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[Display omitted] • E-waste can be strategically converted into energy-storing electrodes. • Interesting core–shell morphology is formed by a facile two-step synthesis process. • The optimized NiSe-120/Cu 4 O x -3 electrode shows an areal capacity of 138.27 µAh cm−2. • Excellent stability is achieved even after 50,000 charge–discharge cycles. • The C-type HSC device exhibits a good areal capacitance of 233.1 mF cm−2. Recently, for energy storage materials, various surfactant-less synthesis methods have been attaining extensive attention from researchers. Herein, we utilized the wasted desoldering copper wicks (E-waste) as the base substrate to synthesize hierarchical core–shell maze-corn-like nickel selenide/copper oxide (NiSe/Cu 4 O x) architectures by a facile two-step synthesis process. Initially, the Cu 4 O x nanorods (NRs) were grown directly over the surface of the flat braided E-waste copper wicks by thermal oxidation, followed by a facile electrodeposition method to coat the pre-existing Cu 4 O x NRs with NiSe nanoparticles. The optimized NiSe-120/Cu 4 O x -3 electrode exhibited superior electrochemical characteristics (138.27 µAh cm−2 at 4 mA cm−2) compared to the other electrodes, owing to the contribution of core and shell materials, and sustained an ultra-long cycling test of 50,000 charge/discharge cycles with an excellent capacity retention of 98.7%. Inspired by commercially available AA battery, the as-synthesized working electrode was coupled with activated carbon-coated nickel foam to fabricate a cylindrical-type (C-type) hybrid supercapacitor (HSC) device, with an areal capacitance of 233.1 mF cm−2 accompanied by an extraordinary cycling efficiency of 99.1%. Furthermore, the C-type HSC device exhibited maximum energy and power densities of 70.9 µWh cm−2 and 14,000 µW cm−2, respectively and it was tested by powering portable electronics for real-time application. [ABSTRACT FROM AUTHOR]

This study utilizes light adsorbing molecule, phenothiazine (PTZ) to reduce graphene oxide (GO) and functionalize into PTZ-rGO aerogel (PTZ-rGO). The UV excited PTZ reduces GO via electron transfer while PTZ is simultaneously oxidized and functionalized onto rGO to produce PTZ-rGO aerogel. The optimum incorporation of PTZ on rGO sheets renders good electrochemical active surface area of 495.71 m2 g−1 and enhances the diffusion behavior up to 41.92%. This pseudocapacitive effect and the excellent surface property provide promising charge storage results of 235.5 F g−1 at 0.5 A g−1. Furthermore, the stable charge-discharge cycles with 92% capacitance retention after 10,000 cycles render it an excellent electrode material for supercapacitor fabrication. [Display omitted] • One-step approach to produce functionalized rGO aerogel by UV excitation. • UV excites phenothiazine to transfer electron to GO for its reduction. • Functionalized phenothiazine produces pseudocapacitive effect. • Phenothiazine functionalized rGO aerogel can be supercapacitor electrode. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen plasma can fabricate disorder layers (3 ∼ 5 nm) on the surface of α-MnO 2. • Abundant oxygen vacancies appeared in the disorder layers of α-MnO 2. • Oxygen vacancies improved the capacitive performance of α-MnO 2 even at high mass loading (12 mg cm−2). The electrochemical performance of high theoretical capacitance MnO 2 is usually restricted to low mass loading electrode due to the slower electron/ion diffusion kinetics in dense electrodes. Defect engineering has been supposed to an effective way to improve the capacitive performance of transition metal oxides. Herein, cactus-like structure MnO 2 was grown on carbon cloth (CC) and treated with N 2 -plasma to obtain the N-MnO 2 electrode with high mass loading of 12 mg cm−2. Benefiting from the hierarchical structure and rich oxygen vacancies, the as-prepared N-MnO 2 electrode delivered a high mass specific capacitance of 443F g−1 and a high areal capacitance of 5320 mF cm−2. Furthermore, the N-MnO 2 electrode released an excellent rate capability with 71.8% capacitance retention at 20 mA cm−2 as well as gratifying cycling life with 96 % capacitance retention after 8 000 cycles at 20 mA cm−2. Moreover, an asymmetrical supercapacitor device assembled by N-MnO 2 and activated CC can achieve a high energy density of 0.56 mWh cm−2 (46 Wh kg−1) at the power density of 5.14 mW cm−2 (420 W kg−1) with good cycle stability. Such facile N 2 -plasma treatment for defect engineering shows great potential in the rational design for advanced supercapacitor electrodes with high mass loading. [ABSTRACT FROM AUTHOR]