Size-Dependent Redispersion or Agglomeration of Ag Clusters on CeO2

Supported metal nanoparticles tend to agglomerate at high temperatures. Herein, we report that Ag clusters supported on CeO2 prepared by a deposition-precipitation method followed by calcination at 200 degrees C undergo size-dependent redispersion or agglomeration processes upon further calcination at 500 degrees C, accompanied by segregation and reduction of Ag+ cations dissolved in CeO2. Fine Ag clusters with a detectable Ag-O coordination shell using EXAFS redisperse, while large Ag clusters only with a detectable Ag-Ag coordination shell agglomerate. We propose that segregation and reduction of Ag+ cations dissolved in CeO2 upon calcination at 500 degrees C create additional surface oxygen vacancies capable of dismantling fine Ag clusters due to strong Ag-surface oxygen vacancy interaction. The catalytic activity of acquired Ag/CeO2 varies sensitively with the dispersions of supported Ag clusters. These results highlight the important role of surface restructuring of oxide supports in redispersing supported metal clusters.

Automated summary

In this study, it was found that Ag clusters supported on CeO2 undergo size-dependent redispersion or agglomeration processes at high temperatures, with segregation and reduction of Ag+ cations dissolved in CeO2 at 500 degrees C. The results demonstrate the significant role of surface restructuring of oxide supports in redispersing supported metal clusters.