Selective Catalytic Behavior Induced by Crystal-Phase Transformation in Well-Defined Bimetallic Pt-Sn Nanocrystals |
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| Authors: | Baraa Werghi Liheng Wu Amani M. Ebrahim Miaofang Chi Haoyang Ni Matteo Cargnello Simon R. Bare |
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| Affiliation: | 1. Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025 USA;2. Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025 USA Department of Chemical Engineering, Stanford University, Stanford, CA, 94305 USA;3. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, 5200, 1 Bethel Valley Rd, Oak Ridge, TN, 37830 USA;4. Department of Chemical Engineering, Stanford University, Stanford, CA, 94305 USA |
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| Abstract: | The Pt-Sn bimetallic system is a much studied and commercially used catalyst for propane dehydrogenation. The traditionally prepared catalyst, however, suffers from inhomogeneity and phase separation of the active Pt–Sn phase. Colloidal chemistry offers a route for the synthesis of Pt–Sn bimetallic nanoparticles (NPs) in a systematic, well-defined, tailored fashion over conventional methods. Here, the successful synthesis of well-defined ≈2 nm Pt, PtSn, and Pt3Sn nanocrystals with distinct crystallographic phases is reported; hexagonal close packing (hcp) PtSn and fcc Pt3Sn show different activity and stability depending on the hydrogen-rich or poor environment in the feed. Moreover, face centred cubic (fcc) Pt3Sn/Al2O3, which exhibited the highest stability compared to hcp PtSn, shows a unique phase transformation from an fcc phase to an L12-ordered superlattice. Contrary to PtSn, H2 cofeeding has no effect on the Pt3Sn deactivation rate. The results reveal structural dependency of the probe reaction, propane dehydrogenation, and provide a fundamental understanding of the structure−performance relationship on emerging bimetallic systems. |
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| Keywords: | bimetallic alloys dehydrogenation dynamics nanocrystals operando structure and size control |
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