A theoretical study of hydrogen chemisorption on Ni(111) and Co(0001) surfaces

To quantify the role of hydrogen in the catalytic formation of hydrocarbons, the binding energy of adsorbed hydrogen species on Ni(111) and Co(0001) surfaces was calculated using density-functional theory within the generalized gradient approximation and the full-potential linearized augmented planewave method. In order to probe a range of potential working conditions of nickel and cobalt catalysts, adsorption of hydrogen as a function of both surface coverage and adsorption site was examined. Our results were in excellent agreement with the small set of experimental values available in the literature. The most stable configurations for hydrogen were adsorption on both three-fold hollow sites on nickel and cobalt surfaces at all surface coverages. In striking contrast to our results reported earlier for the binding energy of carbon and methylidyne, the relative stabilities of hydrogen chemisorption were independent of both the transition metal surface and surface coverage, suggesting that hydrogen plays a limited role in differences in product selectivities observed for hydrocarbon growth reactions on nickel and cobalt surfaces. (C) 1999 Elsevier Science B.V. All rights reserved.