Influence of N-doped concentration on the electronic properties and quantum capacitance of Hf2CO2 MXene

The electronic properties and quantum capacitance of pristine Hf2CO2 (PH) and N-doped Hf2CO2 systems are investigated using density functional theory (DFT). All the doped systems have the metallic characteristics. The redshift of C-p, Hf-d, O-p, and Hf-p states in valence band gradually increases with the increasing N-doping concentration. The quantum capacitance and the electrode type of Hf2CO2 monolayer can be effectively modulated by N-doping. PH and PH systems with N-doped concentration of 78% are potential cathode materials, while PH systems with N-doped concentration of 11%, 22%, 33%, 44%, 56%, and 67% are potential anode materials, PH systems with 89% and 100% N-doped concentration are suitable for symmetric electrode materials in aqueous system. The wide voltage changes the electrode type of PH system with N-doped concentration of 78%, 89% and 100%. The electrode type of N-doping MXene with mixed terminations are further explored.