The Sintering of Au Nanoparticles on Flat {100}, {111} and Zigzagged {111}-Nanofacetted Structures of Ceria and Its Infl
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The Sintering of Au Nanoparticles on Flat {100}, {111} and Zigzagged {111}‑Nanofacetted Structures of Ceria and Its Influence on Catalytic Activity in CO Oxidation and CO PROX O. S. Bezkrovnyi1 · P. Kraszkiewicz1 · W. Mista1 · L. Kepinski1 Received: 21 April 2020 / Accepted: 28 August 2020 © The Author(s) 2020
Abstract The thermal stability of Au nanoparticles on ceria support of various morphology (nanocubes, nanooctahedra, and {111}-nanofacetted nanocubes) in oxidizing and reducing atmospheres was investigated by electron microscopy. A beneficial effect of the reconstruction of edges of ceria nanocubes into zigzagged {111}-nanofacetted structures on the inhibition of sintering of Au nanoparticles was shown. The influence of different morphology of Au particles on various ceria supports on the reducibility and catalytic activity in CO oxidation, and CO PROX of Au/ceria catalysts was also investigated and discussed. It was shown, that ceria nanocubes with flat {110} terminated edges are more suitable as a support for Au nanoparticles, used to catalyze CO oxidation, than zigzagged {111}- nanofacetted structures. Graphic Abstract
Keywords Ceria support · Nanofacetes · Au nanoparticles · Sintering · H2-TPR · Co–oxidation · CO PROX Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10562-020-03370-1) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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1 Introduction As a reducible oxide with facile oxygen vacancy formation and easy conversion between the C e3+ and Ce4+ oxidation states, ceria displays good characteristics both as a catalyst and «active» catalytic support [1]. High efficiency of ceria as active support for noble metal catalysts can be explained by the effective supply of oxygen from ceria to noble metal nanoparticle to form active oxidic sites [2]. Theoretical DFT calculations by Conesa showed that the energy of the formation of oxygen vacancies is structuresensitive, following the sequence {110} Au/ CeO2(NF)≈Au/CeO2(NO). Nevertheless, the catalytic activity of the samples in CO-oxidation follows the sequence Au/ CeO2(NC) > Au/CeO2(NF) > Au/CeO2(NO). The observed difference indicates that the reconstruction of {110} surfaces at the edges of ceria nanocubes into zigzagged {111} structure more strongly declines the efficiency of CO oxidation in H2 stream. The width (T1–T2) of temperature window of the efficient CO oxidation (CO conversion > 50%) follows the sequence: Au/CeO2(NC) > Au/CeO2(NF) > > Au/CeO2(NO). As seen in Table 4, the selectivity of the samples at minimal (T1) temperature of T50 follows the tendency: Au/CeO2(NC)≈Au/ CeO2(NF) > Au/CeO2(NO). It shows that both parameters are the worst for Au/CeO2(NO). The Au/CeO2(NF) sample (annealed at 300 and 500 °C) maintain relatively high Table 4 A comparison of Au/ CeO2(NC), Au/CeO2(NF), and Au/CeO2(NO) catalysts in their performance and selectivity for CO PROX
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