Preparation Of Porous Carbon From Low-rank Coal Based On Potassium Activation And Its Utilization Of Supercapacitors

The development and innovation of high-power energy storage technology can ensure the smooth adjustment of China's energy supply structure;electrolyte ions are adsorbed on the electrode surface during the operation of supercapacitors.Compared with the bulk phase reaction of the battery,the rate of electr icity storage can be greatly improved and power.The supercapacitor carbon-based electrode material is the key component of the supercapacitor,and the synergistic optimization of its activity and stability is the key to improving the multiple performance indexes?energy density,power density,cycle life?of the supercapacitor.China's coal reserves are rich,cheap and easily available.Microscopically,it is a complex carbon-based macromolecule composed of bridging aromatic structures and fat structures.It is an ideal carbon-based precursor;in order to develop high specific surface area,KOH chemical activation is to prepare por ous carbon electrodes The main method of materials at present.However,the traditional KOH chemical activation process has a la rge amount of KOH activator?usually 3-4 times the quality of the carbon source?,high cost,and easy to cause environmental pollution in order to ensure the effect of pore formation.In addition,it is committed to development At the same time as the pore s,the microcrystalline structure of porous carbon often fails to receive attention.In response to the above problems,this paper aims to achieve the structure control of coal-based porous carbon pores and crystallites,and to improve the traditional KOH activation process,a low-order coal alkali oxygen pre-oxidation and potassium/iron synergistic activation method is proposed.The activation process was compared,the effect of the above methods on the pore structure and microcrystalline characteristics of low-rank coal-based porous carbon was studied,and the supercapacitor characteristics were investigated.In this paper,firstly,low-rank coal?Baori brown coal?is used as a carbonaceous precursor,porous carbon is prepared based on the alkaline oxygen pre-oxidation process,and the pore parameters of porous carbon are determined by N₂ adsorption test to analyze the effect of oxidation time on pore development,and We further explored the similarities and differences between the two activation methods and the effect of activation temperature on the pore structure development of porous carbon under the condition of low alkali dosage.After that,the physical and chemical structures of typical samples were analyzed by means of SEM and Raman spectroscopy,and the energy storage characteristics of supercapacitors were evaluated.The results show that alkaline oxygen pre-oxidation can promote the activation effect of potassium group,and the high specific surface area graded porous carbon with a specific surface area of 3413 m²·g^-1 and a pore volume of 2.08 cm³·g^-1 can be obtained under 60 minutes of oxidation.Significantly higher than the sample prepared by direct activation.Moreover,the porous carbon prepared by the alkaline oxygen pre-oxidation process can obtain porous carbon with a specific surface area and pore volume of 1390 m²·g^-1 and 0.78 cm³·g^-1 respectively at a lower ratio.Specific capacitance and good stability.In KOH water-based supercapacitors,the specific capacitance is 98 F·g^-1 at 0.5 A·g^-1,and the specific capacitance is 49 F·g^-1 at 20 A·g^-1.The sample prepared by the traditional activation method with twice the activation dose has the same specific capacitance value and more excellent stability.In order to further improve the coupling structure of pores and crystallites,potassium ferrate is used as an activator in this paper,throu gh the combination of catalytic graphitization of iron-based materials into the potassium-based activation process,the iron-assisted potassium/iron synergistic activation is achieved to prepare a high specific surface area Activated carbon,and explored t he effect of activation temperature and activation dose on the development of pores and crystallites.The porous carbon prepared in this way has a larger specific surface area and higher stability,but when the activation conditions are further enhanced,i t may lead to the complete destruction of the carbon structure,and the overall performance is reduced.The specific surface area of the sample prepared at 900 ? and the same quality of the activator and raw material is as high as 2086 m²·g^-1,and the pore volume is 1.57 cm³·g^-1.The specific capacitance of the sample is 0.5 A·g^-1.The specific capacitance at 140 F·g^-1 and 10 A·g^-1 remains 83 F·g^-1.At the same ratio,the stability and cycle reversibility of samples prepared by KOH activation are significantly worse.Although the calculated capacitance is slightly larger at low current density,due to the irreversible cycle,the actual specific capacitance value will be Much smaller.