Methane oxidation on Pd(111):: In situ XPS identification of active phase
Methane oxidation on Pd(111):: In situ XPS identification of active phase
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DOI：
10.1021/jp068404m
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发表时间：
2007-06-07
影响因子：
3.7
通讯作者：
Zemlyanov, Dmitry
中科院分区：
文献类型：
--
作者：
Gabasch, Harald;Hayek, Konrad;Zemlyanov, Dmitry
通过原位 XPS 研究了在 0.33 mbar 反应混合物中加热和冷却过程中 CH4 和 O-2 (1:5) 之间的反应。在加热过程中，反应速率在 650 K 时表现出最大活性，而在随后的冷却过程中没有发现最大活性。这种动力学滞后归因于光谱观察到的表面氧化态差异。在加热过程中，在 Pd5O4 二维氧化物覆盖表面中块状 PdO 晶种的稳定范围内，反应速率接近 650 K 最大值。另一方面，在冷却过程中没有形成 PdO 晶种，很可能是由于 PdO 在含氧量低于 Pd5O4 的钝化表面氧化物层上成核的动力学限制。
The reaction between CH4 and O-2 (1:5) was studied by in situ XPS during heating and cooling in a 0.33 mbar reaction mixture. During heating, the reaction rate exhibited an activity maximum at 650 K, whereas no activity maximum was found during the subsequent cooling ramp. This kinetic hysteresis was assigned to the spectroscopically observed difference in the surface oxidation state. During heating, the reaction rate approached the 650 K maximum in the stability range of bulk PdO seeds among the otherwise Pd5O4 2D oxide covered surface. On the other hand, no PdO seeds were formed during cooling, most likely due to kinetic limitations of PdO nucleation on a passivating surface oxide layer containing less oxygen than Pd5O4.