Heterogeneous Catalysts Need Not Be so 鈥淗eterogeneous鈥? Monodisperse Pt Nanocrystals by Combining Shape-Controlled Synthesis and Purification by Colloidal Recrystallization
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- 作者：Yijin Kang ; Meng Li ; Yun Cai ; Matteo Cargnello ; Rosa E. Diaz ; Thomas R. Gordon ; Noah L. Wieder ; Radoslav R. Adzic ; Raymond J. Gorte ; Eric A. Stach ; Christopher B. Murray
- 刊名：The Journal of the American Chemical Society
- 出版年：2013
- 出版时间：February 20, 2013
- 年：2013
- 卷：135
- 期：7
- 页码：2741-2747
- 全文大小：572K
- 年卷期：v.135,no.7(February 20, 2013)
- ISSN：1520-5126
文摘
Well-defined surfaces of Pt have been extensively studied for various catalytic processes. However, industrial catalysts are mostly composed of fine particles (e.g., nanocrystals), due to the desire for a high surface to volume ratio. Therefore, it is very important to explore and understand the catalytic processes both at nanoscale and on extended surfaces. In this report, a general synthetic method is described to prepare Pt nanocrystals with various morphologies. The synthesized Pt nanocrystals are further purified by exploiting the 鈥渟elf-cleaning鈥?effect which results from the 鈥渃olloidal recrystallization鈥?of Pt supercrystals. The resulting high-purity nanocrystals enable the direct comparison of the reactivity of the {111} and {100} facets for important catalytic reactions. With these high-purity Pt nanocrystals, we have made several observations: Pt octahedra show higher poisoning tolerance in the electrooxidation of formic acid than Pt cubes; the oxidation of CO on Pt nanocrystals is structure insensitive when the partial pressure ratio pO2/pCO is close to or less than 0.5, while it is structure sensitive in the O2-rich environment; Pt octahedra have a lower activation energy than Pt cubes when catalyzing the electron transfer reaction between hexacyanoferrate (III) and thiosulfate ions. Through electrocatalysis, gas-phase-catalysis of CO oxidation, and a liquid-phase-catalysis of electron transfer reaction, we demonstrate that high quality Pt nanocrystals which have {111} and {100} facets selectively expose are ideal model materials to study catalysis at nanoscale.