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Mesoporous carbon with high mesoporosity could overcome the diffusion limitations in the application fields requiring fast mass transportation. However, traditional templating approaches-derived carbons usually own low mesoporosity resulted from the microporosity dominated nanostructure. Herein, we developed a versatile method adopting self-made Fe(OH)3 as coordinative template to absorb phenols by coordination effect and in situ inducing the polymerization of phenol and formaldehyde to form phenolic resin at Fe(OH)3. Then, the generated H2O and the derived iron oxide from the template upon high temperature could serve as activation regents and mold constructing rich mesoporosity and graphitic structure. The derived products possess foam-like morphology, worm-like mesoporous structure, good graphitization degree, large surface area (1590 m2/g), large pore volume (2.86 cm3/g), uniform pore size distribution (~ 3.1 nm), ultrahigh mesoporosity (98.6%) and exhibit an excellent energy storage performance for aqueous supercapacitor including large energy density of 30.6 Wh/kg, superior capacitance retention of 76.8% and long cycling stability with near 100% capacitance retention after 10 000 cycles at large current density of 20 A/g. The superior capacitance retention for SC implies a wide application potentiality of the developed mesoporous carbon in other fields closely related to fast mass transfer such as catalysis, sorption and so on. [ABSTRACT FROM AUTHOR]

A strategy for the fabrication of graphene oxide (GO) and nitrogen-containing porous carbon (NC) nanocomposites for high-performance supercapacitor electrodes was reported. Driven by the hydrogen bonding and covalent bonding between GO and benzoxazine, GO/NC nanocomposites with different GO content were prepared from a novel polybenzoxazine (PBZ) via a situ ring opening polymerization process coupled with KOH activation technique. The introduction of GO demonstrates a significant effect on the textural property, surface chemistry as well as the electrical conductivity of the nanocomposites, leading to remarkably improvement of the electrochemical behavior. A maximum specific capacitance of 405.6 F g −1 at a current density of 1.0 A g −1 was achieved for GO/NC nanocomposite electrode with GO content of 1.29 wt. % in 6 M KOH electrolyte solution. It also shows better rate capability (267.8 F g −1 at 40 A g −1 ) and cycle durability (95.8% capacitance retention over 5000 cycles) in comparison with the activated PBZ-based nanoporous carbon without GO. Additionally, the as-fabricated GO/NCs symmetric supercapacitor devices in 1 M Na 2 SO 4 can realize a wide operational voltage of 1.8 V, and displays high energy density of 38.6 Wh kg −1 at the power density of 180 W kg −1 , which still maintains 19.9 Wh kg −1 at 32.4 kW kg −1 . [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemically active Oxygen doped carbon (O-PCNs) was fabricated by superbase templated method. • The template basicity on the functionalities and the supercapacitor performances of the derived O-PCNs were disclosed. • The O-PCN-20 is rich in porosity, large in surface area (930 m2/g) and high in active oxygen content (11.4 atom%). • · The O-PCN-20 electrode exhibits large capacitance of 375 F/g@1.0 A/g and energy density of 25.7 Wh/kg@900 W/kg. Templating techniques have been widely adopted for the synthesis of porous carbons, such as oxygen-doped porous carbon nanosheets (O-PCNs), but the effect of the surface characteristics of templates on the surface functionality and performance of a derived carbon has not been well studied. Herein, a series of laboratory-made superbases of K/Mg(OH) 2 with different K/Mg ratios were employed as template to fabricate nanocarbon materials. The aim is to find out how the strength of template basicity could influence the surface functionalities and the supercapacitor performances of the derived O-PCNs. The resulting materials are rich in conjugated hydroxyl and carbonyl groups that are electrochemically active owing to the protection of the conjugated hydroxyl group by KOH and the dehydrogenation step catalyzed by magnesium oxide. Systematic investigations revealed that with the increase of basic strength, the content of the derived electrochemically active oxygen species in the forms of conjugated carbonyl (C O) and hydroxyl (C OH) first increases from 8.4 atom% to 11.4 atom% then decreases to 9.25 atom%. Moreover, the microporosity of the O-PCNs stepwise increases with the rise of KOH loading, ascribable to the effect of KOH etching on the carbon skeleton. The O-PCN-20 templated by 20 % K/Mg(OH) 2 is rich in porosity, large in surface area (930 m2/g) and high in active oxygen content (11.4 atom%). With high active surface area and extra Faradaic capacitance, O-PCN-20 exhibited superior supercapacitor performances including large specific capacitance of 375 F/g@1.0 A/g, high rate capability of 81.1 % (from 1.0 A/g to 20 A/g), energy density of 25.7 Wh/kg@900 W/kg and excellent cycling stability with near 100 % capacitance retentions after 10 000 cycles and more than 86.2 % capacitance retention over 20 000 cycles at large current density of 10 A/g, indicating O-PCN-20 has potential to be used as electrode material for energy storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heterostructure integrated with Fe 0.4 Co 0.6 Se 2 nanobelts and NiCo-P nanosheets is synthesized via a simple two-step electrodeposition. • This core–shell hybrid material has hierarchical porous architecture. • Synergy of two components results in boosted specific capacity and cycling stability. • Hybrid supercapacitor illustrates an energy density of 64.4 Wh kg−1. Exploring novel heterostructure with multiscale nanoarchitectures and modulated electronic structure is crucial to improve the electrochemical properties of electrode materials for supercapacitors (SCs). In this study, a two-step electrodeposition approach which involves suitable efficient procedures, is leading to in-situ preparation of iron cobalt selenide (Fe 0.4 Co 0.6 Se 2) @ nickel cobalt phosphate (NiCo(HPO 4) 2 ·3H 2 O, denoted as NiCo-P) hybrid nanostructure on carbon cloth (CC) substrate. Particularly, depositing two-dimensional (2D) NiCo-P nanosheets on the surface of Fe 0.4 Co 0.6 Se 2 nanobelts results in formation of well-organized Fe 0.4 Co 0.6 Se 2 @NiCo-P nanocomposite with large surface area, hierarchical porous nanoarchitecture as well as numerous electroactive sites, leading to enhanced electroactivity and accelerated mass/electron transfer. Benefiting from its unique nanoarchitecture and synergistic effect of two components, the obtained free-standing Fe 0.4 Co 0.6 Se 2 @NiCo-P electrode demonstrates gravimetric capacity (C m)/volumetric capacity (C d) of 202.3 mAh/g/319.6 mAh cm−3 at 1 A g−1 and good cyclic stability (83.9% capacity retention over 5000 cycles), which are superior to those of pure Fe 0.4 Co 0.6 Se 2 and NiCo-P electrodes. Impressively, it was established that an aqueous hybrid supercapacitor (HSC) based on Fe 0.4 Co 0.6 Se 2 @NiCo-P and rape pollen derived hierarchical porous carbon (RPHPC) achieves gravimetric energy density (E m)/volumetric energy density (E d) of 64.4 Wh kg−1/10.7 mWh cm−3 and a long cycle life with 90.3% capacity retention over 10,000 cycles. This report offers a perspective to design selenide/phosphate heterostructure on conducting substrate for electrochemical energy storage applications. [ABSTRACT FROM AUTHOR]

