First-Principles Study on the Mechanisms for H2 Formation in Ammonia Borane at Ambient and High Pressure

First-principles molecular dynamics calculations were performed to investigate the mechanism on thermal decomposition of H-2 of ammonia borane (NH3BH3) at ambient and high pressure. Under atmospheric pressure, one H-2 molecule was released through an intramolecular reaction of a single NH3BH3. Nudged elastic band calculations show that the activation barrier for the decomposition in the crystalline environment is reduced by almost 1/3 from the gas phase value. When the system is heated under pressure two H-2 were liberated. The reaction follows an intermolecular pathway involving the concerted interaction of three NH3BH3. The results demonstrate the importance and practical significance of pressure on increasing the evolution of H-2 from NH3BH3.