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Redox-mediated conversion of atomically dispersed platinum to sub-nanometer particles

Lykhach Y, Figueroba A, Skala T, Duchon T, Tsud N, Aulicka M, Neitzel A, Veltruska K, Prince KC, Matolin V, Neyman KM, Libuda J (2017)

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Publication Status: Published

Publication Type: Journal article

Publication year: 2017

Journal

Publisher: ROYAL SOC CHEMISTRY

Book Volume: 5

Pages Range: 9250-9261

Journal Issue: 19

DOI: 10.1039/c7ta02204b

Abstract

The stability and the conversion of atomically dispersed Pt2+ species to sub-nanometer Pt particles have been investigated as a function of the Sn concentration in Pt-CeO2 films by means of synchrotron radiation photoelectron spectroscopy, resonant photoemission spectroscopy, and angle-resolved X-ray photoelectron spectroscopy in combination with density functional calculations. The deposition of Sn onto the Pt-CeO2 films triggers the reduction of Ce4+ cations to Ce3+ yielding Sn2+ cations. Consecutively, the redox coupling between the Ce3+ and Pt2+ species triggers the reduction of Pt2+ species yielding sub-nanometer Pt particles. The onset of reduction of Pt2+ species is directly related to the concentration of Ce3+ centers which, in turn, is controlled by the concentration of Sn2+ cations in the Pt-CeO2 film. On average, the formation of 6Ce(3+) centers corresponding to the adsorption of 3Sn atoms gives rise to the reduction of one Pt2+ species. The analysis of the depth distribution of Sn atoms in the Pt-CeO2 films revealed preferential adsorption of Sn2+ at the surface followed by diffusion of Sn2+ ions into the bulk at higher Sn coverages. Density functional modeling suggested that the adsorption of three Sn atoms in the vicinity of the Pt2+ species results in a rearrangement of the local coordination accompanied by substantial destabilization of the Pt2+ species followed by its conversion to Pt-0 atoms. The formation of sub-nanometer Pt particles is coupled with re-oxidation of two Ce3+ centers per one Pt2+ species reduced. Annealing of the Pt-CeO2 films in the presence of metallic Sn also leads to the reduction of the Pt2+ species due to thermally triggered oxidation of metallic Sn residues followed by diffusion of Sn2+ into the bulk. Annealing of the Pt-CeO2 films to temperatures above 600 K results in a loss of Sn yielding sub-nanometer Pt particles supported on nearly stoichiometric and Sn-free CeO2 films.

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APA:

Lykhach, Y., Figueroba, A., Skala, T., Duchon, T., Tsud, N., Aulicka, M.,... Libuda, J. (2017). Redox-mediated conversion of atomically dispersed platinum to sub-nanometer particles. Journal of Materials Chemistry A, 5(19), 9250-9261. https://dx.doi.org/10.1039/c7ta02204b

MLA:

Lykhach, Yaroslava, et al. "Redox-mediated conversion of atomically dispersed platinum to sub-nanometer particles." Journal of Materials Chemistry A 5.19 (2017): 9250-9261.

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