The electroactivity and cyclic stability of transition metal phosphides (TMPs) for supercapacitors are restricted by inadequate redox active sites and huge volume changes during the charging/discharging process. Herein, a three-dimensional (3D) porous Ni 2 P/NiMo-layered double hydroxide (NiMo-LDH) heterostructure with large specific surface and abundant pore channels is explored as a self-supporting supercapacitor electrode. The well-defined hierarchical pore structure can offer numerous electroactive sites and short ion/electron pathways. The generation of heterointerfaces between multi-dimensional Ni 2 P and two-dimensional (2D) NiMo-LDH nanosheets endows the hybrid composite with improved electrical conductivity and structural robustness. Consequently, the special nanoarchitecture design achieves a specific capacity of 198.6 mAh g−1 (2.28 mAh cm−2) at 1 A g−1 and an impressive rate performance of 78.3% at 20 A g−1. More importantly, the assembled Ni 2 P/NiMo-LDH//orange peel-derived porous carbon (OPC) asymmetric supercapacitor (ASC) device delivers a remarkable specific energy of 63.7 Wh kg−1 at a specific power of 1138.3 W kg−1 and long-term cycling stability (91.7% over 10,000 cycles). The research highlights that the hybridization of TMPs and other nanostructured battery-type materials may produce a synergistic effect and boost the capacitive properties. [Display omitted] • 3D porous Ni 2 P/NiMo-LDH heterostructure is constructed. • A combination of Ni 2 P and NiMo-LDH can conquer their shortcomings. • The synergistic effect leads to boosted electrochemical behaviors. • Asymmetric supercapacitor illustrates an energy of 63.7 Wh kg−1/0.95 Wh cm−2. [ABSTRACT FROM AUTHOR]

A simple two-step electrodeposition strategy is firstly developed for the construction of Co 0.85 Se@Ni 3 S 2 hybrid nanosheet arrays, illustrating remarkable electrochemical properties in supercapacitors. [Display omitted] Rational design of porous heterostructured electrode materials for high-performance supercapacitors remains a big challenge. Herein, we report the in situ synthesis of Co 0.85 Se@Ni 3 S 2 hybrid nanosheet arrays supported on carbon cloth (CC) substrate though an efficient two-step electrodeposition method. Compared with pure Co 0.85 Se and Ni 3 S 2 , the well-defined Co 0.85 Se@Ni 3 S 2 heterojunction possesses enriched active sites, improved electrical conductivity, and reduced ion diffusion resistance. Benefiting from its hierarchically porous nanostructure and the synergistic effect of Co 0.85 Se and Ni 3 S 2 , the as-synthesized Co 0.85 Se@Ni 3 S 2 electrode delivers a gravimetric capacitance (C g)/volumetric capacitance (C v) of 1644.1F g−1/3161.7F cm−3 at 1 A g−1, outstanding rate capability of 60.7% capacitance retention at 20 A g−1, as well as good cycling performance of 87.8% capacitance retention after 5000 cycles. Additionally, a hybrid supercapacitor (HSC) device presents a maximum energy density (E) of 65.7 Wh kg−1 at 696.2 W kg−1 with 93.3% cyclic durability after 15,000 cycles. Thus, this work proposes a simple and effective strategy to fabricate porous heterojunctions as high-performance electrode materials for energy storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg-Co-Ni LDH were homogenously grown on the surface of reduced graphene (Mg-Co-Ni LDH/rG- x). • The Mg-Co-Ni LDH/rG- x was fabricated by a novel ball milling combined ion-exchange method. • The present ball milling combined ion-exchange method is versatile and does not needs extra alkali sources or auxiliary assembly reagents. • The Mg-Co-Ni LDH/rG- x based asymmetric supercapacitor achieve high energy density and superlong cycling stability. As an electrode for energy storage, the inherently poor conductivity of metal hydroxides (MHs) can be improved by in situ growth of MHs on conductive carbon based substrates so that their performances on energy storage could be enhanced to a high level. However, the incompatibility of hydrophilic component (metal hydroxides) and hydrophobic counterpart (carbon based materials) makes it difficult to be accomplished. Herein, we presented a scalable and easy-operated strategy by ball-milling combined with ion-exchange technique to grow Mg-Co-Ni LDH (layered double hydroxides) on reduced graphene, in which ball-milling was utilized to disperse the staring material of magnesium acetate on graphene oxide (GO) to obtain the composite of Mg(Ac) 2 /GO. The composite can be in situ transformed to MgO/reduced grapheme (rG) by following heat treatment. While, the ion-exchange reaction could enables the in situ growth of Mg-Co-Ni LDHs on the reduced graphene. The derived products (denoted as Mg-Co-Ni LDH/rG- x) owns nanosheet morphology, surface area of 59–115 m2/g, homogenous elements distribution. As electrode for supercapacitor, the maximum capacitance of 1204F/g@1.0 A/g was achieved and the corresponding asymmetric supercapacitor device shows a large energy density of 44.3 Wh/kg@800 W/kg. Particularly, a superlong cycling stability with 90.5% capacitance retention of the first cycle was attained after continuous charge/discharge for 20 000 cycles at current density of 5.0 A/g, promising great potential for practical energy storage application. The present strategy is simple and scalable that can be widely applied to the synthesis of various hydroxides/oxides or multi-component hydroxides/oxides on carbon substrates forming a composite structure, thus offers a great potential for broad application areas including catalysis, adsorption, energy storage, etc. [ABSTRACT FROM AUTHOR]

