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Stabilization of reduced copper on ceria aerogels for CO oxidation.

ABSTRACT: Photodeposition of Cu nanoparticles on ceria (CeO₂) aerogels generates a high surface area composite material with sufficient metallic Cu to exhibit an air-stable surface plasmon resonance. We show that balancing the surface area of the aerogel support with the Cu weight loading is a critical factor in retaining stable Cu⁰. At higher Cu weight loadings or with a lower support surface area, Cu aggregation is observed by scanning and transmission electron microscopy. Analysis of Cu/CeO₂ using X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy finds a mixture of Cu²⁺, Cu⁺, and Cu⁰, with Cu⁺ at the surface. At 5 wt% Cu, Cu/CeO₂ aerogels exhibit high activity for heterogeneous CO oxidation catalysis at low temperatures (94% conversion of CO at 150 °C), substantially out-performing Cu/TiO₂ aerogel catalysts featuring the same weight loading of Cu on TiO₂ (20% conversion of CO at 150 °C). The present study demonstrates an extension of our previous concept of stabilizing catalytic Cu nanoparticles in low oxidation states on reducing, high surface area aerogel supports. Changing the reducing power of the support modulates the catalytic activity of mixed-valent Cu nanoparticles and metal oxide support.

SUBMITTER: Pitman CL

PROVIDER: S-EPMC9419587 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Stabilization of reduced copper on ceria aerogels for CO oxidation.

Pitman Catherine L CL Pennington Ashley M AM Brintlinger Todd H TH Barlow Daniel E DE Esparraguera Liam F LF Stroud Rhonda M RM Pietron Jeremy J JJ DeSario Paul A PA Rolison Debra R DR

Nanoscale advances 20200903 10

Photodeposition of Cu nanoparticles on ceria (CeO<sub>2</sub>) aerogels generates a high surface area composite material with sufficient metallic Cu to exhibit an air-stable surface plasmon resonance. We show that balancing the surface area of the aerogel support with the Cu weight loading is a critical factor in retaining stable Cu<sup>0</sup>. At higher Cu weight loadings or with a lower support surface area, Cu aggregation is observed by scanning and transmission electron microscopy. Analysis ...[more]

PMID: 36132898

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Project description:Various COx species formed upon the adsorption and oxidation of CO on palladium and silver single atoms supported on a model ceria nanoparticle (NP) have been studied using density functional calculations. For both metals M, the ceria-supported MCOx moieties are found to be stabilised in the order MCO < MCO2 < MCO3, similar to the trend for COx species adsorbed on M-free ceria NP. Nevertheless, the characteristics of the palladium and silver intermediates are different. Very weak CO adsorption and the small exothermicity of the CO to CO2 transformation are found for O4Pd site of the Pd/Ce21O42 model featuring a square-planar coordination of the Pd2+ cation. The removal of one O atom and formation of the O3Pd site resulted in a notable strengthening of CO adsorption and increased the exothermicity of the CO to CO2 reaction. For the analogous ceria models with atomic Ag instead of atomic Pd, these two energies became twice as small in magnitude and basically independent of the presence of an O vacancy near the Ag atom. CO2-species are strongly bound in palladium carboxylate complexes, whereas the CO2 molecule easily desorbs from oxide-supported AgCO2 moieties. Opposite to metal-free ceria particle, the formation of neither PdCO3 nor AgCO3 carbonate intermediates before CO2 desorption is predicted. Overall, CO oxidation is concluded to be more favourable at Ag centres atomically dispersed on ceria nanostructures than at the corresponding Pd centres. Calculated vibrational fingerprints of surface COx moieties allow us to distinguish between CO adsorption on bare ceria NP (blue frequency shifts) and ceria-supported metal atoms (red frequency shifts). However, discrimination between the CO2 and CO32- species anchored to M-containing and bare ceria particles based solely on vibrational spectroscopy seems problematic. This computational modelling study provides guidance for the knowledge-driven design of more efficient ceria-based single-atom catalysts for the environmentally important CO oxidation reaction.

Dataset Information

Stabilization of reduced copper on ceria aerogels for CO oxidation.

Publications

Stabilization of reduced copper on ceria aerogels for CO oxidation.

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