Synthesis And Supercapacitor Properties Of Hybrid Based On {BW₁₂O₄₀} Building Block

Keggin type polyoxometalates are popular research objects at present.Because of their good covalent coordination,they are easy to form single crystal and nano materials with unique structure,and have good application in environmental materials,energy conversion,photocatalysis,pharmacology and so on.[BW₁₂O₄₀]^5-has higher surface charge density and easier coordination with transition metals are conducive to the formation of more coordination compounds.Therefore,two kinds of single crystals were synthesized by hydrothermal method.Throug helemental composition analysis and TG analysis,the molecular formula of the two single crystals is determined to be[{Cu(pz)}{Cu₂(pz)₂(H₂O)₂}(BW₁₂O₄₀)](1)and[Co(en)₃](Hbiz)(H₂biz)[BW₁₂O₄₀](2).Seven kinds of hybrid nanomaterials were synthesized by grinding method.By elemental composition analysis,EDS,EDX and XPS,the chemical formulas are Ag₅BW₁₂O₄₀(3)?Ag-MOF(4)?Ag₅BW₁₂O₄₀@Ag-MOF(5)?Zn-MOF(6)?Ag₅BW₁₂O₄₀@Zn-MOF(7)?Mn-MOF(8)?Ag₅BW₁₂O₄₀@Mn-MOF(9).The results of single crystal test show that the two single crystals synthesized by hydrothermal method are based on{BW₁₂O₄₀}.In the structure,Cu ions are connected by pz ligands to form wavy{Cu-pz}n chains,and each{BW₁₂O₄₀}cluster is connected with Cu1 of{Cu-pz}n chain through oxygen terminal(O17 and O22)to form a 2D layer.In the 2D layer,Cu3 connects three N atoms on three pyrazine ligands and extends to space,forming a novel 3D pomof structure.Compound 2 is composed of a[BW₁₂O₄₀]^5-anion,a[Co(en)₃]²⁺fragment,mono-and biprotonated benzimidazole,and forms 1D to 3D structures by hydrogen bonding or supramolecular interaction,respectively.Compounds 1-9 were used as active materials to test the performance of supercapacitors.The nickel foam was used as a collector and tested in a three electrode system.When the current density is 1 A g^-1,the specific capacitance of the compounds were 1>2,5>3>4,7>6>3,9>3>8;after 5000 cycles,the compounds 1,2,5,7 and 9 were more than 90%,so the double electrode nickel foam system was tested.The specific capacitance is greater than 40 F g^-1at 1 A g^-1.Meanwhile,the energy density is greater than 5 Wh kg^-1,and the power density is about 500 W kg^-1.The photocatalytic degradation of MB,MO and Rh B was tested.Under UV irradiation,the degradation rates of compounds 1,2,5,7 and 9 for MB,MO and Rh B were more than 90%.The degradation rates of compounds 1,2,5,7 and 9 did not change much after five photocatalytic cycles,indicating that they could be used as good photocatalytic materials.The sensor performance of H₂O₂ of compounds 1,5 and 9 were tested.The retention rate of 1000 CV cycles is 86.3%,and the catalytic efficiency is 186.3%for compound 1.The linear equation is I(m A)=-0.047C-27.069,R²=0.9587,the linear range is 5?M-0.27 m M,the signal-to-noise ratio(S/N)is 3,and the detection limit is0.22 m M.For compounds 5 and 9,after 1000 CV cycles,the cycle retention rate was87.2%and 80.3%,and the catalytic efficiency was 176.6%and 159.2%.The linear equation is I(m A)=-0.027C-22.9,R²=0.9635,the linear range is 4?M-0.27 m M,the signal-to-noise ratio(S/N)is 3,and the detection limit is 0.19 m M for compound 5.The linear equation is I(m A)=-0.022C-9.938,R²=0.94,the linear range is 2.5?M-0.27m M,the signal-to-noise ratio(S/N)is 3,and the detection limit is 0.20 m M for compound 9.It can be seen that compounds 1,5 and 9 can be used as H2O2 sensor materials and have better performance,providing basic data for the further application of synthetic compounds.