The electronic structure, surface properties, and in situ N2O decomposition of mechanochemically synthesised LaMnO3.
The electronic structure, surface properties, and in situ N2O decomposition of mechanochemically synthesised LaMnO3.
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DOI：
10.1039/d0cp00793e
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发表时间：
2020-06
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通讯作者：
Rachel H Blackmore;M. E. Rivas;George F Tierney;K. Mohammed;Donato Decarolis;S. Hayama;F. Venturini;G. Held;Rosa Arrigo;M. Amboage;Pip Hellier;Evan W. Lynch;M. Amri;M. Casavola;Tugce Eralp Erden;P. Collier;P. Wells
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作者：
Rachel H Blackmore;M. E. Rivas;George F Tierney;K. Mohammed;Donato Decarolis;S. Hayama;F. Venturini;G. Held;Rosa Arrigo;M. Amboage;Pip Hellier;Evan W. Lynch;M. Amri;M. Casavola;Tugce Eralp Erden;P. Collier;P. Wells
使用机械力化学来制备催化材料是非常有意义的；它提供了一种对环境无害的、无溶剂的路线，并产生了高度复杂的混合非晶相和晶相的结构。研究了球磨气氛对机械化学法制备LaMnO_3的影响及其对N2O分解反应的催化性能。本工作采用高能量分辨荧光检测(HERFD)、X射线近边结构吸收谱(XANES)、X射线发射光谱和X射线光电子能谱(XPS)等手段对机械化学法制备的材料的电子结构性质进行了研究。此外，还进行了利用近环境压力(NAP)-XPS在催化过程中跟踪材料的原位研究，以及模拟制备条件的高压能量弥散EXAFS研究。研究表明，空气和Ar球磨样品之间有明显的差异，其中最显著的变化是用NAP-XPS观察到的。XPS结果发现，在Ar中制备的样品的活性吸附氧物种水平增加，这与表面氧化物空位的存在有关。此外，与空气球磨和溶胶凝胶法合成的LaMnO相比，Ar球磨的LaMnO在较低的温度下表现出更好的催化脱氮活性。用原位NAP-XPS对Ar球磨LaMnO脱除N2O过程中的催化行为进行了评估，结果表明，在室温下，N2O在O1s区域内的相互作用增加。这项研究进一步证明了机械化学制备材料的复杂性，以及如何通过仔细选择表征方法来了解它们的特性。
The use of mechanochemistry to prepare catalytic materials is of significant interest; it offers an environmentally beneficial, solvent-free, route and produces highly complex structures of mixed amorphous and crystalline phases. This study reports on the effect of milling atmosphere, either air or argon, on mechanochemically prepared LaMnO3 and the catalytic performance towards N2O decomposition (deN2O). In this work, high energy resolution fluorescence detection (HERFD), X-ray absorption near edge structure (XANES), X-ray emission, and X-ray photoelectron spectroscopy (XPS) have been used to probe the electronic structural properties of the mechanochemically prepared materials. Moreover, in situ studies using near ambient pressure (NAP)-XPS, to follow the materials during catalysis, and high pressure energy dispersive EXAFS studies, to mimic the preparation conditions, have also been performed. The studies show that there are clear differences between the air and argon milled samples, with the most pronounced changes observed using NAP-XPS. The XPS results find increased levels of active adsorbed oxygen species, linked to the presence of surface oxide vacancies, for the sample prepared in argon. Furthermore, the argon milled LaMnO3 shows improved catalytic activity towards deN2O at lower temperatures compared to the air milled and sol-gel synthesised LaMnO3. Assessing this improved catalytic behaviour during deN2O of argon milled LaMnO3 by in situ NAP-XPS suggests increased interaction of N2O at room temperature within the O 1s region. This study further demonstrates the complexity of mechanochemically prepared materials and through careful choice of characterisation methods how their properties can be understood.