Fundamental Aspects of Ceria Supported Au Catalysts Probed by In Situ / Operando Spectroscopy and TAP Reactor Studies

The  discovery  of  the  activity  of  dispersed  gold nanoparticles  three  decades  ago  paved  the  way  for  a  new  era  in catalysis.  The  unusual  behavior  of  these  catalysts  sparked  many questions  about  their  mechanism  of  work.  In  particular,  Au/CeO2 proved to be an efficient catalyst material in several reactions such as CO oxidation, water gas shift, and CO 2  reduction. Here, we focus on fundamental aspects of highly active Au/CeO 2  catalysts, mainly in the CO  oxidation  for  understanding  their  complex  structure-reactivity relationship,  employing  findings  from  operando  X-ray  absorption spectroscopy at the near and extended Au and Ce L III  energy edges. These  results  were  combined  with  findings  from  in  situ  diffuse reflectance FTIR and Raman spectroscopy, highlighting the changes of adlayer and ceria defects. For a comprehensive understanding, the spectroscopic  findings  will  be  supplemented  by  results  of  the dynamics  of  O2   activation  obtained  from  Temporal  Analysis  of Products  (TAP).  Merging  these  results  illuminates  the  complex relationship among the oxidation state, size of the Au nanoparticles, the  redox  properties  of  CeO2  support,  and  the  dynamics  of  O2  activation.