N-doped oxygen vacancy-rich NiCo₂O₄ nanoarrays for supercapacitor and non-enzymatic glucose sensing

Battery-type transition metal oxides (TMOs) gained great attention as an electrode in a supercapacitor (SC) owing to their high electrochemical activity, however, the performance of SCs influenced by low intrinsic conductivity and lower cycling stability. To address the issues, we propose an effective strategy of nitrogen doping and increasing the oxygen vacancies of hydrothermally synthesized nickel-cobalt oxide (N-O_v/NiCo₂O₄-350) nanowire arrays. The modified electrode has a variable superficial nanoporous architecture and a favorable electronic structure resulting in a greatly increased specific surface area and a suitable electron/ion diffusion network. The synthesized hybrid electrode exhibited a specific capacity of 256 mAh g⁻¹ and a high energy density of 83.18 Wh kg⁻¹ at 203.1 W kg⁻¹. Likewise, a non-enzymatic glucose sensor with N-Ov/NiCo₂O₄-350 achieved a broad linear detection range of 0–555 mM, an ultra-high sensitivity of 29 811.53 μA·mM⁻¹·cm⁻², a short response time of approximately 2.2 s, and a low detection limit of 0.02 μM (S/N = 3). The superior electrochemical and glucose-sensing capabilities of the N-Ov/NiCo₂O₄-350 hybrid nanostructure demonstrated the potential of the electrode.