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.