Degradation of Fatal Toxic Nerve Agents on Dry TiO₂

Abstract

Despite a recent dramatically increased risk of using chemical warfare agents in chemical attacks and assassinations, fundamental interactions of toxic chemicals with other materials are poorly understood, and micromechanisms of their chemical degradation are yet to be established. This represents an outstanding challenge in both fundamental science and practical applications in combat against chemical weapons. One of the most versatile and multifunctional oxides, TiO 2 , has been suggested as a promising material to quickly adsorb and effectively destroy toxins. In this paper, we explore how sarin (also known as GB) adsorbs and decomposes on dry nanoparticles of TiO 2 anatase and rutile phases. We found that both anatase and rutile readily adsorb sarin gas molecules because of a strong electrostatic attraction between the phosphoryl oxygen and surface titanium atoms. The sarin decomposition most likely proceeds via a propene elimination; however, the reaction is exothermic on the rutile (110) surface and endothermic on the anatase (101) surface. High energy barriers suggest that sarin would hardly decompose on pristine dry surfaces of TiO 2 , and degradation reactions can be triggered by defects or contaminants under realistic operational conditions.

High-Temperature Decomposition of Diisopropyl Methylphosphonate on Alumina: Mechanistic Predictions from Ab Initio Molecular Dynamics

“…In our study, we obtained free energy values of 62.75 to 5.24 kJ/mol within the 200–1000 °C temperature range. Recent experiments on CWAs have also been carried out under similar temperatures, including vapor-phase decomposition of DMMP (a sarin surrogate) at 500–800 K, sarin decomposition on TiO 2 nanoparticles at 1000 K, and decomposition of CWAs at 2000 K. ,, Collectively, all of these experiments showed that the temperature ranges studied in this work can also be achieved under operational conditions, and DIMP would decompose on the γ-Al 2 O 3 surface. Due to the structural similarity between DIMP and sarin, our calculations provide additional insight into decomposition mechanisms of both these molecules and elucidate atomic details of sarin decomposition on candidate metal oxide surfaces.…”

“…Figure shows snapshots from our simulations depicting various DIMP adsorption configurations on the alumina surface. As suggested by prior theoretical calculations, − the adsorption via the O atom of the P–OC 3 H 7 moiety is crucial for propene elimination. As the MD simulations progresses, we also observe interactions between the O (in the PO group) and Al atoms.…”

“…Figure 10 summarizes the free energy activation barrier as a function of temperature, which shows that the free energy activation barrier decreases with temperature. Static DFT calculations have obtained free energy activation barrier values of 113 kJ/mol (ZnO surface), 51 108.0 kJ/mol (rutile surface), 53 122.6 kJ/mol (anatase surface), 53 and 53.7 kJ/mol (MoO 2 surface). 52 However, the free energy activation barriers for C−O bond breaking from our simulations are much lower than these previously reported values.…”

High-Temperature Decomposition of Diisopropyl Methylphosphonate (DIMP) on Alumina: Mechanistic Predictions from Ab Initio Molecular Dynamics

“…In our study, we obtained free energy values of 62.75 to 5.24 kJ/mol within the 200 -1000 • C temperature range. Recent experiments on CWAs have also been carried out under similar temperatures, including vapor phase decomposition of DMMP (a sarin surrogate) at 500 -800 K, 58 sarin decomposition on TiO 2 nanoparticles at 1000 K, 53 and decomposition of CWAs at 2000 K. 31,59,60 Collectively, all of these experiments showed that the temperature ranges studied in this work can also be achieved under operational conditions, and DIMP would decompose on the γ-Al 2 O 3 surface. Due to the structural similarity between DIMP and sarin, our calculations provide additional insight into decomposition mechanisms of both these molecules and elucidate atomic details of sarin decomposition on candidate metal-oxide surfaces.…”

High-Temperature Decomposition of Diisopropyl Methylphosphonate (DIMP) on Alumina: Mechanistic Predictions from Ab Initio Molecular Dynamics

“…As suggested by prior theoretical calculations, [51][52][53] the adsorption via the O atom of the P-OC 3 H 7 moiety is crucial for propene elimination. As the MD simulations progresses, we also observe interactions between the O (in the -P=O group) and Al atoms.…”