Screening of Ternary Intermetallic Catalysts Is Possible Using Metallurgical Synthesis: Demonstration on Heusler Alloys

Intermetallic compounds are becoming hot materials as catalysts because they show unique catalytic properties that originate from a unique electronic structure and an atomic ordered surface. Ternary intermetallic catalysts have rarely been reported, which is likely due to the difficulty in synthesizing their supported nanoparticles, the typical form for catalysis research; however, there could be novel catalysts in ternary systems because they have much more elemental combinations than binary systems. They are expected to exhibit novel properties due to the synergy between three elements. Metallurgical methods, such as arc-melting, can easily synthesize intermetallic compounds even in ternary (or more) systems if they are thermodynamically stable. Thus, only metallurgical synthesis enables screening for ternary intermetallic catalysts. The catalyst screening of Heusler alloys, which are a group of ternary intermetallic compounds popular in other research fields, such as magnetics, has been conducted using metallurgical synthesis. The screening revealed fundamental catalytic properties of Heusler alloys for several reactions and identified good catalysts for the selective hydrogenation of alkynes. The systematic control of catalysis was also demonstrated by the substitution of fourth elements using a feature of Heusler alloys. This paper describes the importance of ternary intermetallic catalysts with practical examples of Heusler alloy catalysts and discusses future prospects.