Adsorption of Dimethyl Methylphosphonate on MoO3: The Role of Oxygen Vacancies

Dimethyl methylphosphonate (DMMP) is a common chemical warfare agent simulant and is widely used in adsorption studies. To further increase the understanding of DMMP interactions with metal oxides, ambient pressure X-ray photoelectron spectroscopy was used to study the adsorption of DMMP on MoO3, including the effects of oxygen vacancies, surface hydroxyl groups, and adsorbed molecular water. Density functional theory calculations were used to aid in the interpretation of the APXPS results. An inherent lack of Lewis acid metal sites results in weak interactions of DMMP with MoO3. Adsorption is enhanced by the presence of oxygen vacancies, hydroxyl groups, and molecular water on the MoO3 surface, as measured by photoelectron spectroscopy. Computational results agree with these findings and suggest the formation of methanol through several possible pathways, but all require a proton transferred from a hydroxyl group on the surface.