Density Functional Theory Study The Rare Earth Perovskite Of Xinjiang In The Application Of Vehicle Exhaust Purfication

In this paper,through the investigation of a large number of literatures,and collecting the main rare earth production of geological data and resource data in the Xinjiang region,confirmed that the literature contained in Xinjiang has rich rare earth resources.The rare earth was known as “industrial vitamins” and was widely used in various industries because of its special structure extends more features.Especially in environmental governance,it had a lot of advantages compared with the mineral materials.Air pollution has always been the focus of attention,in recent years,there have been a wide range of haze weather in the most cities in China.The cause of haze was largely due to the growing air pollution caused by the increased emissions of locomotives,which had become an imminent task.Relying on the abundant rare earth mineral resources of Xinjiang to study the treatment of atmospheric pollution of rare earth perovskite catalyst was not only had excellent geographical advantages,but also had the right time to meet the current needs.Therefore,taking into account the above-mentioned problems to be solved and the realistic conditions with rich material basis,using the rare earth perovskite,which be prepared by using the rare earth of Xinjiang as the main mineral raw material,as the research object,and making the simulation software Materials Studio,which be researched and developed by using the density functional theory as the core theory,as the research tool.Firstly,the crystal model of rare earth perovskite LaCoO₃ was established in software.Subsequently,the crystal structure parameters and microelectronic properties were calculated by software investigation to clarify its basic properties.Then,in order to study the impact of the O,La and Co elements of LaCoO₃ of the electronic for NO,Which had the name of "the largest cancer in air pollution",on the LaCoO₃?0 0 1?surface,we designed and calculated the adsorption configuration of NO on two kinds terminal face of the LaCoO₃?0 0 1?surface.Finally,we determined and calculated the reaction path of NO on rare earth perovskite LaCoO₃,and analyzed the calculated results to explore the reaction mechanism of NO and interface.The results of the calculation and analysis can provide some theoretical basis and experiment forecasting for preparing the rare earth perovskite catalysts,which be used to purify the exhaust of locomotives.The main conclusions are as follows:?1?The unit cell parameters of LaCoO₃ calculated by GGA-PBEsol-DN were a = 5.453 ?,Co-O = 1.933 ?,which was the closest to the experimental value,and the deviation was only 0.2%.The band structure,the total density and the density states show that when the energy at-6 eV⁰ eV,the Co atoms interact with the O atoms,and reflect the 3d state of Co and the covalent nature of the 2p state of O.It was found that the Co atoms were located on the octahedral center of the perovskite structure.Such structural properties will cause the 3d electron orbit of Co atom to be split into t2 g and eg orbit,where the eg orbit interacts with the electron orbit of O to change the electron density of Co-O,resulted the bonding orbit and the antibonding orbit of the Co-O of in the LaCoO₃ be impact,then caused the Co-O bond changes.Finally,La-5p and O-2s were found to have covalent interactions with the O-2s,but were relatively weak.This part calculates the crystal structure parameters of LaCoO₃ and the interaction between the electron orbits of the atoms in the structure.?2?The adsorption configuration of NO on the CoO₂ and La O terminal of LaCoO₃ was simulated by the GGA-PBE method,then,we used these configurations to calculate the adsorption properties of NO.From the calculated data of the adsorption energy,the Mulliken and Hirshfeid charges and the project density of sates of the atoms,it was found that the adsorption of NO on the CoO₂ terminal surface was stronger than that of the La O terminal surface,and the N atom of NO was adsorbed on the Co atom of CoO₂-terminal of LaCoO₃ was the most stable form of adsorption,and the project density of sates map shows that the effect of atom Co on LaCoO₃ was excellent for adsorption of NO,derived from Co-3d electron orbit O-2p electron orbit appeared hybridization phenomenon.Consolidate all the results,NO can be adsorbed on the CoO₂ terminal LaCoO₃?0 0 1?surface to form a variety of more stable forms,and proved that LaCoO₃ had a more active contribution to adsorb NO.?3?NO on the rare earth perovskite LaCoO₃ reaction process can be divided into two forms: one was the oxidation,the best reaction path for NO was O₂ ? O^* + O^* ? NO + O^* ? NO₂^* ? NO₂ + O^* ? NO₃^*,the key step of the formation rate of NO₃^* was O₂ decomposition.The completion of this step requires overcome activation barrier of 10.96 eV,and the larger energy barrier directly restricts the product of the rate of production and the progress of the reaction.The second form was reduction,and the best reaction path was NO + NO ? NOON^* ? N₂O^* ? N₂O ? O₂ + N₂.The rate-controlling step for N₂ + O₂ formation was the formation of N₂O,and the energy barrier which needs to be overcome were 0.13 eV,1.27 eV and 0.79 eV in this process.These values indicate that the minimum energy required for the reaction was relatively small.When comparing two results,we found that the minimum energy required for the oxidation of NO was slightly larger than the minimum energy required for NO reduction,which means that NO was more easily reduced during the reaction process on the LaCoO₃ catalyst,and the selectivity of reduction was stronger.