Synthesis and Structural Characterization of SiO2-Supported PtFe Catalysts Prepared from PtFe2(C8H12)(CO)8

Fourier transform infrared (FTIR) and extended X-ray absorption fine structure (EXAFS) spectroscopies were used to characterize the species formed following deposition of a PtFe2(COD)(CO)(8) cluster on SiO2 and removal of the organic ligands. The results indicate that the PtFe2(COD)(CO)(8) cluster initially adsorbs weakly on the SiO2 surface but loses a fraction of the organic ligands during aging under N-2 and thus becomes bonded to the surface. The PtFe2 cluster core remains nearly intact during this process. The organic ligands can be further removed from freshly impregnated species by thermal treatments in either He or H-2 at 350 degrees C. Both treatments lead to the formation of bimetallic surface species with average dimensions on the order of 1 nm. However, these PtFe bimetallic species undergo substantial structural changes under CO oxidation conditions.