PT-195 NMR-STUDY OF PT/TIO2 AND PT/SIO2 CATALYSTS - STRONG METAL SUPPORT INTERACTION

We show that in Pt catalysts 195Pt NMR provides a probe to study the interaction of metal surface atoms with adsorbates or species that have migrated from the support onto the platinum during thermal treatment. The so-called "strong metal-support interaction" (SMSI) of Pt on TiO2 is studied as a function of the size of the Pt particles and compared to the results obtained on SiO2, a nonreducible oxide. Nuclear magnetic relaxation data of the surface Pt nuclei, clean or in the SMSI state, show a metallic type of relaxation via the conduction electrons. The local density of states at the Fermi energy obtained from spectral data and spin-lattice relaxation time measurements is lower on the clean surface atoms than in the bulk but does not change much when going over to the SMSI state. © 1990 American Chemical Society.