Reaction mechanism of preferential oxidation of carbon monoxide on Pt, Fe, and Pt-Fe/mordenite catalysts
Reaction mechanism of preferential oxidation of carbon monoxide on Pt, Fe, and Pt-Fe/mordenite catalysts
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DOI：
10.1016/j.jcat.2005.09.026
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发表时间：
2005-12
影响因子：
7.3
通讯作者：
M. Kotobuki;A. Watanabe;H. Uchida;H. Yamashita;Masahiro Watanabe
中科院分区：
文献类型：
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作者：
M. Kotobuki;A. Watanabe;H. Uchida;H. Yamashita;Masahiro Watanabe
我们研究了一氧化碳在铂/丝光沸石(Pt/M)、铁/丝光沸石(Fe/M)和铂-铁/丝光沸石(Pt-Fe/M)上的优先氧化(PROX)反应，以提纯重整产物以供聚合物电解质燃料电池(PEFC)使用。即使在50∼°C下，PT-Fe/M仍表现出显著的PROX活性，达到极高的空速(即约100%的选择性，SV=105h−1)，尽管铂/M和Fe/M的PREX活性可以忽略不计。CO、H_2和O_2的化学吸附测量表明，在CO和/或H_2的吸附中，铂中心起到了吸附中心的作用，而Fe(主要是FeO)中心只对O_2起到了吸附作用，因此，即使在CO/H_2过剩的气流中，Fe的加入也能为PROX反应保留O_2吸附中心。Pt/M和Fe/M的反应活性较差，这是由于缺乏对CO和/或O2的吸附，而这是朗缪尔-辛谢尔伍德机理所必需的。我们提出了所谓的“双功能机理”，即铂中心作为CO吸附中心，而Fe中心作为O2解离-吸附中心，增强了相邻中心上反应物之间的表面反应。
We have investigated the preferential oxidation (PROX) of carbon monoxide at Pt/mordenite (Pt/M), Fe/mordenite (Fe/M), and Pt–Fe/mordenite (Pt–Fe/M) for a purification of reformates to supply polymer electrolyte fuel cells (PEFCs). Pt–Fe/M exhibited remarkable PROX activity up to an extremely high space velocity (i.e., ca. 100% selectivity, SV=∼105h−1) even at 50 °C, although Pt/M and Fe/M had negligibly small PROX activity. CO, H2, and O2chemisorption measurements demonstrated that Pt sites act as adsorption sites for CO and/or H2and Fe (dominantly FeO) sites only for O2, so that the addition of Fe to Pt/M can preserve O2adsorption sites for the PROX reaction even in CO/excess H2gas flow. The poor reactivity of Pt/M and Fe/M can be ascribed to the lack of CO and/or O2adsorption as the essential requisite for the Langmuir–Hinshelwood mechanism. We propose the so-called “bifunctional mechanism” for the distinctive performance at Pt–Fe/M, where the Pt site acts as a CO adsorption site and the Fe site acts as an O2dissociative-adsorption site and enhances the surface reaction between the reactants on the neighboring sites.