An Investigation of Structure-Catalytic Activity Relationship for Pt-Co/C Bimetallic Nanoparticles toward the Oxygen Reduction Reaction

详细信息    查看全文

• 作者：Bing Joe Hwang ; Sakkarapalayam Murugesan Senthil Kumar ; Ching-Hsiang Chen ; Monalisa ; Ming-Yao Cheng ; Din-Goa Liu ; Jyh-Fu Lee
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：October 25, 2007
• 年：2007
• 卷：111
• 期：42
• 页码：15267 - 15276
• 全文大小：413K
• 年卷期：v.111,no.42(October 25, 2007)
• ISSN：1932-7455

文摘

Carbon-supported Pt-Co alloy nanoparticle catalysts of nominal atomic composition but with different alloyingextents were prepared via a modified Watanabe process by employing microwave heating. Their structurewas studied by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques. Transmissionelectron microscopy (TEM) images indicated that the in-house-prepared Pt-Co alloy nanoparticles (sample-1and sample-2) were well dispersed on the surface of the carbon support with narrow particle size distributionwhich is consistent with XRD grain size values. The catalyst composition obtained from XAS was nearly thesame as that of the nominal value (1:1). The alloying extent values of Pt calculated from XAS measurementsfor sample-2 is similar to that of the commercial E-tek Pt-Co/C. This observation demonstrates the practicalviability of our preparation protocol for Pt-Co/C catalysts. A comparative study was made for the oxygenreduction reaction (ORR) using a thin-film rotating disk electrode method to evaluate the catalytic behaviorof Pt-Co/C and Pt/C catalyst with similar metal loadings and particle sizes. As compared to the Pt/C catalyst,the bimetallic Pt-Co/C of sample-2 exhibited an enhancement factor of 3 in mass activity at 0.95 V towardORR. The enhancement in activity of sample-2 is similar in magnitude to that of the commercial E-tek Pt-Co/C catalyst. It is found that that the samples possessing a high alloying extent of Pt in the cluster enhancesthe activity of the bimetallic Pt-Co/C toward ORR. This observation confirms that the alloying extent of Ptis an important parameter by which one can have control over the fine-tuning of the catalytic activities ofbimetallic nanoclusters. This activity enhancement may originate from the favorable electronic effects of awell mixed alloy underneath a thin "Pt-rich skin" structure of the Pt-Co bimetallic nanoparticles. This kindof thin "Pt-rich skin" is created by the dissolution of Co oxide on Pt-Co bimetallic nanoparticles whilewashing in acidic electrolyte before being subjected to ORR.