Durability and activity of Co2YZ (Y = Mn or Fe, Z = Ga or Ge) Heusler alloy catalysts for dehydrogenation of 2-propanol

Abstract

As a group of ternary intermetallic compounds, Heusler alloys (X₂YZ) can be unique catalysts. Heusler alloys are suitable as a platform to reveal common rules for catalysis by intermetallic compounds because the catalytic properties of various X₂YZ compounds, including partially substituted alloys (e.g., X₂YZ_1−xZ′_x), can be investigated under the same crystal structure. Previous studies on Heusler alloys have reported that the irreversible oxidation of catalysts occurs during the reaction with O₂ and H₂O and that their activity for alkyne hydrogenation does not correlate with the d-band center. For the use of Heusler alloys as a platform to discuss catalytic properties in association with electronic structures of intermetallic states, durability against oxidation should be revealed, and the correlation between the activity and d-band center should be verified. In this study, Co₂YZ (Y = Mn or Fe, Z = Ga or Ge) Heusler alloy catalysts for the dehydrogenation of 2-propanol were investigated. The oxygen atom in 2-propanol molecules and tiny amounts of O₂ and H₂O impurities in liquidous reagents were suitable as mild oxidants to evaluate the durability limit: Co₂FeGe was durable, whereas Mn and Ga were oxidized. The initial activity correlated with the d-band center. These findings are beneficial for the future use of Heusler alloys not only as a platform but also for practical catalysts.