Computational screening toward quantum capacitance of transition-metals and vacancy dope d/co-dope d graphene as electrode of supercapacitors

It is of importance to explore electrode materials with high specific capacitance, improving energy density of supercapacitors. Generally, the composition and structure of electrode materials determines its function. Despite many advantages of graphene, low intrinsic capacitance limits its application in the electrode of supercapacitors. Herein, quantum capacitance of 56 kinds of 3d, 4d and 5d transition-metal and vacancy doped/co-doped graphene, named as TM@G and TM@VG, are screened by density functional theory. We concluded that quantum capacitance (C-q) and density of surface charge (Q(sc)) of graphenebased electrodes can be effectively enhanced with transition-metal and vacancy co-doping, which can be related to shift and/or enhancement of DOS near the Fermi level. Calculated stability (Delta E-b) and Q(sc) imply that Y@G, Ta@VG, Au@VG and Ni@VG are suitable for anode in aqueous systems, while Sc@VG, Y@VG, Fe@VG and Zn@VG for cathode. Cu@VG and Re@VG are more potential for symmetric supercapacitors. Besides, the capacitive performance of graphene can also be enhanced by transition-metal and vacancy co-doping in ionic/organic systems. Noteworthily, in aqueous/ionic/organic systems, Sc@VG and Y@VG are good cathode materials, when Y@G, Ta@VG and Au@VG are superior candidates for anode materials. Therefore, the selection of electrode materials will hold an instructional significance in the development of suporcapacitors. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study screened 56 kinds of transition-metal and vacancy doped/co-doped graphene using density functional theory, and found that quantum capacitance and density of surface charge of graphene-based electrodes can be effectively enhanced with transition-metal and vacancy co-doping, leading to improved capacitive performance in supercapacitors.