Construction of ordered mesoporous carbon (OMC) with two-dimensional morphology and rich redox functionalities may offer the possibility for improving the supercapacitive performances of the OMC-based electrode materials in capacity and rate performance. Herein, a simple approach by assembly soluble phenolic resin with surfactant of F127 on a self-made magnesium hydroxide was developed and applied to the fabrication of ordered mesoporous carbon nanosheet (OMCN). The obtained OMCN possesses weak ordered mesoporous structure, nanosheet morphology, large surface area (1376 m2/g vs soft-templated OMC of 522 m2/g), rich cracks and abundant electroactive oxygen functionalities (13.6%). As electrode for supercapacitor, the OMCN exhibits a two times larger capacity than that of OMC (301 F/g vs 151 F/g) and excellent rate performance with capacitance retention of 84% (vs that of OMC of 62%). For aqueous symmetric supercapacitor in 1.0 M Na 2 SO 4 , the OMCN based electrode achieves an ultrahigh energy density of 25.3 Wh/kg at power density of 2000 W/kg. As cathode material working on the voltage range of 1.5–4.5 V, OMCN also exhibits a superior surface-driven lithium-ion storage performance including large capacity of 140 mAh/g at 0.5 A/g (vs that of OMC of 7.6 mAh/g), good rate performance and long cycle stability with about 96% capacity retention after 2000 cycles at 2A/g, showing a promising candidate for the electrochemical energy storage. Image 1 • Ordered mesoporous carbon nanosheet (OMCN) was simply fabricated. • OMCN owns larger surface area than F127 templated OMC (1375 vs 522 m2/g). • OMCN achieves larger capacity and higher capacitance retention than that of OMC. • OMCN exhibits superior surface-driven lithium-ion storage performance. [ABSTRACT FROM AUTHOR]

[Display omitted] Although transition metal metaphosphates (TMPOs) display special physical/chemical features and high theoretical capacities, their applications for supercapacitors (SCs) are still restricted by their low energy densities and inferior cycling stability. Herein, a novel strategy has been proposed to address these issues through in situ construction of cobalt nickle metaphosphate (Co 0.2 Ni 0.8 (PO 3) 2)@nickel diselenide (NiSe 2) core–shell heterostructure on carbon paper (CP) as a self-supporting flexible electrode for SCs. Particularly, this unique mushroom-like porous nanoarchitecture assembled by one-dimensional (1D) Co 0.2 Ni 0.8 (PO 3) 2 nanorods and zero-dimensional (0D) NiSe 2 nanospheres can expose abundant active sites and afford multi-dimensional channels, which favors rapid electron ions/electron transfer, accelerates the reaction kinetics, and alleviates volume changes during charging/discharging processes. Profiting from its well-aligned 1D/0D nanostructure and strong synergistic effect between Co 0.2 Ni 0.8 (PO 3) 2 and NiSe 2 , the Co 0.2 Ni 0.8 (PO 3) 2 @NiSe 2 /CP electrode delivers a specific capacity of 219.4 mAh/g/0.414 mAh cm−2 at 1 A/g and good cycling stability with capacity retention of 90.7% after 5000 cycles, outperforming many previously reported TMPO-based electrodes in literature. Impressively, an asymmetric supercapacitor (ASC) device assembled with Co 0.2 Ni 0.8 (PO 3) 2 @NiSe 2 as cathode and porous carbon as anode achieves an energy density of 69.2 Wh kg−1 at 736.0 W kg−1 and maintains a capacity retention of 97.6% after 20,000 charge–discharge cycles. This work provides an efficient approach to design multi-dimensional hybrid nanomaterials for high-performance SCs. [ABSTRACT FROM AUTHOR]

