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A flexible self-supporting and binder-free supercapacitor electrode is fabricated by embedding a polypyrrole (PPy) nanostructured network into only one side of a graphene thin film via a spin coating method and a subsequent hydrothermal process. Based on the amphiphilic nature of the graphene oxide (GO) thin film, the well-defined PPy nanoparticles are well dispersed and form a reticular structure on the thin film surface. After reduction treatment at a temperature of 180 °C, the reduced graphene oxide (rGO) thin film not only provides a large accessible surface area for the dispersion of PPy nanoparticles but also acts as a binder-free conductive current collector. The polypyrrole/graphene film (PGF) electrode material exhibits an excellent electrochemical performance in the three-electrode configuration, including a high specific capacitance of up to 455 F g−1 at 1 A g−1 and outstanding cycling stability (97% capacitance retention after 1000 cycles). In addition, the symmetric PGF supercapacitor shows a specific capacitance of up to 49.3 F g−1 at a cell voltage of 1.4 V and exhibits a maximum energy density of 13.4 W h kg−1 at a power density of 700 W kg−1, with 96% capacitance retention after 1000 cycles. This work shows impressive potential in fabricating high-performance flexible electrodes for supercapacitors. [ABSTRACT FROM AUTHOR]

A new redox‐active organic molecule, naphthalene diimide derivative (NDI), is synthesized through the condensation reaction for electrochemical energy storage, in which 1,4,5,8‐naphthalenetetracarboxylic dianhydride and 4‐aminophenol are used as skeleton and substituent, respectively. The NDI is acted as a guest molecule to non‐covalently modify reduced graphene oxide (rGO) and to form an organic molecular electrode (OMEs). The resultant electrode exhibits outstanding performance under the three‐electrode configuration, including specific capacitance (354 F g−1 at 5 mV s−1) and cycling performance (87.2% after 8000 cycles). Furthermore, the electrochemical behaviors of the OMEs are mainly controlled by surface reactions and pseudocapacitance contribution is up to 93% of the total capacity at 100 mV s−1. In addition, a positive electrode (graphene hydrogel‐2,6‐dihydroxynaphthalene (GH‐DN)) is formed by hydrothermal method. At last, an asymmetric device (GH‐DN//rGO‐NDI, ASC) is assembled and a specific capacitance of 111.3 F g−1 is reached. The ASC can deliver a high energy density of 26.3 Wh kg−1 at power density of 0.6 kW kg−1. Moreover, two ASC devices in series may light 81 light‐emitting diodes. It is believed that organic molecule electrodes are candidates for new green energy storage materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new electrode material (CHY/RGO) is prepared. • Chrysin (CHY) are grafted onto the surface of Reduced graphene oxide (RGO) by π-π electrostatic force. • The specific capacitance of CHY/RGO can reach up to 707F g−1 at 1 A g−1. • Density functional theory (DFT) calculation shows CHY are parallel adsorbed on RGO. • CHY/RGO//CHY/RGO device can deliver the energy density of 38 Wh kg−1. In this study, chrysin (CHY) molecules are immobilized on the surfaces of graphene oxide (GO) via π-π interactions to obtain organic molecular-modified reduced graphene oxide (RGO) composite electrode material (CHY/RGO) by one-step hydrothermal. On one hand, CHY molecules can contribute to capacitance through faradic reactions. On the other hand, they act as spacers that impede the accumulation of graphene nanosheets and promote electrolyte ion migration. As a result, CHY/RGO exhibits excellent capacitance performance. The specific capacitance is up to 707F g−1 (1 A g−1), and the capacitance remains 100% after 10 000 circles. In addition, the symmetrical supercapacitor (CHY/RGO//CHY/RGO) displays excellent energy storage performance, achieving an energy density of 38 Wh kg−1 at a power density of 800 W kg−1. Two CHY/RGO//CHY/RGO devices in series is capable of lighting 50 LEDs. Density functional theory (DFT) calculations show that CHY molecules are adsorbed parallel to the RGO by the π-π stacking. The DFT calculations also indicate that the modification of CHY molecules alters the charge distribution on the surface of RGO. Therefore, CHY/RGO composites offer a higher capacitance and superior cycle stability, making them a promising choice for future energy storage electrode materials. [ABSTRACT FROM AUTHOR]

