Ammonia Decomposition with Manganese Nitride–Calcium Imide Composites as Efficient Catalysts. Issue 4 (14th January 2016)

• Record Type: Journal Article
• Authors: Yu, Pei; Guo, Jianping; Liu, Lin; Wang, Peikun; Wu, Guotao; Chang, Fei; Chen, Ping
• Is Part Of: ChemSusChem. Volume 9:Issue 4(2016:Feb.)
• Page Start: 364
• Page End: 369
• Publication Date: 2016-01-14
• Subjects: ammonia -- calcium -- heterogeneous catalysis -- manganese -- nitrides; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.201501498
• Languages: English
• ISSNs: 1864-5631

Abstract

Abstract: Ammonia has high gravimetric and volumetric hydrogen densities and is, therefore, considered a promising carrier for the production of CO x ‐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. Abstract : The Wrath of CaNH : Calcium imide (CaNH) has a strong synergistic effect on Mn6 N5 in catalyzing NH3 decomposition, leading to outstanding catalytic activity. CaNH participates in the catalysis and produces a stable [Ca6 MnN5 ]‐like intermediate, lowering the activation energy for ammonia decomposition. A two‐step catalytic cycle, accounting for the synergistic effect between CaNH and Mn6 N5, is proposed.