Effect of Transition Metal and Nitrogen Co-Doping on QuantumCapacitance of Silicene-Based Electrode Materials br

Exploring 2D electrode materials with highquantum capacitance (CQ) is particularly important to improvethe energy density of electrical double-layer capacitors. Generally,the structure and composition of materials determine theircapacitance characteristics. In this paper, the effects of co-dopingof N and transition metal (TM = Sc-Zn) atoms on the structure,stability, electronic, and capacitive properties of silicene werestudied byfirst-principles calculation. Our results show that the co-doped TMNx-Si systems, especially TMN3-Si, are more stablethan the silicene system doped with N or TM atoms. TMNx-Sisystems have more advantages than single-doped silicene and co-doped graphene in improvingCQand surface charge density (Q).Among all TMNx-Si systems studied, ScN2-Si has the bestCQandQperformance, with maximum values 224.88 mu F/cm2and 74.41 mu C/cm2, respectively. Furthermore, it is observed that theCQandQvalues of ScN2-Si increase monotonically with the increase of doping concentration, but the bias position corresponding tothe maximumCQdoes not change and remains at-0.6 V, which is obviously better than the co-doped graphene system. In thestudied systems, except Sc and Ti, theCQandQvalues of TMN3-Si are obviously higher than those of TMN2-Si and TMN1-Si.