Ammonium heptamolybdate was dissolved in water or oxalic acid solution,and then compounded with TiO₂ to prepare MoO _x ?TiO₂ support,and the VO _x /MoO _x ?TiO₂ catalysts were obtained after loading vanadium by impregnation method.The structure and properties of the catalysts were characterized by XRD,SEM,BET,XPS,H₂?TPR and NH₃?TPD,and its denitration activity and high temperature aging performance were investigated.The results showed that the denitrification efficiency of VMoTiO?F prepared by oxalic acid?assisted dissolution of (NH₄)₆Mo₇O₂₄ was greater than 80.0% at 210 ~ 510 °C,which was better than that of VMoTiH?F prepared by water dissolution.Because there was more MoO _x on the surface of VMoTiO?F,the interaction with VO _x was enhanced,which promoted the production of more low?valence VO _x and surface chemisorbed oxygen (O_α) active species on the surface of the catalyst.At the same time,the interaction between VO _x and MoO _x could also improve the low?temperature redox performance and facilitate the electron transfer in the catalytic process.After high temperature aging,VMoTiH?F had more MoO _x into the TiO₂ lattice than VMoTiO?F,which was helpful to improve the thermal stability of TiO₂.However, anatase TiO₂ in VMoTiO?A was seriously sintered or even partially transformed into inert rutile crystal during high temperature aging,resulting in the loss of surface acid sites and the reduction of redox properties.Therefore,the denitrification performance of VMoTiH?A catalyst was significantly higher than that of VMoTiO?A.

To investigate the effect of donor unit length on the thermoelectric properties of D-A conjugated polymer,three D-A conjugated polymers(PDPP-DTP,PDPP-2DTP,PDPP-3DTP) based on dithieno[3,2-b:2′,3′-d]pyrrole (DTP) with different donor unit lengths were designed and synthesized.The influence of donor unit lengths on the energy levels of the polymers was studied by electrochemical characterization and density functional theory calculations.With ferric chloride as dopant,the polymer films were oxidation doped.Their optical and thermoelectric properties as well as the temperature dependent resistance were discussed.The results show that the HOMO energy levels of the polymers gradually increase with the extension of the length of the DTP-like donor unit,which makes them easier to be oxidatively doped.At the same dopant concentration,the doped polymers exhibit higher conductivity with the extension of the donor unit length.Among them,PDPP-3DTP shows the highest electrical conductivity of 302.3 S/cm,which is much higher than that of PDPP-2DTP(106.2 S/cm) and PDPP-DTP(64.7 S/cm).The charge transport energy barrier of the polymer films gradually decreases with the extension of the length of the donor unit,which is beneficial for the enhancement of electrical conductivity of doped films.However,the Seebeck coefficient of the doped polymer film decreases with the extension of the length of the donor unit,and the final polymer PDPP-2DTP is doped and optimized to have the highest thermoelectric power factor of 19.4 μW/(m·K²).