(617fm) Comparison of Metal-Support Interaction on Pd/α-Fe2O3 Nanorod and Pd/α-Fe2-XMnxO3 nanorod Catalysts
Chao Wang, Emily Freeman, Jochen Lauterbach*
Department of Chemical Engineering, University of South Carolina, Columbia, SC, 29208, U.S.A.
Iron oxide supported Pd catalysts have been studied as model systems for the effect of strong metalâ??support interaction (SMSI) in CO oxidation [1-2]. Such interaction can lead to electron transfer from Pd to Fe2O3, oxygen transfer from Fe2O3 to reduced Pd during reaction, or formation of encapsulated Pd structures. Doping a secondary metal into a metal oxide support can greatly improve CO oxidation activity, which has been reported for Pd-Ce based system , while such effects are rarely investigated in Pd-Fe systems. The metal-support interaction of Pd and doped iron oxide is not yet understood. The surface structure and exposed crystal planes of metal oxide support, on the other hand, can also affect catalytic activity . To gain a better understanding on the SMSI of Pd-Fe system, the interface of Pd and Fe based supports need to be well controlled and are expected to be identical in the catalysts.
In this study, we synthesized Pd supported on Î±-Fe2O3 nanorods and Mn doped Î±-Fe2O3 nanorods with well controlled morphology and surface structure. CO oxidation was used as a probe reaction to evaluate structure-activity relationships. Pd/Î±-Fe2O3 nanorod shows almost 100% CO conversion at 150oC, but zero conversion at 75oC. With Mn doping into Î±-Fe2O3, Pd/Î±-Fe2-xMnxO3 nanorod shows much higher activity at lower temperature and achieves almost 100% CO conversion at 75oC. Detailed catalysts surface structure will be studied by high resolution transmission electron microscopy (HRTEM) to evaluate exposed facets of Fe and Fe-Mn supports, Pd particle size and structure. Electronic structure and oxidation state of Pd are characterized by X-ray photoelectron spectroscopy (XPS). The low temperature redox property and reaction mechanism are studied by temperature-programmed reduction (TPR), CO-O2 pulse reaction and in-situ diffuse reflectance IR Fourier transform spectroscopy (DRIFTs) to give a more comprehensive understanding on metal-support interaction.
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