefore, R&D efforts are increasingly being directed at perfluorosulfonic acid-free membranes that promise greater durability.

Hodgson previously said, “There are new ionomers on the horizon that promise to be more stable under oxidative environments, but they’re not yet at the point where they can match Nafion’s conductivity at scale.”

That conductivity, the ability of Nafion’s hydrated channels to shuttle protons with very low resistance, is why it has remained the industry’s default.

Tightening up water management is also key for manufacturers. Nundy stressed that stacks require ultra-pure, double deionised water with conductivity around 0.01 µS/cm, since even trace cations such as sodium or iron “can be quite detrimental to performance” and quickly show up as S-shaped polarisation curves.

During the webinar, Hodgson noted that stack failures were often linked less to materials science than to system management.

As a result, advanced purification and monitoring systems have become a priority durability measure. Deionisation units, inline conductivity sensors and predictive monitoring are increasingly standard in new hydrogen projects.

Policy support to bridge the lab and field

Electrolyser degradation may be unavoidable, but its pace can be managed. The task for manufacturers like James Cropper now is to translate laboratory insights into field-proven solutions.

However, Nundy stressed that this will take time, with long-term operating data still limited, leaving developers reliant on modelling and stress tests.

“Getting feedback is key for development,” she said. “But it can take quite a long time because the deployment of electrolysers in the field is slow, and we won’t get an answer until there is a failure.”

The lag makes government support even more critical. Nundy argued that most public funding to date has targeted deployment and offtake, rather than the material supply chains that underpin stack lifetimes.

“If the UK wants to build electrolysers with a domestic supply chain, it must support that supply chain. Without it, manufacturers will keep importing materials from abroad. Right now, that support isn’t there.

“You’ll have companies here manufacturing, but still importing their materials from Europe, China, or the US. If we want to double electrolyser lifetime, we need to invest in the supply chain to help develop those solutions,” she concluded.

Originally published by Edward Laity in Why electrolyser degradation needs managing | Technology | H2 View. September 2025.