磷酸法活性炭的三聚氰胺表面改性及其电化学性能研究

为了考察磷酸法活性炭作为双电层电容器电极材料的可行性,通过浸渍三聚氰胺后在500、700、900℃下热处理的方法对活性炭进行了表面改性,分别得到改性活性炭AC-N-500、AC-N-700、AC-N-900,考察不同热处理温度对活性炭表面氮元素结合状态的影响,及其对磷酸法活性炭作为双电层电容器电极材料的电化学性能的影响。采用氮气吸附、元素分析、X射线光电子能谱及电化学测试等方法分析表征活性炭的孔隙结构、元素组成、表面官能团存在形式以及电化学性能。结果表明:随着热处理温度的升高,改性活性炭氮元素含量逐渐下降,由AC-N-500的8.49%下降为AC-N-900的4.16%;三聚氰胺改性活性炭比表面积和总孔容明显降低。改性活性炭中氮元素主要以N-6(吡啶型)、N-5(吡咯型)、N-Q(季氮型)、N-X(氮氧型)4种形式存在;随着热处理温度的升高,N-6和N-5型官能团的比例略微减少并部分转变为N-Q。改性活性炭AC-N-700可制备出比电容达203 F/g(扫描电压1 m V/s)的活性炭电极材料,减小电极与电解液间的阻力有利于离子的渗入和电荷的传导,表明磷酸法活性炭具有作为双电层电容器电极材料的潜力。

Electrochemical Properties of Phosphoric Acid Activated Carbon Modified by Melamine

Phosphoric acid activated carbon, modified by impregnating melamine, was heated at 500, 700,and 900℃ to obtain AC-N-500, AC-N-700 and AC-N-900. The feasibility of these activated carbon for electrode material of electric double layer capacitor ( EDLC) were investigated. The effects of heat temperatures on the nitrogen-containing surface functional groups and the electrochemical properties of the modified activated carbons were also investigated. Nitrogen adsorption, elemental analysis, X-ray photoelectric spectroscopy, and electrochemical workstation were employed to analyze the pore structure, element contents, nitrogen-containing surface functional groups and electrochemical properties of the activated carbons, respectively. The results showed that the content of nitrogen decreased from 8. 49% to 4. 16%, and the specific surface area and total pore volume of the modified activated carbon decreased when the temperature increased from 500℃ to 900℃. It was found that the nitrogen atoms existed in the forms of N-6(pyridinic), N-5(pyrrolic/pyridone), N-Q(quaternary) and N-X(pyridine/N-oxide)on the surface of phosphoric acid activated carbon. The contents of N-6 and N-5 were slightly decreased with the increase of the treatment temperature from 500 to 900 ℃ and were gradually transformed to the N-Q form. The specific capacitance of the electrode material prepared from AC-N-700 could reach 203 F/g, and the material could reduce the resistance between the electrode and the electrolyte, and bring benefit to the conduction of the penetration of ions and charge. This suggested that phosphoric acid activated carbon had the potential as the electrode material of EDLC.