Dramatic catalytic activation of kinetically inert disilane hydrolysis in metallic iron particulate via barrierless chemical dissociation: First-principles study

Disilane (Si₂H₆) is a key substance for chemical industries designing semiconductors and graphene materials. Its reaction mechanism is, however, still elusive, as evident from serious chemical accidents when exposed to open air. Using first-principles density functional theory calculations, we investigate the thermodynamic and kinetic mechanisms of Si₂H₆ hydrolysis, with and without oxidative conditions of adjacent water, oxygen gas and metallic Fe particulates. Despite the remarkable thermodynamic spontaneity, direct hydrolysis is kinetically sluggish due to the high energy barrier. Hydrolysis initiated by O₂ is identified with a multi-step radical mechanism, which is kinetically more favored than the direct hydrolysis. The energy barrier of rate-determining step is, however, still too high for Si₂H₆ to react in a humid and oxidative environment. Surprisingly, we report that metallic iron serves as an of interest heterogeneous catalyst for the Si₂H₆ hydrolysis dramatically lowing the activation energy barrier for the dissociation. Our results propose that fine air particulates including Fe can play a key role in facilitating the explosive reaction of Si₂H₆ potentially leading to severe chemical accidents, otherwise very inert.