Unlocking new catalyst designs: Scientists measure strain in single nanoelectrocatalyst

Catalysis is a chemical reaction that is all around us: from the development of fertilizers, the removal of toxic gases in car exhausts to the functioning of fuel cells that could revolutionise transportation.

Nanocatalysts interest scientists because they can potentially revolutionalise catalysis, as they have a high surface area-to-volume ratio, which allows them to interact more effectively with the reactants and increase the gravimetric catalytic activity compared to conventional catalysts.

However, nanocatalysts are complex materials, far away from single crystal surfaces. Up to recently, scientists have only been able to establish structure-performance relationships on billions of nanoparticles in one go, without any information on the respective contributions of the different catalytic sites.

Surface strain, the distortion of a crystal lattice due to a localized or a global stress, which displaces the atoms from their equilibrium positions, has been studied in catalysts since the 1990s. “We know that the reaction rate on a catalyst is directly linked to its strain, so if we can measure how strain is distributed on the surface of a nanocatalyst, we can accelerate the rate of (electro)catalytic reactions”, explains Fréderic Maillard, scientist at the French National Centre for Scientific Research (CNRS, in French) and co-corresponding author of the paper.

Now a team of scientists led by the CEA, LEPMI/CNRS and the ESRF have measured the strain distribution on the surface of a single nanocatalyst and how it is linked to its electrocatalytic activity. “The study was challenging in that we wanted to study this single nanoparticle while it was working, something that had never been done before under applied electrochemical potential”, explains Marie-Ingrid Richard, scientist at CEA and ESRF visiting scientist and co-corresponding author of the publication.

The team wanted to unveil the 3D structure, including the strain distribution, lattice displacements, shape and faceting of a platinum nanoparticle, a benchmark catalyst for fuel cells and electrolysers. The ESRF played a key role in the research: “The new Extremely Brilliant Source at the ESRF, with unmatched brilliance and coherence, allowed us monitor the changes in structure and morphology of nanocatalysts during in situ conditions”, she adds.

The results provided evidence that strain is heterogeneously distributed in the nanocatalyst, between highly-coordinated ({100} and {111} facets) and under-coordinated atoms (edges and corners), thereby questioning the widely accepted assumption of homogeneous strain distribution.

The second major finding is that strain distribution depends on the electrode, and that it propagates from the surface to the bulk of the platinum nanoparticle under polarization.

“We will now combine these unprecedented results with theoretical work to simulate nanocatalyst interfaces more accurately, so that we can design and synthesise the next generation of catalyst with with tailored activity, selectivity and lifetime”, concludes Maillard.

The results are a step forward in improving nanocatalysts for fuel cells and water electrolyzers, but also to other areas of science such heterogeneous catalysis, nanomechanics and plasmonics.

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 818823).

Reference:

Atlan, C. et al, Nature Materials, 24 April 2023. DOI: 10.1038/s41563-023-01528-x

Text by Montserrat Capellas Espuny.