Oxygen reduction reaction activities of Ni/Pt(111) model catalysts fabricated by molecular beam epitaxy

• Published in: Electrochemistry communications 2010-08, Vol.12 (8), p.1112-1115
• Main Authors: Wadayama, Toshimasa, Todoroki, Naoto, Yamada, Yoshinori, Sugawara, Tatsuya, Miyamoto, Kanji, Iijama, Yuki
• Format: Article
• Language: English
• Subjects: Applied sciences; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Molecular beam epitaxy; Oxygen reduction reaction; Polymer-electrolyte fuel cells; Pt–Ni surface alloy
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2010.05.042

Oxygen reduction reaction (ORR) activities were evaluated for clean Pt(111) and Ni/Pt(111) model catalysts fabricated by molecular beam epitaxy. Exposure of clean Pt(111) to 1.0 L CO at 303 K produced linear-bonded and bridge-bonded CO-Pt IR bands at 2093 and 1858 cm − 1 . In contrast, 0.3-nm-thick Ni deposited on Pt(111) at 573 K (573 K-Ni 0.3 nm /Pt(111)) produced broad IR bands for adsorbed CO at around 2070 cm − 1 ; the separation of reflection high-energy electron diffraction (RHEED) streaks is slightly wider for 573 K-Ni 0.3 nm /Pt(111) than for the clean Pt(111). For 823 K-Ni 0.3 nm /Pt(111), the separation of the RHEED streaks is the same as that for the Pt(111), and a single sharp IR band due to adsorbed CO is located at 2082 cm − 1 . The results suggest that for the 823 K-Ni 0.3 nm /Pt(111), a Pt-enriched outermost surface (Pt-skin) was formed through surface segregation of the substrate Pt atoms. ORR activities for the 573 K- and 823 K-Ni 0.3 nm /Pt(111) as determined from linear sweep voltammetry curves were five times and eight times higher than that for clean Pt(111), respectively, demonstrating that Pt-skin generation is crucial for developing highly active electrode catalysts for fuel cells.