First-principles investigation of nitrogen doping effects on the capacitance behavior of V ₂ CT _<i>x</i> MXenes

Hetero-atom doping is a widely employed strategy to enhance the desired properties of nanomaterials. In this study, we used density functional theory (DFT) to examine the impact of nitrogen doping on the electrochemical performance of V₂CT_<i>x</i>. By considering nitrogen incorporation at various sites, we found that lattice-site doping enhances charge storage capacity, whereas functional-site doping has the opposite effect. This enhancement arises from an increase in redox capacitance or pseudocapacitance, with surface redox activity being the primary mechanism driving the improved capacitance. We also explain the underlying reasons for the contrasting effects of these two doping sites on the electrochemical behavior of V₂CT_<i>x</i>.