Theoretical Investigation of the Degradation Pathway of Phosphorus Containing Nerve Agents on Metal Oxides

The mechanism for the decomposition of chemical warfare agents (CWA), particularly those classified as nerve agents, is investigated. It is experimentally known that metal oxides are capable of decomposing nerve agents with enhanced catalytic activity occurring at vacancy sites. To date, however, a detailed mechanistic study revealing the path of degradation is lacking. The focus of this project is to investigate the different surface planes of zinc oxide as a catalyst for hydrolysis of phosphorus-containing agents and their simulants. In this study, the molecules POH2, POH3, and POH2F, whose phosphorus containing functional group PO is incorporated in most nerve agents, is used as a starting point of interaction. In order to reveal the bonding nature with zinc oxide many different adsorption sites were chosen on both 002 and 100 surface planes. In addition, vacancy sites in the zinc oxide cuts were considered in the calculations. Binding energies were obtained by employing density functional theory (DFT), using the commercially available software VASP. In parallel, experiments were performed to produce zinc oxide powders rich in vacancies by first treating zinc oxide with hydrogen peroxide to form zinc peroxide followed by annealing at which point molecular oxygen is desorbed from the surface, leaving behind a vacancy. These samples were characterized through various techniques and catalytic activity was tested against CWA simulants. Through this combined computational and experimental approach, it is predicted that the results obtained here will not only provide a mechanistic insight towards degradation, but aid in the future development of more efficient catalyst against CWA’s.