木质素基活性炭氮掺杂改性及其电化学性能

以磷酸法木质素基活性炭为原料, 三聚氰胺为氮源、KOH为活化剂, 采用同步掺杂方式制备了氮掺杂活性炭(NAC)。通过BET、XRD、拉曼光谱和XPS表征手段测试了改性后活性炭的结构及其组分, 并通过电化学表征手段, 测试了其作为超级电容器电极材料在几种不同性质电解液中的性能, 初步探究了电解液对电极材料电化学性能的影响机制。实验结果表明: 改性后的活性炭具有丰富的孔结构, 比表面积达到2 332 m²/g, 微孔孔容为1.37 cm³/g, 中孔孔容为0.74 cm³/g, 平均孔径为2.79 nm, 含氮元素7.5%, 其中类石墨型氮(N-Q)结构达到34.6%。丰富的孔结构和氮含量大幅提升了活性炭的电化学性能, 其在水系电解液中展现出了高比电容, 在1 A/g的电流密度下比电容最高可达424 F/g; 在有机系电解液中, 尽管其在1 A/g的电流密度下比电容最高仅为87 F/g, 由于其工作电压窗口更宽(0~2.5 V), 因此具备了更高的能量密度。对结果进行分析, 发现: 活性炭电极材料在水系电解液中的性能主要受电解液水合离子半径影响, 而在有机系电解液中的性能主要受电解液黏度的影响。

Nitrogen-doped Modification and Electrochemical Properties of Lignin-based Activated Carbon

Nitrogen-doped activated carbon(NAC) was prepared by synchronous doping method using phosphoric acid lignin-based activated carbon(LAC) as raw material, melamine as nitrogen source and KOH as activator. The structure and composition of the modified activated carbon were characterized by BET, XRD, Raman spectroscopy and XPS characterization. The electrochemical performance of the modified activated carbon as the electrode material of supercapacitor in several electrolytes with different properties was tested by electrochemical characterization, and the influence mechanism of the electrolyte on the electrochemical performance of electrode material was preliminatively explored. The results indicated that the modified activated carbon has abundant pore structure, with specific surface area of 2 332 m²/g, micropore volume of 1.37 cm³/g, middle pore volume of 0.74 cm³/g, average pore size of 2.79 nm, and nitrogen content of 7.5%, of which graphite-like nitrogen(N-Q) structure content of 34.6%. The rich pore structure and nitrogen content greatly improved the electrochemical performance of activated carbon, and it exhibited high specific capacitance in the aqueous electrolyte. The maximum specific capacitance was 424 F/g at the current density of 1 A/g. In organic electrolyte, its specific capacitance was only 87 F/g at a current density of 1 A/g, while it had higher energy density owing to the wider operating voltage window(0-2.5 V). The results showed that the performance of activated carbon electrode material in aqueous electrolyte was mainly determined by the hydration ion radius of electrolyte, while the performance in organic electrolyte was mainly affected by the viscosity of electrolyte.