PT L-III-EDGE EXAFS STUDIES ON PT-CU-FE ALLOY ELECTROCATALYSTS SUPPORTED ON CARBON

Carbon supported Pt-Cu-Fe alloys with compositions of Pt:Cu:Fe=6:1:1 a nd 2:1:1 have been prepared. Both catalysts exhibit higher specific ac tivities for oxygen reduction than Pt alone. In order to reveal the lo cal structure around Pt, we have performed X-ray absorption experiment at the Pt L-III-edge. The local structure around Pt has been analyzed by fitting the first shell including the Pt-Pt, Pt-Cu, and Pt-Fe cont ributions to EXAFS spectra. The fitted C.N. for both alloys are simila r to that for bulk Pt, indicating that the particle size is not small. The Pt-Pt distances for both alloys are found to be slightly shorter than that of bulk Pt, and the Pt-Cu and Pt-Fe distances decrease as th e amounts of Cu and Fe increase. It is therefore concluded that the ca talytic activity is strongly influenced by the bonding character.