Active Site Dependent Reaction Mechanism over Ru/CeO2 Catalyst toward CO2 Methanation
Active Site Dependent Reaction Mechanism over Ru/CeO2 Catalyst toward CO2 Methanation
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Ru/CeO2 催化剂 CO2 甲烷化的活性位点依赖性反应机制
DOI：
10.1021/jacs.6b02762
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发表时间：
2016-05-18
影响因子：
15
通讯作者：
Duan, Xue
中科院分区：
文献类型：
--
作者：
Wang, Fei;He, Shan;Duan, Xue
金属氧化物表面的氧空位是一种重要的缺陷，在各种催化反应中起着活性位点的作用。本文采用operando光谱方法，分别对Ru/CeO2 （CeO2中有氧空位）和Ru/ α - al2o3（无氧空位）催化的CO2甲烷化反应进行了研究，以期深入了解活性位点依赖的反应机理。在Ru/CeO2催化剂中，利用XANES、IR和Raman等方法揭示了Ce3+、表面羟基和氧空位在实际反应条件下的生成过程及其结构演变。稳态同位素瞬态动力学分析（SSITKA）型原位漂移红外光谱无疑证实了CO2甲烷化在Ru/CeO2催化剂上经历甲酸路线，而氧空位催化甲酸解离成甲醇是决定速率的步骤。相比之下，在Ru/ α - al2o3中，CO2甲烷化在没有氧空位的情况下经过Ru表面的CO路线，证明了活性位点依赖于CO2甲烷化的催化机制。此外，Ru/CeO2催化剂的催化活性评价和振荡反应进一步证明，在Ru/ α - al2o3（125℃vs 250℃）中，氧空位催化速率决定步骤的活化温度比Ru表面低得多。
Oxygen vacancy on the surface of metal oxides is one of the most important defects which acts as the reactive site in a variety of catalytic reactions. In this work, operando spectroscopy methodology was employed to study the CO2 methanation reaction catalyzed by Ru/CeO2 (with oxygen vacancy in CeO2) and Ru/alpha-Al2O3 (without oxygen vacancy), respectively, so as to give a thorough understanding on active site dependent reaction mechanism. In Ru/CeO2 catalyst, operando XANES, IR, and Raman were used to reveal the generation process of Ce3+, surface hydroxyl, and oxygen vacancy as well as their structural evolvements under practical reaction conditions. The steady-state isotope transient kinetic analysis (SSITKA)-type in situ DRIFT infrared spectroscopy undoubtedly substantiates that CO2 methanation undergoes formate route over Ru/CeO2 catalyst, and the formate dissociation to methanol catalyzed by oxygen vacancy is the rate-determining step. In contrast, CO2 methanation undergoes CO route over Ru surface in Ru/alpha-Al2O3 with the absence of oxygen vacancy, demonstrating active site dependent catalytic mechanism toward CO2 methanation. In addition, the catalytic activity evaluation and the oscillating reaction over Ru/CeO2 catalyst further prove that the oxygen vacancy catalyzes the rate -determining step with a much lower activation temperature compared with Ru surface in Ru/alpha-Al2O3 (125 vs 250 degrees C).