Graphene hydrogels (GH), as a derivative of graphene have become a research hotspot in the field of energy storage due to their three-dimensional network structure which can prevent the agglomeration of graphene. The specific capacitance and energy storage ability can be further increased by non-covalent functional graphene hydrogels with organic small molecules. In this work, 4-methylumbelliferone (DTBF) molecules interacted on the surfaces of GH via π-π interactions to get a carbon electrode material (DTBF/GH) by one-step hydrothermal. On the one hand, the DTBF molecules can contribute capacitance by faradic reactions, on the other hand, they can act as spacers to hinder the accumulation of graphene nanosheets, thus enhancing the specific surface area of graphene and promoting the migration of electrolyte ions. As a result, DTBF/GH displays an ultrahigh-specific capacitance. The specific capacitance can reach up to 578 F g−1 (1 A g−1). To verify the influence of electrode material matching on capacitor performance, an asymmetric supercapacitor and a symmetrical capacitor are assembled respectively. Although the specific capacitance of the DTBF/GH material is higher than that of activated carbon (AC), the energy density (E d = 19 Wh kg−1) of the DTBF/GH//AC capacitors is higher than that of the DTBF/GH//DTBF/GH capacitors. It shows that the matching of electrode materials has a great influence on the E d and the power density (P d) of the capacitor. In addition, two DTBF/GH//AC devices in series can light 47 LEDs. [Display omitted] • A new carbon electrode material (DTBF/GH) is prepared. • GH with 3D network structure is conducive to the migration of electrolyte ions. • The specific capacitance of DTBF/GH can reach up to 578 g−1 at 1 A g−1. • The DTBF/GH //AC displays energy density of the 19 Wh kg−1. [ABSTRACT FROM AUTHOR]

In the present work, we report a simple two-step process to fabricate hierarchical porous carbon from biomass. The so-called two-step refers to hydrothermal carbonization of cypress coats followed by activation with KOH. The morphology and porous parameters of the resulting porous carbon can be controlled by adjusting KOH/carbon mass ratio during activating stage. The optimal sample (SHPC-2) has a hierarchically porous structure containing micropores and meso-/macropores, high specific surface areas (1325.9 m2 g− 1) with appropriate pore size and hydrophilous surface properties due to rich nitrogen and oxygen co-doping. The electrochemical measurements show the as-prepared SHPC-2 exhibits a high specific capacitance (345 and 330 F g− 1 at 1.0 A g− 1) and better rate capability (75.4% and 87.8% capacitance retention at 50 A g− 1) in 1 M H2SO4 and 6 M KOH, respectively. Furthermore, the assembled symmetric supercapacitor based on SHPC-2 and filled with 1 M Na2SO4 electrolyte delivers an outstanding energy storage performance (energy density of 30.5 W h kg− 1 at power density 900 W kg− 1) with good cycling stability (86.2% retention after 10000 cycles at 5 A g− 1). These results indicate that the eco-friendly carbon materials derived from biomass have a huge potential in the applications of high-performance electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

A novel tetrahydroxy-anthraquinone zeolitic framework (TZM) with a Viburnum blossom-like structure is synthesized via a simple solvothermal method by using tetrahydroxy-anthraquinone to substitute imidazolate without carbonization at high temperature. Considering the excellent electrochemical performance of the TZM, including a high specific capacitance of 2030 F g−1 at a current density of 1 A g−1, and good cycling stability with a capacitance retention of 94% of the initial capacitance after 1000 cycling charge/discharge measurements, an aqueous TZM//AC asymmetric supercapacitor (ASC) in 1 M KOH electrolyte is successfully fabricated by using the resultant TZM as the positive electrode and activated carbon nanosheets (ACS) as the negative electrode, respectively. The as-assembled aqueous ASC delivers a high energy density of 47.7 W h kg−1 at a power density of 750 W kg−1 with a high potential window of 0–1.5 V. Moreover, for the purpose of exploring the practical application of the active materials, an all-solid-state ASC TZM//ACS device with PVA-KOH gel electrolyte and separator is assembled and connected, which can light up a red light-emitting diode (LED). Its good performance demonstrates that the TZM//ACS ASC is a promising energy-storage system. [ABSTRACT FROM AUTHOR]

