Facile preparation of SnS2 nanoflowers and nanoplates for the application of high-performance hybrid supercapacitors

In this work, the SnS₂ nanoflowers (SnS₂ NFs) were solvothermally prepared in the solvent of ethanol, while SnS₂ nanoplates (SnS₂ NPs) were obtained through the identical conditions except for the solvent of water. The flowers were assembled with numerous nanosheets with very thin thickness, and the NPs exhibited hexagonal shape. When used as the battery-type electrode material for supercapacitors, the SnS₂ NFs delivered a specific capacity of as high as 264.4 C g^?1 at 1 A g^?1, which was higher than the 201.6 C g^?1 of SnS₂ NPs. Furthermore, a hybrid supercapacitor (HSC) was assembled with the SnS₂ as positive electrode and activated carbon (AC) as negative electrode, respectively. The SnS₂ NFs//AC HSC exhibited a high energy density of 28.1 Wh kg^?1 at 904.3 W kg^?1, which was higher than the 24.2 Wh kg^?1 at 844.3 W kg^?1 of SnS₂ NPs//AC HSC. Especially, when the power density was enhanced to the highest value of 8666.8 W kg^?1, the NFs-based device could still hold 20.4 Wh kg^?1. In addition, both HSC devices showed an excellent cycling stability after 5000 cycles at 5 A g^?1. The present method is simple and can be extended to the preparation of other transition metal sulfides (TMSs)-based electrode materials with brilliant electrochemical performance for supercapacitors.     

Simple synthesis of honeysuckle-like CuCo2O4/CuO composites as a battery type electrode material for high-performance hybrid supercapacitors

In this paper, porous CuCo₂O₄/CuO composites with novel honeysuckle-like shape (CuCo₂O₄/CuO HCs) have been prepared for the first time by a simple hydrothermal method and followed with an additional annealing process in air. The unique CuCo₂O₄/CuO HCs consisted of dense and slender petals with length of 1.3–1.5 μm and width of about 50 nm, and possessed a specific surface area of 36.09 m² g^?1 with main pore size distribution at 10.63 nm. When used as the electrode materials for supercapacitors, the CuCo₂O₄/CuO HCs exhibited excellent electrochemical performances with a high specific capacity of 350.69 C g^?1 at 1 A g^?1, a rate capability of 78.6% at 10 A g^?1, and 96.2% capacity retention after 5000 cycles at a current density of 5 A g^?1. In addition, a hybrid supercapacitor (CuCo₂O₄/CuO HCs//AC HSC) was assembled using the CuCo₂O₄/CuO HCs as positive electrode and activated carbon (AC) as negative electrode. The HSC device delivered a specific capacity of 187.85 C g^?1 at 1 A g^?1 and a superior cycling stability with 104.7% capacity retention after 5000 cycles at 5 A g^?1, and possessed a high energy density of 41.76 W h kg^?1 at a power density of 800.27 W kg^?1. These outstanding electrochemical performances manifested the great potential of CuCo₂O₄/CuO HCs as a promising battery-type electrode material for the next-generation advanced supercapacitors with high-performance.     

Facile sonochemical synthesis of strontium phosphate based materials for potential application in supercapattery devices

Among hybrid energy storage devices, supercapattery gained profound research interest due to its ability to give high energy density while maintaining the power density and cyclic stability. Herein, novel low-cost strontium based materials are synthesized by controlled sonochemical method and subsequently calcined at various temperatures. The multiple phases of the material synergistically contributed in the electrochemical charge storage process and give high specific capacity of 220 C g⁻¹ (as-prepared material) and 213 C g⁻¹ (calcined at 200 °C) at 0.5 A g⁻¹. A thorough electrochemical performance of optimized material is investigated as an electrode in asymmetric device. The supercapattery (SP2//AC) exhibits a specific capacity of 103.4 C g⁻¹ at 0.5 A g⁻¹ in the voltage range of 0–1.7 V. Furthermore, supercapattery offers a considerably high specific energy of 24.4 Wh kg⁻¹ at a specific power of 425 W kg⁻¹ and an excellent specific power of 1870 W kg⁻¹ by maintaining specific energy at 14.5 Wh kg⁻¹. In addition, the device retained its specific capacity to 90% after 3000 charging/discharging cycles at 1 A g⁻¹. Strontium based materials could be proposed as an appropriate electrode material for energy storage systems.     

