Nuclear magnetic resonance study of the bonding of carbon monoxide to palladium and platinum surfaces
The 13c and 17o NMR of CO chemisorbed on small particles of Pd and Pt has been observed. The 17o resonance represents the first reported NMR observation of a spin larger than 1/2 adsorbed on a metal surface. At low temperatures, the 13c resonance of CO on Pd is centered at 540 ppm down field from the 13 C resonance of tetramethylsilane (TMS). The line position is interpreted as the sum of a chemical shift of 230 ppm, typical of CO in transition metal carbonyls, and a Knight shift of 310 ppm. The 13c lineshape and spin lattice relaxation time T1 were measured from 77 K to 400 K. The temperature dependence of the T1 is used to confirm the existence of a Knight shift. From the motional narrowing of the NMR line a diffusion energy of 6+2 kcal/mol for CO on the Pd surface is deduced. A C-0 boo:i length of 1.20+.03 A for CO chemisorbed on Pd was measured using a spin echo double resonance (SEOOR) experiment observing the 170 NMR.
Nuclear magnetic resonance (NMR), carbon monozide, palladium sufaces, platinum surfaces, chemisorbed
University of Illinois - Urbana-Champaign
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