Oxygen reduction reaction activities of Pt/Au(1 1 1) surfaces prepared by molecular beam epitaxy

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• 作者：Yuki Iijima ; Yu Takahashi ; Ken-ichi Matsumoto ; Takehiro Hayashi ; Naoto Todoroki ; Toshimasa Wadayama ; ^{wadayamt@material.tohoku.ac.jp}
• 关键词：Oxygen reduction reaction ; Polymer electrolyte membrane fuel cell ; Platinum ; Au(1  ; 1  ; 1) ; Molecular beam epitaxy ; Scanning tunneling microscope
• 刊名：Journal of Electroanalytical Chemistry
• 出版年：2012
• 出版时间：1 October, 2012
• 年：2012
• 卷：685
• 期：Complete
• 页码：79-85
• 全文大小：883 K

文摘

Pt-deposited Au(1 1 1) surfaces were prepared by molecular beam epitaxy (MBE). Surface structures of the samples were verified with reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and infrared reflection absorption spectroscopy (IRRAS) for adsorbed carbon monoxide in an ultra-high vacuum (UHV) condition. The UHV-results show that epitaxial growth of Pt(1 1 1) on clean Au(1 1 1). A 0.3-nm-thick Pt deposition found to almost cover the Au surface. In addition, monoatomic-height Pt islands were observed on the topmost surface. Electrochemical properties were evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) using a rotating disk electrode apparatus set in an N₂-purged glove box. A CV curve of the Pt_0.3nm/Au(1 1 1) recorded in the potential region of 0.05-1.0 V vs. reversible hydrogen electrode (RHE) was similar to that of clean Pt(1 1 1), except for the lack of ¡®butterfly¡¯ peaks at 0.8 V. Oxygen reduction reaction (ORR) activities of the samples were evaluated by kinetic controlled current densities at 0.9 V; the activity of the Pt_0.3nm/Au(1 1 1) was ca. 1.8 times higher than that of the clean Pt(1 1 1). During CV curve measurements of the Pt_0.3nm/Au(1 1 1) in the region of 0.05-1.7 V, a redox feature at 0.13 V became apparent; the ORR activity evaluated after the CV measurements was higher than the as-prepared sample. An UHV-STM image collected after re-transfer from the glove box showed two to three monoatomic-height Pt mounds whose slopes were 10-20¡ã. The results clearly showed that surface defects at the topmost Pt(1 1 1) layer such as steps contribute to the ORR enhancement of MBE-prepared Pt/Au(1 1 1).