SURFACE COVERAGE MEASUREMENTS BY SIMS FOR CO ADSORPTION ON A NUMBER OF METALS AND FOR CO AND H2S COADSORPTION ON NI(110), (100) AND (111)

A detailed study of CO adsorption on Ni(100) utilizing static SIMS and a comparison of the data with surface coverage data from the literature shows that there is a linear relationship between CO coverage and the peak intensity ratios (MCO+/M+ and M2CO+/M+2) of the CO-containing secondary ions, in the region of coverage below which the adlayer becomes compressed. Adsorption isobares were obtained using the intensity ratios and from these, adsorption isosteres were derjved to give heats of adsorption as a function of coverage. These data are in very close agreement with the literature. Confirmatory data were obtained for this relationship for CO adsorption on polycrystalline Ni, Pd, Pt and Cu and Cu(100). The application of this technique of surface coverage measurements to a study of the extent to which H2S coadsorption reduces the coverage of adsorbed CO on Ni(110), (100) and (111) shows that these faces are poisoned in the order (100) > (111) > (110). Surface coverage measurements on the non-closepacked (110) face are affected by the apparent insensitivity of SIMS to adsorbates located in the channels". © 1979."