Sarin Decomposition on a Pt Cluster Supported on Anatase-TiO₂ in Ambient Conditions

Organophosphorus chemical warfare agents (CWAs) such as sarin are highly toxic and inhalation hazards for personnel at risk to exposure to such compounds are typically mitigated using metal-impregnated activated carbon in gas mask filters. In this work we considered anatase (a-) TiO₂ and a Pt cluster supported on a-TiO₂ as potential active filtration materials. Density functional theory (DFT) calculations combined with Fourier transform infrared (FTIR) spectroscopy were used to probe sarin adsorption and decomposition mechanisms. Using the grand canonical basin hopping (GCBH) technique, the structural stability and reactivity of Pt₆O_x clusters supported on a-TiO₂(101) were examined under ambient oxidative conditions, identifying the global minimum and thermodynamically accessible metastable configurations. The Pt₆ cluster is partially oxidized to Pt₆O₁₀ on a-TiO₂ in ambient conditions. The kinetic barriers associated with key bond cleavages decrease in the presence of the Pt cluster compared to the bare a-TiO₂ surface. a-TiO₂ effectively binds phosphonate groups, while the fragments from bond cleavage adsorb to the Pt cluster. The influence of water on sarin adsorption and decomposition was studied to better reflect realistic operating conditions. Sarin was found to displace surface water and chemisorb onto Ti centers. P-O cleavage becomes both thermodynamically and kinetically favorable followed by acetone formation. The presence of water further enhances the thermodynamic stability by facilitating hydrogen bonding with the dissociated fragments. Overall, this combined study reveals that Pt-decorated a-TiO₂ can actively decompose sarin under humid ambient conditions, with synergistic effects between the oxide surface, metal cluster, and water. These insights can guide the development of improved metal oxide-based filtration materials that can both capture and catalytically degrade CWAs in realistic environments.