Battery-type and binder-free MgCo2O4-NWs@NF electrode materials for the assembly of advanced hybrid supercapacitors

In this study, the hetero-structure of MgCo₂O₄ nanowires (MCO-NWs) and microcubes (MCO-MCs) on the skeleton of nickel foam (NF) was realized through a simple hydrothermal method and subsequent annealing treatment, and then served as a binder-free cathode for assembly of high-performance hybrid supercapacitor (HSC). Such synthetic methodology avoided the traditional usage of conductive and binder reagents for the electrode fabrication. The electrochemical tests indicated its battery-type characteristics, and the MCO-NWs@NF exhibited a huge specific capacity (C_s) of 389.0 C g^?1 as well as 86.2% capacity retention when the current density boosted from 1 to 10 A g^?1. The assembled HSC with activated carbon (AC) as anode further demonstrated the advantages of this electrode material. After 5000 cycles at 6 A g^?1, the MCO-NWs@NF//AC HSC showed good long-term cycling stability without any decay in capacitance, and could deliver an energy density (E_d) of 37.9 W h kg^?1 at the power density (P_d) of 958.1 W kg^?1, higher than the 30.4 W h kg^?1 of MCs-based HSC. These impressive results regarding electrochemical performance suggest that MCO-NWs@NF may be a promising candidate to serve as a battery-type material in electrochemical energy storage applications such as HSCs, batteries, and so on.     

Metal-organic frameworks supported Ni–Co–S nanosheet arrays for advanced hybrid supercapacitors

Constructing self-supporting porous electrode material with abundant electrochemical active sites can effectively improve the energy storage capacity of supercapacitors. Herein, a novel electrode material (NCS@Co-ZIF/NF) is developed by depositing zeolitic imidazolate frameworks (Co-ZIF) on nickel foams (NF), which is adopted as a precursor (Co-ZIF/NF) to electrodeposit nickel-cobalt sulfides (NCS). The nanosheet arrays with cross-porous structures provide NCS@Co-ZIF/NF with excellent electrochemical characteristics, including a high specific capacity of 144.4 mAh g^?1 at the current density of 1 mA cm^?2, 60.5% capacity retention at 50 mA cm^?2, and superb long-term cycle stability. Furthermore, NCS@Co-ZIF/NF//AC hybrid supercapacitor is fabricated by using NCS@Co-ZIF/NF as positive electrodes and activated carbon (AC) as negative electrodes, which exhibits a high energy density of 33.9 Wh kg^?1 at a power density of 145 W kg^?1.     

Hybrid high performance supercapacitor based on zeolitic imidazolate frameworks-67-derived nano-structure NiCo2S4

In this work, NiCo₂S₄, nickel-cobalt layered double hydroxides (NiCo-LDH) and CoS₂ electrodes are successfully prepared by using ZIF-67 as the precursor, the results show that NiCo-LDH and NiCo₂S₄ are nano-flower-like structures and CoS₂ exhibits a nano-cage structure. The electrochemical properties of the hybrid supercapacitor assembled with NiCo₂S₄ and activated carbon (AC) as electrodes were tested. As the positive electrode of NiCo₂S₄//AC hybrid supercapacitor, the NiCo₂S₄ electrode has the largest specific capacity of 2934 mAh g^?1 at a current density of 1 A g^?1. The NiCo₂S₄//AC capacitor generates the highest energy density of 38.8 Wh kg^?1 when the power density is 993.0 W kg^?1 and has a nice cycling performance with a capacity retention rate of 81.2% after 10,000 cycles at 5 A g^?1.     

