Researchers at Austria’s TU Wien have found that a much thinner platinum coating could protect components used in hydrogen production. It can potentially reduce the amount of the precious metal needed for these protective layers by around 88%.
The experiments examined platinum-coated titanium bipolar plates used in proton exchange membrane (PEM) water electrolysis.
Under the conditions studied, a coating just 24 nanometers thick remained largely intact and retained good electrical conductivity after electrochemical stress.
The findings point to a possible way to reduce equipment costs. However, the researchers cautioned that the optimal thickness depends on factors including how the coating is manufactured and how uniformly it covers the surface.
Why hydrogen equipment needs platinum
Water electrolysis uses electricity to split water into hydrogen and oxygen. At one electrode, the process produces oxygen, positively charged hydrogen ions (protons), and electrons.
The protons pass through a membrane to the second electrode, where they combine with electrons to form hydrogen. Keeping the equipment operational in this environment is more complicated than the basic reaction suggests.
“Electrolysis creates a chemical environment that is damaging to many metallic components. Metal can dissolve, while oxide layers can form at the same time and impede the flow of electric current,” explained Helmut Riedl-Tragenreif from the Institute of Materials Science and Technology at TU Wien.
“If the system is to remain operational for a long time, the different components have to be carefully matched to one another. Bipolar plates play a particularly important role here, accounting for up to 30% of total system costs,” he added.
These plates support the equipment mechanically, conduct electricity, and help transport water and gases. Titanium resists corrosion well, but an oxide layer forms on its surface and obstructs electrical current.
A thin platinum coating addresses that problem by conducting electricity while protecting the titanium underneath.
A thinner coating survives the tests
The TU Wien team systematically investigated how thick that protective layer needs to be. A 24-nanometer coating proved sufficient under the conditions tested, while an eight-nanometer layer showed clear problems.
Compared with a 200-nanometer coating of the kind currently used in industry, the successful thinner layer represents a potential reduction of around 88% in platinum consumption for the protective coating.
The researchers also examined whether the coatings remained resistant after electrochemical stress, rather than assessing only their initial performance.
“We analyzed the coatings before and after electrochemical stress using high-resolution methods. One particularly important question is whether microscopic defects develop in the coating,” said Riedl-Tragenreif.
Small defects can accelerate damage
A defect in the platinum layer can expose the titanium below to attack. The titanium oxidizes, and small oxygen bubbles may form at the interface, creating mechanical stresses that further damage the coating.
As larger sections detach, more titanium becomes exposed, allowing the damage to accelerate.
The eight-nanometer coating showed clear indications of this process. After electrochemical stress, researchers observed larger defects and found that significantly more titanium and platinum ions had entered the electrolyte.
The 24-nanometer coating remained largely intact, maintained good conductivity, and kept metal ion release at a very low level under the studied conditions.