The Research Of Preparation And Photo-/Thermo-catalytic Properties Of MnO_x/TiO₂ And Co₃O₄

Air pollution has become the focus attention of society nowadays.Among them,volatile organic componds（VOCs）are the most humful and recalcitrance pollution,and they have posed a threat on human’s health and their life quality.The main source of VOCs comes from volatilization of waste gas and home improvement materials.Recently,many methods that aim at dealing with VOCs have appeared,and catalytic degradation technology of semiconductor catalysts is the most efficient,eco-friendly and economic strategy.Organic componds can be photocatalytic degraded by nano-TiO₂ thoroughly without pollute environment.While metal oxidation such as MnO₂ and Co₃O₄ can exhibit highly catalytic activity by heat,and Co₃O₄ nano-crystal has been thought to be the potential substitution of noble metal oxidation catalyst.However,the photocatalytic efficiency of nano-TiO₂ is very low due to its rapid recombination of photogenerated electron and hole,and nano-TiO₂ can only be activated by UV light because its large bad gap.Meanwhile,the reports of dealing with VOCs by Co₃O₄ are not sufficient,and reported methods of synthesis were very complicated.In order to increase the catalytic activity and widen response range of nano-TiO₂,and to improve the catalytic efficiency of Co₃O₄ on VOCs degradation,MnO_x/TNS catalyst and Co₃O₄ catalyst with novel morphology are synthetised as well as their catalytic activity are measured and analysed in this thesis.（1）The nanocomposites of amorphous manganese oxide（MnO_x）supported on anatase TiO₂ nanosheet with dominate{001}facests（TNS）with different Mn/Ti molar ratio were prepared.The MnO_x/TNS nanocompodites were characterized by XRD,SEM,TEM,ICP,XPS,BET,and UV-vis-IR adsorption.MnO_x with the optimum Mn/Ti molar ratio of 0.40 exhibit highly efficient photothermoctalytic activity and excellent durability for the oxidation of recalcitrant and carcinogenic benzene under the full solar spectrum irradiation from a Xe lamp.Remarkably,the CO2 production rate of MnOx/TNS enhances by 99 times as compared to TNS.The highly efficient photothermocatalytic activity of MnO_x/TNS under the irradiation originates from the highly efficient solar light-driven thermocatalysis on MnO_x due to its strong adsorption in entire solar spectrum region and the efficient thermocatalytic activity,which is considerably promoted by a photothermocatalytic synergetic effect.The active species generated by the photocatalysis on TNS migrate to MnO_x via the MnO_x/TiO₂ interface,and accelerate the solar light-driven thermocatalysis on MnO_x in the nanocomposite.（2）Co₃O₄ nanorods with novel morphology has been prepared by hydrothermal method and calcination.The Co₃O₄ nanorods consist of Co₃O₄ nanoparticles connected one by one in a rod shape,and there are many mesoporous within the Co₃O₄ nanorod.Compared with Co₃O₄ nanoparticles and Co₃O₄ nanocubes,the Co₃O₄nanorod with novel morphology exhibits excellent thermocatalytic activity for the oxidation of benzene,when the conversion rate of benzene reaches to 90%,the reaction temperature of Co₃O₄ nanorod decreases by 80℃and 50℃,respectively.When the reaction temperature reaches to 200℃,the CO₂ production rate of Co₃O₄nanorods reaches to 0.173μmol m^-2 min^-1,which is 2.5 times higher than that of Co₃O₄ nanocubes and 7.9 times higher than that of Co₃O₄ nanoparticles.From the result of CO-TPR and O₂-TPO measurement,the lattice oxygen activity of Co₃O₄nanorods in the process of reduction is much higher than Co₃O₄ nanoparticles and Co₃O₄ nanocubes,which is also the reason for the efficient catalytic activity of Co₃O₄nanorods.Under the irradiation of the full spectrum of Xe lamp,Co₃O₄ nanorods exhibit highly efficient catalytic activity and excellent stability.The CO₂ production rate of Co₃O₄ nanorods is 560.01μmol g^-1 min^-1,which is 1.64 times higher than that of Co₃O₄ nanoparticles and 309.40 times higher than that of P25.By measuring the surface temperature and CO-TPR of Co₃O₄ nanorods under the irradiation of Xe lamp,solar light-driven thermocatalysis and photoactivation are found on the Co₃O₄nanorods in the process of catalytic degradation of benzene.