PVP/MF基含氮碳纳米纤维电极材料制备及电性能研究

【作者】 李强；

【导师】 秦川丽；

【作者基本信息】 黑龙江大学 ， 高分子化学与物理， 2015， 硕士

【摘要】 本文将含氮氧原子的聚乙烯吡咯烷酮(PVP)水溶液和高氮含量的三聚氰胺甲醛树脂水溶液(MF)混合液高温裂解制备含氮碳粉末(NC);分别加入尿素造孔剂和KOH活化剂制备多孔含氮碳粉末(NC-U和NC-K),采用涂覆工艺制备电极片及组装超级电容器。同时将PVP和MF混合水溶液通过高压静电纺丝和高温裂解工艺制备具有自撑结构含氮碳纳米纤维薄薄膜(NCF),并进一步直接组装成超级电容器。采用SEM、Raman、TGA、XPS、BET对材料进行表征,采用CV、EIS、恒流充放电方法对材料及其超级电容器进行电化学性能测试,研究微观结构、氮含量及存在类型、比表面积及孔结构、导电性对电极材料及其超级电容器的影响规律。实验结果表明,与NC相比,通过添加尿素和KOH活化后的NC-U和NC-K呈现多孔的蜂窝结构,具有更高的孔隙度。尽管NC-K有高的比表面积(1086.29 m2/g),但因其具有低的氮含量(4.85 at.%),导致它的比电容值很低。经过尿素处理的NC-U不但大量引入了活性氮原子而且在很大程度上提高了材料的比表面积和电导率,更加有利于其电化学性能的提高。添加50%尿素处理的NC-U50的氮原子含量高达13.15 at.%且有效官能团N-6和N-5含量高,比表面积较大(244.67 m2/g),循环伏安法在lmV/s扫描速率下测得比电容值为I48.5F/g,NC-U50及其超级电容器表现出优异的综合性能。含氮碳纳米纤维薄膜NCF呈现100-300纳米左右的纤维相互搭接的3D网状、柔韧的独立自撑结构,PVP和MF的溶液配比及碳化温度对NCF的结构、组成和电化学性能有很大的影响。PVP和MF的溶液配比为1：2,650℃碳化温度下制备的NCF-650的比电容值最高,循环伏安法在lmV/s扫描速率下测得比电容值为202.5F/g。与高比表面积活性炭相比,由于6.13at.%的活性氮原子贡献的赝电容使NCF-650具有更高的比电容值;与粉末状NC-650相比,NCF-650具有更大的比电容是由于一方面NCF-650具有较大的比表面积(173.9m2/g),更有利于能量的存储,另一方面NCF-650的3D网状的纤维薄膜结构使得电极片具有低的内阻。NCF-650为负极组装的超级电容器经过1000次循环测试后其比电容衰减率为8.2%,显示了优异的电化学综合性能。含氮碳纳米纤维薄膜是理想的超级电容器电极材料。更多还原

【Abstract】 In this paper,nitrogen-enriched carbon(NC)was obtained by carbonization of polyvinylpyrrolidone(PVP)containing nitrogen-and oxygen atoms and melamine formaldedyde resin(MF)with the high concentration of nitrogen.NC-U and NC-K were prepared by adding urea and KOH activation method,respectively.The preparation of electrodes and assembly of supercapacitors were finished through the coating process.Meanwhile nitrogen-enriched carbon fiber(NCF)with self-supporting structure was prepared by the electrospinning of PVP/MF mixing aqueous solution and carbonization,and it was assembled into supercapacitor by clamping piece method directly.All samples were characterized by SEM,Raman,TGA,XPS and nitrogen adsorption/desorption.The electrochemical behaviors of samples and supercapacitor electrodes was studied by CV,EIS,galvanostatic charge/discharge test.The influence of microstructure,nitrogen contents and types,specific surface area,pore structure and the conductivity on the electrochemical performances was studied.The results show NC-U and NC-K prepared with the methods of mixing urea and KOH activation presents honeycomb porous structure with higher porosity compared to NC.Although NC-K has the high specific surface area(1086.29m2/g),its specific capacitance is very low because of its lower nitrogen concentration(4.85 at.%).Theurea treatment not only introduces the reactive nitrogen atoms into NC-U but also improves its specific area and conductivity,which is beneficial to electrochemical performances.NC-U50 has the highest Cpe of 148.5 F/g at scanning rate of lmV/s due to the highest nitrogen concentration of 13.15 at.%and SBETof 244.67m2/g-1 and the high concentration of N-6 and N-5.NC-U50 and its supercapacitor show excellent comprehensive performances.Nitrogen-riched carbon nanofiber films present 3D flexible self-supporting structure with 100 to 300nm fibers overlapping each other.The structure,composition and electrochemical properties of NCF was greatly impacted by the ratio of PVP solution and MF solution and carbonization temperature.NCF-650 prepared by the PVP/MF solution ratio of 1:2,carbonization temperature of 650℃ has the highest Cpe of 202.5F/g at scanning rate of ImV/s.Compared to AC with high specific surface area,NCF-650 has higher Cpe due to the active nitrogen atoms of 6.13 at.%,compared to NC-650,NCF-650 has higher specific surface area of 173.9 m2/g than NC-650 which is beneficial to the energy storage.And NCF-650 with 3D fiber film structure has lower impedance.There is only 8.2%decay in specific capacitance of the supercapacitor with NCF-650 ad the negative eletrode over 1000 cycles,indicating the excellent electrochemical performances.Nitrogen-enriched carbon nanofiber film is the ideal electrode materials for supercapacitor.更多还原