Thermal Decomposition of Dimethyl Methylphosphonate on Size-Selected Clusters: A Comparative Study between Copper Metal and Cupric Oxide Clusters

Wang, Linjie; Denchy, Michael; Blando, N.; Hansen, Lucas; Bilik, Ben; Tang, Xin; Hicks, Zachary; Bowen, Kit H.

doi:10.1021/acs.jpcc.1c00952

Cited by 9 publications

(10 citation statements)

References 59 publications

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“…P2p1 exhibits a 2p 3/2 binding energy of 133.9 eV, which is typical of molecularly chemisorbed DMMP. This has been observed in previous studies of ours, as well as the work of others. , P2p2 exhibits a lower 2p 3/2 binding energy of 132.9 eV, which has been previously assigned to surface-bound phosphonate or phosphate decomposition products. , This result shows that DMMP has already begun to decompose by room temperature and is similar to the results of our previous experiments involving room-temperature exposure of (ZrO 2 ) 3 clusters to DMMP …”

Section: Resultssupporting

confidence: 91%

Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected Pt₁Zr₂O₇ Supported on HOPG

et al. 2023

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Chemical warfare agents (CWAs) are a persistent threat facing civilians and military personnel across the modern geopolitical landscape. The development of the next generation of protective and sensing materials stands to benefit from an improved fundamental understanding of the interaction of CWA molecules with the active components of such candidate materials. The use of model systems in well-controlled environments offers a route to glean such information and has been applied here to investigate the fundamental interaction of a nerve agent simulant molecule, dimethyl methylphosphonate (DMMP), with a small cluster model of a single atom catalyst (SAC) active site. The cluster models, Pt1Zr2O7, were prepared by depositing mass-selected cluster anions synthesized in the gas phase onto a 100 K highly oriented pyrolytic graphite (HOPG) substrate surface prepared in ultra-high vacuum (UHV) at sub-monolayer coverage. Upon deposition, the cluster anions lost their charge to the electrically conductive surface to yield free-standing neutral clusters. The HOPG-supported clusters were characterized by X-ray photoelectron spectroscopy (XPS) to determine the oxidation states and chemical environment of the metal atoms present within the clusters. The reactivity of the clusters with DMMP was investigated via temperature-programmed desorption/reaction (TPD/R) and XPS experiments in which the clusters were exposed to DMMP and incrementally heated to higher temperatures. In contrast to two other HOPG-supported clusters, (ZrO2)3 and Pt1Ti2O7, recently investigated in our laboratory, Pt1Zr2O7 decomposed DMMP to primarily evolve a methane species, which was completely absent for the other clusters.

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Section: Resultssupporting

confidence: 91%

Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected Pt₁Zr₂O₇ Supported on HOPG

et al. 2023

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“…However, the barrier to cleave C–H is very high and both P-containing intermediates and alkoxy may poison the surface over time. The phenomenon of surface passivation for sarin is expected and has been before observed on DMMP and DIMP on titania and other metal oxides experimentally such as cupric, manganese, alumina, and iron oxides. ,,− …”

Section: Discussionmentioning

confidence: 59%

Decomposition of the Toxic Nerve Agent Sarin on Oxygen Vacancy Sites of Rutile TiO₂(110)

2023

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To design effective personal protective equipment against chemical attacks, the understanding of chemical warfare agents (CWAs) decomposition chemistry is crucial. Metal oxides, particularly TiO 2 have been found to be promising materials to trap and decompose CWAs. This work explores the possible decomposition pathways of sarin on a model rutile TiO 2 (110) surface with and without the presence of surface oxygen vacancies. Sarin adsorbs on the surface mainly by its P�O unit via a dative P�O-Ti 5c bond, similar to its simulant dimethyl methylphosphonate (DMMP). Sarin decomposition on the pristine surface is possible at 455 K and proceeds via O−C bond cleavage, with a barrier of 1.17 eV, resulting in the production of surface-bonded monofluorophosphate and isopropoxy, while P−OR (R = C 3 H 7 isopropyl) or P−F cleavage is highly activated with barriers larger than 2 eV. However, the production of gas-phase propene after O−C cleavage has a high activation barrier (1.6 eV). In the presence of O vacancies, the barriers to cleave the P−F and P−OR bonds are greatly reduced and these cleavages become possible at a moderate temperature (425 K). In comparison to its simulant DMMP, the decomposition of sarin proceeds faster on the oxygen vacancy as the cleavage of the P−F bond is more facile and the binding of F on surface Ti creates a thermodynamically stable intermediate. The electronic effects of the F ligand also facilitate the P−OR bond cleavage at the O vacancy site. Frequency calculations validate the energy pathways: intact molecular adsorption of sarin can explain the experimental spectrum at room temperature, while further decomposition by C−O or P−F bond cleavage, presumably on the pristine surface and at O vacancies, respectively, is responsible for the spectral evolution seen at 500 K, in agreement with calculated barriers.

