CoNiO2/TiN–TiOxNy composites for ultrahigh electrochemical energy storage and simultaneous glucose sensing

Abstract

We report a rational growth of functional CoNiO₂/TiN–TiO_xN_y composites on flexible Ni foam for ultrahigh energy storage with fast charging capability and simultaneous non-enzymatic glucose detection. The TiN–TiO_xN_y intermediate layer provides both fast electron transport and a uniform growth substrate for polycrystalline mesoporous CoNiO₂ NWs, at the same time preventing corrosion of the Ni substrate. Ultrahigh areal pseudocapacitance of 3181 and 2763 F g⁻¹ (or 3.36 and 2.83 F cm⁻²) is obtained from the CoNiO₂/TiN–TiO_xN_y composite at current densities of 2 and 10 mA cm⁻², respectively; these values are substantially better than those obtained from the plain CoNiO₂ NWs at the same current densities. Furthermore, the CoNiO₂/TiN–TiO_xN_y composite exhibits high flexibility and cycling stability, and can be charged up to 1.64 F cm⁻² within 9 seconds at a high current density of 100 mA cm⁻². Moreover, after being fully charged, the CoNiO₂/TiN–TiO_xN_y composite-based pseudocapacitors can maintain an extended discharge time of hundreds to thousands of seconds, and are demonstrated as power-free sensors for real-time electrochemical detection of glucose, with a detection limit of ∼1 μM.