Why is a noble metal catalytically active? The role of the O-Ag interaction in the function of silver as an oxidation catalyst

TL;DR

This study uses density-functional theory to explore how oxygen interacts with silver surfaces, revealing that thin oxide-like structures are key to silver's catalytic activity in oxidation reactions.

Contribution

It provides a detailed phase diagram of oxygen on Ag(111), identifying stable species and challenging previous ideas about active oxygen forms in catalysis.

Findings

Thin oxide-like structures are most stable under ethylene epoxidation conditions.

Atomic oxygen species are likely responsible for catalytic activity.

Molecular-like oxygen species are less relevant in the catalytic process.

Abstract

Extensive density-functional theory calculations, and taking into account temperature and pressure, affords a comprehensive picture of the behavior and interaction of oxygen and Ag(111), and provides valuable insight into the function of silver as an oxidation catalyst. The obtained phase-diagram reveals the most stable species present in a given environment and thus identifies (and excludes) possibly active oxygen species. In particular, for the conditions of ethylene epoxidation, a thin oxide-like structure is most stable, suggesting that such atomic O species are actuating the catalysis, in contrast to hitherto proposed molecular-like species.