Acetylene hydrogenation catalyzed by bare and Ni doped CeO 2 (110): the role of frustrated Lewis pairs
Acetylene hydrogenation catalyzed by bare and Ni doped CeO 2 (110): the role of frustrated Lewis pairs
复制标题
裸CeO 2 (110)和Ni掺杂CeO 2 (110)催化乙炔加氢：受抑路易斯对的作用
DOI：
10.1039/d2cp00925k
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发表时间：
2022
影响因子：
3.3
通讯作者：
Guo, Hua
中科院分区：
文献类型：
--
作者：
Zhou, Shulan;Wan, Qiang;Lin, Sen;Guo, Hua
近年来，氧化铈（CeO_2）被发现具有催化炔选择加氢的活性，这引起了人们对可还原氧化物催化机理的广泛讨论。本工作采用密度泛函理论（DFT）研究了H2在CeO 2（110）表面和Ni掺杂CeO 2（110）表面上的解离和乙炔加氢反应。与CeO 2（111）表面类似，氧化物表面氧空位（Ovs）形成的阻挫刘易斯对（FLP）促进了催化作用.在CeO_2（110）上，（CeO 2（110）-Ov），两个表面Ce阳离子与一个不相邻的O阴离子形成而对于具有一个（Ni-CeO 2（110）-Ov）或两个（Ni-CeO 2（110）-2Ov）Ov的Ni掺杂CeO 2（110）表面，发现一个Ce和一个不相邻的O反离子形成单Ce/O FLP。DFT计算表明，Ce/O FLP通过异分解机制促进H2解离，而产生的表面O-H和Ce-H物种催化随后的乙炔加氢。对于CeO 2（110）-Ov和Ni-CeO 2（110）-2 Ov，我们的DFT计算表明第一步氢化是速率决定步骤，势垒分别为0.43和0.40 eV。对于Ni-CeO 2（110）-Ov，反应受H2解离控制，势垒为0.41 eV.这些势垒显著低于CeO 2（111）上的势垒（约0.7 eV），解释了实验观察到的二氧化铈（110）面的更高催化效率。速率控制步骤的变化归因于Ce/O FLP中Ce的不同电子性质-更接近费米能级的Ce f态不仅有利于H2的异裂解离，而且导致乙炔氢化的更高势垒。
Ceria (CeO2) has recently been found to catalyze the selective hydrogenation of alkynes, which has stimulated much discussion on the catalytic mechanism on various facets of reducible oxides. In this work, H2 dissociation and acetylene hydrogenation on bare and Ni doped CeO2(110) surfaces are investigated using density functional theory (DFT). Similar to that on the CeO2(111) surface, our results suggest that catalysis is facilitated by frustrated Lewis pairs (FLPs) formed by oxygen vacancies (Ovs) on the oxide surfaces. On bare CeO2(110) with a single Ov (CeO2(110)–Ov), two surface Ce cations with one non-adjacent O anion are shown to form (Ce3+–Ce4+)/O quasi-FLPs, while for the Ni doped CeO2(110) surface with one (Ni–CeO2(110)–Ov) or two (Ni–CeO2(110)–2Ov) Ovs, one Ce and a non-adjacent O counterions are found to form a mono-Ce/O FLP. DFT calculations indicate that Ce/O FLPs facilitate the H2 dissociation via a heterolytic mechanism, while the resulting surface O–H and Ce–H species catalyze the subsequent acetylene hydrogenation. With CeO2(110)–Ov and Ni–CeO2(110)–2Ov, our DFT calculations suggest that the first hydrogenation step is the rate-determining step with a barrier of 0.43 and 0.40 eV, respectively. For Ni–CeO2(110)–Ov, the reaction is shown to be controlled by the H2 dissociation with a barrier of 0.41 eV. These barriers are significantly lower than that (about 0.7 eV) on CeO2(111), explaining the experimentally observed higher catalytic efficiency of the (110) facet of ceria. The change of the rate-determining step is attributed to the different electronic properties of Ce in the Ce/O FLPs – the Ce f states closer to the Fermi level not only facilitate the heterolytic dissociation of H2 but also lead to a higher barrier of acetylene hydrogenation.