Experimental and Theoretical Investigation of Molybdenum Carbide and Nitride as Catalysts for Ammonia Decomposition
- 27 January 2013
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 135 (9), 3458-3464
- https://doi.org/10.1021/ja309734u
Abstract
Constant COx-free H2 production from the catalytic decomposition of ammonia could be achieved over a high-surface-area molybdenum carbide catalyst prepared by a temperature-programmed reduction–carburization method. The fresh and used catalyst was characterized by N2 adsorption/desorption, powder X-ray diffraction, scanning and transmission electron microscopy, and electron energy-loss spectroscopy at different stages. Observed deactivation (in the first 15 h) of the high-surface-area carbide during the reaction was ascribed to considerable reduction of the specific surface area due to nitridation of the carbide under the reaction conditions. Theoretical calculations confirm that the N atoms tend to occupy subsurface sites, leading to the formation of nitride under an NH3 atmosphere. The relatively high rate of reaction (30 mmol/((g of cat.) min)) observed for the catalytic decomposition of NH3 is ascribed to highly energetic sites (twin boundaries, stacking faults, steps, and defects) which are observed in both the molybdenum carbide and nitride samples. The prevalence of such sites in the as-synthesized material results in a much higher H2 production rate in comparison with that for previously reported Mo-based catalysts.Keywords
This publication has 28 references indexed in Scilit:
- Structure–Function Correlations for Ru/CNT in the Catalytic Decomposition of AmmoniaChemSusChem, 2010
- Structure and mechanical stability of molybdenum nitrides: A first-principles studyPhysical Review B, 2007
- Catalytic Synthesis of Ammonia—A “Never‐Ending Story”?Angewandte Chemie International Edition, 2003
- First-principles simulation: ideas, illustrations and the CASTEP codeJournal of Physics: Condensed Matter, 2002
- Generalized Gradient Approximation Made SimplePhysical Review Letters, 1996
- Preparation and catalytic properties of transition metal carbides and nitridesCatalysis Today, 1992
- Reactions of neopentane, methylcyclohexane, and 3,3-dimethylpentane on tungsten carbides: The effect of surface oxygen on reaction pathwaysJournal of Catalysis, 1991
- Soft self-consistent pseudopotentials in a generalized eigenvalue formalismPhysical Review B, 1990
- Catalytic properties of transition metal carbides II. Activity of bulk mixed carbides of molybdenum and tungsten in hydrocarbon conversionJournal of Catalysis, 1989
- A New Phase formed by High-Pressure Treatment : Face-centred Cubic Molybdenum MonocarbideNature, 1961