Activation and diffusion of ammonia borane hydrogen on gold tetramers

One of the most serious candidates for safe storage of high hydrogen densities is ammonia borane, AB. Likewise, one of the most versatile catalysts known is gold in the form of atomic clusters. Taking these elements into account, in this work a density functional theory ‐based study about initial activation, detachment, and diffusion of ammonia borane hydrogen on gold tetramer, as a catalyst model, is developed. It was found that the total process is exergonic and that the hydrogen diffusion occurs with very low energy barriers. The process has a hydrogen detachment energy barrier lower than the one of the uncatalyzed AB, and that is easily overcome by the energy expelled in the previous stage of formation of the initial activated species. Additionally, all the process is assisted by the fluxionality of the gold cluster, and occurs via a unique catalytically activated initial species, which contains a three‐center simultaneous interaction at the catalytically activated zone. Quantum chemical calculations indicate that the process of removal and diffusion of a hydrogen atom from ammonia borane using a gold tetramer cluster is feasible from the thermodynamical and kinetic point of views. The reaction is assisted by the fluxionality of the catalyst, and the initial activation process implies a specific simultaneous interaction among three atoms.