Cracking the code: Why platinum electrodes corrode

28/01/2025 Cracking the code: why platinum electrodes corrode
The culprit: Hydride formation at a platinum surface. Credit: Nature Materials (2025). DOI: 10.1038/s41563-024-02080-y

Scientists from Leiden University and the Department of Energy's SLAC National Laboratory have uncovered the mysterious cause behind the rapid corrosion of platinum electrodes. This study paves the way for more affordable green hydrogen production and more reliable electrochemical sensors.

The research is published in the journal Nature Materials.

It's a strange quirk that has puzzled scientists for decades: for most metals, being negatively polarized protects against corrosion. But platinum electrodes can rapidly break down under these conditions.

That's a problem because electrolyzers and many other electrochemical devices often rely on these negatively polarized platinum electrodes submerged in an electrolyte—essentially saltwater. Although platinum is an expensive but durable and generally stable option, it doesn't stay immune to degradation in these environments.

"Being quite stable doesn't mean it doesn't degrade at all," says Dimosthenis Sokaras, a senior scientist at SLAC and the SLAC team's principal investigator.

What compounds are to blame?

"If you take a piece of platinum and you apply a very negative potential, you can dissolve your platinum in a matter of minutes," says Marc Koper, Professor of Catalysis and surface chemistry at Leiden University, and the Leiden team's principal investigator.

Two prominent theories had attempted to explain this process. Some scientists thought that sodium ions from the electrolyte solution were to blame.

These ions, the thinking went, pushed their way into the platinum's atomic lattice and formed platinides—platinum atoms lugging around positively-charged sodium ions—that peel away. Others suggested a similar process but pointed the finger at both sodium and hydrogen ions—that is, protons—working together to produce platinum hydrides instead.

This means the symmetry is conserved. However, because electrons possess both a quantum spin and a magnetic moment, reversing time — and, therefore, the direction of travel — flips the spin, meaning the symmetry is broken. "If you look at those two electron systems — one where time is progressing normally and one where you're in rewind — they look different, so the symmetry is broken," Amin explained. "This allows certain electrical phenomena to exist."


A schematic of altermagnetic orientation.
A schematic of altermagnetic orientation. The electron spins (arrows) are aligned antiparallel, but their surrounding environment (pink and blue diamonds) are rotated. This gives rise to time-reversal symmetry breaking and strange electronic phenomena. (Image credit: Oliver Amin)

Finding ‘the missing link’ of superconductivity

The team — led by Peter Wadley, a professor of physics at the University of Nottingham — used a technique called photoemission electron microscopy to image the structure and magnetic properties of manganese telluride, a material formerly believed to be antiferromagnetic.

"Different aspects of the magnetism become illuminated depending on the polarization of the X-rays we choose," Amin said. Circularly polarized light revealed the different magnetic domains created by the time reversal symmetry breaking, while horizontally or vertically polarized X-rays allowed the team to measure the direction of the magnetic moments throughout the material. By combining the results of both experiments, the researchers created the first-ever map of the different magnetic domains and structures within an altermagnetic material.

With this proof of concept in place, the team fabricated a series of altermagnetic devices by manipulating the internal magnetic structures through a controlled thermal cycling technique.

"We were able to form these exotic vortex textures in both hexagonal and triangular devices," Amin said. "These vortices are gaining more and more attention within spintronics as potential carriers of information, so this was a nice first example of how to create a practical device."

The study authors said the power to both image and control this new form of magnetism could revolutionize the design of next-generation memory devices, with increased operational speeds and enhanced resilience and ease of use.

"Altermagnetism will also help with the development of superconductivity," Dal Din said. "For a long time, there's been a hole in the symmetries between these two areas, and this class of magnetic material that has remained elusive up until now turns out to be this missing link in the puzzle."

Source: https://tinyurl.com/4w8udrj2 via Phys.Org
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