1D-on-1D cobalt iron selenide @ cobalt nickel carbonate hydroxide nanowire arrays as novel battery-type electrode materials were in-situ assembled on carbon cloth, illustrating outstanding energy storage behavior in hybrid supecapacitors. [Display omitted] • 1D-on-1D CoFe 2 Se 4 @CoNi-CH hybrid nanowires are synthesized. • The heterojunction has accelerated mass transfer and altered electronic structure. • Imitate interaction of two components boosts the mechanical stability. • Hybrid supercapacitor device shows an energy density of 67.3 Wh kg−1. Sluggish kinetics and poor structural stability are two main obstacles hampering the exploration of transition metal selenides (TMSs) for supercapacitor. Developing a reasonable core–shell heterostructure with unique morphology is an effective approach to resolve these issues. Herein, a core–shell cobalt iron selenide (CoFe 2 Se 4) @ cobalt nickel carbonate hydroxide (CoNi-CH) heterostructure is directly fabricated on carbon cloth via an electrodeposition method followed by a hydrothermal reaction. In this well-defined heterostructure, one-dimensional (1D) CoFe 2 Se 4 nanowires function as the cores and CoNi-CH nanowires as the shells, which combines the merits of highly conductive CoFe 2 Se 4 for rapid electron transfer and highly electroactive CoNi-CH for multiple redox reactions. Further, the intimate interaction between CoNi-CH and CoFe 2 Se 4 realizes large surface area with hierarchical network and generates rich heterointerfaces with modified the electronic structure. By virtue of its facile 1D-on-1D nanoarchitecture and synergistic effect, the CoFe 2 Se 4 @CoNi-CH electrode delivers a increased specific capacity of 218.6 mAh g−1 at 1 A-1 and enhanced rate capability (65.5% at 20 A g−1) compared with pure CoFe 2 Se 4 and CoNi-CH. Besides, a hybrid supercapacitor is established by coupling CoFe 2 Se 4 @CoNi-CH cathode and porous carbon anode, which enjoys a maximum energy density of 67.3 Wh kg−1 at 765.9 W kg−1 and prominent durability with 85.4% of capacity retention over 20,000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D tree-like NiCo 2 Se 4 @ZnNi-layered double hydroxide core–shell heterojunctions are synthesized. • The structural merits and synergistic effect contribute to boosted electrochemical behavior. • The hybrid supercapacitor displays an energy of 71.9 Wh kg−1 / 0.22 Wh cm−2. Heterojunction engineering has been proven to be an effective strategy to improve the electrochemical behaviors of electrode materials for supercapacitors, considering the superiority of combining the advantages of different components and achieving a synergistic effect. In addressing this, a rational three-dimensional (3D) tree-like heterojunction of NiCo 2 Se 4 @ZnNi-layered double hydroxide (LDH) was for the first time synthesized by a hydrothermal method to break the limitations of single component. By using the interface engineering strategy, one-dimensional (1D) NiCo 2 Se 4 nanoneedles act as the internal conductive core for the orderly deposition of two-dimensional (2D) ZnNi-LDH nanosheets, forming a special core–shell heterojunction. This design realizes the exposure of numerous active sites and the creation of abundant heterointerfaces and mesopores, which contributes to the accelerated redox reaction dynamics and efficient utilization of active materials. As expected, the NiCo 2 Se 4 @ZnNi-LDH electrode achieves a capacity of 1187.4 C/g (1.54 C cm−2) at 1 A/g and wonderful rate capability. Additionally, a hybrid supercapacitor with NiCo 2 Se 4 @ZnNi-LDH as the cathode and lotus pollen-derived porous carbon as the anode delivers an energy density of 71.9 Wh kg−1 / 0.22 Wh cm−2 at a power density of 743.1 W kg−1 / 2.30 W cm−2 and a capacity retention of 94.2 % over 20,000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] Transition metal phosphides hold great promise for high performance battery-type electrode materials due to their superb electrical conductivity and high theoretical capacity. Unfortunately, the electrochemical properties of single metal or bimetallic phosphides are unsatisfactory owing to their low energy density and poor cyclic stability, and one feasible approach is to introduce heteroatoms to form trimetallic phosphides. Here, novel Fe–Co–Ni–P nanosheet arrays are in situ synthesized on a flexible carbon cloth substrate via an electrodeposition method followed by a phosphorization treatment. Due to the presence of abundant redox active sites, large specific surface area with mesoporous channels, desirable electrical conductivity, modified electronic structure, and synergistic effect of Fe, Co, and Ni ions, the as-prepared Fe–Co–Ni–P electrode displays significantly enhanced electrochemical performance when compared to bimetallic phosphides Fe–Co–P and Fe–Ni–P. Remarkably, the Fe–Co–Ni–P electrode exhibits a large specific capacity of 593.0 C g−1 at 1 A g−1, exceptional rate performance (80.3% capacity retention at 20 A g−1), and good cycling stability (84.2% capacity retention after 5000cycles). Besides, an asymmetric supercapacitor device with Fe–Co–Ni–P electrode as a positive electrode and a hierarchical porous carbon as a negative electrode shows a high energy density of 57.1 Wh kg−1 at a power density of 768.5 W kg−1 as well as excellent cyclability with 88.4% of initial capacity after 10,000cycles. This work manifests that the construction of trimetallic phosphides is an effective strategy to solve the shortcomings of single or bimetallic phosphides for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Free-standing carbon materials are promising supercapacitor electrode materials due to their outstanding properties, such as simple assemble process, high rate performance and good stability etc. We present here the fabrication of novel nitrogen-doped hollow hexagonal carbon nanoprism arrays on carbon fiber cloth for supercapacitor via chemical vapor deposition with ZnO as the sacrifice template. The hexagonal nanoprism structure of ZnO template can be well duplicated by ultrathin nitrogen-doped carbon layer through an in situ carbon deposition process. In this method, the template-removing step is not necessary attributed to the carbothermal reduction reaction between ZnO and carbon during the chemical vapor deposition process. The carbon fibers serve as highways for rapid electron transfer. Meanwhile, the in situ growth of nanoprism arrays on carbon fiber results in intact interface and low interface resistance. The open channel structure of the carbon arrays can shorten the ions diffusion path and facilitate the fast electrolyte transport. All these structural advantages contribute to the excellent rate performance of the fabricated carbon composite with scan rate and current density reaching up to 20 V s−1 and 300 mA cm−2, respectively. The present work paves a new way for designing high-rate and highly stable carbon electrode materials for supercapacitors. Image 1 • N-doped hollow hexagonal carbon nanoprisms are fabricated on carbon fiber (N–HCNP/CF). • Chemical vapor deposition is used to prepare N–HCNP/CF with ZnO as sacrifice template. • The in situ growth of N–HCNP on CF leads to intact interface and low resistance. • The N–HCNP/CF shows excellent rate performance as a supercapacitor electrode material. [ABSTRACT FROM AUTHOR]

