Selective modification of Pt active sites on Pt-Au/C catalysts prepared by surface redox reactions

This study focused on the selective deposition of Au-0 onto (111), (100) faces and (111)/(100) edges of cuboctahedral Pt particles present on the Pt/C(graphite) model system. The Pt-Au/C catalysts were prepared by novel surface redox methods involving the direct reduction (DR) of AuCl4- species onto the Pt particles or reducing these species on the Pt-H interface. i.e., the refilling (RE) method. The presence of Au on the Pt particles was verified by means of high-resolution energy dispersive spectroscopy (EDS), and, after treatment at 300degreesC in H-2, the formation of crystalline Au-0 aggregates was verified by X-ray wide-angle diffraction; further treatments at 500degreesC in H-2 led to a true Pt-Au solid solution. The Monte Carlo simulation methods indicated the selective deposition of Au-0 onto the (111)/(100) edges of the Pt cuboctahedral particles when the relative Au concentration varied from 10 to 50 wt% Au. The catalytic conversion of n-heptane on the Pt-Au/C (DR and RE solids) catalysts presented an oscillatory behavior with respect to Pt/C, indicating modification of the active Pt ensembles. driven by the energy released during the exothermic n-C-7 dehydrogenation and cracking reactions, which should enhance the Au-0 mobility at the Pt particle surface level.