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“…The P 2p spectrum for the nanopowder and mesoporous samples after GB exposure (Figure a) effectively resemble each other. Only a component centered at around 133 eV appears in the P 2p spectrum, commonly observed for GB or DMMP (a simulant for GB) adsorption. ,,,− Figure b displays the F 1s spectrum. Two characteristic components appear in the F 1s region for both samples after GB dosing.…”

Section: Results and Discussionmentioning

confidence: 98%

Titania Nanomaterials for Sarin Decomposition: Understanding Fundamentals

Tsyshevsky

McEntee

et al. 2022

ACS Appl. Nano Mater.

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While TiO2-based materials have been attracting growing interest in combating chemical warfare agents (CWAs), their usefulness and details of chemical mechanisms remain unknown. In this study, we explored the potential of TiO2 nanomaterials as filter materials to degrade sarin (GB), one of the deadliest nerve agents. We performed joint experimental and theoretical studies of the breakdown of sarin gas on three different TiO2 nanomaterials: P25 TiO2, pure anatase TiO2 nanopowder, and mesoporous anatase TiO2. Infrared and X-ray photoelectron spectroscopic measurements of TiO2 nanomaterials upon GB dosing demonstrate that GB readily decomposes on TiO2. The photoelectron spectra indicate the formation of metal fluoride on the surface, implying a mechanism for GB dissociation that involves P–F bond cleavage. Our results reveal that the as-synthesized mesoporous anatase TiO2 exhibits the highest activity toward GB decomposition despite it having the same crystalline structure and a similar surface area as the anatase TiO2 nanopowder. With density functional theory (DFT) calculations, we explore possible causes for the high reactivity of mesoporous TiO2. We modeled sarin decomposition mechanisms on anatase (101) surfaces and considered the effect of frequent defects in materials, such as oxygen vacancies, steps, water, and hydroxyl groups. Calculations show that GB decomposition through P–F bond breaking on the (101) anatase surface can be promoted by a stepped structure and hydroxylation due to both a lower activation energy barrier and lower energy of the final products. Our experiments corroborate that water/hydroxylation facilitates the dissociation of sarin on mesoporous TiO2. Our study suggests that mesoporous TiO2 is an attractive candidate material for use in gas masks and other protective equipment.

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Thermal Decomposition of Dimethyl Methylphosphonate on Size-Selected Clusters: A Comparative Study between Copper Metal and Cupric Oxide Clusters

Cited by 9 publications

References 59 publications

Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected Pt₁Zr₂O₇ Supported on HOPG

Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected Pt₁Zr₂O₇ Supported on HOPG

Decomposition of the Toxic Nerve Agent Sarin on Oxygen Vacancy Sites of Rutile TiO₂(110)

Titania Nanomaterials for Sarin Decomposition: Understanding Fundamentals

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Thermal Decomposition of Dimethyl Methylphosphonate on Size-Selected Clusters: A Comparative Study between Copper Metal and Cupric Oxide Clusters

Cited by 9 publications

References 59 publications

Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected Pt1Zr2O7 Supported on HOPG

Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected Pt1Zr2O7 Supported on HOPG

Decomposition of the Toxic Nerve Agent Sarin on Oxygen Vacancy Sites of Rutile TiO2(110)

Titania Nanomaterials for Sarin Decomposition: Understanding Fundamentals

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Product

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Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected Pt₁Zr₂O₇ Supported on HOPG

Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected Pt₁Zr₂O₇ Supported on HOPG

Decomposition of the Toxic Nerve Agent Sarin on Oxygen Vacancy Sites of Rutile TiO₂(110)