Distorted Surface Ensembles in Platinum-Antimony for the Durable Catalytic Dehydrogenation of Methylcyclohexane.

Geometric and electronic effects are particularly pronounced when catalyzing small molecules, which require small active-metal ensembles. Researchers have been intensively focused on the alloy catalysis of small molecules. However, when large molecules are catalyzed, large active-metal ensembles are preferable to small active-metal ensembles. The catalysis with large ensembles in alloys proceeds more efficiently than that with pure metals because of the geometric and electronic effects of diluent metals. However, it is difficult to significantly improve the catalytic performance because of the limited changes in the geometric and electronic features in active-metal-rich compositions. Thus, we employed distorted active-metal ensembles, which are expected to have unique adsorptivity/reactivity for large molecules. We found that the unique crystal structure of PtSb showed distorted Pt ensembles shaped as isosceles triangles, which differ from the standard Pt ensembles shaped as regular triangles. We used methylcyclohexane dehydrogenation as a proof-of-concept reaction, which shows that the feature of Pt ensembles is crucial for catalytic performance. Theoretical and experimental results revealed that the distorted Pt@PtSb catalyst effectively suppressed the side reactions and exhibited considerably higher durability than the standard Pt ensembles, represented by the Pt@PtSn catalyst, highlighting the importance of the Pt shape.