Intermetallic Compounds: Promising Inorganic Materials for Well-Structured and Electronically Modified Reaction Environments for Efficient Catalysis

Abstract

An overview of the catalytic properties of intermetallic compounds has been made to provide a comprehensive understanding regarding (1) what intermetallic catalysts can do, (2) their fundamental roles in enhanced catalysis, and (3) their advantages over other inorganic materials. A number of chemical transformations using intermetallic catalysts have been surveyed and classified into three major divisionshydrogenation/dehydrogenation, oxidation, and steam reforming and various subsections. The fundamental roles of intermetallic phases obtained from this survey were categorized into four types of effects: (a) electronic, (b) geometric, (c) steric, and (d) ordering effects. The unprecedented steric effects governed by the specific surface structures of intermetallic compounds highlight the unique capabilities of intermetallic materials. On the basis of this overview, we have concluded that intermetallic compounds have the following advantages for fine catalyst design: (i) control of the electronic structure, (ii) a specific and ordered atomic-level structure, and (iii) homogeneity of geometric and electronic structures. Thus, intermetallic compounds are promising inorganic catalyst materials capable of creating a well-designed reaction environment and suitable for developing efficient catalytic systems.

Visualizing Formation of Intermetallic PdZn in a Palladium/Zinc Oxide Catalyst: Interfacial Fertilization by PdHx

“…Intermetallic materials with well‐defined structures and tunable compositions afford unique catalytic properties, and are thus highly desirable for heterogeneous catalysis . For instance, L1 0 ‐type PdZn with lattice parameters of a = b =4.0915 Å and c =3.3426 Å in space group P 4/ mmm , is regarded as a promising catalyst for methanol steam reforming (MSR), the water–gas shift reaction (WGS), alkane dehydrogenation, and selective hydrogenation reactions .…”

“…Intermetallic materials with well-defined structures and tunable compositions afford unique catalytic properties,a nd are thus highly desirable for heterogeneous catalysis. [1] For instance,L 1 0 -type PdZn with lattice parameters of a = b = 4.0915 and c = 3.3426 in space group P4/mmm,i s regarded as apromising catalyst for methanol steam reforming (MSR), the water-gas shift reaction (WGS), alkane dehydrogenation, and selective hydrogenation reactions. [2][3][4][5][6][7] Thee xcellent catalytic performance of intermetallic PdZn is derived from reduction of the ZnO-supported Pd, which give rise to unique electronic properties and structural stability.…”

Effect of Atomic Ordering on the Activity for Methanol and Formic Acid Oxidation of Pt‐Based Electrocatalysts

“…In intermetallic nanocrystals, relative to alloys with randomly ordered atoms, the electronic effect can be strengthened through the combination of localization of electron and directional covalent bonding. In addition, a geometric effect due to the change of bonding length (increased Pt–Pt bond distance) and coordination number during the formation of intermetallic nanocrystals also alter the position of the d ‐band center and thus the catalytic activity . Finally, the Pt‐skin surface, typical of ordered structures, has a larger d ‐band center shift from the Fermi level than the Pt‐skeleton surface, typical of random alloy .…”

“…The intermetallics, instead, with their regular repeating array of surface atoms ensure homogeneity of the “good” sites. Recently, the synthesis and the use of intermetallics in various chemical transformations, such as hydrogenation/dehydrogenation, oxidation, and steam reforming, and their advantages over alloys have been surveyed . Similarly, a higher activity for oxygen reduction of ordered electrocatalysts than disordered ones in the same composition was reported .…”

Unraveling the Role of Site Isolation and Support for Semihydrogenation of Phenylacetylene

“…However, colloidal routes are not suited for large scale catalyst preparation. Thus, the most accessible path to obtain IMCs is via metal precursor impregnation on popular supports such as SiO 2 and Al 2 O 3 . Precise control exerted over the impregnation of the metal salts specifically into high‐surface area mesoporous supports, can lead to well dispersed IMNPs .…”