Coherent X-ray Diffraction Imaging of a Twinned PtRh Catalyst Nanoparticle under Operando Conditions

We performed operando Bragg coherent X-ray diffraction imaging under CO oxidation, as well as oxidizing conditions on a precharacterized single PtRh nanoparticle. We found that this (111) oriented particle with truncated octahedral shape is twinned with a Σ3 twin boundary parallel to the SrTiO₃ (001) support, at the height of the nanoparticle edges. We observed that the average strain at the twin boundary is higher under CO oxidation conditions compared to pure CO or O₂. In addition, we observed that two new facets were forming during the oxidizing/reducing cycles. Furthermore, we observed mixed edge/screw dislocations at the twin boundary, but only where the {111} side facets meet. Inducing such dislocations changes the local strain and the atomic structure of the nanoparticles, which may create more active sites close to the nanoparticle edges.