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Preparation And Capacitance Performance Of Biomass Carbon

Posted on:2019-09-24Degree:MasterType:Thesis
Country:ChinaCandidate:Q WuFull Text:PDF
GTID:2371330551461218Subject:Materials Science and Engineering
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As the only sustainable carbon source available,biomass materials are favored by researchers due to their advantages of wide source,low cost,and greenness.The electrode material,as an important component,determines the electrochemical performance of the supercapacitor.Biomass carbon materials are applied to the energy storage field because of their regulatable pore structure and abundant heteroatom species.In this paper,biomass was used as raw material to prepare biomass porous carbon materials with high specific surface area and rich in heteroatoms.Using eucalyptus leaves as a carbon source,the raw materials were treated by high-temperature carbonization and hydrothermal carbonization,and then activated by NaOH.A high specific surface area nitrogen and oxygen co-doped capacitor carbon was prepared by changing the ratio of activator to carbon precursor.The test found that the hydrothermal method can better retain the skeleton structure in the raw material,so as to form a unique macroporous structure,and then after activation preparation to obtain fractional pore carbon.Compared with the microporous structure prepared by carbonization activation,the hierarchical pore structure is beneficial to the rate performance of the material and the wettability of the electrolyte.It was found that the hydrothermally pre-carbonized material showed better performance.The highest specific surface area of the material is 2061 m2 g-1,and the highest nitrogen and oxygen contents are 3.36 at%and 10.71 at%,respectively.When the mass ratio of activator to carbon precursor is 3:1,the material has the highest specific capacity of 316 F g-1 in 6 mol L-1 KOH electrolyte,and the current density increases 300 times to 30 A g-1,while the capacity is still 239 F g'1 and the capacity retention rate is 75.6%.Using mulberry leaf as carbon source,NaOH as activator,prepared of nitrogen and oxygen co-doped capacitor carbon with high specific surface area by hydrothermal activation.The hydrothermal method preserves the structure of the material to the greatest extent.The specific surface area gradually increases with the increase of the amount of activator,and the highest is 2662 m2 g-1.The highest nitrogen and oxygen contents were 4.28 at%and 12.20 at%,respectively.When the mass ratio of activator to carbon precursor is 3:1,the material has the highest specific capacity of 330 F g-1 in 6 mol L-1 KOH electrolyte,and the current density increases 300 times to 30 A g-1,the capacity still has a 76%retention rate.The spherical biomass yeast powder was selected as raw material,and NaOH was used as an activator to prepare high specific surface area nitrogen and oxygen co-doped capacitor carbon through high-temperature carbonization activation.By combining the test results,it was found that both the specific surface area and the heteroatom content had a close influence on the electrochemical performance of the material.The specific surface area and pore size increase with the proportion of activator,and the electrochemical performance does not increase with it;the heteroatoms provide tantalum capacitors for the system and improve the electrolyte wettability,but at the same time will reduce the conductivity of the material itself,especially oxygen atoms,so the nitrogen atoms and the right amount of oxygen atoms are beneficial to improve the capacitive properties of the material.The specific surface area of the carbon material prepared with an alkali to carbon ratio of 3:1 was as high as 3335 m2 g-1.The specific capacity of the material increases first and then decreases.At a ratio of 1.5:1,the specific capacity of the material reaches a maximum of 368 F g-1,and the current density increases 300 times to 30 A g-1,the capacity still has a 72%retention rate.At a current density of 5 A g-1,the specific capacity retention rate was 89%after 10,000 cycles.Select yeast powder as carbon source,nano-ZnO as template and activator,one-step carbonization and activation to obtain high specific surface area of nitrogen and oxygen co-doping fractionated pore carbon.Thermogravimetric analysis showed that the nano-ZnO was mainly occupied by pores under 700 ?,and activated reaction occurred in the range of 700 ?-850 ?.As the activation temperature increases,the specific surface area of the material increases continuously(up to 2113 m2 g-1),the nitrogen content(up to 6.90 at%)continuously decreases,and the oxygen content drops first and then rises,reaching a maximum at 850 ?(reaching 9.62 at%).At the same time,it was found that the material has good rate performance.The specific capacity of the material is 188 F g-1 when the activation temperature is 850 ?,and the specific capacity of still maintained at 21%of the specific capacity.In addition,the capacity retention rate is 99.5%after 9000 long cycles,which shows excellent long cycle stability.
Keywords/Search Tags:supercapacitor, biomass carbon, hydrothermal method, doped heteroatom, nano-zinc oxide
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