Interconnected NiS-nanosheets@porous carbon derived from Zeolitic-imidazolate frameworks (ZIFs) as electrode materials for high-performance hybrid supercapacitors

Nickel sulfide-based materials have shown great potential for electrode fabrication owing to their high theoretical specific capacitance but poor conductivity and morphological aggregation. A feasible strategy is to design hybrid structure by introducing highly-conductive porous carbon as the supporting matrix. Herein, we synthesized hybrid composites consisting of interconnected NiS-nanosheets and porous carbon (NiS@C) derived from Zeolitic-imidazolate frameworks (ZIFs) using a facile low-temperature water-bath method. When employed as electrode materials, the as-prepared NiS@C nanocomposites present remarkable electrochemical performance owing to the complex effect that is the combined advantages of double-layer capacitor-type porous carbon and pseudocapacitor-type interconnected-NiS nanosheets. Specifically, the NiS@C nanocomposites exhibit a high specific capacitance of 1827 F g⁻¹ at 1 A g⁻¹, and excellent cyclic stability with a capacity retention of 72% at a very high current density of 20 A g⁻¹ after 5000 cycles. Moreover, the fabricated hybrid supercapacitor delivers 21.6 Wh kg⁻¹ at 400 W kg⁻¹ with coulombic efficiency of 93.9%, and reaches 10.8 Wh kg⁻¹ at a high power density of 8000 W kg⁻¹, along with excellent cyclic stability of 84% at 5 A g⁻¹ after 5000 cycles. All results suggest that NiS@C nanocomposites are applicable to high-performance electrodes in hybrid supercapacitors and other energy-storage device applications.     

Synthesis of hollow carbon-incorporated NiCoM (M = Mn,Cu, Zn) layered double hydroxide nanocages for hybrid supercapacitors

Nanostructures and compositions are the most crucial aspects in the design of electrode materials with excellent properties for hybrid supercapacitors (HSCs). In this study, bimetallic CoM-zeolitic imidazolate framework-67 (CoM-ZIF-67, M = Mn, Cu, and Zn) derived nanosheet-constructed hollow carbon-incorporated NiCoM layered double hydroxide nanocages (NiCoM-LDH/C) are successfully synthesized via the thermal annealing and subsequent etching/ion-exchange reaction. As a consequence, the NiCoM-LDH/C materials exhibit significantly improved electrochemical performance. Specifically, the optimized NiCoMn-LDH/C electrode possesses an excellent capacity performance of 888.3 C g^?1 at 1 A g^?1. Moreover, the HSC device assembled by NiCoMn-LDH/C and active carbon delivers a remarkable energy density of 46.5 Wh kg^?1 at a power density of 792.5 W kg^?1 and possesses superior cyclic stability with about 92.05% capacity retention after 5000 cycles. This work may offer a feasible and effective approach for the synthesis of carbon-incorporated ternary layered double hydroxide nanocage materials for high-performance HSC applications.     

Optimizing electrochemical performance of sonochemically and hydrothermally synthesized cobalt phosphate for supercapattery devices

