First-principles study of quantum capacitance of transition metal oxides and nitrogen functionalized graphene as electrode materials for supercapacitor

Abstract

Graphene, with many advantages, is considered an active electrode material for the supercapacitors. However, its actual utilization performance is limited by its low specific capacitance caused by the poor quantum capacitance. In this article, we explored the effects of transition metal oxides (TMOs = MnO, FeO, CoO, NiO, CuO and ZnO) on the geometric structure, electronic properties, quantum capacitance (CQ) and surface storage charge (Q) of graphene-based materials using first-principles method. The findings of this article illustrate the TMOs could stably adsorb on the surface of graphene-based materials, making the systems exhibit metallic characteristic with conducive electron transfer. Around the Fermi level, introducing the electronic states of TMOs makes the modified graphene reveal a considerable CQ and Q in the negative applied voltages, especially the NiO-G system. Furthermore, the TMOs and nitrogen atoms co-modified graphene can further increase the quantum capacitance value, and the selection of electrode materials can be controlled by the N modification. The interesting results can provide a straightforward and effective strategy for designing the selection graphene-based material electrodes applied in high-energy supercapacitor.