Titania Nanomaterials for Sarin Decomposition: Understanding Fundamentals

Abstract

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.

Selective (sono)photocatalytic cleavage of lignin-inspired β–O–4 linkages to phenolics by ultrasound derived 1-D titania nanomaterials

“…The crystallographic nature of all the synthesized and commercial samples was studied by the X-ray diffraction (XRD) method, with all the obtained patterns to be collected in Figure 1 a , while the calculated crystallite sizes, based on Scherer method [27] , to be presented in Table S1 . The P25 sample showed the presence of anatase and rutile phases which are found to be similar as reported previously [28] , [29] . The patterns of all the synthesized samples did not reveal well-defined reflections, a fact linked either to an amorphous nature or/and to very nanoscaled size of crystals.…”

Biomimetic In Situ Self-Assembly of Metal Nanoparticles into Hierarchical 3D Mesostructures: Synthesis, Analysis, and Prospects

“…It was recently demonstrated that mesoporous metal oxides serve as powerful and reliable substrates to decompose lethal toxins (sarin, soman, etc.) (see, for example, refs − and other work by this group). The large porosity (that is, the large surface area) ensures efficiency of the catalytic decomposition process; however, preparation of metal oxides in such architecture remains a challenge.…”

Low-Temperature Decomposition and Oxidation of the Nerve Agent Simulant on Mesoporous Nickel Oxide and Cu-Doped Nickel Oxide

“…Metal oxides have been used in heterogeneous catalysis since the mid-1950s, and their robust nature, low cost, and ability to fully oxidize organic molecules make them a viable option for CWA filtration and decontamination . Several metal oxides that have been studied for sarin and CWA simulant decomposition include TiO 2 , − Al 2 O 3 , Cu x O, , Fe 2 O 3 , , CeO 2 , , and ZrO 2 …”