Enhanced Supercapattery Performance Enabled by Nitrogen-Doped Nb₂O₅ Nanostructures

Nitrogen doping has emerged as a strategy to enhance the electrochemical performance of transition metal oxides. In this work, nitrogen-doped niobium oxide (Nb_N) was synthesized via a thermal treatment using urea as the nitrogen precursor. Structural and compositional analyses of Nb_N confirmed successful nitrogen incorporation without phase changes, leading to improved crystallinity and larger crystallites, with XPS revealing increased oxygen vacancies and Raman analysis indicating local lattice distortion. Electrochemical performance was evaluated in a 2 M KOH electrolyte. Cyclic voltammetry and galvanostatic charge-discharge tests revealed a battery-type electrode behavior with higher specific capacity values at 1 A g^-1 for Nb_N (1297.37 C g^-1) compared to the undoped Nb_U (1108.75 C g^-1). Moreover, Nb_N demonstrated rate capability and superior cycling stability. A supercapattery assembled with Nb_N as the positive electrode and activated carbon as the negative electrode delivered an energy density of 496.65 Wh kg^-1 and a power density of 2771.99 W kg^-1, with remarkable stability over 5000 cycles. Nitrogen doping enhanced the structural and electronic properties of Nb₂O₅, improving its pseudocapacitive behavior and making it suitable for high-performance supercapatteries.