Dynamic platinum nanoparticles respond to hydrogen impulses

Platinum nanoparticles (Pt NPs) are crucial for both energy and chemical applications as they provide sustained high catalytic activity in hydrogen-rich environments: in fuel cells, they catalyse the hydrogen oxidation reaction at the anode; in the chemical industry, they catalyse key reactions for the synthesis of fine chemicals.

Because the structure of NPs is dynamic, and particularly susceptible to relaxation (‘breathing’) upon adsorbing molecules like hydrogen, catalyst design strives to achieve precise control over particle morphology under reaction conditions. This is a major factor in catalytic performance, as well as in the regeneration of deactivated catalysts, but the structural evidence behind it is still somewhat incomplete.

First experimental evidence

According to theoretical models, hydrogen adsorption promotes also a weaker interaction between the Pt NPs and most types of support, which are an essential part of the catalyst, ensuring proper dispersion of the NPs and thus high activity. This effect, if not reversed upon desorption, can degrade the stability and performance of the catalyst during the reaction.

However, experimental evidence of the mobility of Pt NPs has been scarce because of the difficulty in reproducing the relevant hydrogen coverage conditions and at the same time detecting the subtle signatures of structural rearrangement. In addition, neither theoretical models nor experiments have tackled the problem in milder liquid-phase conditions, which are of extreme relevance to industrial processes.

Now, using in situ X-ray total scattering, a team led by ESRF scientists has described how the structure of Pt NPs changes as they shift to/from the support while adsorbing/desorbing hydrogen. They found that the NP structure rearranges in both the gas phase (gaseous H2) and the liquid phase (H2-saturated solvent), to an extent inversely correlated with particle size. These effects are fully reversible, which implies that the NPs are redispersed on the support at each catalytic cycle, and thus demonstrates the stability of the catalyst towards further separation.

New benchmark for nanoparticle experiments

The research took place on beamline ID15A, where a dedicated in situ setup for high-energy X-ray scattering and the subsequent Pair Distribution Function (PDF) analysis captured subtle structural effects happening on a timescale of seconds.

“This quality of time-resolved total scattering data just didn’t exist before the EBS upgrade. However, in situ experiments like these are only as good as the sample environment allows, and to this end the work of the ESRF Sample Environment team and our collaborators has been superb”, says Stefano Checchia, scientist on ID15A and corresponding author of the publication.

This new understanding on how metal nanoparticles behave when hydrogen is bound to their surface could help chemists design catalysts that perform better under reaction conditions in fields as diverse as pharmaceutical chemistry and energy conversion.

“Our work provides a new benchmark for this type of experiments. PDF analysis proved sensitive to the interaction between the nanoparticles and their support, which was not a given. Describing this system in both gas and liquid phase is particularly interesting, as it brings experimental evidence much closer to the actual working conditions of these catalysts”, concludes Daniele Bonavia, first author of the publication and formerly a PhD student at ID15A.

Reference:

Bonavia, D., et al. Nat Commun 16, 9591 (2025). https://doi.org/10.1038/s41467-025-63708-4

Text by Montserrat Capellas Espuny

Top image:  Pt55H91/Al2O3, Pt55H44/Al2O3 and Pt55/Al2O3 models.