As a new type of green electrode material for supercapacitors, redox-active organic molecules have shown great potential due to their fast and reversible redox reactivity, excellent cycle stability and sustainability. However, their electrically insulating nature limits any practical application when they are used alone. Herein, dissected carbon nanotubes (DCNTs) were prepared through a single-step chemical oxidation method to build a unique conductive substrate with 1D nanotubes and 2D graphene nanoribbons. Also, thanks to the abundant oxygen-containing functional groups on the sidewalls of DCNTs, redox-active organic p-phenylenediamine (PPD) molecules can be strongly and massively anchored by a covalent strategy. In this design, DCNTs can serve as a conductive network to ensure efficient electron transport while PPD molecules guarantee a high specific capacitance via the fast and reversible redox reaction. Under the synergy of the two parts, the PPD covalently functionalized DCNT (PPD-C-DCNT) electrode material displays a high capacitance value of 388 F g−1 at 1 A g−1 (ten times higher than that of pristine MWCNTs), a wide electrochemical stable potential window of −0.8 to 0.8 V vs. the SCE reference electrode in 1 mol L−1 H2SO4 and an outstanding electrochemical stability of 85.7% after 10 000 cycles at 5 A g−1. Finally, a novel symmetric supercapacitor (PPD-C-DCNT SSC) was assembled to evaluate the actual energy storage properties of the electrode material. As a result, the PPD-C-DCNT SSC exhibits a maximum energy density of 19.1 W h kg−1 at a power density of 800 W kg−1 in a cell voltage ranging from 0 to 1.6 V. [ABSTRACT FROM AUTHOR]

The naphthoquinone and RuO2 hybrid graphene hydrogel (NQ–RuO2/SGH) composite, which can be a suitable positive electrode material of an asymmetric supercapacitor, is prepared via a two-step process. The RuO2/graphene hydrogel composite (RuO2/SGH) is first synthesized through a simple hydrothermal method by using oxidized graphite (GO) and RuCl3 as raw materials, and then, 1,4-naphthoquinone (NQ) molecules are adsorbed on the exposed graphene hydrogel surface of the RuO2/SGH composite via a π–π stacking interaction. The electrochemical tests show that the NQ–RuO2/SGH composite delivers a high specific capacitance (450.8 F g−1) even at a low RuO2 loading mass (14.6%), meanwhile, an asymmetric supercapacitor (ASC) is constructed by using NQ–RuO2/SGH as the positive electrode and a nitrogen-doped porous carbon material (MNC) as the negative electrode. The electrochemical measurements prove that the energy density of the ASC can reach up to 16.3 W h kg−1 in a 1 M H2SO4 electrolyte. [ABSTRACT FROM AUTHOR]

Design and fabrication of electrochemical energy storage systems with both high energy and power densities are of great importance. The battery-supercapacitor hybrid device (BSH), as one of these systems, has attracted enormous attentions. In this study, a battery-supercapacitor hybrid device was successfully fabricated by using the resultant 3D branched nanoarchitectures carbon nanotubes/Ni(OH) 2 (CNTs/Ni(OH) 2 ) as a positive electrode and the hierarchically porous, nitrogen-doped, interconnected carbon nanosheets (HPN-CNS) as the negative electrodes, respectively. HPN-CNS were prepared from agaric through simultaneous carbonization, activation, and nitrogen-doping method, while 3D branched nanoarchitectures CNTs/Ni(OH) 2 were prepared by deposited Ni(OH) 2 nanosheets on the highly conductive CNTs by a single-step chemical bath deposition. Because of their unique structure, both of the two materials exhibited excellent electrochemical performance. The as-assembled BSH delivered a high energy density of 34 W h kg -1 along with power density of 0.8 kW kg −1 , even at the power density of 16 kW kg −1 , energy density still hold at 22.2 W h kg -1 with the high potential window of 1.6 V. Furthermore, the device showed a good cycling stability with capacitance retention of 75% after 2000 cycles. Such results showed that HPN-CNS and CNTs/Ni(OH) 2 could be expected to serve as promising candidates for assembling high-performance BSH devices. [ABSTRACT FROM AUTHOR]

