Trend of catalytic activity of CO oxidation on Rh and Ru nanoparticles: Role of surface oxide

[Display omitted] ► We investigated catalytic activity of CO oxidation on Rh and Ru nanoparticle arrays. ► The catalytic activity and activation energy before and after the chemical modification. ► The changes in oxidation states that occurred during UV-ozone surface treatment were characterized wit...

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Published in:	Catalysis today Vol. 185; no. 1; pp. 131 - 137
Main Authors:	Kim, Sunmi, Qadir, Kamran, Jin, Sookyoung, Satyanarayana Reddy, A., Seo, Bora, Mun, B.S., Joo, Sang Hoon, Park, Jeong Young
Format:	Journal Article Conference Proceeding
Language:	English
Published:	Amsterdam Elsevier B.V 20-05-2012 Elsevier
Subjects:	activation energy Catalysis Catalytic activity Chemistry CO oxidation Colloidal state and disperse state Exact sciences and technology General and physical chemistry nanoparticles oxidation Oxidation state oxides Physical and chemical studies. Granulometry. Electrokinetic phenomena polyols Rh and Ru nanoparticles Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry UV-ozone surface treatment X-ray photoelectron spectroscopy UV-ozone surface treatment Catalytic activity CO oxidation Rh and Ru nanoparticles Oxidation state Capping Catalytic reaction Growth Nanoparticle Oxides Ozone Transition metal X ray Precursor Surface treatment Chemical reduction Heterogeneous catalysis Chemical modification Monodispersed particle Photoelectron spectrometry Oxidation Polyol Activation energy
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Summary:	[Display omitted] ► We investigated catalytic activity of CO oxidation on Rh and Ru nanoparticle arrays. ► The catalytic activity and activation energy before and after the chemical modification. ► The changes in oxidation states that occurred during UV-ozone surface treatment were characterized with XPS. ► Rh oxide formed during UV-ozone treatment is reactive while Ru bulk oxide is catalytically inactive. Recent studies suggest that surface oxides on transition metal nanoparticles play an important role in determining the catalytic activity of CO oxidation. In this work, we investigated the influence of surface modification of Rh and Ru nanoparticles on the catalytic activity of CO oxidation using UV-ozone surface treatment. Monodisperse Rh and Ru nanoparticles were synthesized by polyol reduction using poly(vinylpyrrolidone) (PVP) as a capping agent. The size of the nanoparticles was controlled by varying the concentration of the Rh and Ru precursors or using the seeded-growth method. The changes that occurred during UV-ozone surface treatment were characterized with X-ray photoelectron spectroscopy, which showed that the oxidation state increased after surface treatment. The catalytic activity and activation energy of Rh and Ru nanoparticle arrays were measured before and after the chemical modification. Our reaction studies indicate that the turnover rate of CO oxidation on Rh nanoparticles increases by a factor of three after UV-ozone treatment due to the formation of catalytically active Rh oxide. In contrast, the catalytic activity of Ru nanoparticles decreases after UV-ozone treatment, suggesting that the Ru bulk oxide formed during UV-ozone treatment is catalytically inactive. The results suggest an intriguing way to tune catalytic activity via engineering of the nanoscale surface oxide.
Bibliography:	http://dx.doi.org/10.1016/j.cattod.2011.09.024
ISSN:	0920-5861 1873-4308
DOI:	10.1016/j.cattod.2011.09.024