High Pressure Carbon Monoxide Oxidation over Platinum (111)
High Pressure Carbon Monoxide Oxidation over Platinum (111)
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DOI：
10.1021/jp401867g
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发表时间：
2013-05-16
影响因子：
3.7
通讯作者：
Over, H.
中科院分区：
文献类型：
--
作者：
Farkas, A.;Zalewska-Wierzbicka, K.;Over, H.
利用红外光谱和原位表面x射线衍射来跟踪催化剂表面的实际结构和化学性质，在毫巴范围内的CO和O-2压力下原位研究了Pt（111）薄膜上CO氧化的动力学。用电容式计和四极杆质谱仪分别在线监测混合气体的总压和反应气体的组成。在过量O-2的温和氧化反应条件下，初始反应由覆盖CO和O混合覆盖层的Pt（111）表面催化，反应温度范围为626 ~ 750 K，表观活化能为45 kJ/mol。如果正在进行的反应使CO含量部分减少，使气态反应混合物变成强氧化反应混合物，则催化活性提高一个数量级。根据原位红外光谱，这种活性态的特征是表面CO覆盖很小，而根据原位SXRD，表面结构被分配为氧化和化学吸附的O覆盖Pt（111）的混合物。表观活化能约为0 kJ/mol，表明活性相中传质受限。
The kinetics of the CO oxidation over a Pt(111) thin film was studied in situ under CO and O-2 pressures in the millibar range, using infrared spectroscopy and in situ surface X-ray diffraction to follow the actual structural and chemical nature of the catalyst surface. The total pressure of the gas mixture and the composition of the reacting gases were monitored online with a capacitive gauge and a quadrupole mass spectrometer, respectively. Under mildly oxidizing reaction conditions with excess O-2, the initial reaction is catalyzed by a Pt(111) surface, which is covered by mixed CO and O overlayer revealing an apparent activation energy 45 kJ/mol in the temperature range 626-750 K. If the CO content is partially depleted by the ongoing reaction so that the gaseous reaction mixture turns into a strongly oxidizing one, the catalytic activity increased by an order of magnitude. This active state is characterized by a vanishingly small surface CO coverage according to in situ RAIRS, while the surface structure is assigned to a mixtures of an oxidic and chemisorbed O covered Pt(111) on the basis of in situ SXRD. An apparent activation energy of about 0 kJ/mol point toward mass transfer limitation in the active phase.