The supercapattery (hybrid energy storage device) has procured miraculous heed for their significant electrochemical performance, constitute combine features of supercapacitor (prodigious power density) and batteries (substantial energy density), still crave for electrode material with better electrochemical conduct. Here, cobalt phosphate ((Co₃(PO₄)₂) nanostructures were synthesized using sonochemical and hydrothermal approach. The SEM, XRD, and EDX were employed to explore surface morphology, crystal structure, and elemental analysis respectively of as synthesized nanomaterials. The electrochemical performance was evaluated in two and three electrode assembly. The maximum specific capacity of 285 C g^-1 at 3 mV/s and 221 C g^-1 at 4.1 A g^-1 has been obtained by sonochemically synthesized nanomaterial (S1). This electrode material with optimum electrochemical performance was further investigated for supercapattery application. Asymmetric device was fabricated, comprising activated carbon as negative and S1 as positive electrode material. The supercapattery device exhibits a specific capacity of 147.2 C g^-1 bearing an outstanding energy density of 34.8 Whkg^?1 with a power density of 425.0 W kg^-1 at 0.5 A g^-1. The device was found to have a remarkable power density of 6800.0 W kg^-1 while retaining an energy density of 10.0 Whkg^?1 with exceptional capacity preservation of 87.2% after 10,000 consecutive GCD cycles even at 8.0 A g^-1. The device performance was further explored in terms of capacitive and diffusion controlled processes and found to have a maximum capacitive contribution of 63.8% at 100 mV s^-1. The sonochemical method was found to be the optimal route to synthesize nanomaterials for energy storage applications.     

High-performance hybrid supercapacitor based on the porous copper cobaltite/cupric oxide nanosheets as a battery-type positive electrode material

In this work, CuCo₂O₄/CuO nanosheets (NSs) and CuCo₂O₄ oblique prisms (OPs) were synthesized at 130 °C with different amounts of hexamethyltetramine (HMTA) and reaction time through a hydrothermal method, and followed by an annealing treatment of precursors in air. The CuCo₂O₄/CuO NSs with 40 nm in thickness possessed a large specific surface area of 43.34 m² g⁻¹ and a mean pore size of 18.14 nm. The electrochemical tests revealed that the CuCo₂O₄/CuO NSs were belonged to the battery-type electrode material and exhibited a specific capacity of 395.55 C g⁻¹ at the current density of 1 A g⁻¹, higher than 258.16 C g⁻¹ for CuCo₂O₄ OPs. A hybrid supercapacitor (HSC) was assembled with activated carbon (AC) as negative electrode and CuCo₂O₄-based materials as positive electrode. The CuCo₂O₄/CuO NSs//AC HSC exhibited a high energy density of 30.18 Wh kg⁻¹ at a power density of 869.62 W kg⁻¹, and showed a fantastic cycling performance with 105.22% capacity retention over 5000 cycles. In contrast, the CuCo₂O₄ OPs//AC HSC delivered an energy density 26.27 Wh kg⁻¹ at 916.74 W kg⁻¹. These impressive electrochemical properties indicate that CuCo₂O₄/CuO NSs may serve as a promising electrode material for the highly capable hybrid supercapacitors in the near future.     

Ni@NC@NiCo-LDH nanocomposites from a sacrificed template Ni@NC@ZIF-67 for high performance supercapacitor

A metal porous carbon (Ni@NC) supported nickel/cobalt layered double hydroxide (NiCo-LDH) (Ni@NC@NiCo-LDH) with a cauliflower morphology was synthesized by a successive double template method. At first a nickel metal-organic framework (Ni-MOF) was prepared and used as a sacrifice template to produce metal porous carbon (Ni@NC). Then the prepared conductive porous carbon material was exploited as a substrate for in-situ growing of ZIF-67 on its surface. Lastly the obtained Ni@NC@ZIF-67 was further used as a sacrifice template to prepare the final electrode material Ni@NC@NiCo-LDH by Ni²⁺ etching and co-precipitation. The cooperation of Ni@NC with excellent conductivity and NiCo-LDH with superior pseudocapacitive property yielded a synergistic effect, which effectively improved the electrochemical performance of the resulted electrode material. And the special flower morphology exposed more redox active sites and provided proper charge transport path for enhanced electrochemical performance. The prepared Ni@NC@NiCo-LDH exhibited a high specific capacitance of 1761.8 F·g^?1 at the current density of 1 A·g^?1. The assembled Ni@NC@NiCo-LDH//AC asymmetric supercapacitor also displayed an acceptable energy density (39.27 Wh·kg^?1 at the power density of 757.21 W·kg^?1) and ultrahigh cycling stability (94.74% capacitance retention after 25000 cycles at 10 A g^?1).     

