Effect of B and O doping on the electronic structure and quantum capacitance of carbon nitride monolayers using first-principles calculations

Abstract

The structural, electronic, and capacitance properties of B- or O-doped carbon nitride monolayers were systematically investigated using first-principles calculations. Different single-atom substitutions (i.e., B or O dopant on a Cx or Ny substitution site) were considered for this work. The substitution site plays an important role in regulating the stability and electronic structure of carbon nitride monolayers. B or O doping could make carbon nitride monolayers produce large local density of states near Fermi level contributed mainly from the hybridization of the 2p states of C, N, and the doped atom (B or O), thus significantly improving conductivity, quantum capacitance, and surface charge density of the structures. The results show that the quantum capacitances of the B-doped carbon nitride monolayers are much greater than those of the B-doped graphene monolayers. Furthermore, B-doped C3N at the C1 site, B-doped tg-C3N4 at the N2 site, and O-doped tg-C3N4 at the N1 site are strongly recommended as the electrodes in symmetrical supercapacitors, while the other doped components could also be used as cathode or anode materials in asymmetrical supercapacitors. The findings of this study suggest that doped carbon nitride structures could be considered as promising electrode materials for supercapacitors.