Probing Quantum Capacitance of Typical Two-Dimensional Lattices Based on the Tight-Binding Model

The quantum capacitance (C-q) of two-dimensional (2D) electrode materials is closely connected with the 2D lattice symmetry and the electronic structures. Understanding the correlation between the 2D lattice structures and their C-q, in particular, unveiling the function of ferromagnetic spin polarization on C-q, enables one to design highly efficient capacitive materials. Herein, the electronic structures, the specific C-q, and the effect of the spin polarization in 2D square, triangular, and hexagonal lattices have been explored to access the origin and the modulation of C-q based on the single-orbital tight-binding model at half-filling. Compared with the nonmagnetic states, it is found that the range of the specific C-q with considerable values is evidently extended in spin-polarized states. Moreover, the specific C-q near the zero bias is greatly improved in the graphene-like hexagonal lattice under the spin-polarized state owing to the improved density of states near the Fermi level. Compared with only considering the nearest neighboring hopping interaction t(1), the next-nearest neighboring hopping interaction t(2) further increases the specific C-q near zero bias, which results from the more localized density of states near the Fermi level. Therefore, the specific C-q of 2D systems could be manipulated through modulating magnetic properties and different electron hopping interactions. These findings would provide a route to design 2D electrode materials with high quantum capacitance.