Identification of a Pt3Co Surface Intermetallic Alloy in Pt–Co Propane Dehydrogenation Catalysts

By L. G. Cesar, Ce Yang, Zheng Lu, Yang Ren, Guanghui Zhang, Jeffrey T. Miller. ACS Catalysis, 2019

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Bimetallic Pt–Co nanoparticles (NPs) were prepared and characterized by scanning transmission electron microscopy, in situ X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction, and catalytic conversion for propane dehydrogenation with and without added H2. In addition, the surface extended X-ray absorption fine structure (EXAFS) obtained by fitting the difference spectrum between the fully reduced and room-temperature-oxidized catalysts suggest that the surface structure remains Pt3Co, although the core changes from Pt to Pt3Co and to PtCo. At low Co loading, the bimetallic nanoparticles form a Pt3Co intermetallic surface alloy with Pt-rich core. With increasing Co loading, a full alloy forms where both the surface and NP compositions are Pt3Co. A further increase in Co loading leads to a Co-rich NP core, likely PtCo, with a surface of Pt3Co. Although Pt–Co intermetallic alloys form two different phases and several morphologies, the surface structures are similar in all catalysts. Although...

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