Structure of activated complex of CO2 formation in a CO + O2 reaction on Pd(110) and Pd(111).
Structure of activated complex of CO2 formation in a CO + O2 reaction on Pd(110) and Pd(111).
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DOI：
10.1021/jp0518456
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发表时间：
2005-08
期刊：
影响因子：
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通讯作者：
K. Nakao;S. Ito;K. Tomishige;K. Kunimori
中科院分区：
文献类型：
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作者：
K. Nakao;S. Ito;K. Tomishige;K. Kunimori
使用红外（IR）化学发光进行稳态CO氧化反应过程中形成的CO2的检查。使用分子束方法在Pd（110）和Pd（111）上形成CO2。在各种分压条件下，CO2形成速率是温度依赖性的。最大形成速率的温度表示为TSmax。在高于TSmax的表面温度下的红外发射光谱分析表明，Pd（111）的平均振动温度（TVAV）高于Pd（110）。反对称振动温度（TVAS）在两个表面上几乎相等。这些结果表明，活化的CO2络合物在Pd（111）上更弯曲，在Pd（110）上更直。此外，TVAV值的差异是小的表面温度小于TSmax。TVAS值在两个表面上均远高于TVAV。只有当表面温度低于TSmax时才能观察到这些现象：它们在较低温度下变得更加明显，这表明活化的CO2形成络合物在两个Pd表面上比在较高表面温度下观察到的更直。结合动力学结果，在较低的表面温度下，较高的CO覆盖率被推断为与CO2形成的线性活化复合物有关。
Examinations of CO2 formed during steady-state CO oxidation reactions were performed using infrared (IR) chemiluminescence. The CO2 was formed using a molecular-beam method over Pd(110) and Pd(111). The CO2 formation rate is temperature dependent under various partial pressure conditions. The temperature of the maximum formation rate is denoted as TSmax. Analyses of IR emission spectra at surface temperatures higher than TSmax showed that the average vibrational temperature (TVAV) is higher for Pd(111) than for Pd(110). The antisymmetric vibrational temperature (TVAS) is almost equal on both surfaces. These results suggest that the activated CO2 complex is more bent on Pd(111) and straighter on Pd(110). Furthermore, the difference in the TVAV value was small for surface temperatures less than TSmax. The TVAS value was much higher than TVAV on both surfaces. These phenomena were observed only when the surface temperature was lower than TSmax: they became more pronounced at lower temperatures, suggesting that the activated complex of CO2 formation is much straighter on both Pd surfaces than that observed at higher surface temperatures. Combined with kinetic results, the higher CO coverage at the lower surface temperatures is inferred to be related to the linear activated complex of CO2 formation.