A Comparison of the Reactivity of the Lattice Nitrogen in Tungsten Substituted Co3 Mo3 N and Ni2 Mo3 N

Samia Al Sobhi; Ihfaf AlShibane; C Richard A Catlow; Angela Daisley; Justin S J Hargreaves; Andrew L Hector; Michael D Higham; Constantinos D Zeinalipour-Yazdi

doi:10.1002/cssc.202300945

A Comparison of the Reactivity of the Lattice Nitrogen in Tungsten Substituted Co₃ Mo₃ N and Ni₂ Mo₃ N

ChemSusChem. 2023 Nov 22;16(22):e202300945. doi: 10.1002/cssc.202300945. Epub 2023 Oct 9.

Authors

Affiliations

¹ School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK.
² School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK.
³ Department of Chemistry, University College London, Kathleen Lonsdale Building, Gower Place, London, WC1E 6BT, UK.
⁴ Rutherford Appleton Laboratory, Research Complex at Harwell, Harwell, Oxon, OX11 0FA, UK.
⁵ School of Chemistry, Cardiff University, Park Place, Cardiff, CF10 1AT, UK.
⁶ Computing, Mathematics, Engineering and Natural Sciences, Northeastern University London, London, E1W 1LP, UK.
⁷ Department of Mechanical and Aerospaces, Brunel University London, London, Uxbridge, UB8 3PH, UK.

PMID: 37703103
DOI: 10.1002/cssc.202300945

Abstract

The effect of the partial substitution of Mo with W in Co₃ Mo₃ N and Ni₂ Mo₃ N on ammonia synthesis activity and lattice nitrogen reactivity has been investigated. This is of interest as the coordination environment of lattice N is changed by this process. When tungsten was introduced into the metal nitrides by substitution of Mo atoms, the catalytic performance was observed to have decreased. As expected, Co₃ Mo₃ N was reduced to Co₆ Mo₆ N under a 3 : 1 ratio of H₂ /Ar. Co₃ Mo_2.6 W_0.4 N was also shown to lose a large percentage of lattice nitrogen under these conditions. The bulk lattice nitrogen in Ni₂ Mo₃ N and Ni₂ Mo_2.8 W_0.2 N was unreactive, demonstrating that substitution with tungsten does not have a significant effect on lattice N reactivity. Computational calculations reveal that the vacancy formation energy for Ni₂ Mo₃ N is more endothermic than Co₃ Mo₃ N. Furthermore, calculations suggest that the inclusion of W does not have a substantial impact on the surface N vacancy formation energy or the N₂ adsorption and activation at the vacancy site.

Keywords: DFT; Mars-van Krevelen; ammonia synthesis; metal nitride; nitrogen vacancies.

Abstract

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