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.

冷却性能和泵浦速率的改进；角分辨热脱附装置中的样品晶体被成功地从90K冷却到50K，泵浦速率提高了约5倍，并且足以将背景信号水平降低到五分之一。 .N_2O 在干净的 Rh(110) 上分解；N_2O 在 60 K 时已分解，并在 70-170 范围内产生五个 N_2 解吸峰K. β_1-N_2 峰值在 165 K 左右，显示出余弦分布，表明 N_2O 解离后，β_2-N_2 峰值出现在表面，β_ 3-N_2 峰值出现在 120K。这些峰值出现在较高的 N_2O 暴露下。并在 [001] 方向上与平面内的表面法线成 68 度准直。另一方面，在少量 N_2O 暴露下观察到 β_4-N_2 和 β_5-N_2 均与表面法线成 68 度进入 [001] 方向。N_2 解吸对残留表面氧的量敏感。选择预热温度，预热温度低于1000 K时，N_2O不分解。1100 K预热后， N_2O 在 100-170 K 时分解，沿 [001] 方向以约 30 度准直发射 N_2，LEED 观察到 30 度组件被认为是在斜坡上形成的。利用近边X射线吸收精细结构在70 K下研究了Rh(110)上吸附的N_2O的取向。在低N_2O暴露下，N_2O在70 K时部分解离，在较高的N_2O覆盖率下，提出了两种吸附形式：站立式和卧式。对Pd(110)的N_2O分解和吸附也得到了类似的结果。