In this work, core-shell NiMoO 4 @MoS 2 nanorods were successfully fabricated via a facile two-step hydrothermal method. By inheriting the merits of high electrical conductivity from MoS 2 nanosheets and high pseudocapacitive activity from NiMoO 4 nanorods, the hierarchical NiMoO 4 @MoS 2 nanocomposite was endowed with improved electrical conductivity, enlarged specific surface area and enriched porosity, consequently enabling fast ion/electron transport and rapid Faradaic reactivity. Benefited from the synergism of NiMoO 4 and MoS 2 , the NiMoO 4 @MoS 2 electrode was superior to the NiMoO 4 and MoS 2 electrode, achieving specific capacitance of 2246.7 F g−1, as well as showing good rate performance and improved cyclic stability (88.4% capacitance retention after 5000 cycles). The asymmetric supercapacitor device composed of the NiMoO 4 @MoS 2 nanorods and hierarchical porous carbon exhibited a high energy density of 47.5 Wh kg−1 at a power density of 0.44 kW kg−1. The device also showed superior long-term cycling stability, retaining 80.2% of initial capacitance after 10 000 cycles. This work provides a simple strategy for scalable synthesis of integrated nanostructures, which holds great promise for the development of advanced supercapacitors. Image 1 • Hierarchical core-shell NiMoO 4 @MoS 2 nanorods were constructed. • The unique heterostructure offers rich electroactive sites for Faradaic reactions. • The NiMoO 4 @MoS 2 electrode shows a high specific capacitance of 2246.7 F g−1. • The assembled hybrid supercapacitor delivers a high energy density of 47.5 Wh kg−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • An all-solid-state (ASS) strategy without using any solvents and activators was developed. • The ASS strategy derived carbon owns abundant nitrogen species and large packing density. • The resultant product show superior supercapacitor performances with both high gravimetric and volumetric performances. Template synthesis of porous carbon with rich functionalities by a scalable strategy without using any solvents and activators will be a green and promising route. Herein, we reported an all-solid-state synthesis strategy by mixing glucose and graphitic carbon nitride (g -C 3 N 4) by milling and then undergoing a segmented carbonization in which first at low temperature of 573 K to polymerize sucrose onto g -C 3 N 4 , then at high temperature of 973 K to carbonized the composite to obtain a porous carbon (denoted as GNC) with abundant nitrogen species over 20 atom% and large packing density (0.91–1.25 g cm−3). Due to the features of large packing density and rich electrochemically-active N species, as electrode for supercapacitive energy storage, the developed GNC exhibit a comparable energy storage level with both high gravimetric energy density of 26.8 Wh kg−1@1000 W kg−1 and volumetric energy density of 30.8 Wh L−1@1150 W L−1, suggesting a potentiality in energy storage field. Importantly, the present strategy owns characteristics of ease of operation, green and scalable, which would be a promising synthesis route towards the fabrication of functional carbon utilizing in many fields like sorption & separation, catalysis, energy storage and so on. [ABSTRACT FROM AUTHOR]

Fabrication of porous carbon from biomass offers a possibility of the practical application of carbonaceous materials. Herein, a nitrogen, sulfur-codoped hierarchically porous carbon (RPHPC) with inherited morphology/microstructure derived from rape pollen is fabricated by direct activation of rape pollen with mixed salts of ZnCl 2 and FeCl 3 for supercapacitors. Originating from the synergetic effect of interconnected, hierarchical pore structure with the inherited spherical morphology, abundant surface opened channels and appropriate amount of doped N, S atoms with proper degree of graphitization, the resultant hierarchically porous carbon displays a high specific capacitance of 361.6 F g−1 at a current density of 1 A g−1 and outstanding rate capability (217.0 F g−1 at 100 A g−1). Significantly, the assembled RPHPC-750//RPHPC-750 symmetrical device delivers a high energy density of 32.2 Wh kg−1 at a power density of 0.089 kW kg−1 and retain an energy density of 10.7 Wh kg−1 even at 4.1 kW kg−1. In addition, it also exhibits superior cycling stabilty with 94.5% capacitance retention after 20,000 cycles at 5 A g−1. Such remarkable results may offer a new perspective to develop high-performance carbon materials from biomass for supercapacitor applications. Image 1 • A nitrogen, sulfur-codoped hierarchically porous carbon is synthesized from rape pollen. • The high specific capacitance of 361.6 F g−1 is obtained at the optimized temperature. • The obtained carbons exhibit excellent rate capability and cyclic stability. • The assembled symmetrical device delivers high energy density. • Graphic abstract. [ABSTRACT FROM AUTHOR]

Abstract Biomass-derived porous carbon materials hold good prospects for application in supercapacitor owing to their natural abundance, low cost, as well as high heteroatoms content. Herein, multi-heteroatom-doped hierarchical porous carbon was prepared via on-step carbonization process by using chestnut shells as raw material and melamine as activation agent. The obtained chestnut shell-derived carbons exhibit a high specific area (691.8 m2 g−1), abundant interconnected micropores/mesopores, proper level of graphitization, considerable content of heteroatoms (∼3.79 at. % N, ∼13.35 at. % O, and ∼0.52 at. % S). Benefiting from these superior characteristics, the obtained carbon electrode exhibits a high specific capacitance (402.8 F g−1 at 0.5 A g−1 in a three-electrode system) and outstanding rate capability (45.3% capacitance retention at 100 A g−1) in KOH electrolyte. The fabricated symmetric supercapacitor delivers a superior energy density of 26.6 Wh kg−1 at a power density of 445.5 W kg−1. In addition, the supercapacitor device shows good cycling stability with a 96.6% capacitance retention after 20,000 cycles. These results demonstrates that the as-prepared carbonaceous materials have great potential for low-cost and high-performance supercapacitors. Graphical abstract Image 1 Highlights • A multi-heteroatom-doped porous carbon is prepared by one-step carbonization of mixtures of chestnut shells and melamine. • The hierarchical carbon electrode exhibits a high specific capacitance and excellent rate capability. • The assembled symmetric supercapacitor delivers a high energy density and superior cycling stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solvent-free strategy was developed to synthesize porous carbon (MIC x) doped with rich Faradaic active oxygen (5.8–8.2 atom%). • The resultant MICx owns surface area of 326–427 m2/g and large packing density of 1.12–1.28 g/cm3. • The MICx based electrode achieves superior supercapacitor performances with both high gravimetric and volumetric performances. In the selection of carbon-based electrode materials for supercapacitive energy storage, it is hard to get one that is high in both gravimetric and volumetric performance because there is a trade-off between them. In the presented work, microporous carbon materials denoted herein as MIC x were synthesized through catechol polymerization in the presence of molten FeCl 3. As complexing agent, the iron species coordinate with catechol oligomers, functioning as template as well as catalyst in the synthesis of the microporous carbon. The in situ formation of micropores and carbonaceous skeleton is induced by the carbonyl/hydroxyl redox pairs upon catalytic graphitization during carbonization. The derived nanocarbons have high microporosity (70.6 %–79.2 %) and rich oxygenate functionalities (carbonyl: 3.3–4.0 atom% and hydroxyl: 2.5–4.2 atom%). The FeC x materials are high in faradaic activity. For example, the FeC873-based electrode displays excellent supercapacitor performances: capacitance of 440F/g@1.0 A/g (equivalent to 537F/cm3@1.0 A/g) and 289F/g@20 A/g (equivalent to 353F/cm3@20 A/g), large energy density of 25.5 Wh/kg@900 W/kg (equivalent to 31.1 Wh/L@1098 W/L), and good cycling stability (ca.100 % capacitance retention after 20 000 continual charge/discharge cycles). [ABSTRACT FROM AUTHOR]

