The electrocatalytic reactions strongly depend on the surface atomic structures of the electrocatalysts. Thus, tuning the surface facets of the nanoparticles can be a powerful tool to control the activity for a specific electrocatalytic reaction. In previous studies, we employed high-resolution transmission electron microscopy to reveal the surface atomic structure of Pt nanoparticles, where the amount of high-index surface facets on Pt nanoparticles was quantified.^1,2 Correlating the surface steps on Pt nanoparticles with the electrochemical activity and stability clearly showed the significant role of surface steps in enhancing intrinsic activity for CO and methanol electro-oxidation.¹ On the other hand, the oxygen reduction reaction (ORR) activity of Pt nanoparticles is not influenced by surface steps in contrast to methanol oxidation reaction (MOR) activity.² More recently, we demonstrate the synthesis of Pd@Ir core−shell concave nanocubes as an advanced electrocatalyst for acidic oxygen evolution reaction (OER). The Pd@Ir core−shell concave nanocubes were successfully prepared by atomic layer-by-layer deposition of Ir atoms on the surface of free-standing Pd nanocubes in a liquid phase. Using X-ray photoelectron spectroscopy (XPS), the right composition and oxidation states of these nanocubes are confirmed. In the 0.1 M HClO₄ electrolyte, the synthesized Pd@Ir concave nanocubes showed significantly increased activity compared to the IrO₂ nanoparticles. The improved activity is mainly due to well-controlled surface structures based on high-index facets. We also observed that the specific activity of Pd@Ir concave nanocubes increased after the chronoamperometry test for 10 hours.

1. S. W. Lee, S. Chen, W. Sheng, N. Yabuuchi, Y.-T. Kim, T. Mitani, E. Vescovo, and Y. Shao-Horn, Roles of surface steps on Pt nanoparticles in electro-oxidation of carbon monoxide and methanol, Journal of the American Chemical Society, 2009; 131(43): p. 15669-15677.
2. S. W. Lee, S. Chen, J. Suntivich, K. Sasaki, R. R. Adzic, and Y. Shao-Horn, Role of surface steps of Pt nanoparticles on the electrochemical activity for oxygen reduction, The Journal of Physical Chemistry Letters, 2010; 1(9): p. 1316-1320.