本文選題：密度泛函理論　切入點(diǎn)：WO_3　出處：《天津理工大學(xué)》2017年碩士論文

【摘要】：隨著工業(yè)自動(dòng)化的迅速發(fā)展,我們對(duì)傳統(tǒng)燃料的需求日益提高。燃燒廢氣中的氮氧化物一直以來(lái)對(duì)自然環(huán)境和動(dòng)植物都有著很大的危害。為了能科學(xué)治理廢氣排放和有效檢測(cè)廢氣濃度,氣體檢測(cè)器應(yīng)運(yùn)而生,它們的基本原理是:通過(guò)把氣體分子在檢測(cè)器表面吸附時(shí)所引發(fā)的一系列物理化學(xué)變化轉(zhuǎn)變?yōu)殡娦盘?hào),從而直觀的表示出氣體濃度的變化。但是由于吸附反應(yīng)十分迅速,實(shí)驗(yàn)結(jié)果常常無(wú)法從微觀角度揭示吸附反應(yīng)歷程。本課題以密度泛函理論為基礎(chǔ),運(yùn)用計(jì)算軟件模擬研究NO和NO_2分子在WO_3表面的吸附反應(yīng)機(jī)理。通過(guò)完整地研究氣體分子在不同吸附位點(diǎn)上的吸附平衡結(jié)構(gòu)和電子轉(zhuǎn)移情況,來(lái)揭示NO和NO_2分子在WO_3表面上的吸附反應(yīng)機(jī)理。通過(guò)搜索過(guò)渡態(tài)和描繪反應(yīng)路徑能量變化,我們深入研究NO分子在WO_3表面的催化氧化過(guò)程,以期用理論結(jié)果指明實(shí)驗(yàn)研究方向,理論研究成果如下:1.模擬研究NO分子在WO_3(001)方向的兩種不同切面上的吸附情況,在不同切面上同時(shí)考慮了氧缺陷對(duì)于吸附的影響。吸附能的結(jié)果表示出NO在以鎢氧原子為切面的WO_3表面吸附效果最好;氧缺陷的存在增加了WO_3對(duì)于NO氣體的敏感性。在以鎢氧原子為切面的WO_3表面上,有氧缺陷的表面比完美表面多轉(zhuǎn)移0.24e。2.模擬研究NO_2分子在WO_3(001)方向的兩種不同切面上的吸附情況。在以氧原子為切面的WO_3表面,橋位氧原子會(huì)與NO_2分子發(fā)生反應(yīng),生成類硝酸鹽。在以鎢氧原子為切面的WO_3表面,NO_2分子的一個(gè)氧原子會(huì)填補(bǔ)到氧缺陷位上,剩余的NO分子則吸附在五配位的鎢原子上。NO_2在不同切面的吸附反應(yīng)中會(huì)引起WO_3表面的電阻升高。3.模擬研究NO分子在以鎢氧原子為切面的WO_3(001)表面上的催化氧化反應(yīng)。計(jì)算結(jié)果表明,在NO分子高覆蓋度的情況下,NO分子傾向于和WO_3表面的晶格氧原子發(fā)生反應(yīng)并產(chǎn)生吸附態(tài)的NO_2,這會(huì)導(dǎo)致WO_3出現(xiàn)氧缺陷;而在低覆蓋度的情況下,氧分子吸附在WO_3表面上解離為氧原子,NO分子會(huì)與吸附態(tài)的氧原子發(fā)生反應(yīng)。所以NO分子的覆蓋度高低會(huì)影響反應(yīng)歷程。
[Abstract]:With the rapid development of industrial automation, Our demand for traditional fuels is increasing. Nitrogen oxides in burning exhaust gas have always been a great hazard to the natural environment, animals and plants. Gas detectors emerge as the times require. Their basic principle is to convert a series of physical and chemical changes caused by the adsorption of gas molecules on the surface of the detector into electrical signals. But because the adsorption reaction is very rapid, the experimental results often can not reveal the adsorption reaction process from the microscopic point of view. This topic is based on density functional theory. The adsorption mechanism of no and NO_2 molecules on the surface of WO_3 was studied by computer simulation. The adsorption equilibrium structure and electron transfer of gas molecules at different adsorption sites were studied. By searching the transition state and describing the energy change of the reaction path, we studied the catalytic oxidation process of no molecule on the surface of WO_3, with a view to pointing out the experimental research direction with the theoretical results. The theoretical research results are as follows: 1. Simulating the adsorption of no molecules on two different tangent planes in the WO _ 3C _ (001) direction, At the same time, the effect of oxygen defect on adsorption was considered on different surface. The adsorption energy showed that no adsorbed best on the surface of WO_3 with tungsten oxygen atom as the tangent plane. The presence of oxygen defects increases the sensitivity of WO_3 to no gas. On the surface of WO_3 with tungsten oxygen atoms as the tangent plane, The surface of oxygen defect transfers 0.24e.2. the adsorption of NO_2 molecules on two different sections in the direction of WO _ 3 / 001) is simulated. On the surface of WO_3 with oxygen atom as the plane, the oxygen atom at the bridge will react with the NO_2 molecule. The formation of nitrate-like nitrates. An oxygen atom of the NOS2 molecule on the surface of WO_3 with tungsten oxygen atoms as the cut will fill in the oxygen defect site. The remaining no molecules were adsorbed on five-coordinated tungsten atoms. NOS2 could cause the resistance of WO_3 surface to increase in different surface adsorption. 3. The catalytic oxidation reaction of no molecules on the WO _ 3T _ (001) surface with tungsten oxygen atom as the tangent plane was studied by simulation. The results of the calculation show that. No molecules tend to react with lattice oxygen atoms on the surface of WO_3 and produce adsorbed no _ 2 under the condition of high coverage of no molecules, which will lead to oxygen defects in WO_3, while in the case of low coverage, The oxygen molecule adsorbed on the surface of WO_3 is dissociated that the no molecule will react with the oxygen atom in the adsorbed state, so the coverage of no molecule will affect the reaction process.
【學(xué)位授予單位】：天津理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O647.31

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