As an industrial material for supercapacitive energy storage, commercial activated carbons (AC) could achieve a satisfactory gravimetric performances by electric double layered capacitance (EDLC) due to their rich microporosity, but the volumetric performances are usually poor resulted from the low packing density. Herein, we presented a strategy to address this tradeoff relationship and to achieve both high gravimetric and volumetric performance by filling the macro/mesoporosity with extra nitrogen doped carbon. The reconstructed activated carbon could inherit most of microporosity from the parent AC, while the macro/mesoporosity of them was greatly decreased, resulting in increase of packing density and the improvement of surface hydrophilicity. Benefited from the increase of packing density and maintenance of microporosity, the resultant activated carbon achieves greatly enhanced energy storage level including three times higher capacitance of 384 F cm−3@ 1.0 A/g (vs 128 F cm−3@ 1.0 A/g for pristine AC), high rate capability of 73.4% (vs 59.2% for pristine AC), larger energy density of 27.5 Wh L−1@ 900 W L−1 (vs 10.0 Wh L−1@747 W L−1). Importantly, the present strategy provides a facile and unique method to process activated carbon, which offers a possibility improving the energy storage level of the commercial activated carbon. [Display omitted] • Commercial activated carbon (AC) was processed by filling the macro/mesoporosity. • The filled AC owns increased packing density and more nitrogen functionalities. • The filled AC achieves greatly enhanced supercapacitor performances. [ABSTRACT FROM AUTHOR]

The performance of hybrid supercapacitors is restricted by inferior matched electrochemical kinetics of cathode and anode materials, leading to unsatisfactory energy density and poor cyclic stability. Herein, hierarchically porous cobalt iron selenide (Co 0.7 Fe 0.3 Se 2) @ nickel cobalt phosphate (NiCoPO) nanosheet arrays are successfully fabricated on carbon cloth substrate via an electrodeposition method, a hydrothermal treatment, followed by an electrodeposition process. The well-designed Co 0.7 Fe 0.3 Se 2 @NiCoPO cathode material not only combines the merits of high electrical conductivity of Co 0.7 Fe 0.3 Se 2 and high electrochemical activity of NiCoPO, but also generates interaction and synergistic effect between two constituents. Profiting from its unique core-shell heterostructure with short ion transfer roadways and enhanced conductivity, Co 0.7 Fe 0.3 Se 2 @NiCoPO electrode yields a specific capacity of 887.4 C g−1 at 1 A g−1, splendid rate capability of 86.2% capacity retention at 20 A g−1, along with a wonderful cycling stability of 91.1% over 5000 cycles. Besides, a Co 0.7 Fe 0.3 Se 2 @NiCoPO//porous carbon hybrid supercapacitor achieves a maximum energy density of 68.0 Wh kg−1 at 826.6 W kg−1 and outstanding long-term cycling performance with 95.7% initial capacity over 10,000 cycles. Our results propose an efficient approach to construct selenide/phosphate heterojunction with special morphology and nanostructure for advanced energy storage devices. [Display omitted] • 2D/2D heterojunction of Co 0.7 Fe 0.3 Se 2 @NiCoPO are synthesized. • Hierarchical Co 0.7 Fe 0.3 Se 2 @NiCoPO nanosheet arrays expose efficient surface area. • Synergy of dual components results in boosted capacitive properties. • Hybrid supercapacitor realizes an energy density of 68.0 Wh kg−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical NiSe 2 -Fe 3 Se 4 @NiCoB core–shell nanosheet arrays are fabricated. • This hybrid has rich crystalline/amorphous interfaces and regulated structure. • Cooperative effect leads to enhanced electrochemical performance. • An asymmetric supercapacitor with energy of 72.7 Wh kg−1 is achieved. Optimizing the electrode structure and interface is a promising approach to achieve high energy density asymmetric supercapacitors. In this study, a core–shell heterostructure based on crystalline nickel iron selenide (NiSe 2 -Fe 3 Se 4) and amorphous nickel cobalt boride (NiCoB) is for the first time in-situ fabricated on carbon cloth substrate though a hydrothermal approach, a selenization process, followed by a chemical precipitation method. In this well-defined hybrid material (denoted as NiSe 2 -Fe 3 Se 4 @NiCoB), the close combination of NiSe 2 -Fe 3 Se 4 nanosheets core and NiCoB nanosheets shell results in a large specific surface area with rich open channels, and numerous crystalline/amorphous interfaces with regulated electronic structure. Owing to its unique hierarchical pore architecture and synergistic effect of dual battery-type materials, the resultant NiSe 2 -Fe 3 Se 4 @NiCoB electrode displays a specific capacity of 887.0C g−1 at 1 A g−1, wonderful rate retention (71.3% at 20 A g−1), and good cycling stability (86.4% after 5000cycles). Additionally, the assembled NiSe 2 -Fe 3 Se 4 @NiCoB//porous carbon asymmetric supercapacitor illustrates a remarkable energy density of 72.7 Wh kg−1 at 710.7 W kg−1, and exceptional cycling life with capacity retention of 91.1% over 20,000cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Expired coffee derived carbons (HCDC) achieves high packing density of 1.81–1.83 cm3/g. • The derived HCDC owns rich nitrogen (4.5 atom%) and oxygenic (12.0 atom%) functionalities. • The HCDC electrode achieves high gravimetric and volumetric capacitance of 312F/g and 567F/cm3. • The HCDC electrode exhibits a high volumetric energy density of 27.8 Wh/L@1820 W/L. Clean production of activated carbon from household expired food provide an alternative way to get value-added product thus benefits waste reutilization and environmental protection. Herein, we fabricated N, O co-doped activated carbons (HCDC) from expired coffee to by a green route of direct water vapor carbonization/activation approach. In our approach, the expired coffee was firstly grinded and then carbonized under water vapor atmosphere. The derived HCDC owns low surface area (172–184 m2/g), large packing density (1.81–1.83 cm3/g), rich redox-active nitrogen (4.5 atom%) and oxygenic (12.0 atom%) functionalities. As electrode for supercapacitor, the HCDC achieves a high gravimetric capacitance of 312F/g at 1.0 A/g (vs 258F/g of commercial AC) and the value can be maintained 223F/g at 20 A/g, showing a high rate capability of 71.5%. Particularly, because of the large packing density, the HCDC exhibits an excellent volumetric supercapacitor performances: ultrahigh volumetric capacitance of 567F/cm3 (vs 165F/cm3 of commercial AC) and large energy density of 27.8 Wh/L@1820 W/L (vs 7.5 Wh/L@576 W/L for commercial AC) and superlong cycling stability with near 100 capacitance retention after continual 30 000 cycles at large current density of 9.0 A/g, suggesting a promising application for practical energy storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • FeCoP nanosheets@Ni substituted Co carbonate hydroxide nanoarrays were in situ fabricated on carbon cloth. • The smart combination and synergistic effect of core-shell architecture provided rapid ion/electron transfer pathways. • The battery-type electrode showed a capacity of 795.5 C g−1 with high-rate capacity. • The constructed hybrid supercapacitor device owned an energy density of 72.7 Wh kg−1. Developing advanced battery-type electrode materials with versatile morphologies and micro-/nanostructures is crucial to realize high-performance hybrid supercapacitors with high energy density and excellent cycle life. Herein, a facile approach is proposed to design free-standing FeCoP nanosheets decorated by Ni substituted Co carbonate hydroxide (Ni-CoCH) nanoneedles on carbon cloth as a novel cathode for hybrid supercapacitor. This smart hetero-network assembled by conductive FeCoP nanosheets as a core and redox active Ni-CoCH nanoneedles as a shell exhibits increased surface area, improved availability of redox active sites, and facilitated ion/electron transport for faradaic reactions when compared to a single component. Benefiting from its unique core/shell nanostructure, multifunctionality and synergistic effect of two components, the as-prepared FeCoP@Ni-CoCH electrode acquires a high specific capacity of 795.5 C g−1 at a current density of 1 A g−1 and outstanding rate capability and good long-term cyclic stability (89.7% of the initial capacitance after 5000 cycles). Furthermore, a hybrid supercapacitor device consisting of FeCoP@Ni-CoCH as cathode and hierarchical porous carbon as anode in 2 M KOH electrolyte delivers a high energy density of 72.7 Wh kg−1 at a power density of 404.9 W kg−1 and superior cyclic stability. [ABSTRACT FROM AUTHOR]

