Quantum Capacitance of Silicene-Based Electrodes from First-Principles Calculations

Silicene with a budded atomic layer has double surfaces with a high surface/volume ratio similar to nano carbon materials and is expected to have potential applications for supercapacitors. With first-principles calculations, it is found that introduction of vacancy defects with the doping in silicene can enhance the quantum capacitance of silicene-based electrodes. The enhancement of quantum capacitance is attributed to the presence of localized states around the Fermi level. Furthermore, the quantum capacitance is observed to increase with the increase of the defect's concentration. It is also observed that the localized states around the Fermi level lead to spin polarization in the cases of B-doping and S-doping near the vacancies.