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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]

• Trimetallic oxides (CuMnCoO 4) was synthesized by hydrothermal method. • CuMnCoO 4 exhibits a high specific capacitance of 1715F g−1 at 1 A g−1). • Distinct morphology and combined synergistic effect are responsible for outstanding results. • The AS shows high power and energy density and long-term cycling life. Novel star-shaped trimetallic oxides (CuMnCoO 4) have been synthesized employing hydrothermal method and favorably compared to the Co 3 O 4 and bimetallic (MnCo 2 O 4) oxides. The star-shaped CuMnCoO 4 consisted of bundles of orderly layered and loosely interconnected nanoneedles with a hole in the center; each nanoneedle was composed of single-crystalline nanoparticles. Its distinctive structural features significantly increased the electrochemically active sites and facilitated the mass and charge transports. Furthermore, the three transition metal cations in the trimetallic oxide contributed to the multiple redox reactions. Consequently, CuMnCoO 4 exhibited a significantly enhanced capacitance (1,715F g−1 at 1 A g−1) and outstanding cycling stability, compared to those of Co 3 O 4 (742F g−1) and MnCo 2 O 4 (1,305F g−1). Additionally, an asymmetric supercapacitor (AS) (assembled with CuMnCoO 4 , as the positive electrode, and activated carbon (AC), as the negative electrode) exhibited a high energy density (E) of 40.1 W h kg−1, at a power density (P) of 799 W kg−1, thereby highlighting CuMnCoO 4 as a promising candidate for energy storage. This research can also pave the way for the study of new spinel-trimetallic compounds with EES applications. [ABSTRACT FROM AUTHOR]

Porous carbon materials were synthesized by a simple one-step pyrolysis of disodium ethylenediamine tetraacetate (Na 2 EDTA) under different temperature (650, 750 and 850 °C). Several characterization technologies were employed to evaluate the as-synthesized samples. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy tests were carried out to study the electrochemical property of the samples. The capacitive deionization (CDI) performance of the three samples-based electrodes was investigated and compared. The obtained results showed that pyrolysis temperature played a key role in the formation of the final products with different pore structure and heteroatom content, such as nitrogen and oxygen. Electrochemical performance measurement revealed that 750 °C sample exhibited the highest specific capacitance, the smallest diffusive resistance and charge-transfer resistance, and good conductivity. The salt electrosorption capacity of 750 °C samples were 8.02 mg g−1 at a low initial concentration of NaCl solution (25 mg L−1) and 27.75 mg g−1 at a high initial concentration of NaCl (500 mg L−1). The outstanding CDI performance of 750 °C material can be contributed to its high specific surface area and suitable pore structure. As a low-cost and processable precursor, Na 2 EDTA exhibited promising application prospect in large-scale CDI process. • Na 2 EDTA was employed as nitrogen- and oxygen-rich carbon precursors to fabricate porous carbon material (PC) through one-step pyrolysis process. • The existence of large amount of alkaline –COONa functional groups in Na 2 EDTA exhibited self-activated effect during the pyrolysis process, which simplified the fabrication of PC materials and avoided the usage of pore-forming agent. • The PC sample under 750 °C pyrolysis temperature showed the highest specific surface and pore volume and then a satisfying electrosorption capacity (8.02 and 27.75 mg g−1 with 25 and 500 mg L−1 initial concentration of NaCl solution, respectively). • Excessive high N content in PC sample may have contribution to the specific capacitance but did not do much to the increase of electrosorption capacity. [ABSTRACT FROM AUTHOR]