• Copper chloride was an efficient activator to prepare N, O, S self-doped porous carbons. • CuCl 2 activated hierarchical porous carbon exhibited large surface area of 1722.5 m2 g−1 and high yield of 39.6%. • A large specific capacitance and superior rate performance were achieved. • The symmetric supercapacitor showed high energy density of 30.4 Wh kg−1 under 496.0 W kg−1. ga1 Facile preparation of carbon-based electrode materials with high specific surface area and controllable pore structure through a green and mild strategy is highly desirable for high-performance supercapacitors. Here, hierarchically porous carbon materials were prepared by three types of metal chlorides, including ZnCl 2 , FeCl 3 , and CuCl 2. Compared with porous carbons obtained by traditional ZnCl 2 or FeCl 3 activation, hierarchically porous carbon obtained by a facile CuCl 2 activation possessed higher yield, larger specific surface area, more developed hierarchical pore structure, and higher heteroatom contents. Benefiting from the synergy of unique morphology, hierarchical pore architecture with abundant micro-/mesopores and coexistence of numerous redox-active nitrogen and sulfur funtionalities, the as-prepared hierarchically porous carbon activated by CuCl 2 exhibited superior electrochemical performance in aqueous electrolyte, including a large specific capacitance of 389.3 F g−1 at a current density of 1 A g−1, excellent rate capability and good cycling stability in a three-electrode system. Moreover, the assembled carbon-based symmetric supercapacitor based on CuCl 2 -activated carbon electrode delivered a significantly increased energy density of 30.4 Wh kg−1 at a power density of 496.0 W kg−1 in comparison to ZnCl 2 or FeCl 3 -activated carbon electrodes. Therefore, CuCl 2 activation is proved to be an effective chemical activation agent for the synthesis of biomass-derived carbon materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