Three-dimensional nitrogen-doped carbon nanosheets framework (N-CNF) has been obtained starting with cellulose acetate. The product is prepared through a so-called one-step method that carbonization, activation and nitrogen-doping occur simultaneously. The resultant N-CNF shows an architecture like graphene hydrogel with interconnected hierarchical porous structure, N-doping with high nitrogen content (8.7 wt%) and high specific surface area (1003.6 m 2 g −1 ). The N-CNF electrode displays excellent electrochemical performances due to the unique architecture and pseudocapacitance contribution from heteroatoms. In the three-electrode configuration, the N-GNF achieves a high specific capacitance of 242 F g −1 at 1 A g −1 and displays ultrahigh rate capability (83.4% capacitance retention at 100 A g −1 ) in 6 mol L −1 KOH electrolyte. The symmetric supercapacitor (SSC) based N-CNF exhibits energy density as high as 60.4 Wh kg −1 (at a power density of 1750 W kg −1 ) and 17.9 Wh kg −1 (at 850 W kg −1 ) in ionic liquid and aqueous electrolytes, respectively. It is surprised that the single device filled by ionic liquid electrolyte is able to light easily 60 red light-emitting diodes (LEDs, 2.2 V) in parallel after charging for only 10 s, showing an excellent energy storage/release performance. [ABSTRACT FROM AUTHOR]

Chemical oxidation is used to cut and unzip multi-walled carbon nanotubes in the transverse direction and the axial direction to form graphene oxide nanoribbon (GONR). Ruthenium oxide/reduced graphene oxide nanoribbon composite (RuO2/rGONR) with a 72.5 wt% RuO2 loading is synthesized through an aqueous-phase reaction, in which GONR is served as starting material, followed by mild thermal treatment in ambient air. The resulting RuO2/rGONR composite achieves specific capacitance up to 677 F·g−1 at the current density of 1 A·g−1 in three-electrode system using 1 mol·L−1 H2SO4 as electrolyte. The resultant electrode exhibits an excellent rate capability (91.8% retention rate at 20 A·g−1). Especially, the symmetric supercapacitor assembled on the basis of RuO2/rGONR electrode delivers high energy density (16.2 Wh·kg−1) even at the power density of 9885 W·kg−1, which is very essential for supercapacitors. [ABSTRACT FROM AUTHOR]

In the present work, a three-dimensional (3D) porous framework of RuO2/reduced graphene oxide hydrogels (RuO2/RGOH) was prepared by a facile one-step hydrothermal method. In this hybrid hydrogel, RuO2 nanoparticles were homogeneously dispersed on the exfoliated RGO sheets. The as-prepared RuO2/RGOH electrode shows excellent supercapacitive performances with high specific capacitance (345 F g−1 for 15% RuO2 loading), good rate capability and a long electrochemical cycling life (without decaying after 2000 cycles). Furthermore, RuO2 in the hybrid can contribute a capacitance as high as 1365 F g−1, which is comparable to its theoretical value. These excellent results originate from the factors that the 3D porous network structure provides a more accessible surface area and facilitates an electron and proton injecting/expelling process in the electrochemical reaction. This work provides a facile method for preparing graphene-based composite materials with remarkable capacitive performances. [ABSTRACT FROM AUTHOR]

