Theory of chemisorption of hydrogen on transition metals and their alloys

A theoretical discussion is given of the changes in the heat of chemisorption of a hydrogen atom upon alloying a group-VIII metal with a group-IB metal. The emphasis is on two concepts: the ensemble effect and the ligand effect. The ensemble effect ascribes the changes in the heat of chemisorption primarily to changes in the geometry of the adsorption complex, whereas the ligand effect also takes into account changes in bond strength due to a different intrinsic activity of the bonding metal atoms.