Deciphering the Nature of Ru Sites in Reductively Exsolved Oxides with Electronic and Geometric Metal–Support Interactions Full article
Journal |
The Journal of Physical Chemistry C
ISSN: 1932-7447 , E-ISSN: 1932-7455 |
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Output data | Year: 2020, Volume: 124, Number: 46, Pages: 25299-25307 Pages count : 9 DOI: 10.1021/acs.jpcc.0c07203 | ||||||||||
Tags | Aliphatic compounds; Blue shift; Catalyst activity; Cerium compounds; Electron transport properties; Fluorspar; Fourier transform infrared spectroscopy; Hydrogenation; Metals; Nuclear magnetic resonance; Probes; Propylene; Red Shift; Samarium compounds; X ray absorption spectroscopy; X ray photoelectron spectroscopy | ||||||||||
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Affiliations |
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Funding (7)
1 | Federal Agency for Scientific Organizations | 0333-2016-0002 (АААА-А16-116121510087-5) |
2 | Russian Foundation for Basic Research | 19-43-540004 (АААА-А19-119090590009-9) |
3 | Russian Foundation for Basic Research | 19-29-10003 (АААА-А19-119100890052-8) |
4 | Russian Science Foundation | 19-13-00172 |
5 | Swiss National Science Foundation | 4879135 (R’Equip) |
6 | Fondation Claude et Giuliana | |
7 | Swiss National Science Foundation | 200020_156015 |
Abstract:
The reductive exsolution of metallic Ru from fluorite-type solid solutions Ln2Ru0.2Ce1.8O7 (Ln = Sm, Nd, La) leads to materials with metal–support interactions that influence the electronic state and the catalytic activity of Ru. In situ X-ray absorption spectroscopy at the Ru K-edge identified that with increasing temperature, the exsolution of Ru from Sm2Ru0.2Ce1.8O7 in a H2 atmosphere proceeds via an intermediate Ruδ+ state, that is, Ru4+→Ruδ+→Ru0. X-ray photoelectron spectroscopy (XPS) established that, in parallel (H2 atmosphere at ca. 500 °C), also Ce4+ ions reduce to Ce3+, which is accompanied by an electron transfer from the reduced host oxide to the exsolved Ru0 clusters, creating Ruδ− states. Low-temperature diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) using CO as a probe molecule reveals a red shift of the CO adsorption bands by ca. 18 cm–1 when increasing the temperature during the H2 treatment from 300 to 500 °C, consistent with an increased π-backdonation from more electron-rich Ru species to CO. However, at a lower reduction temperature of ca. 100 °C, a blue-shifted CO band is observed that is explained by a Lewis-acidic Ruδ+–CO adduct. Nuclear magnetic resonance (NMR) signal enhancement in parahydrogen-induced polarization experiments was used as a structure-sensitive probe and revealed a decreasing propene hydrogenation rate with increasing exsolution temperature, accompanied by a notable enhancement of propane hyperpolarization (ca. 3-fold higher at 500 °C than at 300 °C). These data suggest that the exsolved, subnanometer-sized Ru species are more active in propene hydrogenation but less selective for the pairwise addition of p-H2 to propene than Ruδ− sites engaged in a strong metal–support interaction.
Cite:
Naeem M.A.
, Burueva D.B.
, Abdala P.M.
, Bushkov N.S.
, Stoian D.
, Bukhtiyarov A.V.
, Prosvirin I.P.
, Bukhtiyarov V.I.
, Kovtunov K.V.
, Koptyug I.V.
, Fedorov A.
, Müller C.R.
Deciphering the Nature of Ru Sites in Reductively Exsolved Oxides with Electronic and Geometric Metal–Support Interactions
The Journal of Physical Chemistry C. 2020. V.124. N46. P.25299-25307. DOI: 10.1021/acs.jpcc.0c07203 WOS Scopus РИНЦ
Deciphering the Nature of Ru Sites in Reductively Exsolved Oxides with Electronic and Geometric Metal–Support Interactions
The Journal of Physical Chemistry C. 2020. V.124. N46. P.25299-25307. DOI: 10.1021/acs.jpcc.0c07203 WOS Scopus РИНЦ
Dates:
Submitted: | Aug 6, 2020 |
Accepted: | Oct 3, 2020 |
Published online: | Nov 10, 2020 |
Published print: | Nov 19, 2020 |
Identifiers:
Web of science | WOS:000592958800016 |
Scopus | 2-s2.0-85096621238 |
Elibrary | 45128167 |
Chemical Abstracts | 2020:2284222 |
OpenAlex | W3100520437 |