The reduced graphene oxide (RGO)/bisphenol A (BPA) composites were prepared by an adsorption-reduction method. The composites are characterized by X-ray diffraction (XRD), UV-vis, thermogravimetric (TG) analysis, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The results confirm that BPA is adsorbed on the basal plane of RGO by π-π stacking interaction. Furthermore, the electrochemical behaviors were evaluated by cyclic voltammetry, galvanostatic charge/discharge techniques and electrochemical impedance spectroscopy (EIS). The results show that the RGO/BPA nanocomposites exhibit ultrahigh specific capacitance of 466 F·g−1 at a current density of 1 A·g−1, excellent rate capability (more than 81% retention at 10 A·g−1 relative to 1 A·g−1) and superior cycling stability (90% capacitance decay after 4000 cycles). Consequently, the RGO/BPA nanocomposites can be regarded as promising electrode materials for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Transition metal sulfides (TMSs) have been widely researched as promising electrode materials for supercapacitors because of their high theoretical capacitance and rich redox reactive sites. In this work, tremella-like core-shell Co 9 S 8 @NiCo 2 S 4 heterogeneous nanosheets were directly grown on Nickel foamed (NF) through the hydrothermal+electrodeposition method to obtain a self-supporting electrode. Benefiting from its unique tremella-like structure, ultra-thin nanosheets, and the positive synergies between Co 9 S 8 and NiCo 2 S 4 , the prepared Co 9 S 8 @NiCo 2 S 4 @NF electrode presents a high specific capacity of 513 C g−1 (specific capacitance ~1026 F g−1) at 1 A g−1 with superior rate capability (62.8% capacitance retention rate at 10 A g−1). Furthermore, the fabricated Co 9 S 8 @NiCo 2 S 4 @NF//active carbon (AC) hybrid supercapacitor displays a high energy density of 30 Wh kg−1 at a power density of 731.8 W kg−1 and superior cycling stability. The results prove that the strategy of hydrothermal+electrodeposition is a very effective method for the preparation of energy storage and conversion materials with unique core-shell morphology. [Display omitted] • An integrated Co 9 S 8 @NiCo 2 S 4 @NF electrode is prepared. • Co 9 S 8 @NiCo 2 S 4 @NF presents a tremella-like porous structure. • The specific capacitance of Co 9 S 8 @NiCo 2 S 4 @NF can reach up to 1026 F g−1 at 1 A g−1. • A Co 9 S 8 @NiCo 2 S 4 @NF//AC hybrid supercapacitor is constructed. • The Co 9 S 8 @NiCo 2 S 4 @NF//AC displays a high energy density of 30 Wh kg−1. [ABSTRACT FROM AUTHOR]

In the present work Mn3O4/reduced graphene oxide hydrogel (Mn3O4-rGOH) with three dimensional (3D) networks was fabricated by a hydrothermal self-assembly route. The morphology, composition, and microstructure of the as-obtained samples were characterized using powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry analysis (TG), atomic absorption spectrometry (AAS), field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM). Moreover, the electrochemical behaviors were evaluated by cyclic voltammogram (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The test results indicated that the hydrogel with 6.9% Mn3O4 achieved specific capacitance of 148 F·g−1 at a specific current of 1 A·g−1, and showed excellent cycling stability with no decay after 1200 cycles. In addition, its specific capacitance could retain 70% even at 20 A·g−1 in comparison with that at 1 A·g−1 and the operating window was up to 1.8 V in a neutral electrolyte. [ABSTRACT FROM AUTHOR]

• The 3D bifunctional electrode was constructed via in-situ growth of MOF-74(Ni) and electrochemical deposition of NiCo LDH. • CC@MOF-74(NiO)@NiCo LDH demonstrates an ultra-high area specific capacitance, superior rate capability for supercapacitor. • The electrode also exhibits ultra-low detection limit, wide detection range for glucose detection. • The synergistic effect of unique structure and bimetal promote the diffusion of ions and reduce mass transfer resistance. The 3D self-supporting multistage structure CC@MOF-74(NiO)@NiCo LDH electrode was successfully synthesized, which demonstrated ultra-high specific capacitance, cyclic stability, excellent electrocatalytic performance and selectivity, providing a new reference for the research of bifunctional materials in the field of supercapacitors and non-enzymatic glucose sensors. [Display omitted] The bifunctional electrode materials for supercapacitors and non-enzymatic glucose sensors have attracted the researchers' great interest due to their excellent electrochemical performance. In this work, three-dimensional self-supporting multistage structure CC@MOF-74(NiO)@NiCo LDH electrode has been successfully prepared through a facile hydrothermal and electrochemical deposition method. Benefiting from the unique three-dimensional flower-like multistage structure, the optimized CC@MOF-74(NiO)@NiCo LDH electrode exhibits an excellent specific capacitance of 9.73 F cm−2 and a superior rate capability of 77.65% at a high current density of 50 mA cm−2. Besides, the material has a superior capacitance retention rate of 84.09% after 5000 cycles. Furthermore, the fabricated CC@MOF-74(NiO)@NiCo LDH//CC@NiCo 2 O 4 @NiFe LDH ASC device exhibits a high energy density of 22.85 Wh kg−1 and the power density of 1750 W kg−1 at the current density of 10 mA cm−2. Moreover, the as-prepared CC@MOF-74(NiO)@NiCo LDH shows an outstanding electrocatalytic performance in glucose detection, including a high sensitivity of 1699 μA mM−1 cm−2, a low detection limit of 278 nM (S/N = 3) and a wide linear range of 10 μM–1.1 mM and 1.5–9 mM. The electrode also has good long-term stability and remains 93.29% of the original current density after 35 days. The unique three-dimensional flower-like structure of MOF-74 and two-dimensional layered double hydroxides (LDHs) nanosheets structure provide a larger specific surface area and improve the conductivity of the MOF-74(NiO). Furthermore, the synergistic effect of the bimetal Ni-Co provides more active sites for electrochemical reactions and shortens the ion transport path. Accordingly, the fabricated CC@MOF-74(NiO)@NiCo LDH has great potential application prospects in the field of supercapacitors and non-enzymatic glucose sensors. [ABSTRACT FROM AUTHOR]