High energy density PbO2/activated carbon asymmetric electrochemical capacitor based on lead dioxide electrode with three-dimensional porous titanium substrate

A PbO₂/AC asymmetric electrochemical capacitor (AEC) with energy density as high as 49.4 Wh kg⁻¹, power density of 433.2 W kg⁻¹ and specific capacitance of 135.2 F g⁻¹ was fabricated with PbO₂ electrodeposited on three-dimensional porous titanium (3D-Ti/PbO₂) and activated carbon. The high electrochemical active surface of 3D-Ti/PbO₂ resulted in high specific capacity making it suitable for use as positive electrode in PbO₂/AC AEC. The fabricated AEC demonstrated good power performance with an energy density conservation of 30 Wh kg⁻¹ at power density of 2078 W kg⁻¹. The fabricated AEC also showed excellent cycling stability with capacitance retention of 99.2% after 1000 cycles.     

Polyaniline-silver-manganese dioxide nanorod ternary composite for asymmetric supercapacitor with remarkable electrochemical performance

Metal oxide incorporated with a conductive polymer have shown great potential as high-performance energy storage devices. In this report, polyaniline wrapped silver decorated manganese dioxide (PANI/Ag@MnO₂) nanorods were successfully synthesized and used as positive electrode material. Cyclic voltammetry, galvanostatic charge discharge and electrochemical impedance spectroscopy were employed to investigate the electrochemical activities. The overall result demonstrates that as prepared PANI/Ag@MnO₂ nanorod performed better supercapacitor activities compared to Ag@MnO₂ and pure MnO₂. The PANI/Ag@MnO₂ nanocomposite exhibited a high specific capacitance of 1028.66 F g^?1 at a current density of 1 A g^?1 (nearly close to the theoretical capacitance of MnO₂). A detail investigation of the synergic effect of PANI, Ag and MnO₂ on electrochemical properties is presented sequentially. The assembled (PANI/Ag@MnO₂//AC) asymmetric supercapacitor device showed a high energy density of 49.77 W h kg^?1 at power density of 1599.75 W kg^?1. The facile and cost-effective production of PANI/Ag@MnO₂ demonstrates a high specific capacitance and energy density with long life cycle introduces this material as a prospective candidate for energy management.     

Constructing 3D honeycomb-like CoMn2O4 nanoarchitecture on nitrogen-doped graphene coating Ni foam as flexible battery-type electrodes for advanced supercapattery

Reasonable structural design is significant to enable the performance in advanced energy storage devices. Herein, a 3D honeycomb-like CoMn₂O₄ nanoarchitecture (CMO) on nitrogen-doped graphene (NG) coating Ni foam (denoted as Ni/NG/CMO) flexible battery-type electrode was prepared by a facile two-step hydrothermal strategy. The honeycomb-like CoMn₂O₄ arrays not only provide abundant active sites but can also be closely combined with the Ni foam/NG substrate, which enables high reversible capacity and good cycle stability during the long cycles. Benefiting from the compositional features and 3D honeycomb-like nanoarchitecture, the Ni/NG/CMO composite electrode displays improved electrochemical performance with remarkable specific capacity of 527.0C g⁻¹ at a current density of 1 A g⁻¹, outstanding rate capability (338.6C g⁻¹ even at 20 A g⁻¹). In addition, a flexible binder-free supercapattery device has been assembled with Ni/NG/CMO as positive electrode and 3D Ni/NG as negative electrode. Such a supercapattery delivers a high energy density of 44.1 Wh·kg⁻¹ at 992.6 W kg⁻¹, 20.3 Wh·kg⁻¹ at 12430.0 W kg⁻¹ as well as excellent cycling durability. The 3D honeycomb-like Ni/NG/CMO could be considered as an advanced flexible battery-type material for high capacity and energy density fields.     

