Structural evolution of aluminum hydride nanoparticles in water using ReaxFF molecular dynamics method

Metal hydride combustion is highly exothermic and is applied in energetic applications, such as propulsion, pyrotechnics, and fuel cell systems. Aluminum hydride (AlH3) is a fascinating material because of its high hydrogen content, combustion heat, and low toxicity. In this study, the reactive molecular dynamics simulations were preformed to investigate the fundamental oxidation mechanism of AlH3 nanoparticles (AHNPs) by H2O. Two self-dehydrogenation mechanisms of AHNPs were elucidated. One is the H-2 formations on the shell, which firstly hinders the oxidation of AHNPs by H2O. Another is the emergence of H-2 bubbles in the core, which induces the microexplosion of AHNPs above 1500 K. The microexplosion of AHNPs accelerates the oxidation of Al by H2O. H2O decomposes on Al surface to form Al-OH. Herein, the decomposition of OH with the assistance of three Al atoms was first reported. The oxidation of Al by H2O can directly generate H-2 at 3500 K. The results shed light on the complicated interplay between morphological evolution and external conditions. It provides insights into the dehydrogenation mechanism of metal hydride nanoparticles at the atomic level.