Mechanism of ammonia formation on Rh(111) studied by dispersive near-edge X-ray absorption fine structure spectroscopy
Mechanism of ammonia formation on Rh(111) studied by dispersive near-edge X-ray absorption fine structure spectroscopy
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DOI：
10.1021/jp906833v
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发表时间：
2010-01
影响因子：
3.7
通讯作者：
M. Nagasaka;H. Kondoh;K. Amemiya;I. Nakai;T. Shimada;Reona Yokota;T. Ohta
中科院分区：
文献类型：
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作者：
M. Nagasaka;H. Kondoh;K. Amemiya;I. Nakai;T. Shimada;Reona Yokota;T. Ohta
用色散近边X射线吸收精细结构(色散-NEXAFS)谱研究了Rh(111)面上氨气生成的反应机理。氮气包覆的Rh(111)表面在恒定的表面温度(330−390K)下暴露于气态氢气(1.0−5.0×10−7Torr)中，生成的氨气立即从表面解吸出来。氮K边NEXAFS光谱的连续数据采集使我们能够监测反应过程中表面物种的覆盖率变化。N和NH的标准谱之和很好地再现了NEXAFS谱。我们发现，作为稳定中间体的NH物种不仅可以加氢生成NH3，而且在缺氢条件下还可以分解为N和H。反应级数分析表明，NH分解发生在NH的二维岛的外围，而NH3的生成很可能发生在整个NH岛上。我们建议采取两步反应……
The reaction mechanism of ammonia formation on a Rh(111) surface was investigated by means of dispersive near-edge X-ray absorption fine structure (dispersive-NEXAFS) spectroscopy. Nitrogen-covered Rh(111) surfaces were exposed to gaseous hydrogen (1.0−5.0 × 10−7 Torr) at constant surface temperatures (330−390 K) to form ammonia which desorbs immediately from the surface. Continuous data acquisition of nitrogen K-edge NEXAFS spectra enables us to monitor coverage changes of surface species during the progress of the reaction. The obtained NEXAFS spectra were well reproduced by summation of the standard spectra for N and NH. We found that the NH species, which is considered as a stable intermediate, is not only hydrogenized to NH3, but also decomposed into N and H under H2-lacking conditions. The reaction-order analyses indicate that the NH decomposition occurs at periphery of 2-dimensional islands of NH while the NH3 formation takes place most likely over the entire NH islands. We propose a two-step react...