Yao Xinlong, Ji Yi, Huang Zheng-Qing, Zhao Zhenchao, Gao Pan, Guo Meiling, Liu Xuebin, Meng Caixia, Fu Qiang, Chang Chun-Ran, Bao Xinhe, Hou Guangjin
State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
J Am Chem Soc. 2024 Sep 4;146(35):24609-24618. doi: 10.1021/jacs.4c08258. Epub 2024 Aug 23.
Dihydrogen complexes, which retain the H-H bond, have been extensively studied in molecular science and found to be prevalent in homogeneous and enzymatic catalysis. However, their counterparts in heterogeneous catalysis, specifically nondissociative chemisorbed dihydrogen binding on the catalyst surface, are rarely reported experimentally. This scarcity is due to the complexity of typical material surfaces and the lack of effective characterization techniques to prove and distinguish various dihydrogen binding modes. Herein, using high-pressure operando solid-state NMR technology, we report the first unambiguous experimental observation of activated dihydrogen binding on a reduced ceria catalyst through interactions with surface oxygen vacancies. By employing versatile NMR structural and dynamical analysis methods, we establish a proportional relationship between the degree of ceria surface reduction and dihydrogen binding, as evidenced by NMR observations of H-D through-bond coupling (), relaxation, and proton isotropic chemical shifts. NMR analysis further reveals the participation of bound dihydrogen species in a room-temperature ethylene hydrogenation reaction. The remarkable similarities between surface-activated dihydrogen in heterogeneous catalysis and dihydrogen model molecular complexes can provide valuable insights into the hydrogenation mechanism for many other solid catalysts, potentially enhancing hydrogen utilization.
保留H-H键的二氢配合物在分子科学中已得到广泛研究，并发现其在均相催化和酶催化中普遍存在。然而，它们在多相催化中的对应物，特别是催化剂表面上非解离化学吸附的二氢结合，很少有实验报道。这种稀缺性是由于典型材料表面的复杂性以及缺乏有效的表征技术来证明和区分各种二氢结合模式。在此，我们使用高压原位固态核磁共振技术，首次明确地通过与表面氧空位的相互作用，实验观察到还原氧化铈催化剂上活化的二氢结合。通过采用通用的核磁共振结构和动力学分析方法，我们建立了氧化铈表面还原程度与二氢结合之间的比例关系，这通过H-D通过键耦合（）、弛豫和质子各向同性化学位移的核磁共振观察得到证明。核磁共振分析进一步揭示了结合的二氢物种参与室温乙烯加氢反应。多相催化中表面活化的二氢与二氢模型分子配合物之间的显著相似性，可以为许多其他固体催化剂的加氢机理提供有价值的见解，可能提高氢的利用率。