• Bases of MgO and g-C 3 N 4 function as template and nitrogen sources, respectively. • The derived carbon (WNLC) owns hierarchical porosity and worm-nest-like morphology. • The WNLC exhibits large surface area (1061 m2/g) and high nitrogen contents (21.3 atom%). • The WNLC electrode in aqueous electrolyte achieves ultrahigh energy density of 53.2 Wh/kg. Because of the instability and uncontrollability of the nitrogen-containing precursor upon high-temperature carbonization, it is very hard to obtain nanocarbon with high nitrogen content over 10 atom% and controllable electrochemically-active nitrogen species. Herein, we report a role-divided templating/doping strategy for the fabrication of porous nanocarbon supercapacitor materials with all-electroactive nitrogen species and ultrahigh energy density based on MgO and g-C 3 N 4 , in which MgO first acts as a polymerization catalyst to form carbon source and then as template for porous structure, while the g-C 3 N 4 acts as a single nitrogen source. Systematic investigations reveal that the carbonization temperature and the single g-C 3 N 4 nitrogen source are vital to obtaining all-electroactive nitrogen species. The obtained nanocarbon (WNLC973-C1N5) owns a worm-nest-like morphology, high surface area and all-electrochemically-active nitrogen functionalities (21.3 atom%). The symmetric supercapacitor based on WNLC973-C1N5 achieves an energy density of 53.2 Wh/kg at a power density of 1000 W/kg, about four times bigger than that of normal carbon-based material. This work highlights the importance of the special nitrogen source to form the all-electrochemically-active nitrogen functionalities for high-performance energy materials and presents facile strategy to fabricate carbon-based materials for extensive applications, such as catalyst, adsorbent, catalyst support, energy material and so on. [ABSTRACT FROM AUTHOR]

• By phenol-keto tautomerism and amination polymerization, N,O-doping nanosheets was fabricated. • Through the introduction of MgO followed by carbonization, there was the generation of nanosheets. • THB-PP-MgO-700 achieves a maximum energy density of 45.8 Wh/kg at a specific power of 550 W/kg. The introduction of faradaic-active heteroatoms into the lattice of porous carbon materials with open accessibility could enhance the capacitance of a supercapacitor by providing extra pseudocapacity. Herein, a new strategy based on phenol-keto tautomerism and amination polymerization/dehydrocarbonation was developed for the construction of porous N,O-doped carbon nanosheets. By a facile two-step method of impregnation and carbonization, m -trihydroxybenzene and piperazine were polymerized and then carbonized on the surface of MgO hard template. After the removal of hard template, the resulting N,O-doped carbon nanosheets were used as electrode materials for supercapacitors. The derived THB-PP-MgO-750 material has nanosheet morphology, amorphous nature, rich defects, as well as large surface area of 811 m2/g and pore volume of 0.90 cm3/g. With high content of N (8.5 atom%) and O (19.3 atom%), THB-PP-MgO-750 displays superior performances including high capacity of 335 F/g at 1.0 A/g (maintaining 197 F/g at 20 A/g), high energy density of 45.6 Wh/kg at power density of 549.8 W/kg, and long cycling stability with 99% capacitance retention after 10 000 charge/discharge cycles at 6.0 A/g, displaying huge application potential. The method is facile and versatile, thus providing an alternative approach for batch synthesis of N,O-doped carbonaceous electrode materials for energy storage. [ABSTRACT FROM AUTHOR]

The development of novel pseudocapacitve materials with optimal nanostructures has tremendous potential in enhancing the electrochemical properties of supercapacitors. Herein, NiHPO 3 ·H 2 O nanorods were prepared via an one-step hydrothermal method. Benefiting from its high electrical conductivity, unique one-dimensional rode-like morphology and hierarichical pore structure, NiHPO 3 ·H 2 O nanorods favor electron and ion transport and provide abundant electrochemical active sites for redox reactions. When applied as positive electrode for pseudocapacitor, the proposed NiHPO 3 ·H 2 O electrode shows a high specific capacitance of 1405.6 F g−1 at 1 A g−1, outstanding rate capability (64.2% capacitance retention at 10 A g−1) along with good cycling stability (77.3% capacitance retention after 5000 cycles). Furthermore, the assembled asymmetric supercapacitor using NiHPO 3 ·H 2 O as a positive electrode and pine pollen-derived hierarchical porous carbon as a negative electrode delivers a high energy density (42.6 Wh kg−1 at a power density of 449.1 W kg−1) and a long cycle life (84.7% retention after 10,000 cycles). These findings provide new opportunities to synthesize novel transition metal phosphites for supercapacitors. Image 1 • NiHPO 3 ·H 2 O nanorods were synthesized via hydrothermal reaction. • The unique nanostructure provides electrochemical active sites for redox reactions. • The NiHPO 3 ·H 2 O electrode delivers a specific capacitance of 1405.6 F g−1. • The constructed asymmetric supercapacitor exhibits an energy density of 42.6 Wh kg−1. [ABSTRACT FROM AUTHOR]

The rational design and fabrication of flexible pseudocapacitive materials with high energy density and superior cycling stability is desirable to high-performance supercapacitors. A hybrid FeNiP@CoNi-LDH assembled from FeNiP nanosheets and CoNi-LDH nanosheets have been vertically grown on carbon cloth via a sequential hydrothermal reaction, phosphorization treatment and electrodeposition strategy. The as-prepared FeNiP@CoNi-LDH possesses a large surface area, 3D interconnected nanosheet arrays architecture, hierarchical pore structure, and abundant active sites with multiple valances, which provides rapid electron and mass transfer channels within its conducive network. Impressively, as a binder-free electrode for supercapacitors, the FeNiP@CoNi-LDH electrode exhibits a high specific capacitance of 2280.6 F g−1 at a current density of 1 A g−1, outstanding rate capability (1222.2 F g−1 at 20 A g−1), and significantly improved cyclic stability (70.4% capacitance retention after 5000 cycles) compared to pure FeNiP and CoNi-LDH nanosheets, owing to its well-designed nanostructure and synergetic effect between two well-matched pseudocapacitive materials. Besides, an aqueous asymmetric supercapacitor device based on FeNiP@CoNi-LDH and porous carbon delivers a maximum energy density of 87.3 Wh kg−1 at a power density of 408.8 W kg−1, and an excellent cycling stability with a capacitance retention of 73.9% after 20,000 cycles. Image 1 • FeNiP@CoNi-LDH nanosheets arrays were grown on carbon cloth. • FeNiP@CoNi-LDH shows a capacitance of 2280.6 F g−1 at 1 A g−1. • The synergistic effect contributes to improved electrochemical performance. • The assembled hybrid supercapactor exhibits 87.3 Wh kg−1 at 408.8 W kg−1. [ABSTRACT FROM AUTHOR]