Near-Ambient Pressure Oxidation of Silver in the Presence of Steps: Electrophilic Oxygen and Sulfur Impurities
Artikel i vetenskaplig tidskrift, 2024

The oxidation of Ag crystal surfaces has recently triggered strong controversies around the presence of sulfur impurities that may catalyze reactions, such as the alkene epoxidations, especially the ethylene epoxidation. A fundamental challenge to achieve a clear understanding is the variety of procedures and setups involved as well as the particular history of each sample. Especially, for the often-used X-ray photoemission technique, product detection, or photoemission peak position overlap are problematic. Here we investigate the oxidation of the Ag(111) surface and its vicinal crystal planes simultaneously, using a curved crystal sample and in situ X-ray photoelectron spectroscopy at 1 mbar O2 near-ambient pressure conditions to further investigate surface species. The curved geometry allows a straightforward comparative analysis of the surface oxidation kinetics at different crystal facets, so as to precisely correlate the evolution of different oxygen species, namely nucleophilic and electrophilic oxygen, and the buildup of sulfur as a function of the crystal orientation. We observed that emission from both surface and bulk oxide contributes to the characteristic nucleophilic oxygen core-level peak, which arises during oxygen dosing and rapidly saturates below temperatures of 180 °C. The electrophilic oxygen peak appears later, growing at a slower but constant rate, at the expenses of the surface oxide. Electrophilic oxygen and sulfur core-levels evolve in parallel in all crystal facets, although faster and stronger at vicinal surfaces featuring B-type steps with {111} microfacets. Our study confirms the intimate connection of the electrophilic species with the formation of adsorbed SO4, and points to a higher catalytic activity of B-type stepped silver surfaces for alkene epoxidation or methane to formaldehyde conversion.

sulfur accumulation

silver oxidation

near ambient pressure photoemission spectroscopy

curved crystal

catalytic substrate

Författare

F. Schiller

Donostia International Physics Center

Consejo Superior de Investigaciones Científicas (CSIC)

Khadiza Ali

Chalmers, Mikroteknologi och nanovetenskap, Kvantkomponentfysik

Consejo Superior de Investigaciones Científicas (CSIC)

Anna A. Makarova

Freie Universität Berlin

Sabine V. Auras

Consejo Superior de Investigaciones Científicas (CSIC)

Fernando Garcia-Martinez

Deutsches Elektronen-Synchrotron (DESY)

Consejo Superior de Investigaciones Científicas (CSIC)

Alaa Mohammed Idris Bakhit

Consejo Superior de Investigaciones Científicas (CSIC)

R. Castrillo-Bodero

Consejo Superior de Investigaciones Científicas (CSIC)

Ignacio J. Villar-García

Universidad CEU San Pablo

El Sincrotrón ALBA

J. Enrique Ortega

Donostia International Physics Center

Universidad del Pais Vasco / Euskal Herriko Unibertsitatea

Consejo Superior de Investigaciones Científicas (CSIC)

Virginia Pérez-Dieste

El Sincrotrón ALBA

ACS Catalysis

21555435 (eISSN)

12865-12874

Ämneskategorier (SSIF 2011)

Fysikalisk kemi

DOI

10.1021/acscatal.4c02985

Mer information

Senast uppdaterat

2025-03-09