Rationally designed NiMn LDH@NiCo2O4 core–shell structures for high energy density supercapacitor and enzyme-free glucose sensor

Exploring high-efficiency and low-cost bifunctional electrodes for supercapacitors and sensors is significant but challenging. Most of the existing electrodes are mostly single-functional materials with simple structure. Herein, NiCo2O4 nanowires as the core and NiMn layered double hydroxide (LDH) as the shell is directly grown in situ on carbon cloth (CC) to form a heterostructure (NiMn LDH@NiCo2O4/CC). The performance in supercapacitors and enzyme-free glucose sensing has been systematically studied. Compared with a single NiCo2O4 nanowire or NiMn LDH nanosheet, the heterogeneous interface produced by the unique core–shell structure has stronger electronic interaction and abundant active surface area, which shows excellent electrochemical performance. Electrochemical tests demonstrate that the NiMn LDH@NiCo2O4/CC core–shell electrode possesses an area specific capacitance of 2.40 F cm−2 and a rate capability of 76.22% at 20 mA cm−2. Simultaneously, asymmetric supercapacitor is assembled with it as the positive electrode and NiFe LDH@NiCo2O4/CC as the negative electrode. The supercapacitor possesses an energy density of 47.74 Wh kg−1 when the power density is 175 W kg−1, revealing excellent performance and maintains cycle stability of 93.48% after 6000 cycles at 10 mA cm−2. Additionally, the electrode applied as enzyme-free glucose sensor electrode also displays outstanding sensitivity of 2139 μA mM−1 cm−2, wide detection range (2 μM−3 mM and 4–8 mM) and low detection limit of 210 nM, representing good anti-interference performance. This work reveals the multi-metal synergy and rationally designed core–shell structure is critical to the electrochemical performance of bifunctional electrodes.