Atomically Flat Pt Skin and Striking Enrichment of Co in Underlying Alloy at Pt3Co(111) Single Crystal with Unprecedented Activity for the Oxygen Reduction Reaction

Shun Kobayashi; Makoto Aoki; Mitsuru Wakisaka; Teppei Kawamoto; Ryo Shirasaka; Kohei Suda; Donald A Tryk; Junji Inukai; Toshihiro Kondo; Hiroyuki Uchida

doi:10.1021/acsomega.7b01793

Atomically Flat Pt Skin and Striking Enrichment of Co in Underlying Alloy at Pt₃Co(111) Single Crystal with Unprecedented Activity for the Oxygen Reduction Reaction

ACS Omega. 2018 Jan 17;3(1):154-158. doi: 10.1021/acsomega.7b01793. eCollection 2018 Jan 31.

Authors

Affiliations

¹ Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan.
² Division of Life, Medical, Natural Sciences and Technology, Organization for Advanced and Integrated Research, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 658-8501, Japan.
³ Division of Environmental Engineering, Graduate School of Engineering, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan.
⁴ Fuel Cell Nanomaterials Center, University of Yamanashi, 6-43 Miyamae-cho, Kofu 400-0021, Japan.
⁵ Division of Chemistry, Graduate School of Humanities and Sciences, Ochanomizu University, Ohtsuka, Bunkyo-ku, Tokyo 112-8610, Japan.

Abstract

By the use of in situ scanning tunneling microscopy and surface X-ray scattering techniques, we have clarified the surface structure and the layer-by-layer compositions of a Pt skin/Pt₃Co(111) single-crystal electrode, which exhibited extremely high activity for the oxygen reduction reaction. The topmost layer was found to be an atomically flat Pt skin with (1 × 1) structure. Cobalt was enriched in the second layer up to 98 atom %, whereas the Co content in the third and fourth layers was slightly smaller than that in the bulk. By X-ray photoelectron spectroscopy, the Co in the subsurface layers was found to be positively charged, which is consistent with an electronic modification of the Pt skin. The extremely high activity at the Pt skin/Pt₃Co(111) single crystal is correlated with this specific surface structure.