Synthesis And Application Of Vanadium-phosphorus Oxides Materials Controlled By Ionic Liquids

The composite metal oxidations of vanadium-phosphorus oxides(V-P-O)are widely used in chemical industry and energy storage field,but the shortcomings of low utilization ratio,harsh condition and insufficient production capacity still exist.It is of great significance for high value development and utilization of these compounds.In this paper,the structures of two typical vanadium-phosphorus oxides[(VO)2P2O7(VPO),VOPO4·2H2O(HVPO)]are regulated by the introduction of functionalized ionic liquids(ILs),and the corresponding mechanisms are put forward by characterization analysis and theoretical calculation.The conclusions are as followed.(1)A novel "function-oriented design" strategy was proposed to design and develop single-component additive polyoxometalate-ionic liquids(POM-ILs)with dual-function to enhance VPO catalytic activity of selective oxidation of n-butane to maleic anhydride.And the synergistic interaction of anions and cations of POM-ILs was illuminated combined with characterizations.The IL-cations guide the growth of the catalyst precursor to ordered nanolamellar structure.Correspondingly,it makes the catalyst exhibit a unique mesh-hole structure and benefit exposure of the active surface(200)of(VO)2P2O7.The POM-anions decompose into the defective O-P-Mo compound and cause more oxygen vacancies and crystal defects formed on the surface of VPO after activation.Besides,we established a specific method to divide the poly-acids(?,?,?-acid)sites to describe the acidic properties on the surface of VPO by NH3-TPD in qualitatively and quantitatively and related with catalytic performance.(2)Utilizing the ILs to achieve the physicochemical exfoliation of the bulk HVPO,which constructed by hydrogen bonds between lamellae to maintain the structure,and successfully obtaining ultrathin 2D crystalline nanosheets with high dispersion and fully exposed crystal planes.Combining density functional theory(DFT)and characterization analysis to propose the exfoliation mechanism of hydrogen bond destruction and recombination.And due to the existence of the new hydrogen bonding system,the 2D nanosheets are not easy to reassemble.It is found that the 2D crystalline nanosheets have a quenching effect on the photoluminescence of ionic liquids,and have good electrochemical properties such as reducing the battery impedance(about 5 times less than the blank)and reducing the redox potential difference.In this paper,functionalized ionic liquids are used to strengthen and exfoliate the two typical vanadium-phosphorus oxides,which provides a good reference for the development and utilization of new vanadium-phosphorus oxides.At the same time,the strategies and ideas proposed in this paper can also be applied to the utilization and development of other composite metal oxides.