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Porous microspheres copper cobalt carbonate hydroxides (Cu x Co 2−x CH) pseudocapacitive electrode material comprised of nanoplates via a facile hydrothermal method were presented. Significantly, the crystalline structure, morphology and electrochemical performance of the Cu x Co 2−x CH can be readily manipulated by varying the Cu/Co molar ratios. Among various stoichiometries of Cu x Co 2−x CH porous microspheres studied, Cu 1.79 Co 0.21 CH consisted of nanoplates with a mean thickness of ∼35 nm showed a high specific capacitance of 789 F g −1 at a current destiny of 1 A g −1 and good rate ability. Furthermore, the optimized Cu 1.79 Co 0.21 CH electrode also exhibited remarkable high cycling stability, ca 77.5% after 3000 charge/discharge cycles at current density of 5 A g −1 . An asymmetric device was constructed from optimized Cu 1.79 Co 0.21 CH materials on nickel foam (NF) as cathode electrode and graphene on NF as anode electrode in a 6 M KOH electrolyte. The asymmetric Cu 1.79 Co 0.21 CH/NF//graphene/NF supercapacitor device delivered a specific capacitance of 60.5 F g −1 in a potential range of 0–1.6 V. A high energy density of 21.5 W h kg −1 was achieved at the power density of 200 W kg −1 . More significantly, the designed device exhibited excellent cycling stability with 73.3% capacity retention after 5000 cycles. [ABSTRACT FROM AUTHOR]

Highlights: [•] Porous carbons were prepared using endothelium corneum gigeriae galli as precursor. [•] Surface and structural properties strongly depend on carbonization temperatures. [•] Resultant carbons possess nitrogen heteroatom and high surface areas. [•] ECGG-900 sample exhibits excellent electrochemical capacitive performances. [ABSTRACT FROM AUTHOR]

In this study, we synthesized binder-free NiCo2O4@NiCo2O4 nanostructured materials on nickel foam (NF) by combined hydrothermal and cyclic voltammetry deposition techniques followed by calcination at 350 °C to attain high-performance supercapacitors. The hierarchical porous NiCo2O4@NiCo2O4 structure, facilitating faster mass transport, exhibited good cycling stability of 83.6% after 5000 cycles and outstanding specific capacitance of 1398.73 F g−1 at the current density of 2 A·g−1, signifying its potential for energy storage applications. A solid-state supercapacitor was fabricated with the NiCo2O4@NiCo2O4 on NF as the positive electrode and the active carbon (AC) was deposited on NF as the negative electrode, delivering a high energy density of 46.46 Wh kg−1 at the power density of 269.77 W kg−1. This outstanding performance was attributed to its layered morphological characteristics. This study explored the potential application of cyclic voltammetry depositions in preparing binder-free NiCo2O4@NiCo2O4 materials with more uniform architecture for energy storage, in contrast to the traditional galvanostatic deposition methods. [ABSTRACT FROM AUTHOR]

In this work, a facile two-step hydrothermal method was reported to grow hierarchical flower-like NiAl layered double hydroxide (LDH) directly on 3D nickel foam (NF) which was further coated with 2D graphene nanosheets (GNS) layers as binder-free supercapacitor electrode. The positive and negative effects of GNS on the electrochemical performance of LDH-NF electrode were investigated in detail. The prepared LDH-NF/GNS electrode maintained an enhanced specific capacity of 165.6 C g −1 after 4000 cycles at a high current density of 40 A g −1 . Furthermore, a hybrid supercapacitor, with LDH-NF/GNS and GNS-NF as the positive and negative electrodes, achieved an energy density (31.5 Wh kg −1 at a power density of 400 W kg −1 ) and super long-term cycle stability (a specific capacity of 67.2 C g −1 at 5 A g −1 after 5000 cycles with 80% retention). This study not only opens up the possibility of engineering LDH-NF/GNS into a promising electrode, but also highlights the positive and negative roles of GNS on LDH-NF as binder-free electrodes for further development of high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Highlights: [•] 3D Co(II) ions modified graphene aerogels were prepared by one-step hydrothermal process. [•] The aerogel electrodes showed hybrid supercapacitor behaviors. [•] The aerogel electrodes exhibited high rate capability and long-term cycling stability. [Copyright &y& Elsevier]

We report the synthesized mixture of MXene and Ni Co LDH on nickel foam by an electrodeposition technique. The specific capacitance of the mixture attained 983.6 F g −1 at a discharge current of 2 A g −1 , which is greater than that of pure MXene. Compared to Ni Co LDH, the sample created through electrodeposition provided a better rate capability of 983.6 F g −1 at 2 A g −1 and 536.6 F g −1 at 50 A g −1 and cycling stability with 76% retention after 5000 cycles at 30 A g −1 . Moreover, a solid-state asymmetric supercapacitor with MXene-LDH as the positive electrode and multi-walled carbon nanotube coated on the nickel foam as the negative electrode delivers high energy density (36.70 Wh kg −1 at the power density of 1.44 kW kg −1 ), which outperforms the other devices reported previously. [ABSTRACT FROM AUTHOR]

Abstract: Novel mesoporous carbon has been synthesized using rod-like nano-hydroxyapatite (HA) particles as templates, sucrose as carbon precursor by polymerizing, carbonizing and the removal of templates with HCl solution. In the process, HA not only acted as an endotemplate but also an exotemplate producing micropores and mesopores. Subsequently, mesoporous carbon was modified by HNO3 solution with different concentration. The morphology, pore structure, and surface functional groups of the as-obtained samples are analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller method (BET), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The electrochemical performance for electrochemical capacitors is evaluated in a 1M H2SO4 aqueous solution. The results manifest that the structrue of resultant carbon with a high surface area (719.7m2 g−1) and large pore volume (1.51cm3 g−1) is the replica of HA. After modification, the surface area and pore volume mesoporous carbons slightly decrease, while their electrochemical performance have been significantly improved with the increase of the capacitance from 125.7 to 170.1Fg−1 and a non-decayed cycle life over 5000 cycles for HA-C-0.15N. [Copyright &y& Elsevier]