Correlation between the Knight shift of chemisorbed CO and the Fermi levellocal density of states at clean platinum catalyst surfaces

We have investigated the Pt-195 and C-13 nuclear magnetic resonance (NMR) s pectroscopy of clean-surface platinum catalysts and of CO chemisorbed onto Pt catalyst surfaces. We use Knight shift, relaxation, and J-coupling data to deduce information about the Fermi level local density of states (E-f-LD OS) at catalyst surfaces. There is a linear correlation between the Knight shifts of chemisorbed CO and the clean surface Ef-LDOS of platinum onto whi ch the CO is bound, as determined by C-13 and Pt-195 NMR. The correlation a mounts to similar to 12 ppm/Ry(-1).atom(-1), the same as that which can be deduced for CO on palladium, as well as from the electrode potential depend ence of C-13 Knight shifts and infrared vibrational frequencies, nu(CO), an d the relationship between vco and the E-f-LDOS at clean platinum surfaces. The ability to now directly relate metal and adsorbate electronic properti es opens up new avenues for investigating metal-ligand interactions in hete rogeneous catalysis and electrocatalysis.