The Nature of Electrophilic Oxygen : Insights from Periodic Density Functional Theory Investigations

TL;DR

This study uses periodic DFT calculations to investigate the nature of electrophilic oxygen on silver surfaces, challenging previous notions and proposing a triatomic molecular species as the electrophilic entity involved in epoxidation.

Contribution

It provides new insights into the chemical nature of electrophilic oxygen on Ag surfaces, suggesting it is a triatomic molecular species rather than atomic or diatomic.

Findings

No evidence supports O$_{ele}$ as atomic or diatomic.

A triatomic molecular species shows signatures of electrophilicity.

Insights could impact the understanding of catalytic epoxidation mechanisms.

Abstract

Increasing demand of ethylene oxide and the cost of versatile chemical ethene has been a driving force for understanding mechanism of epoxidation to develop highly selective catalytic process. Direct epoxidation is a proposed mechanism which in theory provides 100\% selectivity. A key aspect of this mechanism is an electrophilic oxygen (O$_{ele}$) species forming on the Ag surface. In the past two and half decades, large number of theoretical and experimental investigations have tried to elucidate formation of O$_{ele}$ on Ag surface with little success. Equipped with this rich literature on Ag-O interactions, we investigate the same using periodic DFT calculations to further understand how silver surface and oxygen interact with each other from a chemical standpoint. Based on energetics, L\"{o}wdin charges, topologies and {\it pdos} data described in this study, we scrutinize the established notions of O$_{ele}$. Our study provides no evidence in support of O$_{ele}$ being an atomic species nor a diatomic molecular species. In fact, a triatomic molecular species described in this work bears multiple signatures which are very convincing evidence for considering it as the most sought for electrophilic entity.