Nitrogen-doped black titania for high performance supercapacitors

For energy storage system, it is still a huge challenge to achieve high energy density and high power density simultaneously. One potential solution is to fabricate electrochemical capacitors (ECs), which store electric energy through surface ion adsorption or redox reactions. Here we report a new electrode material, heavy nitrogen-doped (9.29 at.%) black titania (TiO2-x:N). This unique hybrid material, consisting of conductive amorphous shells supported on nanocrystalline cores, has rapid N-mediated redox reaction (TiO2-xNy + zH(+) + ze(-) <-> TiO2-xNyHz), especially in acidic solutions, providing a specific capacitance of 750 F g(-1) at 2 mV s(-1) (707 F g(-1) at 1 A g(-1)), great rate capability (503 F g(-1) at 20 A g(-1)), and maintain stable after initial fading. Being a new developed supercapacitor material, nitrogen-doped black titania may revive the oxide-based supercapacitors.