A high-performance supercapacitor based on N-doped TiO₂ nanoparticles

Titanium dioxide (TiO₂) is one of the most commercialized metal oxides due to its abundance, low cost, and environmental friendliness. However, its potential for application in electrochemical energy storage devices especially as an electrode material for supercapacitors is limited. In this study, Nitrogen-doped TiO₂ (N-doped TiO₂) nanoparticles are synthesized through a sol–gel method and their supercapacitive performance is compared with that of TiO₂ nanoparticles. X-ray photoelectron spectroscopy (XPS) analysis of N-doped TiO₂ proves successful doping of nitrogen into the crystal lattice of the TiO₂ nanoparticles with a concentration of 4.1 atom%. Electrochemical properties of the synthesized materials are investigated with a three-electrode system in 3.0 M KCl as the aqueous electrolyte. Electrochemical characterizations proved that nitrogen doping of TiO₂ nanoparticles provided an enhanced supercapacitive performance including, specific capacitance of 311 F g⁻¹ at 1 A g⁻¹, 98.9% capacitance retention after 4000 cycles, and a better rate capability than that of bare TiO₂ nanoparticles. Results of this study clearly demonstrate that small amount of nitrogen doping into the crystal lattice of TiO₂ nanoparticles significantly improves their supercapacitive performance.