Electrodeposited nickel nanocone/NiMoO4 nanocomposite designed as superior electrode materials for high performance supercapacitor

A nickel nanocone-modified NiMoO₄ hybrid (NiMoO₄/NNC) on Ni foam (NF) substrate is engineered to enhance the capacitance performance of NiMoO₄ via facile and convenient electrodeposition strategy, followed by hydrothermal method. The presence of nickel nanocone (NNC) increases the density of reaction active sites of NiMoO₄/NNC/NF, which can shorten the charge diffusion pathway and boost ionic/electronic conductivities. As expected, the NiMoO₄/NNC/NF, as a prospective electrode material, presents appreciable electrochemical properties. Remarkably, the NiMoO₄/NNC/NF electrode demonstrates a high specific capacitance of 2813 F g^?1 at 3 A g^?1 and manifests considerable cycling durability with a retention of 94% of the initial capacitance over consecutive 5000 cycles. Furthermore, a NiMoO₄/NNC/NF//AC/NF asymmetric supercapacitor displays a great electrochemical performance by delivering high energy density (43 Wh kg^?1) and power density (821 W kg^?1) as well as notable durableness (10% decay after 5000 cycles). The presented results suggest that NiMoO₄/NNC/NF can be considered as a binder-free electrode for highly stable supercapacitors.     

Sulphur-reduced graphene oxide composite with improved electrochemical performance for supercapacitor applications

In this research, carbon nanorods/fibers materials were successfully synthesized from sulphur-reduced graphene oxide (RGO-S) composite by using an improved Hummers' method. Morphological, structural, compositional and textural characterization of the composite material were obtained via scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The electrochemical performance of the composite sample as a promising supercapacitor electrode revealed a peak specific capacity of 113.8 mAh g⁻¹ at 0.5 A g⁻¹ estimated via GCD curves in 6 M KOH aqueous electrolyte. The half-cell could retain a columbic efficiency of about 98.7% with a corresponding energy efficiency of about 98.5% over 2000 constant charge/discharge cycle at a specific current of 5 A g⁻¹. Remarkably, an assembled hybrid device with carbonized iron cations (C-FP) and the RGO-S composite delivered high energy and power densities of 35.2 Wh kg⁻¹ and 375 W kg⁻¹ at 0.5 A g⁻¹ within a 1.5 V operating potential, respectively. A good cycling stability performance with an energy efficiency of 99% was observed for the device for up to 10,000 cycling at a specific current of 3 A g⁻¹.     

Walnut shell-derived hierarchical porous carbon with high performances for electrocatalytic hydrogen evolution and symmetry supercapacitors

Walnut Shell-derived hierarchical porous carbon has been successfully synthesized by the efficient KOH activation process. The hierarchical porous carbon material activated at 600 °C, has the specific micropore area of 1037.31 m² g⁻¹ and micropore volume of 0.51 cm³ g⁻¹, which leads to have electrochemical performances of the hydrogen evolution reaction (HER) and supercapacitors. Specifically, as the hydrogen evolution reaction electrocatalyst, the walnut shell-derived carbon material activated at 600 °C exhibits a lower onset potential of 6.00 mV, a smaller Tafel slope of 69.76 mV dec⁻¹ and outstanding stability above long-term cycling. As a supercapacitor electrode material, the sample possesses specific capacitance of 262.74 F g⁻¹ at 0.5 A g⁻¹, the remarkable rate capability of 224.60 F g⁻¹ at even 10 A g⁻¹ and good long-term stability. A symmetric supercapacitor shows the highly energy density of 7.97 Wh kg⁻¹ at a power density of 180.80 W kg⁻¹. This novel and low-cost biomass material is very promising for the electrocatalytic water splitting and supercapacitors.     

