PREPARATION OF PLATINUM GOLD BIMETALLIC CATALYSTS BY REDOX REACTIONS

Bimetallic Pt-Au/SiO2 catalysts were prepared by reduction of AuCl4- u sing hydrogen preadsorbed on a parent monometallic Pt/SiO2 catalyst. I n fact during that preparation a direct redox reaction can occur betwe en the reduced platinum and AuCl4-. At low gold coverage the additive is deposited statistically on the whole surface of platinum particles (the reducer is H preadsorbed on Pt). At high gold coverage the additi ve is preferentially deposited on the high index planes of platinum pa rticles (by direct redox reaction). During the formation of Pt-Au bime tallic entities sintering of platinum can occur as a result of simulta neous oxidation and reduction of platinum.