Abstract
In this work we elucidate the main steps of the CO oxidation mechanism over Au/CeO2(111), clarifying the course of CO adsorption at a broad variety of surface sites as well as of transmutations of one CO species into another. By combining transient spectroscopy with DFT calculations we provide new evidence that the active centers for CO conversion are single gold atoms. To gain insight into the reaction mechanism, we employ Modulation Excitation (ME) DRIFT spectroscopy in combination with the mathematical tool of Phase Sensitive Detection to identify the active species and perform DFT calculations to facilitate the assignments of the observed bands. The transient nature of the ME-DRIFTS method allows us to sort the observed species temporally, providing further mechanistic insight. Our study highlights the potential of combined transient spectroscopy and theoretical calculations (DFT) to clarify the role of adsorbates observed and to elucidate the reaction mechanism of CO oxidation over supported gold and other noble-metal catalysts.
Highlights
Ceria, especially in combination with noble metal nanoparticles, is a widely used catalyst for oxidation reactions such as CO oxidation or the water–gas shift reaction [1–6]
CO oxidation over supported noble metal catalysts has been investigated for a long time and in numerous studies, a profound understanding of the dynamics of the different CO adsorbate structures has not been achieved to date
Many features of the CO oxidation mechanism over Au catalysts were clarified previously, some important details are still missing, such as processes related to the initial CO adsorption and the subsequent adsorbate rearrangement
Summary
Especially in combination with noble metal nanoparticles, is a widely used catalyst for oxidation reactions such as (preferential) CO oxidation or the (reverse) water–gas shift reaction [1–6]. CO oxidation over supported noble metal catalysts has been investigated for a long time and in numerous studies, a profound understanding of the dynamics of the different CO adsorbate structures has not been achieved to date To this end, new mechanistic insight may be expected from a combination of transient time-resolved DRIFT spectra with theoretical calculations of possible adsorbate structures such as vibrational frequencies and adsorption energies. MES and PSD are used to extract the dynamics from timeresolved spectra during periodic modulation of one process variable (in our case the concentration of one reactant) and to separate it from all time-constant signals (spectator species) as well as from the statistical background noise, providing valuable information on active species often hidden in conventional spectra This is achieved via Fourier transformation of the time-resolved into phase-resolved spectra according to Eq (1): te. As will be illustrated below for Au/CeO2, the combination of transient ME-DRIFTS with theoretical DFT studies allows to obtain a more profound understanding of the first reaction steps of CO oxidation and especially the crucial CO adsorption processes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
