Tang Yu, Wei Yuechang, Wang Ziyun, Zhang Shiran, Li Yuting, Nguyen Luan, Li Yixiao, Zhou Yan, Shen Wenjie, Tao Franklin Feng, Hu Peijun
Institute of Molecular Catalysis and In Situ/Operando Studies, State Key Laboratory of Photocatalysis on Energy and Environment, and College of Chemistry , Fuzhou University , Fuzhou 350116 , China.
Department of Chemical and Petroleum Engineering , University of Kansas , Lawrence , Kansas 66045 , United States.
J Am Chem Soc. 2019 May 8;141(18):7283-7293. doi: 10.1021/jacs.8b10910. Epub 2019 Apr 25.
Heterogeneous catalysis performs on specific sites of a catalyst surface even if specific sites of many catalysts during catalysis could not be identified readily. Design of a catalyst by managing catalytic sites on an atomic scale is significant for tuning catalytic performance and offering high activity and selectivity at a relatively low temperature. Here, we report a synergy effect of two sets of single-atom sites (Ni and Ru) anchored on the surface of a CeO nanorod, CeNiRuO. The surface of this catalyst, CeNiRuO, consists of two sets of single-atom sites which are highly active for reforming CH using CO with a turnover rate of producing 73.6 H molecules on each site per second at 560 °C. Selectivity for producing H at this temperature is 98.5%. The single-atom sites Ni and Ru anchored on the CeO surface of CeNiRuO remain singly dispersed and in a cationic state during catalysis up to 600 °C. The two sets of single-atom sites play a synergistic role, evidenced by lower apparent activation barrier and higher turnover rate for production of H and CO on CeNiRuO in contrast to CeNiO with only Ni single-atom sites and CeRuO with only Ru single-atom sites. Computational studies suggest a molecular mechanism for the observed synergy effects, which originate at (1) the different roles of Ni and Ru sites in terms of activations of CH to form CO on a Ni site and dissociation of CO to CO on a Ru site, respectively and (2) the sequential role in terms of first forming H atoms through activation of CH on a Ni site and then coupling of H atoms to form H on a Ru site. These synergistic effects of the two sets of single-atom sites on the same surface demonstrated a new method for designing a catalyst with high activity and selectivity at a relatively low temperature.
多相催化作用发生在催化剂表面的特定位点上，即便在催化过程中许多催化剂的特定位点难以轻易识别。通过在原子尺度上管理催化位点来设计催化剂，对于调节催化性能以及在相对较低温度下提供高活性和选择性具有重要意义。在此，我们报道了锚定在CeO纳米棒表面的两组单原子位点（Ni和Ru），即CeNiRuO的协同效应。这种催化剂CeNiRuO的表面由两组单原子位点组成，它们对于使用CO重整CH具有高活性，在560℃时每个位点每秒产生73.6个H分子的周转速率。在此温度下产生H的选择性为98.5%。锚定在CeNiRuO的CeO表面上的单原子位点Ni和Ru在高达600℃的催化过程中保持单分散且呈阳离子状态。与仅具有Ni单原子位点的CeNiO和仅具有Ru单原子位点的CeRuO相比，这两组单原子位点发挥协同作用，这通过CeNiRuO上产生H和CO的较低表观活化能垒和较高周转速率得以证明。计算研究表明了所观察到的协同效应的分子机制，其源于：（1）Ni和Ru位点在CH活化方面的不同作用，即在Ni位点上形成CO以及在Ru位点上使CO分解为CO，以及（2）在通过在Ni位点上活化CH首先形成H原子，然后在Ru位点上使H原子偶联形成H方面的顺序作用。同一表面上这两组单原子位点的这些协同效应展示了一种在相对较低温度下设计具有高活性和选择性催化剂的新方法。
