The Synthesis Of Platinum Catalytic Material Preparation And Catalytic Mechanism Of First Principles

The synthesis and catalytic performance of Pt/Al2O3catalyst are studied by the first principle density functional theory method.The starting reactant of synthetic Pt/Al2O3catalyst is Al and Pt, which become the intermetallic compound or solid solution by melting, and then dusting, milling and finally heat-treated. The content of Pt is3wt%. Regardless of the reactants is intermetallic compound or solid solution, the Al or Pt atom is bonded with O atoms to form oxidation in the reaction. The stability and formation is compared by calculated the thermodynamic properties of several alloys, by drawn the initial steps of the reaction. Then there is calculated the oxide of Al and Pt by the first principle, and gotten the information of energy, electron distribution, population, and bonding character between the different oxide. The results show that Al atoms more easily combine O atoms to form oxide than Pt atoms. The thermodynamic properties that gained by the crystals’phonon nature in Al-Pt-0system which is calculated by the first principle, and then resulted the ground state free energy variation with temperature. The results show that the AlxPty alloy, α-Al2O3, part of PtxOy and Pt can be stable at room temperature; there the most stable is a-Al2O3at low temperatures. The final product is Pt, and α-Al2O3or γ-Al2O3by calculating the energy of varieties of alloys and AlxOy, PtxOy while do not consider the experiment of uncontrollable reasons. We use the CASTEP module in Materials Studio to calculate the model of Pt on Al2O3(100)-(111) grain boundary in order to understand to precipitate Pt. The results show the energy of the system is minimum while Pt atoms in the position of the grain boundary, and the diffusion activation energy of Pt atoms diffused from Al2O3(100) to the grain boundary lower than from Al2O3(111) by used LTS/QST. The theoretical calculations of this paper is basal consistent with the analysis of phase and micro structure of the prepared Pt/Al2O3catalyst by SEM and XRD.Pt is a good car exhaust catalysts, with excellent catalytic CO oxidation. To simulate the CO oxidation reaction on Pt low index surfaces, we considere the adsorption behavior of O2and CO molecules on the Pt surface.We contrast the adsorption energy between O2and CO on the different adsorbed sites of Pt (100),(110),(111) surface. The results show the adsorption energy of O2in the three surface are negative so the reaction is exothermic, as well as CO on Pt (100) and (110) surface, while the reaction of CO on Pt (111) surface is endothermic. Compared to the two kinds of gas adsorbed can be seen that O-is more easily absorbed than CO. Therefore, the oxidation of CO on Pt surface should be the first step that O2adsorbed to the Pt (100),(110),(111) surface so O-O bond is activated, afterward CO react with activated O to CO2. Finally we find the three surface catalytic CO oxidation as follows:Pt(110)>Pt(100)>Pt (111).