Studies of Adsorbate Structure and Dynamics on Catalytic Surfaces with NMR Spectroscopy: CO on Metals.
01 January 1990
NMR studies of absorbed CO illustrates the methodology of NMR spectroscopy and demonstrate results attainable in a comprehensive application to a heterogeneous catalytic system. This review is divided into two sections: adsorbate structure and dynamics. CO adsorbs on dispersed metals in at least three forms: linear- and bridge-bonded CO on metal particles and multicarbonyls on isolated metal atoms. Broadline sup (13) C NMR spectra of CO on Ru and Rh reveal distinct powder patterns for each type, which provides quantitative site distributions and descriptions of the site geometries. High resolution spectra obtained by magic-angle spinning provide isotropic shifts which support the separation of the overlapping broadline components. The metallic character of the dispersed metal particles is revealed through susceptibility broadening and large Knight shifts.