> ## Content Index
> Fetch the complete content index at: https://research-pop.com/llms.txt
> Use this file to discover other available public pages before exploring further.

# Charles University and University of Trieste-led team tracks Ir and Ti-support degradation inside a working PEM electrolyzer
- URL: https://research-pop.com/charles-university-and-university-of-trieste-led-team-tracks-ir-and-ti-support-degradation-inside-a-working-pem-electrolyzer/
- Published: 2026-09-24T09:00:45.000Z
- Updated: 2026-09-24T09:00:45.000Z
- Author: ResearchPOP

![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-24-at-10.45.38.png)

Source: [https://doi.org/10.1021/jacs.6c04230](https://doi.org/10.1021/jacs.6c04230?ref=research-pop.com)

## At a glance

Operando small- and wide-angle X-ray scattering follows iridium nanoparticles and titanium-based supports during 3,000 square-wave cycles between 0 and 2.0 V in complete proton-exchange-membrane water-electrolyzer assemblies.

The three supports protect different parts of the catalyst. Ir/TiO₂ begins with the highest oxygen-evolution activity, but its Ir particles grow from 1.49 to 2.19 nm. Ir/TiC keeps the Ir particle size close to 1.45 nm while losing about 80% of its support crystallinity and showing pronounced Ti migration. Ir/TiN displays intermediate changes in both the metal particles and the support.

The study shows why Ir particle size alone cannot define an anode’s stability. A support may limit metal coarsening while undergoing substantial structural loss of its own. The Ir nanoparticles, support phase and catalyst layer must be followed together under the same operating history.

## Background

Proton-exchange-membrane, or PEM, water electrolyzers can operate at high current density and produce hydrogen using a compact membrane-electrode assembly. Their anodes, however, experience acidic conditions and high potentials during the oxygen-evolution reaction. Iridium remains one of the most effective catalyst materials in this environment, but its scarcity motivates efforts to use smaller particles and lower loadings.

Dispersing nanoscale Ir on a conductive support can expose more metal surface per unit mass. The resulting catalyst depends on two components remaining functional. The Ir particles need to retain their accessible surface, while the support must preserve conductivity, structure and contact with the catalyst layer. Repeated start–stop operation can alter both components.

Post-mortem microscopy compares a catalyst before and after operation, but it cannot show when particle growth or support degradation begins during cycling. Operando small-angle X-ray scattering, or SAXS, provides statistical information about nanoparticle size inside the complete assembly. Wide-angle X-ray scattering, or WAXS, follows crystalline phases in the supports. Combining the two measurements allows metal and support changes to be observed during the same voltage protocol.

## Research question

The study examines how Ir nanoparticle growth and degradation of TiO₂, TiN and TiC supports develop together during repeated start–stop cycling in complete PEM-electrolyzer membrane-electrode assemblies.

## Inside the study

The researchers prepared anodes containing Ir nanoparticles supported on TiO₂, TiN or TiC and incorporated them into complete membrane-electrode assemblies. Each system was subjected to 3,000 square-wave cycles between 0 and 2.0 V, with each potential held for 5 s. This cycling protocol repeatedly moves the anode between an idle-like state and a strongly oxidizing condition.

![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-24-at-10.45.49.png)

The electrochemical measurements first establish that the three supported catalysts respond differently. Ir/TiO₂ begins with the highest oxygen-evolution performance, but loses about 40% of its electrochemically active area and activity during cycling. The decline creates a basis for comparing the electrochemical response with the structural changes observed by X-ray scattering.

The operando SAXS measurements follow the Ir nanoparticles throughout the 3,000 cycles. For Ir/TiO₂, the scattering signal shifts towards larger particles. Quantitative analysis gives an increase in mean Ir particle size from 1.49 to 2.19 nm. This pronounced growth is consistent with loss of accessible Ir surface as the initially small particles coarsen.

![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-24-at-10.45.59.png)

Ir/TiC shows a different pattern. Its Ir particles remain close to 1.45 nm, indicating much smaller changes in metal-particle size. Ir/TiN lies between these cases, with the Ir particles reaching about 1.60 nm. From the perspective of Ir coarsening alone, TiC appears to provide the strongest size retention and TiO₂ the weakest.

