Mechanisms of H2 generation for metal doped Al16M (M = Mg and Bi) clusters in water

• H2 generation behavior of Al16Mg and Al16Bi clusters was measured.
• A feasible mechanism for hydrolysis reaction of Al–Bi alloy was proposed.
• Bi in Al16Bi cluster can accelerate proton-transport in hydrolysis reaction.

We have systematically investigated the hydrolysis mechanism of metal doped Al16M (M = Al, Mg and Bi) clusters with H2O molecules and proposed a reasonable elucidation for the experimentally observed fast H2 generation rate and high H2 yield in the Al–Bi based composite. Mg and Bi showed negative effect on the dissociation process of the first H2O molecule, but accelerated further H2 generation process. The investigation of persistent hydrolysis reactions demonstrated that the proton-transfer way makes the aluminum–water reaction a lasting process in the long-term H2 generation in existence of Bi atom, which explains not only the previously observed fast H2 generation rate but also high H2 yields in the Bi added Al powder. Our experimental results of hydrogen generation form Al–Bi (Mg) mixture and water are in good agreement with the theory prediction. The facilitated hydrolysis reaction in Al16Bi cluster is attributed to the weakened hydroxide adsorption with the presence of Bi in the aluminum cluster, which is the key factor to accelerate the proton-transfer process.