Dimethyl Methylphosphonate Decomposition on Cu Surfaces:  Supported Cu Nanoclusters and Films on TiO₂(110)

Abstract

The thermal decomposition of dimethyl methylphosphonate (DMMP), which is a simulant molecule for organophosphorus nerve agents, has been investigated on Cu clusters as well as on Cu films deposited on a TiO(2)(110) surface. Scanning tunneling microscopy studies were conducted to characterize the cluster sizes and surface morphologies of the deposited Cu clusters and films. Temperature-programmed desorption experiments demonstrated that the surface chemistry of DMMP is not sensitive to the size of the Cu clusters over the range studied in this work. DMMP reaction on an annealed 40 monolayer Cu film resulted in the desorption of H(2), methane, methyl, formaldehyde, methanol, and molecular DMMP, and reaction on the small (4.4 +/- 0.9 nm diameter, 1.8 +/- 0.6 nm height) and large (10.7 +/- 1.9 nm diameter, 4.8 +/- 1.0 nm height) Cu clusters generated similar products. Formaldehyde and methane production is believed to occur via a methoxy intermediate on the Cu surface. These products are favored on the higher coverage Cu films that completely cover the TiO(2) surface since competing reaction pathways on TiO(2) are suppressed. X-ray photoelectron spectroscopy studies showed that DMMP begins to decompose on the Cu clusters upon adsorption at room temperature and that atomic carbon, atomic phosphorus, and PO(x) remain on the surface after DMMP decomposition.

Thermal desorption of dimethyl methylphosphonate from MoO3

“…The O 1s binding energy of the methoxy group is about 532.8 eV. The appearance of the phosphoryl group overlaps with other DMMP decomposition studies, such as methanol (32 amu) [20], dimethyl ether (46 amu) [21,22], methane (16 amu) [20,21] or H 2 [20,21], strongly implying intact desorption under these conditions.…”

“…surface as PO x ; this species begins to form at 323 K and is often seen in studies of DMMP decomposition on metal oxides [18,20,21]. The lack of a resolvable corresponding O 1s component is reasonable considering the small amount of PO x compared to the bulk oxygen.…”

Adsorption and Decomposition of DMMP on Size‐Selected (WO3)3 Clusters

“…Using DMMP as a model molecule, the reactivity of many metals and metal oxides toward DMMP has been studied, i. e. MoO 3 , Cu, CuO, MgO, ZnO, CeO 2 , TiO 2 , Y 2 O 3 etc.. As illustrated in these studies, DMMP usually undergoes a step‐wise loss of methoxy groups on the metal oxide surface, resulting in methanol being observed as a common hydrolysis reaction product for DMMP on many oxide surfaces . In addition to the hydrolysis reaction, reduction processes are also observed when surface defects, i. e. oxygen vacancies, are present .…”

Thermal and catalytic methods used for destruction of chemical warfare agents

“…Due to the lack of publications regarding the thermal decomposition of sarin as well as other chemical warfare agents from the group of paralytic-convulsive compounds, this part of the work describes the results of tests on the imitation sarin-dimethyl methylphosphonate (DMMP). Ma et al (2000) examined the thermal distribution of DMMP on the surface of copper clusters and on a thin layer of copper deposited on the surface of TiO 2 . Dimethyl methylphosphonate was introduced into the reaction chamber as a liquid so that the resulting concentration of its vapors was maximal to provide a saturated vapor mixture in the reaction zone.…”