The support measurements reverse part of that picture. WAXS shows that the TiO₂ phase remains comparatively stable while the Ir particles grow. The TiC support loses about 80% of its crystallinity even though the Ir size remains nearly constant. TiN again occupies an intermediate regime, losing roughly 50% of its support crystallinity while showing moderate Ir growth.

![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-24-at-10.46.07.png)

Post-mortem transmission electron microscopy provides local images that support the particle-size trends derived statistically from SAXS. The microscopy shows pronounced Ir coarsening on TiO₂ and smaller Ir-size changes on TiC. The two methods contribute different views: SAXS follows a particle population during cycling, while microscopy examines selected regions after the experiment.

![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-24-at-10.46.13.png)

X-ray photoelectron and absorption spectroscopies add information about chemical-state and coordination changes. These measurements track changes in Ir and in the titanium-based support chemistries, connecting the scattering-derived loss of crystallinity and particle growth with oxidation and reconstruction at the catalyst–support interface.

![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-24-at-10.46.25.png)

The team then examines complete membrane-electrode-assembly cross-sections using scanning electron microscopy and energy-dispersive X-ray mapping. Ti migration is most pronounced for Ir/TiC, consistent with the severe loss of TiC crystallinity. The observation extends the analysis beyond nanoparticle size and local surface chemistry to redistribution across the catalyst layer.

![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-24-at-10.46.36.png)

Taken together, the measurements reveal three distinct degradation balances. TiO₂ largely preserves its support phase but allows substantial Ir growth. TiC limits Ir coarsening while undergoing extensive support degradation and Ti migration. TiN shows moderate changes in both components. None of the three supports simultaneously minimizes every form of structural change under the reported cycling conditions.

## Takeaways and outlook

The study does not produce a single stability ranking based on one measurement. Ir/TiO₂ performs best initially and retains support crystallinity, but the Ir nanoparticles grow strongly. Ir/TiC preserves Ir size, but the support loses most of its crystalline signal and Ti moves through the membrane-electrode assembly. Ir/TiN occupies an intermediate position in both respects.

This comparison shows why the stability of low-Ir PEM anodes must include both catalyst and support. Retaining small Ir particles is not sufficient if the conductive support reconstructs, loses crystallinity or migrates. Preserving the support alone is also insufficient if Ir coarsening removes active surface area.

By combining operando SAXS and WAXS with electrochemistry, post-mortem microscopy, spectroscopy and cross-sectional elemental mapping, the authors connect nanoscale particle changes with support degradation inside a functioning device architecture. The approach provides a way to evaluate catalyst–support pairs under realistic cycling histories rather than relying only on initial performance or final-state images.

## About the researchers

Lucinda Blanco-Redondo (Charles University) is the first author. Yevheniia Lobko (Charles University) is the corresponding author.

The other authors are Marco Bogar, Yurii Yakovlev, Jaroslava Nováková, Simone Pollastri, Alina Madalina Darabut, Miquel Gamón Rodríguez, Giovanna Marussi, Matteo Crosera, Michal Mazur, Milan Dopita, Viacheslav Kalinovych, Roberto Biagi, Heinz Amenitsch, Rodolfo Taccani and Iva Matolínová. The participating institutions include Charles University, the University of Trieste, the University of Modena and Reggio Emilia, ELETTRA Sincrotrone Trieste, the National Research Council of Italy and Graz University of Technology.

## Original research

Lucinda Blanco-Redondo, Yevheniia Lobko, Marco Bogar, Yurii Yakovlev, Jaroslava Nováková, Simone Pollastri, Alina Madalina Darabut, Miquel Gamón Rodríguez, Giovanna Marussi, Matteo Crosera, Michal Mazur, Milan Dopita, Viacheslav Kalinovych, Roberto Biagi, Heinz Amenitsch, Rodolfo Taccani and Iva Matolínová. “Operando Tracking of Iridium and Titanium Support Degradation in Proton-Exchange-Membrane Water Electrolyzers.” *Journal of the American Chemical Society* (2026). DOI: [10.1021/jacs.6c04230](https://doi.org/10.1021/jacs.6c04230?ref=research-pop.com). Open access. 

---

## Research POP Notes

This article reflects the independent interpretation of the Research POP team and does not represent the views of the authors, their institutions or the journal. If you identify any inaccuracies or have concerns regarding the content, figures or attribution, please contact us at [team.researchpop@gmail.com](mailto:team.researchpop@gmail.com). We will review the matter promptly and make corrections or remove the relevant material where appropriate.