15-18 March 2021
Europe/Berlin timezone

Tracking the facet-resolved strain state of a PtRh nanoparticle under catalytic reaction conditions

17 Mar 2021, 15:55


Oral contribution In situ / in operando studies In situ / in operando studies


Thomas F. Keller (FS-NL (FS-NL Fachgruppe Mikroskopie))


Oxide-supported nanoparticles are important heterogeneous catalysts. The nanoparticles shapes and type of facets are decisive for the catalyst activity and lifetime. During a catalytic reaction, the nanoparticle may be subject to shape changes, and segregation in alloys may adjust the termination of the surface to a changing gas environment.

Here we report on the evolution of the 3D strain state in a single alloy PtRh nanoparticle operando followed by coherent X-ray diffraction imaging (CXDI). At a temperature of T=700 K the nanoparticle environment was switched between the gas compositions (I) inert Ar, (II) CO+Ar, (III) CO+O$\textrm{}_{2}$+Ar and (IV) CO+Ar resembling different adsorption and catalytic reaction scenarios on the nanoparticle surface.

SrTiO$\textrm{}_{3}$ supported nanoparticles were grown by co-deposition of Pt and Rh and annealed in UHV to induce the equilibrium shape. A single nanoparticle was pre-selected in an SEM and subsequently, hierarchical Pt fiducial markers were deposited in the vicinity of the selected nanoparticle and used to re-locate the same particle in the X-ray beam.

The nanoparticle exhibited solely low index <100> and <111> type facet surfaces, intriguingly showing distinct, facet-family specific strain states. Under the catalytic reaction condition (III) we observed significant strain relaxations for all facets accompanied with a preferential segregation of Rh to the nanoparticle surface, in line with density functional theory calculations (DFT). The Rh enrichment on the facets turned out to be non-reversible under the subsequent CO reduction condition (IV) as compared to the identical previous gas condition (II).

Tracking the dynamics of facet-specific structural reorganizations of the nanoparticle is one key for the future design of heterogeneous catalysts with optimized efficiency and selectivity.

Primary authors

Young Yong Kim (DESY) Thomas F. Keller (FS-NL (FS-NL Fachgruppe Mikroskopie)) Dr Tiago J. Goncalves (Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology) Dr Manuel Abuin (Deutsches Elektronen-Synchrotron (DESY)) Henning Runge (DESY) Luca Gelisio (DESY) Jerome Carnis (DESY FS-PS) Dr Vedran Vonk (Deutsches Elektronen-Synchrotron (DESY), FS-NL (Nanolab), Deutschland) Dr Philipp N. Plessow (Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology) Ivan Vartaniants (FS-PS (FS-Photon Science)) Andreas Stierle (FS-NL (Nanolab))

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