【作者】 王斌；

【导师】 路春美；

【作者基本信息】 山东大学 ， 动力工程及工程热物理， 2022， 硕士

【摘要】 近年来,我国挥发性有机物(VOCs)排放量居高不下,严重危害国民的身心健康。催化燃烧技术是遏制其污染的最高效手段之一,其核心是研制高活性、高稳定性的催化剂。异质界面为催化剂提供了新的物理化学性质,由其引入的缺陷结构直接影响催化剂的结构、活性和反应路径。因此,本论文以设计新型异质界面催化剂为目标,研究纳米复合“AB2O4@MOx“催化剂的高效构建方法,及其中的温度依赖酸性位点效应;随后,以异质界面结构为载体,负载贵金属Pd2+单原子,实现强金属-载体相互作用,成功研制出高活性异质界面VOCs(甲苯和丙烷)催化燃烧催化剂。取得的创新性研究成果如下:层状双金属氢氧化物(LDHs)衍生非贵金属催化剂的异质界面效应研究:LDHs前驱体中二价和三价金属阳离子均匀分布的性质,研制合成了非贵金属纳米复合“AB2O4@MOx”催化剂,实现尖晶石(AB2O4)和氧化物(MOx)在纳米尺度上的结合。实验结果表明:具有宽广异质界面的“AB2O4@MOx”催化剂的活性和反应速率明显高于物理混合的“AB2O4+MOx”催化剂。界面附近出现了严重的晶格条纹模糊和晶格畸变,这表明强界面相互作用有利于缺陷结构的产生,从而增强其催化反应活性。非贵金属催化剂异质界面的优化效应研究:“AB2O4@MOx”催化剂中Co离子被选择性地掺杂到AB2O4晶格中,占据A、B位,但其中的MOx物种并没有受到任何影响。A、B位中的Co离子在200℃下,显著富集了 Bronsted酸位,催化剂表面对于丙烷的吸附能力增强;在350℃下,削弱了 Cu-O键,促进了氧空位的产生并且富集了 Lewis酸位。同时Co离子还能显著降低氧空位的形成能,掺杂的Co离子与原始阳离子之间的离子半径差异导致AB2O4相的晶格畸变,促进了缺陷结构的形成。酸刻蚀诱导的贵金属催化剂的异质界面效应研究:利用酸刻蚀方法成功合成了贵金属“AB2O4@MOx”异质结构催化剂。Pd2+单原子被锚定在AB2O4和MOx的晶格中,其嵌入促进了氧空位的产生。电子能量损失谱表明:对比界面处和AB2O4晶相,界面处存在着具有更高活动性的冗余配位氧,有利于VOCs的深度氧化;对比界面处和MOx晶相,界面处存在着丰富的氧空位,有利于气相O2的吸附和解离,从而提升VOCs催化燃烧的低温性能。贵金属催化剂异质界面的构效机制与反应路径研究:Pd2+单原子与“AB2O4@MOx”载体间存在着强金属-载体相互作用。异质界面促进了扭曲PdiO4的产生,该构型可在室温下被CO还原为Pd1O3,随后可活化气相O2形成Pd1O5,从而在室温下实现对CO的高效催化燃烧;异质界面的原生氧空位降低了 Pd2+单原子的氧配位数,诱导了Pd1O3的形成;扭曲Pd1O4、Pd1O3和Pd1O5提高了“AB2O4@MOx”载体的晶格氧活动性,从而实现了对甲苯的高效催化燃烧。更多还原

【Abstract】 In recent years,the emission of volatile organic compounds(VOCs)in China has remained high,which causes damage to human health,and the catalytic combustion technology is one of the most efficient means to curb its pollution.The core of the catalytic combustion is the design of catalysts with high activity and high stability.Heterostructured interfaces provide catalysts with new physicochemical properties,at which the defect structures directly affect the structure,activity,and reaction pathways of catalysts.Therefore,this thesis aimed to design novel catalysts with heterostructured interface.We investigated efficient synthesis methods for the nanohybrid "AB2O4@MOx" catalysts and the effect of temperature-dependent acid site.Subsequently,the strong metal-support interaction was achieved by using the heterostructured interface as a carrier and supporting Pd2+single atom.Based on this,we successfully developed the highly active catalysts with heterostructured interface for the catalytic VOCs(toluene and propane)combustion.The results obtained are as follows:Effect of heterostructured interface of the LDHs-derived non-noble metal catalysts:Based on the uniform distribution of divalent and trivalent metal cations in the layered double hydroxides(LDHs)layers,we synthesized nanohybrid "AB2O4@MOx" catalysts(non-noble metal),realizing the spinel(AB2O4)and oxide(MOx)combined on the nanoscale.The activity and reaction rates of the "AB2O4@MOx"catalysts with a broad interface were significantly higher than those of the physically mixed"AB2O4+MOx"catalysts.Severe lattice fringe blurring and lattice distortion appeared near the interface,which indicated that the strong interfacial interaction was favorable for the generation of defect structures,thus increasing the catalytic activity.Optimization effect of heterostructured interface of the non-noble metal catalysts:Co cations were selectively doped into the AB2O4 lattice and occupied the A and B sites,but the MOx species of the"AB2O4@MOx" catalyst were not affected in this process.The main effects of A&B-sites Co were as follows:At 200℃,the Br?nsted acid sites were significantly enriched,and the adsorption capacity of the catalyst surface for propane was enhanced;At 350℃,the Cu-O bond was weakened,which promoted the generation of oxygen vacancies and enriched Lewis acid sites.At the same time,the formation energy of oxygen vacancies was significantly reduced.In addition,the difference in ionic radius between the doped Co cations and the original cations led to lattice distortion of the AB2O4 phase,which promoted the formation of defect structures.Effect of heterostructured interface of the noble metal catalysts prepared by acid etching method:"AB2O4@MOx" catalysts(noble metal)were synthesized by an acid etching method.The Pd2+single atoms were anchored on the lattice of AB2O4 and MOx,and its anchoring promoted the generation of oxygen vacancies.The electron energy loss spectrum showed that:comparing the interface with the AB2O4 phase,there was redundant coordination oxygen at the interface,and the redundant coordination oxygen possessed higher lattice oxygen activity,which was beneficial to the deep oxidation of VOCs;compared with MOx species,there were abundant oxygen vacancies at the interface,which was conducive to the adsorption and dissociation of gas-phase O2,thereby improving the low-temperature performance of the catalytic VOCs combustion.Structure-activity mechanism and reaction routes of heterostructured interface of the noble metal catalysts:There was a strong metal-support interaction between the Pd2+ single atoms and "AB2O4@MOx" support:the interface promoted the generation of distorted Pd1O4,which could be reduced to Pd1O3 at room temperature.Pd1O3 could then activate gas-phase O2 to form PdiO5,thereby achieving efficient catalytic combustion of CO at room temperature;the native oxygen vacancies on the support reduced the oxygen coordination number of Pd2+single atoms,inducing the formation of Pd1O3;the distorted Pd1O4,Pd1O3,and Pd1O5 enhanced the lattice oxygen mobility of the "AB2O4@MOx" support,thereby realizing the efficient catalytic combustion of toluene.更多还原