Seedless Polyol Synthesis and CO Oxidation Activity of Monodisperse (111)- and (100)-Oriented Rhodium Nanocrystals in Sub-10 nm Sizes

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• 作者：Yawen Zhang ; Michael E. Grass ; Wenyu Huang ; Gabor A. Somorjai
• 刊名：Langmuir
• 出版年：2010
• 出版时间：November 2, 2010
• 年：2010
• 卷：26
• 期：21
• 页码：16463-16468
• 全文大小：1012K
• 年卷期：v.26,no.21(November 2, 2010)
• ISSN：1520-5827

文摘

Monodisperse sub-10 nm (6.5 nm) sized Rh nanocrystals with (111) and (100) surface structures were synthesized by a seedless polyol reduction in ethylene glycol, with poly(vinylpyrrolidone) as a capping ligand. When using [Rh(Ac)₂]₂ as the metal precursor, (111)-oriented Rh nanopolyhedra containing 76% (111)-twinned hexagons (in 2D projection) were obtained; whereas, when employing RhCl₃ as the metal precursor in the presence of alkylammonium bromide, such as tetramethylammonium bromide and trimethyl(tetradecyl)ammonium bromide, (100)-oriented Rh nanocubes were obtained with 85% selectivity. The {100} faces of the Rh nanocrystals are stabilized by chemically adsorbed Br⁻ ions from alkylammonium bromides, which led to (100)-oriented nanocubes. Monolayer films of the (111)-oriented Rh nanopolyhedra and (100)-oriented Rh nanocubes were deposited on silicon wafers in a Langmuir−Blodgett trough to make model 2D nanoarray catalysts. These nanocatalysts were active for CO oxidation by O₂, and the turnover frequency was independent of nanoparticle shape, consistent with that previously observed for Rh(111) and Rh(100) single crystals.