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Heteroatom‐doped‐carbon with high electrochemical performance is crucial for the development of advanced carbonaceous materials for energy use. However, achieving homogeneous doping while maintaining electrochemically active microstructure remains challenging. Herein, a feasible hydrothermal protocol to fabricate uniformly N‐doped carbon spheres by in‐situ treatment of glucose and melamine was shown. Melamine served as the soft template to introduce heteroatom dopants while releasing gases to enrich the porous structure. Profiting from the structural directing effect of melamine along with an effective fabrication route, the as‐prepared material presented multiple electrochemically advantageous features including a high surface area, a hierarchical porous structure at different levels, abundant heteroatom doping, etc., and thus delivered high supercapacitance. This work provided an effective strategy for fabrication of carbonaceous scaffold for advanced heterostructured energy materials. [ABSTRACT FROM AUTHOR]

Abstract This work introduces a two-step method to fabricate nanoporous (Co-Ni)@(CoO,NiO) nanocomposites with different Ni/Co ratios (2:1, 1:1 and 1:2) by using hydrogen plasma-metal reaction (HPMR) and chemical dealloying techniques. These nanocomposites with average diameters of 43, 44 and 52 nm are nearly-spherical in shape and contain many micropores. The electrode based on the nanocomposite with Co/Ni ratio of 1:1 exhibits the highest initial specific capacitance of 676 F/g at 1A/g and the best rate capability (77% retention at 10 A/g). The subsequent cycling process continuously activates the electrodes based on these nanocomposites, and remarkably enhances their capacitance. The electrode with Co/Ni ratio of 1:1 achieves the highest capacitance of 2051 F/g at 1 A/g after 1000 cycles. The high pseudocapacitive performance of the (Co-Ni)@(CoO,NiO) nanocomposites is mainly attributed to the nanoporous structure which facilitates fast electron/ion transport, the existence of Co-Ni core which serves as an efficient channel for electron conduction to the current collector, and the continuous activation with formation of electrochemically active materials. This specific nanoporous nanocomposite opens a new way to develop the high performance supercapacitor. Graphical abstract Image 1 Highlights • (Co-Ni)@(CoO,NiO) nanocomposites were prepared by chemical dealloying method. • These nanocomposites were nearly-spherical in shape and contained many micropores. • The electrode with Co/Ni of 1:1 showed the highest initial capacitance of 676 F/g. • The sample also achieved the largest capacitance of 2051 F/g after 1000 cycles. • This was due to the continuous formation of electrochemically active materials. [ABSTRACT FROM AUTHOR]

Graphical abstract Due to synergistic interaction of NiCo-LDH nanosheets and embedded Co 9 S 8 nanoparticles, the as-prepared NiCo-LDH/Co 9 S 8 hybrids on carbon fibers exhibit excellent capacity performance and cycling stability with a high rate capability of 93.1％when used as positive electrode materials for asymmetric supercapacitors. Highlights • The NiCo-LDH/Co 9 S 8 hybrids nanosheet arrays based on MOFs are synthesized. • The embedded Co 9 S 8 nanoparticles are formed by selective sulfurization. • At 50 mV s−1, the capacitive contribution of CC@NiCo-LDH/Co 9 S 8 is up to 86.9％. • The supercapacitor achieves an outstanding electrochemical property. Abstract Metal-organic frameworks (MOFs) with tunable pore size, stable porous architectures and large specific surface areas have been widely used as precursors for supercapacitor electrode materials. Herein, MOF-derived hollow nickel cobalt layered double hydroxide (NiCo-LDH) nanoarrays embedded with selectively formed Co 9 S 8 nanoparticles on flexible carbon fibers (CC@NiCo-LDH/Co 9 S 8) are reported. The 2D hollow NiCo-LDH framework from self-templated transformation of MOFs enhances the flow efficiency of ions at interlayers to further reduce the resistance of ion transportation. Significantly, the embedded Co 9 S 8 nanoparticles from selective sulfurization of Co exhibit rich active sites and intimate contact of LDH/Co 9 S 8 , which effectively improves the electrochemical properties of CC@NiCo-LDH/Co 9 S 8 hybrids, such as electrical conductivity, capacity performance and structural stability. Due to synergistic interaction of NiCo-LDH nanosheets and embedded Co 9 S 8 nanoparticles, the as-prepared CC@NiCo-LDH/Co 9 S 8 electrode material exhibits an ultrahigh capacitance of 2438 F g−1 at 5 A g−1. Furthermore, the as-assembled asymmetric supercapacitor (ASC) device of CC@NiCo-LDH/Co 9 S 8 //activated carbon (AC) achieves a maximum energy density of 38.0 Wh kg−1 at 800.0 W kg−1 and outstanding cycling stability with 93.1％ retention of the initial capacitance after 5000 cycles. [ABSTRACT FROM AUTHOR]

Carbon materials have been widely used as electrode materials for supercapacitors, while the current carbon precursors are mainly derived from fossil fuels. Biomass-derived carbon materials have become new and effective materials for electrodes of supercapacitors due to their sustainability, low pollution potential, and abundant reserves. Herein, we present a new biomass carbon material derived from water hyacinth by a novel activation method (combination of KOH and HNO3 activation). According to the electrochemical measurements, the material presents an ultrahigh capacitance of 374 F g−1 (the current density is 1 A g−1). Furthermore, the material demonstrates excellent rate performance (105 F g−1 at a higher density of 20 A g−1) and ideal cycling stability (87.3% capacity retention after 5000 times charge–discharge at 2 A g−1). When used for a symmetrical supercapacitor device, the material also shows a relatively high capacity of 330 F g−1 at 1 A g−1 (a two-electrode system). All measurements suggest the material is an effective and noteworthy material for the electrodes of supercapacitors.

Metal ions (Al3+and Co2+) co-doped α-Ni(OH)2/graphene hybrid materials had been successfully synthesized by a facile chemical co-precipitation route. X-ray diffraction (XRD) patterns revealed the successful phase transmission from β-Ni(OH)2to α-Ni(OH)2after Al3+doping and the continuously enlarged interlayer distance of α-Ni(OH)2after subsequent Co2+doping. Due to its large interlayer distance, mesoporous structure and highly conductively graphene (GNS), the as-obtained Al-Co co-doped α-Ni(OH)2/GNS composite (Al-Co-Ni/GNS) showed an ultrahigh specific capacitance of 2257 F g−1at 2mV s−1as well as good cycling stability with 77% of the initial capacitance retention after 1000 cycles in 6M KOH aqueous solution. [ABSTRACT FROM AUTHOR]

Carbon materials have been widely used as electrode materials for supercapacitors, while the current carbon precursors are mainly derived from fossil fuels. Biomass-derived carbon materials have become new and effective materials for electrodes of supercapacitors due to their sustainability, low pollution potential, and abundant reserves. Herein, we present a new biomass carbon material derived from water hyacinth by a novel activation method (combination of KOH and HNO3 activation). According to the electrochemical measurements, the material presents an ultrahigh capacitance of 374 F g−1 (the current density is 1 A g−1). Furthermore, the material demonstrates excellent rate performance (105 F g−1 at a higher density of 20 A g−1) and ideal cycling stability (87.3% capacity retention after 5000 times charge–discharge at 2 A g−1). When used for a symmetrical supercapacitor device, the material also shows a relatively high capacity of 330 F g−1 at 1 A g−1 (a two-electrode system). All measurements suggest the material is an effective and noteworthy material for the electrodes of supercapacitors. [ABSTRACT FROM AUTHOR]