Effect of Alloy Composition and Crystal Face of Pt-Skin/Pt100–x Co x [(111), (100), and (110)] Single Crystal Electrodes on the Oxygen Reduction Reaction Activity

• Published in: Journal of physical chemistry. C Vol. 121; no. 21; pp. 11234 - 11240
• Main Authors: Kobayashi, S, Wakisaka, M, Tryk, D. A, Iiyama, A, Uchida, H
• Format: Journal Article
• Language: English
• Published: American Chemical Society 01.06.2017
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.6b12567

We have examined and compared for the first time the oxygen reduction reaction (ORR) activities at a series of (111), (100), and (110) faces of Pt100–x ­Co x single crystals as a function of Co content x with rotating disk electrodes in air-saturated 0.1 M HClO4 solution. The low energy electron diffraction and low energy ion scattering indicated that the topmost surfaces of Pt–Co­(111), (100), and (110) have well-defined (1×1) Pt-skin layers as a result of annealing in pure H2. Among the three faces examined, the effect of Co content was found to be the most dramatic for the (111) face: specifically, the j k values on the Pt-skin/​Pt–Co­(111) electrodes increased greatly as x increased and reached a maximum value at x = 27 atom %, which is ca. 27 times larger than that for pure Pt(111). On the Pt-skin/​Pt100–x ­Co x ­(110) electrodes, the j k values reached a maximum at x = 18 atom %, which is 4 times larger than that of pure Pt(110). Unlike other faces, the Pt-skin/​Pt–Co­(100) electrodes exhibited a weak dependence of j k on the Co content x. The overall order of activity was (100) < (110) ≪ (111), so that the enhancement factor for j k on the (111) face was unique, being significantly larger than the others. Our results can provide an important insight for the significant increase in the ORR activity depending not only on the alloy composition but also on the atomic arrangement of the exposed Pt-skin surface.