, Volume 7, Issue 1-4, pp 27-51

Hydrogen adsorption on supported cobalt, iron, and nickel

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Abstract

This paper emphasizes concepts and fundamentals relating to the kinetics, energetics, and stoichiometries of adsorption of hydrogen on supported cobalt, iron and nickel, with emphasis on nickel. Relationships between catalyst and adsorption properties and the application of hydrogen chemisorption to the measurement of metal surface areas are discussed. Evidence is presented for nonstoichiometric adsorption of hydrogen on supported metals and the results are interpreted in terms (i) reversibility of adsorption and (ii) interactions of hydrogen with metal oxides present on or near metal crystallites. Contamination of the metal surface by support moieties can cause (i) the appearance of new adsorption states of hydrogen at higher binding energies and (ii) an increase in the adsorption activation energy for hydrogen which can lead to severe kinetic limitations in the adsorption process. Precalcination treatments and promoters such as potassium also cause the appearance of new high temperature adsorption states and significantly increase the adsorption activation energy for hydrogen.