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Two-dimensional Ti 3 C 2 MXene with high bulk density can act as prospective electrode material to construct high volumetric energy density supercapacitors. Herein, a series of nitrogen-doped Ti 3 C 2 (N-Ti 3 C 2) films are successfully synthesized by adjusting the quantity of urea using a facile solvothermal method. The incorporation of nitrogen atoms can enlarge interlayer spacing and diminish -F terminal groups of Ti 3 C 2 to promote the diffusion and intercalation of electrolyte ions, and bring about defect sites to provide more electrochemical reactive sites, thus improving the specific capacitance of N-Ti 3 C 2. As a result, the 2.0 N-Ti 3 C 2 film shows the highest volumetric capacitance of 2898.5 F cm−3 at scan rate of 2 mV s−1 in 3 M H 2 SO 4 solution, which is mainly attributed to its high pyridinic N content and low -F terminal groups. Density functional theory (DFT) calculations indicate that the doped N atoms have a higher adsorption energy for protons to enhance the pseudocapacitance of 2.0 N-Ti 3 C 2 electrode, and the increased density of states demonstrate the improvement of its electric conductivity after N doping, which promotes the rate performance of 2.0 N-Ti 3 C 2 electrode. The assembled symmetric supercapacitor based on 2.0 N-Ti 3 C 2 film delivers a high volumetric energy density of 40.8 Wh L−1 and good cycling stability. Our work provides an effective and alternative strategy to improve capacitance of other MXenes for high-performance supercapacitors. [Display omitted] • Flexible nitrogen-doped Ti 3 C 2 films are synthesized by a solvothermal method. • Nitrogen atoms can enlarge interlayer spacing and generate defect sites in Ti 3 C 2. • High pyridinic N can act as electron-donors to absorb more electrolyte ions of H+. • Low -F terminal groups are beneficial to enhance pseudocapacitance of N-Ti 3 C 2. • Optimal 2.0 N-Ti 3 C 2 shows a volumetric capacitance of 2898.5 F cm−3 at 2 mV s−1. [ABSTRACT FROM AUTHOR]