Electrode materials with excellent performance are urgently demanded for supercapacitors. Herein, heterogeneous nanostructure Co 9 S 8 /Ni 3 S 2 supported on conductive Ni foam (Co 9 S 8 /Ni 3 S 2 /NF) is fabricated using zeolite imidazole frameworks (ZIFs) as the sacrificial template. The Co 9 S 8 /Ni 3 S 2 /NF electrode shows an outstanding specific capacitance of 1356 F g−1 at a current density of 1 A g−1 and still remained 1145 F g−1 at 10 A g−1. The enhanced electrochemical performance should be attributed to the superior structural characteristics, the abundant active sites, the rich redox reactions, the strongly synergistic effect in heterogeneous sulfide composition and the good conductivity resulted from the NF and the Co 9 S 8 /Ni 3 S 2 /NF. Meanwhile, to further evaluate the practical application value of the Co 9 S 8 /Ni 3 S 2 /NF electrode, a hybrid supercapacitors (HSCs) device is constructed using Co 9 S 8 /Ni 3 S 2 /NF as positive electrode and activated carbon (AC) as negative electrode, and it displays a high energy density of 48.2 Wh kg−1 at a power density of 799.6 W kg−1 and a superior long-term cycling stability with 82% of initial capacitance after 8000 cycles. In addition, two as-assembled capacitors in series can light 7 LED bulbs. This strategy of obtaining multi-metal sulfides from Co/Ni-ZIF precursor provides a new perspective to design and develop electrode materials for high-performance hybrid supercapacitors. [Display omitted] [ABSTRACT FROM AUTHOR]

Rational designing and preparing of electrode materials with desirable electrochemical performance by a simple, efficient and safe method is of great significance for electrochemical energy storage devices, but it is also challenging. In this study, ultrafine CoNi 2 S 4 nanowire arrays directly grown on carbon cloth (CC) are synthesized by sulfuration of Co–Ni hydroxide precursor. Benefiting from the high conductivity, the synergistic effect between Co and Ni ions and open self-supporting three-dimensional (3D) nanoarchitectures constructed by 1D CoNi 2 S 4 ultrafine nanowires, the as-obtained CoNi 2 S 4 @CC electrode exhibits excellent electrochemical capacitance performances: high specific capacitance of 1872 F g −1 at 1 A g −1and 1565 F g −1 at 5 A g−1. Meanwhile, a battery-supercapacitor hybrid (BSH) device is fabricated using the as-obtained CoNi 2 S 4 @CC as the positive electrode and porous carbon nanosheets (PCNS) derived from wood fungus as the negative electrode. The constructed BSH exhibits a high energy density of 37.2 Wh kg −1 at a power density of 0.75 kW kg−1, as well as a robust long-term cycling stability (97.6% capacitance retention after 10 000 charge-discharge cycles at a constant current density of 1 A g−1). These outstanding results verify CoNi 2 S 4 material has potential application in the energy storage field and it has been explored and expected to be the promising electrode materials for the supercapacitor. Image 1 • CoNi 2 S 4 @CC with 3D porous structure is prepared by a facile hydrothermal method. • 3D structure is constructed by 1D ultrafine nanowires vertically to the surface of CC. • The as-fabricated CoNi 2 S 4 @CCexhibited ultrahigh specific capacitance of 1872F g -1 at 1 A g -1. • CoNi 2 S 4 @CC//PCNS BSH device was constructed. • The CoNi 2 S 4 @CC//PCNS BSH device showed high energyand excellent cycling stability. [ABSTRACT FROM AUTHOR]

