双离子液体基多孔炭的制备与电化学性能

以质子型离子液体1-氢-3-乙烯基咪唑硫酸氢盐(HVImHSO₄)为主炭源, 以1-丁基-3-甲基咪唑六氟磷酸盐(BMImPF₆)为助剂, 在氮气气氛、 1000 ℃下一步炭化得到氮、 磷、 硫共掺杂多孔炭. 通过N₂吸附-脱附、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线衍射(XRD)、 拉曼光谱(Raman)、 热重分析(TGA)和X射线光电子能谱(XPS)等技术对多孔炭进行了分析表征. 结果表明, 多孔炭的孔结构以微孔为主, 最高比表面积可达1111 m²/g, 其微晶结构中无定形碳和石墨化碳并存; 多孔炭中的氮主要以季氮(N-Q)、 吡咯氮(N-5)和吡啶氮(N-6)的形式存在, 磷以磷-氧(N—O—P)键合形式为主, 硫主要以噻吩硫(C—S—C)为主. 在6 mol/L KOH溶液、 三电极体系中, 多孔炭在0.5 A/g电流密度下的比电容为138 F/g; 在10 A/g电流密度下的比电容为100 F/g; 在2 A/g电流密度下循环充放电10000次, 其比电容保持率为95.8%, 显示出良好的电化学性能.

Preparation and Electrochemical Performance of Porous Carbons Prepared from Binary Ionic Liquids †

Nitrogen, phosphorus and sulfur co-doped porous carbons(PCs) were prepared with a protic ionic liquid 1-hydrogen-3-butylimidazolium hydrogen sulfate(HVImHSO₄) as precursor and 1-butyl-3-methylimi-dazolium hexafurophosphate(BMImPF₆) as assistant through one-step carbonization process at 1000 ℃ in nitrogen atmosphere. The PCs were characterized by nitrogen adsorption-desorption, scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Raman spectroscopy, thermo-gravimetric analysis(TGA) and X-ray photoelectron spectroscopy(XPS). The results showed that the PCs mainly had micro pores and the specific surface area could be up to 1111 m²/g under m(BMImPF₆)/m(HVImHSO₄)=0.4. The amorphous and disordered graphitic layers were dominant in PCs. Nitrogen bonding state was mainly N-Q(N substituted groups of aromatic graphite structure), phosphorus was mainly in O—P type groups, and sulfur was attributed to C—S—C of thiophene-type sulfur. Meanwhile, the capacitance of PC-BMImPF₆-0.5 was 138 F/g at 0.5 A/g and 100 F/g at 10 A/g, the retention ratio was 95.8% after being cycled for 10000 times at 2 A/g in the electrolyte of 6 mol/L KOH. A simple and easy method for preparation of N, P and S co-doped PCs from ionic liquids has been provided, and the PCs have a certain extent application prospect in supercapacitor electrode materials.