First-principles study of quantum capacitance on doped or adsorbed graphyne as supercapacitor electrode

Quantum capacitance (CQ) is one of the key parameters that determine the energy density of supercapacitors. In this paper, density functional theory (DFT) was used to explore the effects of different types of B and N doping, and the adsorption of transition metal atoms Au (Ag, Cu, Ti, Mn) on the structural stability, CQ and surface storage charge of graphyne (GY). We found that the CQ of GY can be adjusted by changing the type of adsorbed transition metal and the concentration of doped B and N atoms, improving the defect that the CQ of GY tends to zero at a negative potential. The CQ and surface storage charges of GY monotonically increase with increasing N and B doping concentrations under positive and negative bias voltages, respectively. The adsorption of Ti atoms at the most stable position increases the CQ of GY to 66.1 μF/cm2, (0.22 V), improved CQ at low potential. The research results provide an effective and simple new idea for the design of high energy density GY supercapacitors.