PT-195 NMR OF POLYMER-PROTECTED PT PD BIMETALLIC CATALYSTS/

Colloids of Pt, Pt0.8Pd0.2, and Pt0.2Pd0.8 particles of approximately 2.5 nm diameter with poly (N-vinyl-2-pyrrolidone) as protecting agent were dried, and the Pt-195 NMR spectrum and nuclear spin-lattice relax ation rates were measured. The spectra indicate that the particles are indeed bimetallic and that the composition of their interior correspo nds well to the nominal value. A strong variation of catalytic activit y of these systems with composition around Pt0.2Pd0.8 has been reporte d in the literature. We suggest that this effect is related to corresp onding variations in the local densities of electronic states at the F ermi energy on the surface sites of the catalytic metal.