表面含氧官能团对活性炭电化学性能的影响

采用浓硝酸对椰壳活性炭和各壳活性炭进行液相氧化改性后，制成了以KOH为电解液的超级电容器的炭电极，研究表面含氧官能团在碱性电解液中对电容器电极的电化学性能的影响．运用低温N2吸附、XPS和FTIR表征活性炭孔结构和表面性质．研究结果表明，氧化后活性炭的比表面积和孔容降低，表面含氧量增大．且经硝酸氧化后炭表面的含氧官能团含量发生了变化，即在内酯基的含量减少的同时，羟基、羰基和菝基的含量增加，其中羟基含量的增幅最大．在50mA／g电流密度下经过100次充放电循环，氧化后的椰壳活性炭和杏壳活性炭质量比电容分别达到193 F/g和150F／g，均比氧化前提高了30％以上．由XPS的分析结果判断，羟基对电极比电容提高的贡献最大．同时，在大电流充放电时，氧化后炭电极的比电容的衰减率明显低于氧化前．

Effects of Oxygen Functional Groups on the Electrochemical Performance of Activated Carbon

Coconut shell activated carbon(AC) and apricot shell activated carbon(LAPC) were modified by liquid-phase oxidation method using concentrated nitric acid as oxidant,and then were made into the electrodes of supercapacitors in KOH electrolyte to study the influence of oxygen functional groups on the electrochemical performance of electrode material in alkaline electrolyte.The four modified samples were characterized by using N_2 adsorption,X-ray photoelectron spectra(XPS) and Fourier transform infrared spectroscopy(FTIR).The results showed that,with high concentration HNO_3 treatment,the surface area and pore volume of the carbons decreased,while the surface oxygen content increased and the content of oxygen functional groups changed.Under 50 mA/g,after 100 times charge-discharge the specific capacitance of the oxides of AC and LAPC reached 193 F/g and 150 F/g respectively,which are both 30~0/_0 higher than those of the original samples.According to the results of XPS,the increase of capacitance is mainly due to the increase of hydroxyl.Moreover,it was found that with the increase of current density,the decreasing amplitude of discharge capacitance of the modified carbon samples was much lower than that of unmodified samples.