N8 stabilized single-atom Pd for highly selective hydrogenation of acetylene
N8 stabilized single-atom Pd for highly selective hydrogenation of acetylene
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DOI：
10.1016/j.jcat.2020.12.009
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发表时间：
2021-03
影响因子：
7.3
通讯作者：
Maocong Hu;Zhiyi Wu;Z. Yao;Joshua Young;L. Luo;Yingge Du;Chongmin Wang;Z. Iqbal;Xianqin Wang-Xianqin
中科院分区：
文献类型：
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作者：
Maocong Hu;Zhiyi Wu;Z. Yao;Joshua Young;L. Luo;Yingge Du;Chongmin Wang;Z. Iqbal;Xianqin Wang-Xianqin
单原子催化剂在许多反应中显示出良好的应用前景，但仍面临着合成简单、稳定性好等诸多挑战。本文采用循环伏安法合成了一种负载于N8路易斯碱物种上的单原子钯催化剂（Pd 1-N8/CNT）。该催化剂在40 °C乙炔选择加氢反应中表现出较长的稳定性和较高的C2 H4选择性。在NaN 3溶液中，以PdO/CNT为工作电极，在三电极装置中进行了循环伏安（CV）. HAADF-STEM证实单原子Pd位点被成功分离。XPS测量和Bader电荷计算表明，在CV处理后，N8有效地合成在CNT衬底上，而单原子Pd通过附着到N8的末端N而稳定。乙炔程序升温脱附（C2 H2-TPD）和密度泛函理论（DFT）计算表明，C2 H2更倾向于在单个Pd原子上形成π键，而H2则在Pd旁边的N原子上解离，而不是在Pd上解离.协同效应有利于C2 H4的形成，但阻止乙炔完全氢化为C2 H6。这一工作为设计和合成具有孤立单原子位置的更高选择性的催化剂开辟了新的视角。
Single-atom catalysts show a promising future in many reactions even though great challenges still remain such as facile synthesis and long stability. In this work, a single-atom Pd catalyst attached to a designed N8Lewis base species (Pd1-N8/CNT) is synthesized with cyclic voltammetry (CV) method. The catalyst demonstrates long stability and enhanced C2H4selectivity in selective hydrogenation of acetylene at 40 °C. CV is carried out in a three-electrode setup with PdO/CNT as the working electrode in NaN3solution. HAADF-STEM confirms single-atom Pd sites are successfully isolated. XPS measurements and Bader charge calculations indicate N8is effectively synthesized on CNT substrate after CV treatment while single-atom Pd is stabilized by attaching to the end N of N8. Acetylene-temperature programed desorption (C2H2-TPD) and density functional theory (DFT) calculations suggest C2H2favors the π bonding on single Pd atom, while H2dissociates on the N atom (next to Pd) instead of conventionally on Pd. The synergistic effect favors C2H4formation but prevents full hydrogenation of acetylene to C2H6. This work opens up a new perspective to design and synthesize more selective catalysts with isolated single-atom sites.