A comparative study of various polyelectrolyte/nanocomposite electrode combinations in symmetric supercapacitors

A more practical, nontoxic and cheaper electrolyte, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) was used to construct supercapacitors with different nanocomposite electrodes. The flexible devices were fabricated including active carbon (AC) electrode and nanocomposites electrodes of AC/nano-silica (nano-SiO₂) and AC/multiwalled carbon nanotubes (MWCNTs) at various weight percentages. The symmetrical cell made from AC electrodes generated a maximum specific capacitance (Cs) of 315 F g⁻¹ at 0.5 A g⁻¹. The energy density of this device was 55.5 Wh kg⁻¹ at a power density of 690 W kg⁻¹. Excellent performance was achieved after 5000 charge-discharge cycles where the supercapacitor maintains 92% of its activity. The energy storage capability of the supercapacitors was also investigated with the addition of nano-SiO₂ and MWCNTs. The Cs of the supercapacitors made with the electrodes AC/nano-SiO₂ (5%, 10%, 25% and 50%) were 172, 228, 247 and 55 F g⁻¹, respectively. Similarly, the capacity of the device including the electrodes of AC/MWCNTs (5%, 10%, 25% and 50%) varied as 191, 244, 93 and 20 F g⁻¹ at 0.5 A g⁻¹. The maximum energy density of the devices having nano-SiO₂ and MWCNT were 44.4 Wh kg⁻¹ and 43.8 Wh kg⁻¹, respectively at a power density of 520 W kg⁻¹. A supercapacitor with certain dimension successfully operated a light-emitting diode (LED).     

Self-assembly of novel cobalt iron phosphate nanoparticles for the solid-state supercapattery and high-performance hydrogen evolution reaction

In this article, we report the preparation of novel cobalt iron phosphate nanoparticles which are self-assembled for energy storage, energy conversion, and sustainability. The self-assembled nanoparticles provide an efficient pathway for the transfer of electrons from the bulk of the materials to the interface of the electrode. This hypothesis has been derived from the analysis based on the electrochemical results for the supercapacitor-based energy storage and hydrogen evolution. The electrode consisting of self-assembled nanoparticles exhibits a maximum specific capacity of 280 C g⁻¹ at a specific current of 1 A g⁻¹. The cyclic voltammetric results suggest the prominent charge storage is by the faradaic reaction which has been concluded from Dunn's approach. The supercapattery device utilizing activated carbon (AC) as the negative electrode and cobalt iron phosphate as the positive electrode exhibit a specific capacity of 210 C g⁻¹ at 2 A g⁻¹ while the specific energy of 47.6 Wh kg^-1 at 1.6 kW kg⁻¹. Furthermore, the electrode actively catalyzes the electrochemical hydrogen evolution reaction and it can be lowering the overpotential required by the hydrogen generation. It exhibits the overpotential of 197 mV while the electrode represents the long-time (24 h) consistency for hydrogen production. These results indicate that the novel cobalt iron phosphate nanoparticles could be a potential candidate for energy storage and conversion purposes.     

Dual carbon source method to fabricate hierarchical porous carbon with three-dimensional interconnected network structure toward advanced energy storage device

Selective fabrication of carbon materials with developed specific surface area and hierarchical porous structure is essential for high-performance carbon-based supercapacitors. Direct carbonization of organic acid salts represents a strategy that can produce porous carbon with high specific surface area, but it is still hindered by low carbon yield, impeding its large-scale application. Herein, a biomass-derived hierarchical porous carbon with large specific surface area is prepared via a facile one-pot calcination method. The optimal SCPC-4 sample presents three-dimensional interconnected network structure and plentiful heteroatom content. Hence, it delivers a large specific capacitance of 321 F g^?1 at a current density of 1 A g^?1, and negligible capacitance loss after 10,000 cycles at 10 A g^?1. In addition, the assembled SCPC-4 based symmetric supercapacitor exhibits an energy density of 21.2 Wh kg^?1 at a power density of 900 W kg^?1. This cost-effective binary biomass carbon source route provides a great possibility for the mass production of high-yield porous carbon materials.