Pt submonolayers on metal nanoparticles—novel electrocatalysts for H2 oxidation and O2 reduction
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- 作者：Sasaki ; K. ; Mo ; Y. ; Wang ; J.X. ; Balasubramanian ; M. ; Uribe ; F. ; McBreen ; J. ; Adzic ; R.R.
- 关键词：Pt monolayer ; Ru nanoparticles ; Au nanoparticles ; H2 oxidation ; O2 reduction ; CO tolerance
- 刊名：Electrochimica Acta
- 出版年：2003
- 出版时间：November 15, 2003
- 年：2003
- 卷：48
- 期：25-26
- 页码：3841-3849
- 全文大小：517 K
文摘
Novel electrocatalysts based on Pt submonolayer deposits on Ru and Au nanoparticles, and on a Au(111) surface, have been prepared by two new methods for noble metal monolayer deposition. These were tested for H2 and H2/CO oxidation and O2 reduction kinetics. Our recently reported methods for controlled submonolayer-to-multilayer deposition of Pt involve spontaneous deposition of Pt on Ru and Pt deposition by redox replacement of a Cu upd monolayer on Au. The Pt mass-specific activity for H2 oxidation of the PtRu20 electrocatalyst was found to be three to four times higher than that of commercial catalysts at 25°C. The CO tolerance appears to be also higher than those of commercial catalysts under conditions of rotating disk experiments. Fuel cell tests at 80°C have shown practically the same activity of the PtRu20 electrocatalyst for H2 oxidation as that of the catalyst containing a 10× larger Pt loading. Extended X-ray absorption fine structure spectroscopy measurements showed that Pt is coordinated with three to four Ru atoms in this catalyst, with a bond length of 2.68 Å between Pt and Ru as in PtRu alloys. A Pt0.75Pd0.25 monolayer on Au/C is a very active electrocatalyst for O2 reduction that equals the activity of a Pt/C catalyst with a 2.5 times larger Pt loading. The activity of a Pt monolayer on Au(111) is also considerable. A single Tafel slope of −110 mV for the Pt0.75Pd0.25/Au/C catalyst, and a −120 mV for Au(111), may indicate a smaller adsorption of OH on Pt and Pt0.75Pd0.25 on Au in comparison with bulk or nano Pt. Further work utilizing a Pt monolayer on metal nanoparticles seems to be a promising approach for both reduction of noble metal loading and designing electrocatalysts with improved properties.