Catalytic Degradation of a Chemical Warfare Agent Simulant: Reaction Mechanisms on TiO2-Supported Au Nanoparticles

Abstract

High-vacuum transmission infrared spectroscopy is used to investigate the reaction pathways of the chemical warfare agent simulant dimethyl methylphosphonate (DMMP) on nanoparticulate Au/TiO2 and pure TiO2. The infrared spectral signature of adsorbed CO, a major reaction product, is used to track the oxidation state of Au and Ti during the reaction. We find that small, <5 nm, Au particles on the surface of TiO2 activate this material toward the oxidative degradation of DMMP, in contrast to pure TiO2, which is an effective sorbant for DMMP, but little decomposition of this molecule occurs. The direct comparison of the chemistry on the samples reveals that two mechanisms may be responsible for the catalytic activity of the TiO2-supported Au nanoparticles. One mechanism occurs under anaerobic conditions, where vapor-phase DMMP reacts upon adsorption to form a variety of organic products and adsorbed CO. The active species in this initial oxidation channel is the lattice oxygen that most likely exists around ...