DYNAMICS OF HYDROGEN AT THE SURFACE OF SUPPORTED RUTHENIUM

One-dimensional (1D) and two-dimensional NMR exchange measurements were performed to probe the dynamics of hydrogen adsorption on highly dispersed silica-supported ruthenium particles at pressures from 10(-4) to 600 Torr and temperatures between 292 and 400 K. We found three distinct NMR resonances, alpha(l), alpha(M), and beta, respresenting hydrogen interacting with the metal surface. The character of motion of the three hydrogen species was inferred from 1D and 2D NMR experiments. Also, two types of exchange processes were found: (i) a slow chemical exchange occurring on a submillisecond time scale between alpha(M) and beta and (ii) a fast exchange between weakly adsorbed hydrogen and hydrogen in the gas phase, with both hydrogen species contributing to the beta NPR line.