Study On The Catalytic Decomposition Efficiency And Mechanism Of Ozone Over C@CeMnO_x Catalys

In recent years,photochemical smog occurs frequently in China,the trouble of ozone pollution is increasingly serious.Excessive ozone concentration will cause cardiovascular disease and damage the respiratory system and seriously endangering human health.Therefore,the decomposition technology of ozone has important significance.The catalytic method has attracted extensive attention of researchers because of its safety,high efficiency,low price and no secondary pollution to the environment.Manganese oxide catalyst has excellent performences due to its accessibility and diverse lattice structures.However,at high relative humidity（RH）conditions,the activity of Mn oxide-based catalysts is diminished.Water vapor has a severe influence on catalytic performance in ozone decomposition,with H₂O molecules competing with ozone for adsorption on the oxide surface,leading to a decrease in catalytic activity.In this study,the catalyst was designed and prepared according to the structure and performance characteristics of carbon and manganese based multi-element metal oxide composites.Hydrophilic functional groups were introduced into the catalyst to regulate its catalytic activity under high humidity.Theβ-cyclodextrin was used as a carbon precursor to associate with Mn²⁺and metal ions X（Fe,Ce,Co,Ni,Cu）to form molecule-ion adducts,carbon-coated type transition metal doped manganese oxide catalysts have been successfully synthesized and characterized.600-Ce_0.5Mn₁CD₁ showed ozone conversion of 91.5%for 60?ppm O₃ under relative humidity（RH）of 95%and space velocity of 300?L·g^-1?·h^-1 after 6?h at room temperature,which show the highly active and RH resistive catalysts for decomposition of ozone.The 600-Ce_0.5Mn₁CD₁ has formed cerium-manganese complex oxide composed of Ce O₂ and Mn₂O₃,which had more oxygen vacancies than catalysts doped with other transition metals,so it exhibited high activity for the decomposition of ozone.Different ratios ofβ-cyclodextrin to metal ions have been employed to obtain insight in the regulatory role ofβ-cyclodextrin.600-Ce_0.5Mn₁CD_0.25 showed ozone conversion of97.8%,which is far superior to the performance of the 600-Ce_0.5Mn₁CD₀（27.5%）.Finally,these catalysts prepared fromβ-cyclodextrin are able to ozone elimination more efficiently than the control sample.The-OH and-COOH groups on the surface of the carbon layer formed byβ-cyclodextrin and the high content of oxygen vacancies in the cerium-manganese complex oxide play a key role in the decomposition of ozone under high humidity.The effect of calcination temperature on the catalyst was explored by fixed n（Ce）:n（Mn）:n（CD）=0.5:1:0.25 and changed the calcination temperature of the catalyst.The catalytic activity of 600-Ce_0.5Mn₁CD_0.25 was still the highest,which was due to the higher surface oxygen vacancy and-OH,-COOH on the surface of carbon layer at the calcination temperature of 600°C.The C-OH on the surface of the carbon layer began to be oxidized to the-C=O,finally was oxidized to-COOH and number of surface oxygen vacancies play a key role during the decomposition of ozone.This study provides a new idea for the development of high-efficiency ozone decomposition catalysts with excellent moisture resistance.