Dynamics of ammonia borane using neutron scattering

Abstract We have used both the backscattering (HFBS) and time-of-flight (DCS) neutron spectrometers to investigate proton dynamics in ammonia borane, a compound of intense interest as a model for ‘chemical hydrogen storage’ materials. Results indicate that the deposition of ammonia borane on a mesoporous silicate results in longer proton residence times and lower energy barriers for proton motion compared to bulk ammonia borane. The reduced activation energy for proton motions may partly explain the improved thermolysis and lowering the activation barrier for the loss of the first equivalent of H 2 . In addition, the phonon density of states for neat ammonia borane compares well with other spectroscopic results, with the intense peak at 22 meV assigned to the librational NH 3 and BH 3 modes, whereas ammonia borane on MCM-41 displays a broad, featureless spectrum indicating a poorly crystalline material.