Rationally designed NiMn LDH@NiCo ₂ O ₄ core–shell structures for high energy density supercapacitor and enzyme-free glucose sensor

Abstract

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, NiCo₂O₄nanowires as the core and NiMn layered double hydroxide (LDH) as the shell is directly grown<i>in situ</i>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 NiCo₂O₄nanowire 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^-2and 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^-1when 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<i>μ</i>A mM^-1cm^-2, wide detection range (2<i>μ</i>M^-3mM 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.