Hydrogen Adsorption on Metal Surfaces

Abstract

For a variety of reasons, the interaction of gaseous hydrogen with solid surfaces of metals and semiconductors has found widespread interest in the past, and countless experimental and theoretical investigations have been performed in this field. The term ‘interaction’ primarily focuses on the adsorption of the hydrogen molecule on the metal surface, but in principle it also includes a possible penetration of the hydrogen into the bulk crystal as well as a reaction with the bulk material to form the respective metal hydride. Both these interaction phenomena play a major role in practical chemistry and physics: The hydrogen adsorption step is considered a central reaction in heterogeneously catalyzed hydrogeration reactions. In forming an adsorptive bond to the metal certain other bonds of an adsorbed molecule may become weakened or even cleaved, and new species are easily formed by the subsequent surface reaction which normally is of a Langmuir-Hinshelwood type, i.,e., both partners react from the adsorbed state. The desired (gaseous) products leave the surface by thermal desorption under the reaction conditions and can be separated from the reaction mixture.