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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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In this work, iron and zinc phosphite [FeP and Zn 3 P 2 (ZnP)] crystals were individually decorated on a flexible, freestanding, and three-dimensional (3D) graphene sponge material (GSM) through a facile and cost-effective electrodeposition method. With the synergistic effect between metal phosphite (MP) particles and graphene, 3D FeP/GSM and ZnP/GSM electrodes displayed excellent electrochemical performances with high specific capacitances of 1872 and 908 F/g at a current density of 1 A/g and remarkable cycling stabilities (85% and 70% retention after 10 000 cycles), respectively. Owing to their superior properties, two asymmetric supercapacitor (ASC) circuits were assembled by employing FeP/GSM and ZnP/GSM as the positive electrodes and GSM as the negative electrode. The FeP/GSM//GSM and ZnP/GSM//GSM ASCs exhibited high energy densities of 265 and 62 Wh/kg with high power densities of 5545 and 3050 W/kg, respectively. Furthermore, as-designed devices showed great stability as retaining 80% and 70% of their initial capacitance after a consecutive 10 000 cycles of galvanostatic charge-discharge processes. These results demonstrated that MP/GSMs can be used as promising electrode materials for flexible ASC applications.