High-performance ternary cobalt-based metal oxides, especially ZnCo 2 O 4 , have attracted increasing attention as promising electrode materials for supercapacitors. However, there are still great challenges for the as-reported ZnCo 2 O 4 materials, such as self-aggregation during repeated discharging-charging process and low packing density. To tackle the above issues, it is envisaged as an efficient strategy to combine the advantages of both hierarchical porous micro/nanostructures and self-supporting electrode to fabricate a free-standing hierarchical micro/nanostructured ZnCo 2 O 4 electrode. Herein we propose an efficient and simple synthetic strategy for the controllable synthesis of self-supporting hierarchical porous cactus-like ZnCo 2 O 4 material directly grown on Ni-foam using a facile hydrothermal method with post-calcination treatment. Furthermore, a growth mechanism is also proposed. The as-prepared cactus-like ZnCo 2 O 4 material possesses unique structural merits, such as hierarchical porous structures, large specific surface area, robust structural stability, and strong connections between the substrate and the ZnCo 2 O 4 active material. The unique cactus-like ZnCo 2 O 4 film electrode displayed excellent electrochemical performance, including a high specific capacity of 1115.7 F g−1 at 1 A g−1 and remarkable long cycle stability with 80.8% capacity retention after 30,000 cycles. A practical asymmetric supercapacitor (ASC) device was assembled using cactus-like ZnCo 2 O 4 and active carbon, which showed an excellent energy density of 35.4 Wh kg−1 at high power density of 160.1 W kg−1 and superior cycle stability (62.5% capacity retention after 30,000 cycles at 1 A g−1). All these results show that such hierarchical porous ZnCo 2 O 4 micro/nanostructured films are a promising candidate for high-performance supercapacitors for energy storage application. [Display omitted] • 3D hierarchical porous cactus-like ZnCo 2 O 4 film is grown on Ni foam. • A growth mechanism of the 3D cactus-like ZnCo 2 O 4 film is proposed. • The cactus-like ZnCo 2 O 4 electrode shows 80.8% capacitance retention after 30,000 cycles at 5 A g−1. • The ZnCo 2 O 4 @NF//AC asymmetric supercapacitor exhibits an excellent energy density and power density. [ABSTRACT FROM AUTHOR]

In the present work, water-soluble electroactive methyl green (MG) has been used to non-covalently functionalize reduced graphene oxide (RGO) for enhancing supercapacitive performance. The microstructure, composition and morphology of MG–RGO composites are systematically characterized by UV–vis absorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical performances are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). The fast redox reactions from MG could generate additional pseudocapacitance, which endows RGO higher capacitances. As a result, the MG–RGO composite (with the 5:4 mass ratio of MG:RGO) achieve a maximum value of 341 F g −1 at 1 A g −1 within the potential range from −0.25 to 0.75 V and provide a 180% enhancement in specific capacitance in comparison with pure RGO. Furthermore, excellent rate capability (72% capacitance retention from 1 A g −1 to 20 A g −1 ) and long life cycle (12% capacitance decay after 5000 cycles) are achieved for the MG–RGO composite electrode. [ABSTRACT FROM AUTHOR]

