Probe of the Surface of a Heterogeneous Catalyst: Double NMR of Carbon Monoxide Chemisorbed on Highly Dispersed Platinum

Abstract

The detailed NMR line of $^{195}\mathrm{Pt}$ atoms in the surface layer of small particles of Pt metal on which CO has been chemisorbed has been observed. The surface $^{195}\mathrm{Pt}$ are resolved from the $^{195}\mathrm{Pt}$ resonances of atoms deeper in the particle by spin-echo double resonance between $^{195}\mathrm{Pt}$ and $^{13}\mathrm{C}$. The $^{195}\mathrm{Pt}$ resonance position and $^{13}\mathrm{C}$-$^{195}\mathrm{Pt}$ indirect spin coupling are found to be very similar to those in diamagnetic Pt-carbonyl molecules. The results show that CO bonds via the C atom and verify that concepts deduced from studies of large single crystals are valid for the small particles.