Quantum capacitance of supercapacitor electrodes based on germanene influenced by vacancy and co-doping: A first-principles study

Abstract

Germanene with high volume/surface ratio similar to graphene is expected to be promising electrodes for supercapacitors. Based on first-principles method, the stability, quantum capacitance, and surface charge storage of vacancy-defected, doped and co-doped germanene were studied. The results suggested that the enhancement of quantum capacitance (CQ) by introducing of transition-metal dopants (Ti, Cr, Mn, and Co) were more effective than that of B/N/Al-dopants. Furthermore, the co-doped germanene exhibited higher quantum capacitance than single-doped, which also owned very high CQ at negative local potential and was potential used as cathode materials for supercapacitors. The presence of vacancy-defect improved the CQ of germanene, whereas the co-doped defected germanene can’t exhibit any advantages than co-doped prefect germanene. In other words, the co-doping is more effective than vacancy-defect to enhance the quantum capacitance of germanene.