A RAIRS, TPD and femtosecond laser-induced desorption study of CO, NO and coadsorbed CO + NO on Pd(111)
A RAIRS, TPD and femtosecond laser-induced desorption study of CO, NO and coadsorbed CO + NO on Pd(111)
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DOI：
10.1039/c6ra13722a
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发表时间：
2016-07
期刊：
影响因子：
3.9
通讯作者：
J. Butorac;Emma Wilson;H. Fielding;W. A. Brown;R. Minns
中科院分区：
文献类型：
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作者：
J. Butorac;Emma Wilson;H. Fielding;W. A. Brown;R. Minns
在这里，我们提出了一个系统的研究CO， NO和CO + NO的吸附和激光诱导解吸Pd（111）表面在许多不同的覆盖。我们首先使用反射-吸收红外光谱（RAIRS）和温度程序解吸（TPD）来表征表面。实验表明，NO对预吸附的CO有明显的置换作用，但CO对预吸附的NO的影响要小得多。在这两种情况下，CO的首选结合位点被NO占据，将其取代到不太有利的吸附位点。飞秒激光诱导解吸（fs-LID）表明，Pd（111）上CO的解吸遵循幂律，与CO的覆盖度无关，但Pd（111）上的NO在高覆盖度时明显偏离幂律曲线，出现饱和现象。这说明NO的LID截面远大于CO， NO在Pd（111）上的光活性高于CO在Pd（111）上的光活性。有趣的是，对于Pd（111）上的CO + NO，我们发现共吸附对光脱附过程有很强的影响，并且无论两个分子的给药顺序如何，上覆层的结构对控制光脱附产物也很重要。
Here we present a systematic study of the adsorption and laser induced desorption of CO, NO and CO + NO from a Pd(111) surface at a number of different coverages. We begin by characterising the surfaces using reflection–absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD). Experiments show that NO displaces pre-adsorbed CO considerably, but that CO has a much smaller effect on pre-adsorbed NO. In both cases, the preferred binding sites of CO are occupied by NO, displacing it to less favourable adsorption sites. Femtosecond laser induced desorption (fs-LID) shows that desorption of CO on Pd(111) follows a power law and is fairly independent of CO coverage, but for NO on Pd(111) we observe a clear deviation from a power law curve at higher coverages, with saturation being observed. This suggests that the cross-section for LID of NO is much larger than that for CO and that NO on Pd(111) is more photoactive than CO on Pd(111). Interestingly, for CO + NO on Pd(111) we find that coadsorption has a strong influence on the photodesorption process and that the structure of the overlayer is also important in controlling the photodesorption products, regardless of the order in which the two molecules are dosed.