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Effect of Transition Metal and Nitrogen Co-Doping on Quantum Capacitance of Silicene-Based Electrode Materials

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posted on 2022-03-21, 17:37 authored by Xiaojie Chen, Peixian Wang, Jiaming Jin, Bin Song, Pimo He
Exploring 2D electrode materials with high quantum capacitance (CQ) is particularly important to improve the energy density of electrical double-layer capacitors. Generally, the structure and composition of materials determine their capacitance characteristics. In this paper, the effects of co-doping of N and transition metal (TM = Sc–Zn) atoms on the structure, stability, electronic, and capacitive properties of silicene were studied by first-principles calculation. Our results show that the co-doped TMNx–Si systems, especially TMN3–Si, are more stable than the silicene system doped with N or TM atoms. TMNx–Si systems have more advantages than single-doped silicene and co-doped graphene in improving CQ and surface charge density (Q). Among all TMNx–Si systems studied, ScN2–Si has the best CQ and Q performance, with maximum values 224.88 μF/cm2 and 74.41 μC/cm2, respectively. Furthermore, it is observed that the CQ and Q values of ScN2–Si increase monotonically with the increase of doping concentration, but the bias position corresponding to the maximum CQ does not change and remains at −0.6 V, which is obviously better than the co-doped graphene system. In the studied systems, except Sc and Ti, the CQ and Q values of TMN3–Si are obviously higher than those of TMN2–Si and TMN1–Si.

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