The dissociative adsorption of hydrogen on Pt(111): actuation and acceleration by atomic defects.
The dissociative adsorption of hydrogen on Pt(111): actuation and acceleration by atomic defects.
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氢在 Pt(111) 上的解离吸附：原子缺陷的驱动和加速。
DOI：
10.1063/1.3530286
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
G. Comşa
中科院分区：
文献类型：
--
作者：
B. Poelsema;K. Lenz;G. Comşa
氢原子在原子表面缺陷处的解离即使不是决定性的，也是最终导致氢原子化学吸附在Pt（111）上的事件链中的主要步骤。这适用于气相分子的垂直动能从8到60 meV，即，涵盖与氢化反应相关的范围。在本研究中，我们以可控的方式可逆地改变了同一晶体上的缺陷密度，从而获得了这种见解。信息已来自测量的吸附动力学作为覆盖的函数。两个不同的吸附通道进行区分。第一，间接的，普遍存在于较低的H-覆盖，并涉及捕获到一个非容纳的分子前体状态，然后在步骤网站的解离，如我们最近的论文中所描述的。第二个，占主导地位，在较高的覆盖率和不可忽略的缺陷密度，服从二级朗缪尔动力学。在此，解离吸附直接发生在具有0.24个晶胞的横截面的台阶部位（初始粘附概率为台阶密度的24%）。这些结果与热程序脱附数据一致：直接通道是导致热脱附谱中低温峰出现的原因，通常用β（1）表示，而间接通道则用β（2）状态表示。这两个通道对氢动能垂直分量的依赖性明显不同：间接通道表现出指数为1.9 ± 0.1的幂律行为，而直接通道则完全不表现出垂直能量依赖性。
The dissociation of hydrogen at atomic surface defects is the strongly dominant, if not the decisive, step in the chain of events eventually leading to chemisorbed H-atoms on Pt(111). This holds for perpendicular kinetic energies of the gas phase molecules from 8 to 60 meV, i.e., covering the range relevant to hydrogenation reactions. This insight has been gained in the present study in which we reversibly varied the defect density on one and the same crystal in a controlled way. Information has been derived from measuring the adsorption kinetics as a function of coverage. Two distinct adsorption channels are distinguished. The first, indirect one, prevails at lower H-coverage and involves capture into a non-accommodated molecular precursor state followed by dissociation at step sites as described in our recent paper. The second one, dominant at higher coverage and non-negligible defect densities, obeys second order Langmuir kinetics. Here the dissociative adsorption takes place directly at step sites with a cross section of 0.24 unit cells (initial sticking probability 24% of the step density). These results are consistent with thermally programmed desorption data: the direct channel is responsible for the emergence of the low temperature peak in thermal desorption spectroscopy, usually denoted with β(1), while the indirect channel is represented by the β(2) state. The dependence on the perpendicular component of the hydrogen kinetic energy is distinctly different for the two channels: the indirect one shows power law behavior with an exponent 1.9 ± 0.1, while the direct one shows no perpendicular energy dependence at all.
DOI：
10.1073/pnas.82.20.6723
发表时间：
1985-01-01
影响因子：
11.1
作者：
YANG, WT;PARR, RG
通讯作者：
PARR, RG