Operando XAS and XRD measurements to elucidate the deactivation/reactivation behaviour of Pt-Rh mono and bimetallic TWCs

This study aims at the fundamental understanding of the deactivation/reactivation behaviour of mono and bimetallic Pt-Rh/Al2O3 TWCs for the simultaneous removal of CO, NOx and HCs under harsh and dynamic reaction conditions. Preliminary catalyst characterization indicates that sintering, restructuring and/or segregation processes occur at high temperatures depending on the catalyst composition and aging conditions, which result in pronounced changes in the catalytic activity. Starting with well-defined mono and bimetallic catalysts, the evolution of each noble metal will be monitored by in situ/operando XAS measurements at the Pt L3 and/or Rh K edges, while the overall phase changes will be identified by in situ/operando XRD investigations. After exposing the catalysts to progressively higher temperatures and rapid changes in the gas atmospheres, their regeneration ability will be studied during following activity cycles with/without catalyst pre-treatment steps.