Synthesis Of CeO₂-based Catalyst Modified By H₂O₂ And Their Thermocatalytic Decomposition Performance Of Dimethyl Methylphosphonate

Chemical agents and toxic industrial gases will cause a potential threat to life and health of citizens,once released into the air due to other accidents,disasters and warfare.Wide suitable chemical protection technology is still a hot issue in military application research.Thermal catalytic decomposition is an effective path to quickly convert the macromolecular toxic substances in chemical agents into non-toxic substances such as CO₂ and H₂O,which has great application prospects.In this paper,CeO₂nanorods and CeO₂nanorods modified by H₂O₂ catalyst were prepared by the hydrothermal reaction method.Using dimethyl methylphosphonate（DMMP）as the catalyst object,the thermal catalytic decomposition performance of ceria under different calcination time conditions was studied.The results showed that the samples calcined for 5 hours of two types of catalysts have better catalytic performance.The protection time of the CeO₂#5 catalyst was up to 27 hours,and the protection time of the modified H₂O₂-CeO₂#5 catalyst reached 34 hours.Among them,the H₂O₂ modified material’s surface defects increase significantly,with exposing different crystal faces and playing a role in adjusting the Ce³⁺/Ce⁴⁺,surface oxygen and lattice oxygen content.Calcination at 400℃for 5 hours can improve the crystallinity and other characteristics of the material and improve the catalytic performance of the material.Further research on the deactivated catalyst found that the Ce³⁺content in the poisoned catalyst increased significantly after the reaction,and the inclusion of phosphorus and oxygen species accumulated in the by-products was the main reason for the deactivation of the catalyst.The Pt-supported material was completed by the dual hydrothermal method to further optimize the thermal catalytic decomposition performance of the ceria-based catalyst for DMMP.The Pt supporting process aggravated the corrosion of the nanorods,and the continued fracture of the nanorods caused CeO₂ which is peeled off the surface of the rods in the form of flakes.In the control experiment,the nanorods were completely sliced.The protection experiment showed that the supported catalyst prepared by the dual hydrothermal method had a protection time of more than 240 hours for DMMP,and the product accumulated in the reaction bed was tested as a phosphorus oxide compound.In addition,this reaction confirmed the influence of the nano-morphology of cerium oxide on the catalytic performance.The complex crystal surface of the modified nanorod is conducive to the adsorption and degradation of DMMP,while the exposed crystal faces of the nanosheets are single,showing a poor protective effect of DMMP.In situ infrared spectroscopy was used to analyze the thermal catalytic decomposition reaction process of DMMP on CeO₂.The results showed that:DMMP molecules are adsorbed on CeO₂ molecules through phosphoryl oxygen P=O.After the P-OCH₃ bond is broken,the methoxy-bound hydrogen is released in the form of methanol,and the P-CH₃ may be combined with the lattice oxygen to form methanol.The final product is attached to the surface of the catalyst in the form of phosphorous oxygen compound PO_x.The research in this paper confirms the remarkable effect of cerium oxide material in the thermal catalytic decomposition of DMMP and the gain effect of H₂O₂ modifier on the material,which provides a reference for cerium oxide material in the thermal catalytic decomposition of chemical agents.