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

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 H ₂ 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 Al ₁₆Bi 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.