Direct Experimental Observation of in situ Dehydrogenation of an Amine-Borane System Using Gas Electron Diffraction

Aliyu M. Ja'O (1) , Sarah L. Masters (1) , Derek A. Wann (2) , Conor D. Rankine (2) , Joao P. F. Nunes (2) , Jean-Claude Guillemin (3)

1 University of Canterbury [Christchurch]
2 University of York [York, UK]
3 ISCR - Institut des Sciences Chimiques de Rennes

In situ dehydrogenation of azetidine-BH 3 , which is a candidate for hydrogen storage, was observed with the parent and dehydrogenated analogue subjected to rigorous structural and thermochemical investigations. The structural analyses utilized gas electron diffraction supported by high-level quantum calculations, whilst the pathway for the unimolecular hydrogen release reaction in the absence and presence of BH 3 as a bifunctional catalyst was predicted at CBS-QB3 level. The catalyzed dehydrogenation pathway has a barrier lower than the predicted B-N bond dissociation energy, hence favoring the dehydrogenation process over the dissociation of the complex. The predicted enthalpy of dehydrogenation at CCSD(T)/CBS level indicates mild reaction conditions would be required for the hydrogen release and that the compound is closer to thermoneutral than the linear amine boranes. The entropy and free energy change for the dehydrogenation process show that the reaction is exergonic, energetically feasible and will proceed spontaneously towards hydrogen release; all important factors for hydrogen storage.

Domaines: Chimie

Aliyu M. Ja'O, Sarah L. Masters, Derek A. Wann, Conor D. Rankine, Joao P. F. Nunes, et al.. Direct Experimental Observation of in situ Dehydrogenation of an Amine-Borane System Using Gas Electron Diffraction. Journal of Physical Chemistry A, 2019, 123 (32), pp.7104-7112. ⟨10.1021/acs.jpca.9b05522⟩. ⟨hal-02278399⟩