The Synthesis And The Reaction Of CO Oxidation Over The Supported Pt/Fe₂O₃Catalyst

The low-temperature CO catalytic oxidation is one of the most attractive researchtopics in the field of catalysis in recent years. Supported noble metal catalysts haveexcellent catalytic performance in CO oxidation. Especially, supported gold catalystscould complete oxidize CO to CO2at room temperature or even below zero.However, the poor stability of supported gold catalysts during the reaction processlimited its application. The supported platinum catalysts show a higher stabilitywhereas the low-temperature activity of these catalysts is relatively poor and thecomplete oxidation of CO is usually achieved at a higher reaction temperature.In previous work, a series of supported platinum catalysts was prepared by acolloid deposition method. The Pt/Fe₂O₃catalyst showed high activity for COoxidation and stability at room temperature. With this background, the influence ofvarious parameters was systematically investigated on the Pt NPs particle size. Theformation process of the Pt NPs was also studied. Based on the results ofphysicochemical characterizations （i.e., TEM, XRD, XPS and TPR）, the structureand redox property of the Pt/Fe₂O₃catalysts were combined with the catalyticactivities to evaluate and understand the relevant literature of the nature of activecenter and the mechanism of CO oxidation over the Pt/Fe₂O₃catalysts. The mainresearch contents and results are showed as follows:1. The influence of various parameters on platinum particle sizeThe Pt particles with various particle sizes could be effectively prepared in thenanoscale by changing the concentration of H2PtCl6as well as the volume ratio ofEG/H₂O in the solution. The process of formation of platinum colloid wasinvestigated by the UV-vis. A mechanism for the formation of Pt NPs may beproposed. First, the coordination of EG with Pt species was formed in the EG solution. When a certain amount of NaOH was added into the solution, ahydroxide-chloride exchange should happen. The Pt⁴⁺species was reduced to Pt⁰at88℃by some EG species. As the presence of H₂O in alkaline solution, the H₂Owould coordinate with Pt species and the Pt complexes were not very stable andeasily reduced By EG species. Then, the relatively larger Pt particles were obtained,indicating the nucleation of platinum seems not to proceed rapidly, but the nucleargrowth occurs in the solution, resulting in a larger particle size of Pt.2. The nature of the active center and catalytic mechanism CO oxidation overthe Pt/Fe₂O₃catalystsA series of Pt/Fe₂O₃catalysts （i.e., Pt/Fe₂O₃-a, Pt/Fe₂O₃-b and Pt/Fe₂O₃-c） wasprepared by a colloid deposition route, to investigate the structure of catalyst activesites and the mechanism of CO oxidation. Pt/Fe₂O₃-b exhibited relatively highcatalytic activity and stability, which could completely oxidize CO even at roomtemperature. A systematical study of supported Pt catalysts by means of transmissionelectron microscopy, X-ray photoelectron spectroscopy, temperature programmedreduction, time-resolved CO titration and in-situ DRIFT spectra is reported. Thestructure of platinum-support interface （i.e., Pt-O-Fe） was relatively easily formedover the Pt/Fe₂O₃-b catalyst, which displayed high activity for CO oxidation at lowtemperature. Furthermore, the interaction （i.e., Pt-O-Fe） may also play a crucial rolein activating the oxygen species and weakening the intensity of CO-Pt bond at lowtemperature，showing excellent catalytic activity in CO oxidation at low temperature.