活化温度对石墨烯/碳纳米片电容的影响

Effect of activation temperature on capacitance of graphene/carbon nanosheet

以原位合成的酚醛树脂为碳源、氧化石墨烯片为形貌导向剂,制备石墨烯/碳纳米片,再在500℃、600℃、700℃和800℃下进行KOH活化,探究活化温度对电容性能的影响。用XRD、SEM、拉曼光谱和低温N2吸脱附实验对样品进行分析,用恒流充放电与循环伏安法进行电化学性能测试。KOH活化不会破坏碳纳米片形貌,提高活化温度,可增加活化样品的比表面积和孔容;随着活化温度的提高,比电容增加;当活化温度超过700℃后,样品的比电容会降低。以0. 2 A/g的电流在0~1 V充放电,活化温度为700℃时,样品(H700)比电容最高达230 F/g。当电流增加到20. 0 A/g时,H700的比电容为175 F/g;在10 A/g下循环10 000次,H700的容量保持率为98. 6%。

Graphene/carbon nanosheets were prepared by utilizing the in situ formed resorcinol-formaldehyde polymer as the carbon source and graphene oxide sheets as shape-directing agent, then activated by KOH at 500℃,600℃, 700℃ and 800℃ to investigate the effect of activation temperature on the capacitance performance. The samples were characterized by means of XRD, SEM, Raman spectra and low temperature N2 adsorption-desorption tests. Electrochemical performance was investigated by galvanostatic charge/discharge tests and cyclic voltammetry ( CV ) test. The morphology of the carbon nanosheets remained after KOH activation. The specific surface area and pore volume of the samples were increased by raising the temperature of KOH activation. By raising the activation temperature, the specific capacitance were improved. The specific capacitance reduced when the activation temperature exceeded 700℃. The sample obtained by 700℃ activation ( H700) had the highest specific capacitance of 230 F/g at 0. 2 A/g in 0 - 1 V. When the current was increased to 20. 0 A/g,the H700 retained a specific capacitance of 175 F/g. After 10 000 cycles at 10 A/g, the H700 had a capacitance retention rate of 98. 6%.