First-principles study of the origin of alkali promotion of reactivity of metal surfaces

TL;DR

This study uses first-principles calculations to uncover how alkali metals enhance the reactivity of metal surfaces by altering surface potentials, providing insights into catalytic promotion and optical properties.

Contribution

It reveals the mechanism behind alkali promotion of metal surface reactivity through changes in surface potential and reactivity indices, a novel insight into catalytic enhancement.

Findings

Alkali adsorption increases and delocalizes the reactivity index of Cu and Pd surfaces.

Surface potential features caused by alkali adsorbates drive the promotion effect.

Clues to optical properties of alkali-adsorbed quantum wells are provided.

Abstract

Alkali metals are known as efficient promoters in heterogeneous catalysis but the nature of this phenomenon is as yet not understood. Our first principles calculations reveal a huge increase and delocalization of the isoelectronic reactivity index of Cu and Pd surfaces on alkali adsorption. We trace this phenomenon to an unusual feature in the surface potential formed by the adsorbate and propose it as a driving force for the "promotion effect". Our results also provide clues to some of the unusual optical properties of quantum wells formed when alkali adsorb on Cu surfaces.