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Bimetallic Ru-Co Clusters derived from Confined Alloying process within Zeolite-imidazolate Frameworks for Efficient NH3 Decomposition and Synthesis Jian Yang, Dongsheng He, Wenxing Chen, Wei Zhu, Hui Zhang, Shan Ren, Xin Wang, Qinghua Yang, Yuen Wu, and Yadong Li ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b14134 • Publication Date (Web): 20 Oct 2017 Downloaded from http://pubs.acs.org on October 22, 2017
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ACS Applied Materials & Interfaces
Bimetallic Ru-Co Clusters derived from Confined Alloying process within Zeolite-imidazolate Frameworks for Efficient NH3 Decomposition and Synthesis Jian Yang,† Dongsheng He, § Wenxing Chen, ‡ Wei Zhu, ‡ Hui Zhang, ‡ Shan Ren, ‡ Xin Wang, † Qinghua Yang, † Yuen Wu,*,† and Yadong Li*,‡ †
Center of Advanced Nanocatalysis (CAN-USTC), University of Science and Technology of China, Hefei, Anhui 230026 (China) ‡
Department of Chemistry and Collaborative Innovation Center for Nanomaterial Science and Engineering, Tsinghua University, Beijing 100084, China
§
Materials Characterization and Preparation Center (MCPC), Southern University of Science and Technology of China, Shenzhen, Guangdong 518055, China
‡
Key Laboratory of Oil and Gas Field Applied Chemistry of Sichuan Province, the Center of New Energy Materials and Technology, College of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu, 610500, China
Keywords: RuCo clusters, Ru clusters, NH3 decomposition and synthesis, confinement effect, Ru3(CO)12. ABSTRACT: Herein, a series of carbocatalysts containing Ru–based clusters have been prepared by the assistance of zeolite-imidazolate frameworks (ZIFs). The introduction of Ru is based on the adsorption of well-defined Ru3(CO)12 within the cavity of ZIFs and following decomposition at 900 °C. Moreover, without breaking the skeleton and porosity of ZIFs, the as-generated Ru species would bond with the Co nodes in-situ to form bimetallic Ru-Co Clusters if the Cobearing MOFs was utilized as the host. Within the confined space of ZIFs, the assembly of Ru and Co could be rationally designed and their structures could be sophisticatedly controlled at atomic scale. Among these Ru-based compositions, the Ru-Co Clusters@N-C exhibited remarkable catalytic activity for the NH3 decomposition to H2 and NH3 synthesis versus Ru-Co NPs@N-C, Ru Clusters@N-C and Ru NPs@N-C. This study may open up a new routine to synthesize metallic clusters or other sub-nano structures by the confinement of ZIFs.
Introduction: Considering serious environmental pollution issues, hydrogen have received increased attention, because it was generally recognized as a clean alternative to 1 fossil fuels. Due to the high hydrogen densities and huge annual production of ammonia, producing hydrogen from decomposition of ammonia is more promising way than that 2-4 of reforming process from carbonaceous substances. Unluckily, due to the high activation energy of ammonia, its decomposition barely occured without catalysts even temperature is elevated to 973 K. To date, finding active catalysts which can decompose ammonia at low temperature with fast reaction rate is highly demanded. Ruthenium (Ru) based catalyst are well recognized as one of the most efficient catalysts for the ammonia decomposition due to its 5,6 optimal heat of chemisorption of nitrogen. Recent studies
revealed the catalytic behavior is strictly related to the microstructures of Ru-based catalysts such as defects, electron transfer between metal-metal bond, interplay 7-9 between metal and surrounding ligands, and so on. However, the accurate control over the sub-nano structures is challenging because of their strong tendency to aggregate and rearrange into bulky counterparts. To realize the preparation of sub-nano Ru-based catalysts and achieve the modulation at atomic scale, the primary factor which should be consider is the avoidance of overgrowth and migration of Ru atoms. Recently, Lou and other workers have demonstrated using metal-organic frameworks (MOFs) could host polyoxometalates (POM) and further produce porous molybdenum carbide and molybdenum dioxide small nanocrystallites through in situ and 10-12 Baek and cohomogeneous carburization reaction. workers have synthesized small Ru nanoparticles@C2N by pyrolytic polymer, which show the high activity of hydrogen 13 evolution reaction (HER) compared with commercial Pt/C. Li and co-workers have reported a series of Mo-based HER catalysts by the confinement of UIO-66 whose formula of 14 unit cell is Zr24O120C192H96. To achieve the control over the sub-nano structures (
