EXAFS study of silver clusters in zeolites

Abstract

The EXAFS measurements on Ag K-edge have been carried out at 298K on completely Ag+-exchanged zeolite 4A(Ag-4A) with different dehydration treatments. In the Fourier transforms F(r) of EXAFS spectra there appear two distinct peaks. By two-shell curve-fitting analysis it is found that the Ag ion-framework oxygen and Ag-Ag contact distances decrease as the color of Ag-4A changes from white (fully hydrated) to brown (fully dehydrated). The coordination number of Ag atom (Ag0) around a central Ag0, 9.0±0.5, for brown Ag-4A suggests a formation of a silver cluster with Ag0-Ag0 contact distance of 2.81 Å.