Conversion of NO into N2 over γ-Mo2N

Mohammednoor Altarawneh, Zainab Jaf, Hans Oskierski, Zhong Tao Jiang, Jeff Gore, Bogdan Z. Dlugogorski

Research output: Contribution to journalArticle

Abstract

Cubic molybdenum nitride (γ-Mo2N) exhibits Pt-like catalytic behavior in many chemical applications, most notably as a potent catalyst for conversion of harmful NOx gases into N2. Guided by experimental profiles from adsorption of 15NO on γ-Mo214N, we map out plausible mechanisms for the formation of the three isotopologues of dinitrogen (14N2, 15N2, and 14N15N) in addition to 14N15NO. By deploying cluster models for the γ-Mo2N(100) and γ-Mo2N(111) surfaces, we demonstrate facile dissociative adsorption of NO on γ-Mo2N surfaces. Surfaces of γ-Mo2N clearly activate adsorbed 15NO molecules, as evidenced by high binding energies and the noticeable elongation of the N-O bonds. 15NO molecule dissociates through modest reaction barriers of 24.1 and 28.1 kcal/mol over γ-Mo2N(100) and γ-Mo2N(111) clusters; respectively. Dissociative adsorption of a second 15NO molecule produces the experimentally observed Mo2OxNy phase. Over the 100 surface, subsequent uptake of 15NO continues to occur until the dissociated O and N atoms occupy all 4-fold hollow and top sites. We find that, the direct desorption of 15N2 from the Mo2OxNy-like phases phase requires a sizable energy barrier to precede. Considering a preoxygen surface covered cluster reduces this energy barrier only marginally. Desorption of 15N2 molecules takes place upon combination of two adjacent N atoms from top sites via a low-energy multistep Langmuir-Hinshelwood mechanism. Dissociative adsorption of gaseous 15NO molecules at surface Mo-N bonds weakens the Mo-N bonds and leads to formation of 14N15N molecules (where 14N denotes a nitrogen atom originated from surfaces of γ-Mo2N crystals). Liberation of 14N2 molecules occurs via surface diffusion of two surface N atoms on the (111) N-terminated surface. Formation of 14N15NO proceeds via direct abstraction of a surface 14N atom by a gaseous 15NO adduct.

Original languageEnglish
Pages (from-to)22270-22280
Number of pages11
JournalJournal of Physical Chemistry C
Volume120
Issue number39
Early online date2 Sep 2016
DOIs
Publication statusPublished - 6 Oct 2016
Externally publishedYes

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    Altarawneh, M., Jaf, Z., Oskierski, H., Jiang, Z. T., Gore, J., & Dlugogorski, B. Z. (2016). Conversion of NO into N2 over γ-Mo2N. Journal of Physical Chemistry C, 120(39), 22270-22280. https://doi.org/10.1021/acs.jpcc.6b04107