Can a Photosensitive Oxide Catalyze Decomposition of Energetic Materials?

Abstract

Organic–inorganic interfaces provide both intrigues and opportunities for designing systems that possess properties and functionalities inaccessible by each individual component. In particular, the electronic, catalytic, and defect properties of inorganic surfaces can significantly affect the adsorption, decomposition, and photoresponse of organic molecules. Here, we choose the formulation of TiO2 and trinitrotoluene (TNT), a highly catalytic oxide and a prominent explosive, as a prototypical example to explore the effect of a catalytic oxide additive on the photosensitivity of energetic materials. We show that whether or not a catalytic oxide additive can help molecular decompositions under light illumination depends largely on the band alignment between the oxide surface and the energetic molecule. For the composite of TiO2 and TNT, the lowest unoccupied molecular orbitals (LUMOs) of TNT merge within the conduction band (CB) of TiO2. As such, no optical transition corresponding to available laser energies is observed. However, oxygen vacancy can lead to electron density transfer from the surface to the energetic molecules, causing an enhancement of the bonding between molecules and surface and a reduction of the molecular decomposition activation barriers. Therefore, when other (than optical) forms of energy (shock, heat, etc.) flow into molecules, molecular decompositions may be triggered more easily.