A Comparison of the Reactivity of the Lattice Nitrogen in Tungsten Substituted Co3Mo3N and Ni2Mo3N

The effect of the partial substitution of Mo with W in Co3Mo3N and Ni2Mo3N 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, Co3Mo3N was reduced to Co6Mo6N under a 3 : 1 ratio of H-2/Ar. Co3Mo2.6W0.4N was also shown to lose a large percentage of lattice nitrogen under these conditions. The bulk lattice nitrogen in Ni2Mo3N and Ni2Mo2.8W0.2N 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 Ni2Mo3N is more endothermic than Co3Mo3N. Furthermore, calculations suggest that the inclusion of W does not have a substantial impact on the surface N vacancy formation energy or the N-2 adsorption and activation at the vacancy site.

Automated summary

The effect of partial substitution of Mo with W in Co3Mo3N and Ni2Mo3N on ammonia synthesis activity and lattice nitrogen reactivity was investigated. It was found that the catalytic performance decreased with the introduction of tungsten. Furthermore, substitution with tungsten did not have a significant effect on lattice nitrogen reactivity, but resulted in a loss of lattice nitrogen in Co3Mo2.6W0.4N and Ni2Mo3N.