Influence of Size-Induced Oxidation State of Platinum Nanoparticles on Selectivity and Activity in Catalytic Methanol Oxidation in the Gas Phase
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- 作者：Hailiang Wang ; Yihai Wang ; Zhongwei Zhu ; Andras Sapi ; Kwangjin An ; Griffin Kennedy ; William D. Michalak ; Gabor A. Somorjai
- 刊名：Nano Letters
- 出版年：2013
- 出版时间：June 12, 2013
- 年：2013
- 卷：13
- 期：6
- 页码：2976-2979
- 全文大小：344K
- 年卷期：v.13,no.6(June 12, 2013)
- ISSN：1530-6992
文摘
Pt nanoparticles with various sizes of 1, 2, 4, and 6 nm were synthesized and studied as catalysts for gas-phase methanol oxidation reaction toward formaldehyde and carbon dioxide under ambient pressure (10 Torr of methanol, 50 Torr of oxygen, and 710 Torr of helium) at a low temperature of 60 掳C. While the 2, 4, and 6 nm nanoparticles exhibited similar catalytic activity and selectivity, the 1 nm nanoparticles showed a significantly higher selectivity toward partial oxidation of methanol to formaldehyde, but a lower total turnover frequency. The observed size effect in catalysis was correlated to the size-dependent structure and oxidation state of the Pt nanoparticles. X-ray photoelectron spectroscopy and infrared vibrational spectroscopy using adsorbed CO as molecular probes revealed that the 1 nm nanoparticles were predominantly oxidized while the 2, 4, and 6 nm nanoparticles were largely metallic. Transmission electron microscopy imaging witnessed the transition from crystalline to quasicrystalline structure as the size of the Pt nanoparticles was reduced to 1 nm. The results highlighted the important impact of size-induced oxidation state of Pt nanoparticles on catalytic selectivity as well as activity in gas-phase methanol oxidation reactions.