Aliovalent-Doping Effects on the Surface Activity of Mesoporous CeO2 toward Nerve Agent Simulant DMMP Decomposition

Aliovalent doping is frequently used as a strategy to modify the chemical and physical behavior of fluorite-type CeO2. Ceria has been proven to be active toward room-temperature decomposition of dimethyl methylphosphonate (DMMP), a chemical warfare agent simulant. Here, we systematically explore how alio-doping influences the interaction between mesoporous CeO2 and DMMP molecules at room temperature and under ambient conditions. We dope mesoporous CeO2 with 10, 20, and 30% Y3+ and perform in situ diffuse reflectance infrared Fourier transform spectroscopy and ex situ solid-state 31P NMR to understand surface speciation after exposing the mesoporous metal oxides to DMMP. We also monitor the reaction product methanol via mass spectrometry. All the measurements consistently show that doping with Y3+ gradually impedes the reactivity of mesoporous CeO2 toward DMMP decomposition. X-ray photoelectron spectroscopy and CO adsorption infrared indicate that Y3+ doping may cause decreased activity of mesoporous CeO2 by increasing hydroxylation and limiting the exposure of the active (111) surface. La3+- and Gd3+-doped mesoporous CeO2 also display similar decreased activity toward DMMP decomposition compared with pure mesoporous CeO2, implying a general trend of impact of alio-doping on CeO2 interacting with DMMP. We conclude that control of surface hydroxylation and preferred crystal surface exposure are key toward improving the performance of CeO2 toward DMMP dissociation.