Activation of Methane by Tungsten Carbide and Nitride Cluster Cations

J Phys Chem A. 2020 Jul 2;124(26):5274-5279. doi: 10.1021/acs.jpca.0c00749. Epub 2020 Jun 18.

Abstract

Gas-phase reactions of tungsten carbide and nitride cluster cations, WnCm+ (n = 1-5, m ≤ 5) and WnNm+ (n = 1-6, m ≤ 2), with methane are investigated at near thermal energies. Most of the clusters react readily with CH4 to form WnCm+1H2+ or WnNmCH2+ under single collision conditions, in contrast to the almost no reactivity of pure tungsten clusters. This result indicates that the introduction of carbon or nitrogen atoms can enhance the reactivity of tungsten clusters toward the CH4 dehydrogenation. In addition, the formation and the release of an ethylene molecule are strongly suggested in the reaction of WC+ with CH4 as a minor reaction channel. Nearly all the nitride cluster cations, WnNm+ (n ≥ 2), exhibit higher reactivity than their corresponding carbides, WnCm+, whereas WN+ is less reactive than WC+. Furthermore, the multiple collision reactions of the highly reactive tungsten nitride species such as WN+ and W4N+ lead to the formation of WnNmCxH2x+ (x = 2, 3), which shows that the dehydrogenation of more than one CH4 molecule occurs.