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Peculiar nitrogen desorption on rhodium surfaces and the decomposition mechanism of nitrogen oxides

铑表面特殊的氮脱附及氮氧化物的分解机理

基本信息

批准号：
13640493
负责人：
MATSUSHIMA Tatsuo
金额：
$ 0.51万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640493/
关键词：
nitrogen oxide rhodium catalyst product desorption process nitrous oxide decomposition inclined desorption nitrogen desorption angular distribution of desorption 窒素酸化物分解機構

项目摘要

Improvements of cooling performance and pumping rates ; A sample crystal in the angle-resolved thermal desorption apparatus was successfully improved to be cooled from 90K to 50K. The pumping rate was increased about 5 times and high enough to reduce the background signal level to one fifth.N_2O decomposition on clean Rh(110) ; N_2O is already decomposed from 60 K and yields five N_2 desorption peaks in the range of 70-170 K. β_1-N_2 peaking at around 165 K shows a cosine distribution, indicating desorption from N_2 trapped once on the surface after N_2O dissociation. Β_2-N_2 peaked at 140 K and β_ 3-N_2 at 120K. These peaks appeared at higher N_2O exposures and collimate at 68 degrees from the surface normal in the plane in the [001] direction. On the other hand, both β_4-N_2 and β_5-N_2 were observed at small N_2O exposures. These collimate 68 degrees off the surface normal into the [001] direction.N_2 desorption is sensitive to the amount of residual surface oxygen. The amount was controlled by selecting pre-heating temperature, N_2O is not decomposed when the pre-heating is below 1000 K. After the pre-heating at 1100 K, N_2O is decomposed at 100-170 K, emitting N_2 collimated at around 30 degrees along the [001] direction. A (1x2) missing-row structure was observed by LEED. The 30 degree component was proposed to be formed on declining terraces on the missing-row structure.The orientation of adsorbed N_2O on Rh(110) was examined at 70 K by near-edge X-ray absorption fine structure. N_2O is partly dissociated at 70 K at low N_2O exposures. At higher N_2O coverage, two adsorption forms, standing and lying, were proposed.Similar results were obtained on Pd(110) for N_2O decomposition and adsorption.

改进冷却性能和泵送速率；在角分辨热解吸装置中，成功地将样品晶体从90K冷却到50K。泵送速率提高了约5倍，高到足以将背景信号电平降低到1 / 5。N_2O在清洁Rh（110）上的分解；N_2O在60 K时已经分解，在70 ~ 170 K范围内产生了5个N_2解吸峰。β_1-N_2在165 K附近的峰呈余弦分布，表明N_2O解离后被捕获在表面的N_2发生了解吸。Β_2-N_2在140k时达到峰值，β_ 3-N_2在120K时达到峰值。这些峰出现在较高的N_2O暴露下，并在平面上与表面法线呈68度的方向准直[001]。另一方面，在少量的N_2O暴露下，β_4-N_2和β_5-N_2同时存在。这些从表面法线向[001]方向准直68度。n2脱附对表面氧残留量敏感。通过选择预热温度控制N_2O的用量，当预热低于1000k时，N_2O不会分解。1100 K预热后，N_2O在100-170 K分解，沿[001]方向准直30度左右发射出N_2。LEED观察到（1x2）缺行结构。建议在失行结构的下降梯田上形成30度分量。在70 K下，用近边x射线吸收精细结构检测了吸附在Rh（110）上的N_2O的取向。在低N_2O暴露下，N_2O在70k时部分解离。在较高的N_2O覆盖率下，提出了两种吸附形式：站立和躺卧。Pd（110）对N_2O的分解和吸附也得到了类似的结果。