Breathing Pt nanoparticle imaged using in situ BCDI

International audience; The relationship between surface strain and the rate of a (electro-)catalytic reaction was unveiled by Hammer and Nørskov using density functional theory (DFT) calculations [1,2]. They proposed that the rate of the sluggish oxygen reduction reaction (ORR) would be enhanced on Pt-based catalysts binding *OH species ca. 0.10 - 0.15 eV more weakly than Pt(111), [1, 2] later experimentally verified using a Pt3Ni(111)-skin surface.[3] Nevertheless these predictions did not translate to Pt-based nanocatalysts, in part because these feature present multiple catalytic sites with a range of binding energies. Also, DFT calculations consider catalytic surfaces in vacuum, i.e. in the absence of water molecules and electric field. Hence, an in situ picture of how strain is distributed on Pt-based surfaces is still lacking.In this contribution, we took benefit of recent advances in Bragg Coherent Diffraction Imaging (BCDI) [4, 5] and of the fourth generation Extremely Brilliant Source of the European Synchrotron (ESRF-EBS, Grenoble, France) to map strain over Pt nanoparticles in electrochemical environment. Our results reveal that strain is heterogeneously distributed between highly- and weakly-coordinated surface atoms, and propagates from the surface to the bulk of the Pt nanoparticle as (bi)sulphates anions adsorb on the surface.