Filtration systems for absorption and decomposition of chemical warfare agents (CWAs) are the first line of defense against exposure to these toxic compounds. Composite materials (such as ASZM-TEDA) commonly used in filtration systems consist of high-surface-area carbon supports impregnated with various metal oxides, including CuOx and MoOx. Despite decades of work to develop highly effective and versatile filtration materials, little is known about the mechanisms of CWA degradation by material surfaces and filter deactivation/poisoning, in part due to the challenges involved with spectroscopic characterization of filtration material surfaces under operating conditions. Enabling the rational design of more advanced filtration and decomposition materials for broad-spectrum protection against CWAs and other toxic industrial compounds requires a sophisticated understanding of the chemical mechanisms behind CWA sorption and degradation on the molecular scale. We will present the APXPS study of adsorption and decomposition of dimethyl methylphosphonate (DMMP), a CWA simulant, on polycrystalline oxide surfaces of copper and molybdenum. APXPS enables examination of these surfaces and adsorbed species upon exposure to DMMP and other common atmospheric gases, such as water vapor. We find that DMMP adsorbs mostly intact on MoOx surfaces, and our results suggest that undercoordinated metal atoms and/or surface hydroxyl groups are the adsorption sites. Multiple decomposition products are observed on CuOx surfaces, and the oxidation state of the metal appears to influence the decomposition pathway. Complementary density functional theory (DFT) studies corroborate our experimental findings and are used to propose likely decomposition pathways.

Adsorption and decomposition of a chemical warfare agent simulant on copper and molybdenum oxides

253rd National Meeting (2017)

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