Study On Electrochemical Performance Of Homopolymolybdic Acid Hybrids Prepared By Grinding Method

In recent years,due to the over-exploitation and utilization of fossil energy such as petroleum,coal,and natural gas,serious energy shortages have caused widespread concern.Therefore,the development and effective storage of new energy is very important.Supercapacitors are the main energy storage devices,but the development of electrode materials is very important.Polyoxometalates（POMs）are one of the important candidate materials,but they have small specific surface area,low conductivity,and are not stable enough in electrolyte have seriously affected its application.Therefore,it is particularly important to prepare POMs that can overcome the above-mentioned influencing factors.For this reason,this paper uses a simple grinding method to form a structure with different pore diameters between the metal and the organic ligand,and embed the POMs in it to form POM@MOFs,systematically study the properties of its super capacitors.Using Ag NO3 and H3BTC as raw materials,the white powder Ag-MOF was obtained by grinding,and then mixed and grounded with Ag6Mo7O24 synthesized by the solution method for 1 hour to obtain a gray-yellow powder{Ag6Mo7O24}@Ag-MOF.obtained by grinding.Using it as the precursor,the Ag/Mo O3@GC-C3N4 composite material was calcined at a certain temperature.Ag-MOF,Ag6Mo7O24,{Ag6Mo7O24}@Ag-MOF and Ag/Mo O3@GC-C3N4 are used as electrode materials,and nickel foam is used as the current collector to test the performance of supercapacitors.In the three-electrode system,when the current density is 1A g^-1 The specific capacitances are 110.6,156.2,320.8 and 427.4F g^-1,respectively,which are higher than those of the carbon cloth current collector.At 10A g^-1,after 5000 cycles,the specific capacitance retention rates were 68.9%,83.3%,98.2%and 94.7%,respectively.The energy density of the foamed nickel symmetrical double electrode system is 4.5,4.7,11.1 and 28.1 Wh kg^-1;the power density is 399.7,358.5,600.1 and 506.7 W kg^-1,respectively.Ag-MOF,Co3Mo7O24 and Ni3Mo7O24 were used as raw materials,mixed and ground in an agate mortar for 1 hour to obtain gray-pink powder{Co3Mo7O24}@Ag-MOF and gray-green powder{Ni3Mo7O24}@Ag-MOF samples,respectively.Co3Mo7O24,{Co3Mo7O24}@Ag-MOF,Ni3Mo7O24and{Ni3Mo7O24}@Ag-MOF are electrode materials and nickel foam as the current collector have been tested for supercapacitor performance.When the current density is 1A g^-1with three electrodes system,the specific capacitance is 256.2,260.7,204.5 and 217.8F g^-1,respectively.At 10A g^-1,after 5000 cycles,the specific capacitance retention rate is91%,99.8%,85.2%and 93.75%,respectively.The foamed nickel symmetrical dual electrode system has energy densities of 2.3,4.9,1.5,and 10.5 Wh kg^-1,and power densities of 350.8,355.1,249.5,and 399.8 W kg^-1,respectively.In addition,a crystal material with a molecular formula of（4,4-H2bipy）2[PMo^ⅤMo^Ⅵ11O40]was synthesized by hydrothermal method.The compound is composed of a variable-valence[PMo^ⅤMo^Ⅵ₁₁O₄₀]⁴⁺and two double-protonated bipy.Through the action of supramolecular,a multi-dimensional structure is formed.The supercapacitor performance test was carried out using it as the electrode material and the foamed nickel as the current collector.When the current density is 1A g^-1 with three electrodes,the specific capacitance is 263.9F g^-1,and when the current density is 10A g^-1,the capacitance is measured by 5000 cycles,the specific capacitance retention rate was76.9%.The energy density of the foamed nickel symmetrical two-electrode system is5.34 Wh kg^-1;the power density is 399.67 W kg^-1.The sensor properties of the four compounds{Ag6Mo7O24}@Ag-MOF,{Co3Mo7O24}@Ag-MOF,{Ni3Mo7O24}@Ag-MOF,Ag/Mo O3@C3N4 for H2O2 were studied.The catalytic efficiencies for 40 m M H2O2 were 181.45%,101.55%,191.93%,181.87%;after 1000 cycles,the retention rates are 78.89%,85.24%,81.66%,80.56%,respectively;the linear ranges are 7?M-0.27m M,7?M-0.43m M,9?M-0.27m M,0.25?M-0.43 m M;the detection limits are 0.45?M,0.61?M,0.77?M,0.64?M,respectively.Using methylene blue（MB）,rhodamine B（Rh B）and methyl orange（MO）as probes,the photocatalytic properties of the compounds were studied.The degradation rate of MB was all over 93%within 140 minutes.The degradation rate of the product is above 62%and 85%respectively.After 5 cycles,the retention rate is above 88%.