Capacitance Properties Of Tungsten-based Materials With Precursor Of{PW₁₂O₄₀}@MOFs

Polyoxometalates?POMs?has unique electrical,optical,mechanical and magnetic properties.In recent years,POMs nanoparticles were loaded with carriers or formed composite materials to give full play to the properties of the two materials.It has been paid attention to by the scientific workers.In catalysis,energy conversion and storage,sensors and other materials science applications,gradually become a new research hotspot of POMs.Metal Organic Frameworks?MOFs?is composed of metal ions and organic ligands through the coordination bond assembly of highly ordered molecular sieve material with pore structure.It is an ideal POMs carrier.Through the perfect combination of POMs and MOFs?POMOFs?,the shortcomings of components can be overcome to achieve the effect of adding functions.Therefore,MOFs provides a new and feasible way for the design and preparation of solid materials based on polyacid salt.In recent years,the research of this composite material as the key component of electrode material in energy storage device has attracted much attention.Both case of POMOFs compounds were prepared by solution method using {PW₁₂O₄₀} as the precursor and calcination of preparation of carbon oxide and carbon nitride tungsten composite material.The structure and morphology characterization of samples before and after calcination were characterized by infrared spectroscopy?IR?,raman spectroscopy?Raman?,X-ray diffraction?XRD?,thermal field emission scanning electron microscope?SEM?,transmission electron microscopy?TEM?and carries on the adsorption and electrochemical properties in this paper.{PW₁₂O₄₀}@Cu-Melamine has been first synthesized with melamine,phosphotungstic acid and copperacetate by solution method,in which the keggin-type W-based POMs with Cu-MOF to form POMOFs.A composite of Cu-W/W₂N@C has been prepared by calcining {PW₁₂O₄₀}@Cu-Melamine at 800?.The precursor and calcined sample were used as electrode materials for supercapacitors.Both capacitance is 982.6 and 1032.7 F g?-1? under the current density of 4.3A g?-1?.At the current density of 22 A g?-1?,both show excellent cycling stability with 95% and 97% capacity retention after 2000 cycles.The second compound of {PW₁₂O₄₀}@Cu-BTC based on the first compound,in which the ligand melamine were replaced with 1,3,5-benzenetricarboxylate.At the same time,{PW₁₂O₄₀}@Cu-BTC calcined at 700,750,800,850,900 to get compounds to ?test adsorption dyes?MB,Rh B,MO?.Cu-WO_x@C compound in 800?show highly adoption effect for dyes.The adoption rate reached 97%?45min?,97.9%?80min?and 96.2%?24min?,respectively.The adsorption kinetics and adsorption isotherms of methyl orange solution were further studied,and the results showed that the adsorption was consistent with chemical adsorption and multi-layer adsorption.{PW₁₂O₄₀}@Cu-BTC and Cu-WO_x@C as supercapacitor electrode materials exhibit an excellent capacity.The specific capacitance of {PW₁₂O₄₀}@Cu-BTC is 2361 F g?-1? at a current density of 4.3 A g?-1? with 81% retention after 5000 cycles at a current density of 22 A g?-1?.The specific capacitance of Cu-WO_x@C is 4531 F g?-1? at a current density of 4.3 A g?-1?.After 5000 cycles,it capacitance retention rate was 93% at a current density of 22 A g?-1?.The fabricate aqueous symmetric supercapacitor by using Cu-WO_x@C electrode exhibited a wide voltage of 1.8 V with a maximum energy density of 229 Wh kg^?-1? and a maximum power density of 11.9 k W kg^?-1? in 4.3 A g?-1?.The Cu-WO_x@C electrode show excellent supercapacitor performance conpared with other WO_x-based supercapacitors.