Platinum Metal Catalysts of High-Index Surfaces: From Single-Crystal Planes to Electrochemically Shape-Controlled Nanoparticles

Abstract

Nanoparticles of platinum group metals (PGM) supported on diverse substrate materials are widely used catalysts in many important fields such as modern chemical industry, petrochemical industry, automobile exhaust purification, and fuel cells. Due to the extremely high cost and rare reserve of the PGM on the earth, to further improve the catalytic activity, stability, and utility efficiency of PGM nanoparticles is the key issue in relevant industrial development as well as the challenge of basic research of science and technology. This feature article summarizes at first the relationship between surface structure and catalytic functionality gained by using metal single-crystal planes as model electrocatalysts, which reveals that high-index planes, i.e., the planes denoted by a set of Miller indices (hkl) with at least one index being larger than unit, with high density of atomic steps and kinks, exhibit generally high catalytic reactivity and stability. Next, guided by the knowledge acquired in model electrocatalysis, we put emphasis upon the electrochemically shape-controlled synthesis of Pt and Pd nanocrystals (NCs) bounded by high-index facets, including tetrahexahedral NCs with 24 {hk0} facets, trapezohedral NCs with 24 {hkk} facets, concave hexoctahedral NCs with 48 {hkl} facets, and multiple twinned nanorods with {hk0} facets. Finally, challenging issues and future prospects in this exciting field are outlined.Natural Science Foundation of China [20673091, 20433060, 20503023, 20873113, 20833005]; Mnistry of Science and Technology of China [2009CB220102, 2007DFA40890

Shape‐Dependent Electrocatalysis: Oxygen Reduction on Carbon‐Supported Gold Nanoparticles

“…However, as shown in previous studies, [64][65][66] shape is expected to be a prerequisite for a particular surface structure. Thus, quasi-spherical nanoparticles can be considered as polyoriented, non-specificallysurface-structured catalyst materials, as no preferred facets are exposed.…”

Gold nanocrystals with variable index facets as highly effective cathode catalysts for lithium–oxygen batteries

“…It can be seen from Figure 3d 4 , that when a TOH is viewed along the [110] direction, four edge-on facets can be projected, as indicated by the arrows. 22 The Miller indices of the edge-on facets of a TOH can be determined through an analysis of the projection angles. 23 The values of the three different angles, α, β and γ, corresponding to different Miller indices of a perfect TOH crystal, are given in Supplementary Table S1.…”

“…22 Accordingly, the {111}, {221}, {331} and {441} planes consist of 1, 2, 3 and 4 atomic widths of (110) terraces with one (001) step, respectively, as shown in Supplementary Figure S11a. The atomic models of {100}, {111} and {441} planes are shown in Supplementary Figures S11b, c 1 and d 1 , respectively.…”

Concave Cubic Gold Nanocrystals with High-Index Facets

“…[4][5][6] In the case of catalysis, not only the shape of the particle but also the exposed crystalline faces are important, which can have a marked influence on both activity and selectivity. 17,18 Interestingly, most synthetic methods to date yield nanostructures with convex shapes enclosed by lowindex {111}, {100}, and/or {110} facets, and there are very few methods [19][20][21][22] that allow one to realize nanostructures with highindex faces. Herein, we describe how seed-mediated methods, originally developed by Murphy et al 23,24 and El-Sayed et al, 25 can be modified with the appropriate surfactant to yield a novel class of high-index {720}-faceted Au concave nanocubes.…”