Developing flexible, lightweight, and portable energy storage systems have become a necessity with the advent of wearable electronic devices in modern society. We report a novel, easy, and low-cost way to fabricate flexible bimetallic metal–organic framework (MOF) doped graphene sponge (GS) free-standing materials (ZnCo-MOF/GS). The electrochemical behavior of the flexible ZnCo-MOF/GS was probed via galvanostatic charge–discharge, electrochemical impedance spectroscopy, and cyclic voltammetry. The morphological and structural studies of this material were performed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectrometry. ZnCo-MOF/GS exhibited a high specific capacitance of 695 F/g at 1.0 A/g and excellent cyclic stability with 78% retention after a 7500 cycle test in 3.0 M KOH. Furthermore, a ZnCo-MOF/GS based symmetric supercapacitor (SC) was fabricated, and this flexible device displayed a specific capacitance of 302 F/g at 1.0 A/g, an energy density of 108 W h/kg, and a power density of 5037 W/kg. Moreover, this flexible SC kept its excellent performance at severe bending conditions. We believe that our electrode with its outstanding electrochemical performance has a great potential in energy storage applications, especially for lightweight and flexible electronics.

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Dopamine (DA) is a significant catecholamine neurotransmitter in human metabolism, and DA is related to several critical illnesses. Accurate detection of DA is important to diagnose these diseases. Here, we demonstrated a flexible electrochemical sensor, ZnS nanoparticles decorated composite graphene paper electrode (CGPE), for the detection of DA. CGPE was prepared via mold‐casting method using ZnS/graphene oxide dispersion followed by thermal reduction treatment. The characterization of the flexible CGPE was investigated through various techniques. The electrochemical tests were carried out to study the electrocatalytic properties of CGPE against DA oxidation. Compared to graphene paper electrode (GPE), the oxidation of DA occurred at about 250 mV lower potential on CGPE, and peak current density increased about 2 times. Our sensor exhibited high sensitivity in linear range of 0.1–2300 μM of DA with a limit of detection (LOD) of 0.0042 μM. Furthermore, CGPE has selectively detected DA even in the medium containing AA and UA which are biologically active interfering molecules. Besides, the sensor showed many attractive properties such as high durability, stability, and reproducibility and it was successfully applied for the determination of DA in real samples for practical applications.

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