Spectroscopic studies of methyl paraoxon decomposition over mesoporous Ce-doped titanias for toxic chemical filtration

Abstract

The ever-constant threat of chemical warfare agents (CWA) motivates the design of materials to provide better protection to warfighters and civilians. Cerium and titanium oxide are known to react with organophosphorus compounds such Sarin and Soman. To study the decomposition of methyl paraoxon (CWA simulant) on such materials, we synthesized ordered mesoporous metal oxides (MMO) TiO2, CexTi1−xO2 (x = 0.005, 0.5, 0.10, 0.15) and CeO2. We fully characterized TiO2 and Ce-doped TiO2 and found phase-pure oxides with cylindrical hexagonally packed pores and high surface areas (176–252 m2/g). Methyl paraoxon decomposition was tracked through UV/Vis and found Ce0.15Ti0.85O2 to decompose the most methyl paraoxon, but CeO2 to be the most reactive when normalized to surface area. The surface area normalized rate constant (kSA) for CeO2 was 3–4.6 times larger than that of TiO2 and the CexTi1−xO2 series. While TiO2 and CexTi1−xO2 for 0.05 ≤ x ≤ 0.10 displayed no significant differences in the kinetics, the mostly amorphous Ce0.15Ti0.85O2 displayed a slight increase in reactivity. Our findings indicate that the nature of the cation, Ce4+ vs Ti4+, is less important to methyl paraoxon reactivity on these MMOs compared to other factors such as crystal structure type.