XANES study of the support effect on the state of platinum catalysts

Pt LIII and LII-edges XANES clarified the oxidation state of platinum catalysts supported on various metal oxides. The acid-base property seemed one of the most dominant factors to control the electron state of platinum. On the reduced samples, there was a tendency that acidic support reduced the 5d-electron density of platinum, while the oxidized samples on acidic support contained more metallic platinum. The latter tendency agreed well with high activity of platinum catalysts on acidic supports toward propane combustion in oxidizing condition, and it was explained by a hypothetical mechanism for prevention of oxidation of platinum by acidic supports. (au)