Catalysis-tunable Heusler alloys in selective hydrogenation of alkynes: A new potential for old materials

Heusler alloys (X₂YZ) are well-established intermetallic compound materials in various fields because their function can be precisely adjusted by elemental substitution (e.g., X₂YZ_1-xZ′x). Although intermetallic compound catalysts started attracting attention recently, catalysis researchers are not familiar with Heusler alloys. We report their potential as novel catalysts focusing on the selective hydrogenation of alkynes. We found that Co₂MnGe and Co₂FeGe alloys have great alkene selectivity. Mutual substitution of Mn and Fe (Co₂Mn_xFe_1-xGe) enhanced the reaction rate without changing selectivity. The substitution of Ga for Ge decreased the selectivity but increased the reaction rate monotonically with Ga composition. Elucidation of these mechanisms revealed that the fine tuning of catalytic properties is possible in Heusler alloys by separately using ligand and ensemble effects of elemental substitution.