Abstract: We report a one-step fabrication of α-iron oxyhydroxide/reduced graphene oxide (α-FeOOH/rGO) composites, in which the ferrous sulfate (FeSO4·7H2O) are used as the iron raw and reducing agent to grow goethite (α-FeOOH) and reduce graphite oxide (GO) to rGO in the same time. The morphology, composition and microstructure of the as-obtained samples are systematically characterized by thermogravimetric (TG) analysis, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and FT-IR. Moreover, their electrochemical properties are investigated using cyclic voltammetry and galvanostatic charge/discharge techniques. The specific capacitance of 452 F g−1 is obtained at a specific current of 1 A g−1 when the mass ratio of α-FeOOH to rGO is up to 80.3:19.7. In addition, the α-FeOOH/rGO composite electrodes exhibit the excellent rate capability (more than 79% retention at 10 A g−1 relative to 1 A g−1) and well cycling stability (13% capacitance decay after 1000 cycles). These results suggest the importance and great potential of α-FeOOH/rGO composites in the applications of high-performance energy-storage. [Copyright &y& Elsevier]

• A fluorenone molecule electrode was reported, in which DHFO was anchored on GO to form hierarchical porous hydrogel. • The redox peak position of DHFO/rGO is located near 0.75 V, which is suitable for positive electrode in EES. • An ASC was assembled and delivered high energy density (28.57 Wh Kg−1), finally lighted 45 LED bulbs. Here, we report an organic molecule electrode for more efficient energy storage, in which 2,7-Dihydroxy-9-fluorenone (DHFO) molecules are anchored on interconnected and highly conductive graphene sheets by non-covalent π–π interactions. The optimal DHFO/rGO composite can reach a high specific capacitance of 412.3 F g−1 at scan rate of 5 mV s−1 in 1 mol L−1 H 2 SO 4 aqueous electrolyte with a satisfactory capacitive retention of 91% after 10,000 consecutive constant galvanostatic charge-discharge at current density of 5 A g−1. And it is worth noting that the Faraday current response peaks occurs within the positive potential range around 0.75 V, which is more suitable for positive electrode materials of supercapacitors with high performances. Additionally, charge storage mechanism and binding interactions of DHFO on graphene was evaluated based on the density functional theory (DFT) calculations. To match with the consequent positive electrode, AQ functionalized graphene (AQ/rGO) was prepared as negative electrode. Benefiting from the companionable match of two electrodes in structure, charge quantity and kinetics, the as-assembled asymmetrical supercapacitor (DHFO/rGO//AQ/rGO) delivers a maximum energy density of 28.57 Wh kg−1 along with 0.62 kW kg−1, and excellent cycle stability (82.3% specific capacitance retention after 10,000 cycling at 5 A g−1). Two tandem DHFO/rGO//AQ/rGO devices could light 45 LEDs. [Display omitted] [ABSTRACT FROM AUTHOR]

• BAQ and DHBQ are anchored on graphene to form organic molecules electrodes. • The BAQ (DHBQ)/rGO electrodes achieve capacitance all in excess of 400 F g−1 at 1 A g−1. • DFT calculations are employed to understand the experimental mechanism. • The two ASCs device in series easily lights 47 red light-emitting diodes compounding in parallel. Organic molecules electrodes with high electrochemical reversibility has enormous potential in energy storage. Here, benz[a]anthracene-7, 12-quinone (BAQ) and 2, 5-dihydroxy-p-benzoquinone (DHBQ) are anchored on reduced graphene oxide (rGO) [BAQ (DHBQ)/rGO] by non-convent method to form the porous 3D dry aerogels. The optimal BAQ (DHBQ)/rGO electrode materials display capacitance all in excess of 400 F g−1 at current density of 1 A g−1 and an excellent rate capability in 1 M H 2 SO 4 electrolyte. And BAQ/rGO and DHBQ/rGO are used respectively as the negative and positive electrode to fabricate the asymmetric supercapacitor (ASC), which achieves high energy density of 30.33 Wh kg−1 with power density of 802.9 W kg−1. Finally, 47 light-emitting diode (LED) bulbs aligned in a 'NWNU' shape are lit by two ASCs device in series, demonstrating its outstanding energy storage performance. Moreover, density functional theory (DFT) calculations are employed to understand the adsorption orientations, binding interactions and charge storage mechanism of BAQ on rGO surface, elucidating the superior electrochemical performance of the tested organic molecule electrode. In short, quinones non-covalently modified graphene is a promising and effective strategy for energy storage devices in future. [ABSTRACT FROM AUTHOR]