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Investigation on Surface Catalytic Mechanism and Bulk Oxygen Transport Rpoperties Based on SrCoO3-δ

Author: HouFeiFan
Tutor: Lv
School: Harbin Institute of Technology
Course: Condensed Matter Physics
Keywords: Density functional theory Geometry optimization Molecular Dynamics Transition state search SrCoO3-δ
CLC: TM911.4
Type: Master's thesis
Year: 2011
Downloads: 30
Quote: 0
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Abstract


SrCoO 3-δ -based perovskite oxide material is an important class of functional materials, and - electronic hybrid due to its having ion conductivity, and was originally used as oxygen permeable membrane material. The the cubic phase SrCoO 3-δ exhibit a high ion - electronic mixing conductance and therefore a large number of research SrCoO 3-δ base material substitution of the A sites or B sites in order to improve its structure stability and electrochemical properties. In recent years, alternative through the A bit and the B bit portion SrCoO 3-δ -based perovskite oxides (of Ba 0.5 Sr 0.5 ) (Co. 0.8 Fe 0.2 ) the O 3-δ (BSCF) As the solid oxide fuel cell (SOFC) the application of the cathode material also become the hot research field. This article is based on density functional theory (DFT), using the first principles calculations to study SrCoO 3-δ -based oxygen catalytic mechanism of the cathode surface and bulk oxygen transport properties. First, build a low index (100), (110) plane and study the stability of the surface thereof, the results showed that the (110) plane and unstable due to the presence of large polarization. Further, by the oxygen in the (110) surface adsorption optimization calculations to determine the best adsorption sites. Secondly, the use of molecular dynamics of oxygen containing the defect 1 × 1,2 × 1 (110) surface adsorption dissociation process, the result showed that the 2 × 1 (110) plane surface of the adsorption process of dissociation almost no barrier, The adsorption process is chemical adsorption, and 1 × 1 (110) surface adsorption dissociation process there is a big barrier, transition state of the solution of the oxygen molecules from the. In addition, the 1 × 1 (110) of the adsorption process, the population analysis, and detailed exposition of the oxygen from the adsorbent, dissociation into the oxygen vacancy of the charge-transfer mechanism. On the other hand, namely the use of Ba Fe partially replace SrCoO 3-δ the supercell in A bit and B site ions build three equivalent (Ba 0.5 Sr 0.5 ) (Co 0.75 Fe 0.25 ) O 3-δ model. Further three models were constructed equivalent and non-equivalent oxygen vacancies calculated bulk oxygen vacancy formation energy, and summarizes the changes in the law, and analyzes the reasons. Finally, the transition state search neighbor oxygen vacancy diffusion into the the lattice oxygen after Ba-Sr-Co/Fe formation of triangular faces, given the diffusion process of the transition state barrier from the mark size and electronic structure the angle explained partial lattice expansion and posture barrier transition. The calculations show that the oxygen diffusion barrier with neighboring oxygen vacancy formation, around the lattice oxygen is not equivalent to the oxygen vacancies, the lattice oxygen diffusion exist direction selectivity. Completely disordered distribution of cations and oxygen vacancies macro does not exhibit this characteristic.

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