Preparation Of MOFs Based Porous Carbon And Study On Supercapacitor Performance In Aqueous Electrolyte

As a new kind of power storage,supercapacitors have attracted much attention because of their short charge and discharge time,good cycle performance,large power density,and environmental friendliness.However,the main drawback of supercapacitors is lower energy density.Electrode materials and electrolyte are two core factors affecting the electrochemical performance of supercapacitors.Therefore,the development of excellent capacitive performance electrode materials and high-voltage window electrolytes is an extremely important issue in the research field of supercapacitors.In this paper,the development of high specific capacitance of porous carbon materials and high voltage window aqueous electrolyte for the purpose,hydrothermal synthesis of a variety of metal organic framework compounds for the carbon precursor,two kinds of porous carbon materials were prepared by different methods,and the microscopic morphology of porous carbon was characterized by material characterization,the porous carbon was applied to the electrode material of supercapacitors and the aqueous solution of citrate was used as the electrolyte to systematically study the supercapacitors performance.The main work of this thesis is as follows:?1?Metal-organic framework compounds are formed by the transition metal and oxygen-containing or nitrogen-containing organic ligand,organic ligand is rich in carbon and contains N,P and other heteroatoms.In this paper,the metal-organic framework compounds Ni₃?BTC?₂?Me₂NH?₃ as a carbon precursor,porous carbon were prepared by pre-carbonization-KOH activation,the effect of carbonization temperature on the properties of porous carbon NMFC-T was investigated,the electrochemical performance of porous carbon NMFC-800 was studied by three-electrode system.The results show that the porous carbon NMFC-800 has the highest specific surface area of 1143 m² g^-1,the mesopore proportion reaches more than 80%,KOH as the electrolyte,the current density of 1A g^-1 of the specific capacitance of 211 F g^-1,after 5000 cycles,the capacitor retention rate of81.04%.Porous carbon NMFC-800 has excellent super capacitor performance and good cycle stability.?2?The metal-organic frameworks compound[Zn₃?OH??BTC?₂(C₄N₂H₁₁)?H₂O?]_n was used as carbon precursor to prepare the nitrogen-doped porous carbon ZMFC-T by one-step carbonization process.We investigated the influences of carbonization temperature on the specific surface area,pore size distribution and electrochemical properties.The results show that nitrogen-doped porous carbon ZMFC-800 has a specific surface area of 1557 m² g^-1,an average pore size of 3.85 nm,and nitrogen content of 5.25%,in KOH electrolyte,the porous carbon exhibits excellent supercapacitive performance(a large specific capacitance of 273 F g^-1 at a current density of 1 A g^-1)after 5000 cycles and good cycle stability?the capacitor retention rate of 81.04%?.?3?Using nitrogen-doped porous carbon ZMFC-800 as the electrode material and citrate solution as the electrolyte,the optimum concentration was obtained through optimization,on this basis,the citrate solution voltage window was examined.The stable voltage windows of C₆H₅Na₃O₇ and C₆H₅K₃O₇ electrolytes are 1.9 V?-1.1 V-0.8 V?,2.0 V?-1.2 V-0.8 V?.Through two-electrode system test,the specific capacitance of ZMFC-800 in 1 M C₆H₅Na₃O₇ and C₆H₅K₃O₇ electrolytes was 120 F g^-1 and 111F g^-1 at 0.5 A g^-1 respectively.The experimental results show that:1 M C₆H₅Na₃O₇ and C₆H₅K₃O₇ electrolyte have excellent electrochemical properties,can be used as a new high stability voltage window of the aqueous electrolyte.