Electrochemical Performance of Nitrogen-Doped TiO₂ Nanotubes as Electrode Material for Supercapacitor and Li-Ion Battery

Electrochemical anodized titanium dioxide (TiO₂) nanotubes are of immense significance as electrochemical energy storage devices owing to their fast electron transfer by reducing the diffusion path and paving way to fabricating binder-free and carbon-free electrodes. Besides these advantages, when nitrogen is doped into its lattice, doubles its electrochemical activity due to enhanced charge transfer induced by oxygen vacancy. Herein, we synthesized nitrogen-doped TiO₂ (N-TiO₂) and studied its electrochemical performances in supercapacitor and as anode for a lithium-ion battery (LIB). Nitrogen doping into TiO₂ was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical performance of N-TiO₂ nanotubes was outstanding with a specific capacitance of 835 µF cm^-2 at 100 mV s^-1 scan rate as a supercapacitor electrode, and it delivered an areal discharge capacity of 975 µA h cm^-2 as an anode material for LIB which is far superior to bare TiO₂ nanotubes (505 µF cm^-2 and 86 µA h cm^-2, respectively). This tailor-made nitrogen-doped nanostructured electrode offers great promise as next-generation energy storage electrode material.