Effect of modulation by adsorption and doping on the quantum capacitance of borophene

Electric double-layer supercapacitors (EDLCs) have attracted much attention in the energy storage field due to their advantages such as high output power, long service life, safety and high efficiency. However, their low energy density limits their application. Aiming at the problem of the low energy density of EDLCs, improving quantum capacitance (C(Q)) of electrode materials is an effective strategy. In this paper, we systematically studied the effects of vacancy, doping, and metal atom adsorption on the C(Q) of borophene using first-principles calculations. The results show that S and N doping greatly enhance the charge accumulation of borophene at positive and negative potential, respectively. The maximum C(Q) values of S-doped and N-doped borophene are 157.3 μF cm(−2) (0.38 V) and 187.8 μF cm(−2) (−0.24 V), respectively. Both of them can serve as ideal candidates for the positive (S-doped one) and negative (N-doped one) electrodes of EDLCs. Besides, metal Al atom-adsorbed borophene can also effectively enhance the C(Q), with a maximum value of 109.1 μF cm(−2).