Electrodes fabricated using graphene are quite promising for electric double layer capacitors. However graphene has the limitations of low ‘Quantum Capacitance (QC)’ near fermi level due to the presence of Dirac point that can be modified by doping graphenewith suitable dopant. The density functional theory DFT calculations are performed for doped graphene using Boron, Sulphur and phosphorus as dopants to improve the quantum capacitance of electrodes fabricated using graphene. The calculations are performed at temperatures of 233, 300 and 353 °K. From present calculations no significant temperature dependence of quantum capacitance is observed, however a marked increase in QC of value above 58μFcm^-2 is seen. Forphosphorus and Sulphur doped graphene a significant energy gap shift of ~ 1.5 eV from the Fermi level is observed that significantly increases the QC at Fermi level to a high value of ~ 35 μFcm^-2. With boron dopant as well, a shift of energy gap ~ 1.25eV from the Fermi level is observed. The shift in Dirac point increases quantum capacitance at Fermi level that in turn can increase the energy density of supercapacitor remarkably. The effect of increasing doping concentration on quantum capacitance is also investigated. These results suggest that doping of graphene may result in significant increase in QC near Fermi level, if the dopants are selected carefully depending upon the use of graphene as a positive or negative electrode. The results of these calculations reveal that the problem of low QC of graphene in the range of interest can be addressed by modifying itssurface and structure chemistry which may increase energy density in supercapacitors.

中文翻译：

---

杂原子掺杂石墨烯单层的物理性质与超电容性能的关系

使用石墨烯制造的电极对于双电层电容器非常有前途。但是，由于存在狄拉克点，可以通过在石墨烯中掺入适当的掺杂剂来改性，从而使石墨烯在费米能级附近具有“量子电容（QC）”低的局限性。使用硼，硫和磷作为掺杂剂对掺杂石墨烯进行密度泛函DFT计算，以提高使用石墨烯制造的电极的量子电容。计算在233、300和353°K的温度下进行。从目前的计算中，未观察到量子电容的显着温度依赖性，但是在58μFcm ^-2以上的值的QC显着增加。被看到。对于磷和硫掺杂的石墨烯，从费米能级到约1.5 eV的明显能隙位移被观察到，这使费米能级下的QC显着增加到〜35μFcm ^-2的高值。同样使用硼掺杂剂，可以观察到能隙从费米能级偏移1.25eV。狄拉克点的移动增加了费米能级的量子电容，进而可以显着增加超级电容器的能量密度。还研究了增加掺杂浓度对量子电容的影响。这些结果表明，如果根据石墨烯作为正极或负极的使用来谨慎选择掺杂剂，则石墨烯的掺杂可能会导致费米能级附近的QC显着增加。这些计算结果表明，可以通过改变石墨烯的表面和结构化学性质（可能会增加超级电容器的能量密度）来解决石墨烯在关注范围内的低QC问题。