title: Ammonia Decomposition with Manganese Nitride-Calcium Imide Composites as Efficient Catalysts.
abstract: Ammonia has high gravimetric and volumetric hydrogen densities and is, therefore, considered a promising carrier for the production of COx -free molecular H2 for forthcoming energy systems. Alkaline earth metals are generally regarded as structural promoters of catalysts and employed in numerous catalytic processes. Here, we report that calcium imide (CaNH) has a strong synergistic effect on Mn6 N5 in catalyzing the decomposition of NH3 , leading to a ca. 40 % drop in apparent activation energy. At 773 K, the H2 formation rate over a Mn6 N5 -11CaNH composite catalyst is about an order of magnitude higher than that of Mn6 N5 and comparable to the highly active Ni/SBA-15 and Ru/Al2 O3 catalysts. Analysis by means of temperature-programmed decomposition (TPD), X-ray diffraction (XRD), and X-ray absorption near edge spectroscopy (XANES) reveal that CaNH participates in the catalysis via forming a [Ca6 MnN5 ]-like intermediate, thus altering the reaction pathway and energetics. A two-step catalytic cycle, accounting for the synergy between CaNH and Mn6 N5 , is proposed.
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, PR China.|University of Chinese Academy of Sciences, Beijing, 100049, PR China.
authors.forename: Pei
authors.initials: P
authors.lastname: Yu
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, PR China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Guo
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, PR China.
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, PR China.|University of Chinese Academy of Sciences, Beijing, 100049, PR China.
authors.forename: Peikun
authors.initials: P
authors.lastname: Wang
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, PR China.
authors.forename: Guotao
authors.initials: G
authors.lastname: Wu
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, PR China.|University of Chinese Academy of Sciences, Beijing, 100049, PR China.
authors.forename: Fei
authors.initials: F
authors.lastname: Chang
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, PR China. pchen@dicp.ac.cn.|State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of sciences, Dalian, 116023, PR China. pchen@dicp.ac.cn.|Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, PR China. pchen@dicp.ac.cn.
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry; D017895:Manganese Compounds / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy; D014961:X-Ray Diffraction
chemical_list: D017610:Calcium Compounds; D017895:Manganese Compounds; D000641:Ammonia; D006859:Hydrogen
keywords: ammonia; calcium; heterogeneous catalysis; manganese; nitrides