Boosting Supercapacitor Performance of TiO₂ Nanobelts by Efficient Nitrogen Doping

Abstract

TiO₂ has great potential in the application of biocompatible supercapacitors. Unfortunately, because of its semiconducting nature, TiO₂ exhibits poor electrical conductivity and extremely low specific capacitance. Doping with other atoms is a facile way to enhance electrochemical activity of TiO₂. However, the restricted solubility of substitutional dopants in bulk largely impaired the effectiveness of doping, resulting in quite limited capacitance improvement. To overcome this issue, we propose a two‐step approach to efficiently dope TiO₂ nanobelts with nitrogen. High‐level nitrogen doping (6.1 at. %) was achieved in the distinct crystalline core/disordered shell structured TiO₂, boosting the specific capacitance of TiO₂ from 4 F g⁻¹ to 216 F g⁻¹. Employing compressible, light‐weight three‐dimensional graphene as current collector, the symmetrical cell exhibits a volumetric energy density of 9.6 mWh cm⁻³, highly comparable with the supercapacitors based on conventional pseudocapacitive materials. These encouraging findings unambiguously smash the capacitance bottleneck of TiO₂ and open the door towards the application of TiO₂ in energy‐storage systems.