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

Abstract

In an effort to develop the next frontier filtration material for chemical warfare agent (CWA) decomposition, we synthesized mesoporous NiO and Cu_xNi_1-xO (x = 0.10 and 0.20) and studied the decomposition of CWA simulant diisopropyl fluorophosphate (DIFP) on their surfaces. Mesoporous NiO and Cu_xNi_1-xO were fully characterized and found to be a solid solution with no phase separation up to 20% copper dopant. The synthesized materials were successfully templated producing ordered mesoporous metal oxides with high surface areas (67.89- 94.38 m²/g). Through Raman spectroscopy, we showed that pure NiO contained a high concentration of Ni²⁺ vacancies, while Cu²⁺ reduced these defects. Through in situ infrared spectroscopy, we determined the surface species formed, potential pathways, and driving factors for decomposition. Upon exposure of DIFP, all materials produced similar decomposition products CO, CO₂, carbonyls, and carbonates. However, decomposition reactions were sustained longer on mesoporous NiO, facilitated by the higher Ni²⁺ vacancy concentration. NiO was further studied with DIFP, first at low dosing temperatures (-50 °C), which still resulted in the production of CO and carbonates, and then, second, with a higher pretreatment temperature, which showed the importance of terminal hydroxyls/water to fully oxidize decomposition products to CO₂. Mesoporous NiO demonstrated high decomposition and oxidation capabilities at temperatures below room temperature, all without any external excitation or noble metals, making it a promising frontier filtration material for CWA decomposition.