Highly dispersed,high performance Pt and PtRu catalysts,supported on multiwalled carbon nanotubes(CNTs),were prepared by a high pressure organic colloid method.The particle sizes of the active components were as small as 1.2 nm for Pt and 1.1 nm for PtRu,and the active Pt surface areas were 295 and 395 m2/g,respectively.The catalysts showed very high activities toward the anodic oxidation of methanol,evaluated by cyclic voltammetry,being up to 4 times higher than that of commercial Johnson Matthey Hispec 2000 Pt/XC-72R and 5 times better than Hispec 5000 PtRu/XC-72R catalysts.In a full air/hydrogen fuel cell,a membrane-electrode assembly prepared using our Pt/CNT and PtRu/CNT catalysts showed 50% and 100% higher performances than those prepared with commercial Johnson Matthey Pt/XC-72R and PtRu/XC-72R catalysts for the same Pt loading and operating conditions.
PdPt bimetallic catalysts that employ CeO2-modified carbon black as a support have been prepared using an organic colloidal method. PdPt/CeO2-C shows excellent performance toward the anodic oxidation of formic acid. The effects of varying both Pd to Pt ratio and CeO2 content have been investigated. The optimal Pd to Pt atomic ratio is 15, indicating that addition of small amounts of Pt can significantly enhance the activity of the catalyst. When the CeO2 content in the catalyst reaches as high as ~15 wt.%, the catalyst shows the maximum activity. Adding CeO2 not only enhances the catalytic activity of the material, but may also change the mechanism of its catalysis of the anodic oxidation of formic acid. PdlsPh/15CeO2-C exhibited 60% higher activity than Pd/C, and had a negative shift in onset potential of more than 0.1 V. Based on characterization by X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and transmission electron microscopy, the interactions between the components are revealed and discussed in detail.
