| The key to solving the energy crisis lies in the development and management of renewable energy.Supercapacitor has realized the efficient storage and distribution of electric energy because of its excellent performance,such as large power density,good cycle stability,high charge and discharge efficiency,and promoted the application and popularization of renewable energy.The performance of supercapacitors is affected by many factors,but the core content of the study is the electrode active material,which is an important part of the supercapacitor.The well-known materials,carbon materials is the most widely used,it has a high surface area,a wide range of sources,environment-friendly,good chemical stability and so on.Therefore,in order to develop a new type of supercapacitor with better performance,it is necessary to study the electrochemical performance of carbon materials.Shanxi,as a big province of coal in China,is now in a special period of economic transformation.The utilization of low-grade coal resources is an important way to ensure the sustainable development of the economy.Humic acid is the main organic component of coal,and it is very important to prepare high-value functional carbon material by simple activation process.In the process of preparing activated carbon by chemical activation,one is to use an external activator and the other is activated by the selection of organic matter with salt ions.In addition to increasing the specific surface area by activation,the electrochemical properties of the activated carbon can also be improved by adjusting the pore size or introducing a heteroatom on the surface.Therefore,in this paper,humic acid salt as raw material,through the different carbon source and different types of activator selection and optimization to achieve the preparation of high performance super capacitor electrode material.The main research contents are as follows:1.Potassium humic acid(HA-K),nitro humic acid(HA-N)and sodium humic acid(HA-Na)were used as precursors to carbonize different porous carbon in N2 atmosphere at 800℃,using cyclic voltammetry and galvanostatic charge/discharge by electrochemical performance test.At the current density of 0.1 A·g-1,three kinds of porous carbon were 122 F·g-1,117 F·g-1,81 F·g-1,respectively.Therefore,the next proces is to use HA-K as the carbon precursor.2.With HA-K as carbon precursor,CH3 COOK,KOH and CaCO3 with different activation mechanisms were selected to investigate the effects of different activation conditions on the structure and properties of the activated carbon.The results showed that when using CH3 COOK as activating agent,activated carbon CK-CH3 COOK formation had the highest specific surface area(1160 m2·g-1),and the pore size was mainly microporous;in 2 M KOH,the specific capacitance is as high as 270 F·g-1,while CK-KOH and CK-CaCO3 were 206 F·g-1,106 F·g-1,respectively.It can be seen that CH3 COOK is the optimal activator.3.Using HA-K as precursor and CH3 COOK as activator,the activated carbon was optimized by adjusting the ratio of HA-K/CH3 COOK,and its electrochemical behavior in three typical aqueous electrolytes was examined.The specific surface area and pore volume of these activated carbons increased by 790 m2·g-1 and 0.358 cm3·g-1 compared with the non-activated ones.The pore size of the sample CK-2 is about 0.5 nm,which is more compatible with the size of the electrolyte ion or solvated ion K+/OH-,thus exhibiting the best electrochemical performance in the 2 M KOH electrolyte.The specific capacitance is 311 F·g-1.After XPS and elemental analysis,it was known that the CK-2 surface of the sample contained a certain amount of N/O functional group,which provided additional pseudo capacitance effect.Therefore,the specific capacitance is the result of the synergistic effect of double layer capacitance and pseudo capacitance.The symmetrical capacitor,which was composed of sample CK-2,is still stable after 10000 cycles,which showed its excellent practical application potential. |
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