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Joo, Sang Hoon
Nanomaterials & Catalysis Lab
Research Interests
  • Catalyst, energy conversion, fuel cells, electrolyzer, ORR, HER, OER

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Colloidally Synthesized Monodisperse Rh Nanoparticles Supported on SBA-15 for Size- and Pretreatment-Dependent Studies of CO Oxidation

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Title
Colloidally Synthesized Monodisperse Rh Nanoparticles Supported on SBA-15 for Size- and Pretreatment-Dependent Studies of CO Oxidation
Author
Grass, Michael E.Joo, Sang HoonZhang, YawenSomorjai, Gabor A.
Issue Date
2009-05
Publisher
AMER CHEMICAL SOC
Citation
JOURNAL OF PHYSICAL CHEMISTRY C, v.113, no.20, pp.8616 - 8623
Abstract
A particle size dependence for CO oxidation over rhodium nanoparticles of 1.9-11.3 nm has been investigated and determined to be modified by the existence of the capping agent poly(vinylpyrrolidone) (PVP). The particles were prepared using a polyol reduction procedure with PVP as the capping agent. The Rh nanoparticles were subsequently supported on SBA-15 during hydrothermal synthesis to produce Rh/SBA-15 supported catalysts for size-dependent catalytic studies. CO oxidation by O(2) at 40 Torr CO and 100 Torr O(2) was investigated over two series of Rh/SBA-15 catalysts: as-synthesized Rh/SBA-15 covering the full range of Rh sizes and the same set of catalysts after high temperature calcination and reduction. The turnover frequency at 443 K increases from 0.4 to 1.7 s(-1) as the particle size decreases from 11.3 to 1.9 nm for the as-synthesized catalysts. After calcination and reduction, the turnover frequency is between 0.1 and 0.4 s(-1) with no particle size dependence. The apparent activation energy for all catalysts is similar to 30 kcal mol(-1) and is independent of particle size and thermal treatment. Infrared spectroscopy of CO on the Rh nanoparticles indicates that the heat treatments used influence the mode of CO adsorption. As a result, the particle size dependence for CO oxidation is altered after calcination and reduction of the catalysts. CO adsorbs at two distinct bridge sites on as-synthesized Rh/SBA-15, attributable to metallic Rh(0) and oxidized Rh(I) bridge sites. After calcination and reduction, however, CO adsorbs only at Rh(0) atop sites. The change in adsorption geometry and oxidation activity may be attributable to the interaction between PVP and the Rh surface. This capping agent affect may open new possibilities for the tailoring of metal catalysts using solution nanoparticle synthesis methods.
URI
https://scholarworks.unist.ac.kr/handle/201301/6649
URL
http://www.scopus.com/inward/record.url?partnerID=HzOxMe3b&scp=66149162788
DOI
10.1021/jp901288m
ISSN
1932-7447
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CHM_Journal Papers
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