In our work, we successfully design boron (B) and nitrogen (N) co-doped porous carbon tube bundle (B/N-PCTB) electrode materials which are directly derived from the biomass of dandelion fluff. The low-tortuosity, and open and porous structures contribute to electron transport along the tube wall and unimpeded ion diffusion inside the carbon tubes. The incorporation of heteroatoms into PCTBs can bring extra pseudocapacitance and double layer capacitance to enhance the overall capacitance. Benefiting from the hollow and open microstructure and heteroatom doping, the optimized B/N-PCTB electrode (active materials: 2.6 mg cm−2) possesses an impressive specific capacitance of 355 F g−1 at 1 A g−1. Even with an ultrahigh loading mass of 40 mg cm−2, the electrode still has a relatively high specific capacity of 216 F g−1 at 1 A g−1. The assembled symmetric cell with an active material loading of 80 mg cm−2 (cathode: 40 mg cm−2; anode: 40 mg cm−2) shows a superior volumetric energy density of 12.15 W h L−1 at the power density of 699.84 W L−1. The facile yet high-performance porous carbon tube bundle is a promising material which can be applied in many other fields such as lithium ion batteries, hydrogen evolution reaction, and heavy metal ion adsorption.

A three-dimensional (3D) catalyst electrode of Co3O4 nanosheets in situ formed on reduced graphene oxide modified Ni foam (Co3O4/rGO@Ni foam) for H2O2 electroreduction is prepared by a two-step hydrothermal method. In the first step, graphene oxide sheets are reduced and formed on the skeleton of Ni foam and Co3O4 nanosheets are synthesized intermixed with the rGO sheets through the second step. The Co3O4 nanosheets are made up of plentiful nanoparticles and there are many nanoholes among these nanoparticles which are beneficial for the sufficient contact between H2O2 and the catalyst. The morphology and phase composition of the Co3O4/rGO@Ni foam electrode are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrocatalytic activity of the as-prepared electrode is investigated by cyclic voltammetry (CV) and chronoamperometry (CA). From the results, it can be seen that in 2 mol L−1 NaOH and 0.5 mol L−1 H2O2, the reduction current density of H2O2 on the Co3O4/rGO@Ni foam electrode is 450 mA cm−2 at −0.8 V which is much higher than that on Co3O4 directly supported on Ni foam. This obvious increase of the current density can be attributed to the increase of the surface area of the electrode after the addition of rGO. Also, the interpenetration of rGO and Co3O4 nanosheets improves the electron and ion transport ability of the electrode which leads to a good electrocatalytic activity and stability of the Co3O4/rGO@Ni foam electrode.

A highly sensitive electrochemical sensor for the detection of ascorbic acid (AA) was first fabricated using network-like carbon nanosheets (NCN) as an enhanced electrode modifier. Novel carbon nanosheets were synthesized from willow catkin via a high temperature carbonization and chemical activation process with the aid of potassium hydroxide (KOH). The formation of porous and interconnected structures of the resulting product was characterized by various experiment techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and nitrogen isothermal adsorption–desorption technique. The network-like carbon nanosheet modified glassy carbon electrode (NCN/GCE) exhibited excellent electrocatalytic activity for the electrochemical oxidation of ascorbic acid owing to the unique network-like and partially graphitic structure. The amperometric curve of AA on the NCN/GCE showed a quick current response, a fine linear consistency of the peak current with the concentration of AA, a low detection limit and an excellent selectivity. Based on these excellent properties, a new sensing platform was developed and verified by the determination of ascorbic acid in commercial injections.

A highly sensitive electrochemical sensor for the detection of ascorbic acid (AA) was first fabricated using network-like carbon nanosheets (NCN) as an enhanced electrode modifier. Novel carbon nanosheets were synthesized from willow catkin via a high temperature carbonization and chemical activation process with the aid of potassium hydroxide (KOH). The formation of porous and interconnected structures of the resulting product was characterized by various experiment techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and nitrogen isothermal adsorption–desorption technique. The network-like carbon nanosheet modified glassy carbon electrode (NCN/GCE) exhibited excellent electrocatalytic activity for the electrochemical oxidation of ascorbic acid owing to the unique network-like and partially graphitic structure. The amperometric curve of AA on the NCN/GCE showed a quick current response, a fine linear consistency of the peak current with the concentration of AA, a low detection limit and an excellent selectivity. Based on these excellent properties, a new sensing platform was developed and verified by the determination of ascorbic acid in commercial injections.

•Pd@Ti Ps reveal higher catalytic activity than Pd@Ti plate.•Pd@Ti Ps show unique 3D structure with a large surface area.•Pd@Ti Ps exhibit good stability for H2O2 electroreduction in acidic mediumAn especial current collector of Ti pillar arrays (Ti Ps) is prepared by a facile hydrothermal etching method. The Ti Ps substrate can be applied in acidic medium for its excellent stability, and the large specific surface area of this substrate is highly beneficial to the contact between electrolyte and catalyst. Pd deposited on the Ti Ps substrate is selected to be the catalyst for H2O2 reduction due to its remarkable electrocatalytic activity and stability. The structure and phase composition of the Pd modified Ti Ps (Pd@Ti Ps) electrode are studied through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and inductive coupled plasma emission spectrometer (ICP). The electrocatalytic property of the Pd@Ti Ps electrode is studied through cyclic voltammetry (CV) and chronoamperometry (CA). According to the results, the Pd@Ti Ps electrode exhibits a high reduction current density of 220 mA cm−2 at −0.2 V in 2 mol L−1 H2SO4 and 0.5 mol L−1 H2O2 which is greatly larger than that on Pd modified Ti plate (Pd@Ti plate) electrode. The activation energy of H2O2 reduction on this electrode is 19.77 kJ mol−1. The low activation energy and high electrocatalytic activity indicate that the as-prepared electrode can be applied as a potential cathode for fuel cell.Download high-res image (133KB)Download full-size image

•ABNiAu is flexible and binder-free.•ABNiAu owns good stability in alkaline solution.•ABNiAu exhibits high electrocatalytic performance for NaBH4 oxidation.A binder-free and flexible Au electrode is prepared by spontaneous deposition of Au onto a A4 (A4-paper)-8B (8B pencil)-Ni Film substrate (ABNi) which is assembled by electrodeposition of nanoscale Ni particles on the surface of A4 paper coated by 8B pencil. The morphology and phase structure of the (A4-paper)-8B (8B pencil)-Ni Film-Au (ABNiAu) electrode are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer and X-ray diffractometer. The catalytic activity of the ABNiAu electrode for NaBH4 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The electrode exhibits a high electric conductivity and the activity substance attaches to the surface of paper substrate tightly and does not fall off at all and the nanoscale Ni and NiAu alloy enhance the broken of the BH bond in the BH4−, all of which lead to a high catalytic activity for NaBH4 electrooxidation. The oxidation current density reaches 300 mA cm−2 in 1 mol dm−3 NaOH and 0.1 mol dm−3 NaBH4 at −0.2 V. The exchanged electrons (n) is 6.0 (8.0 in theory), which indicates that the ABNiAu electrode has much higher utilization efficiency of the fuel than our reported LaNi5/Pd (n = 4) electrode.

ZnCo2O4 nanocluster particles (NCPs) were prepared through a designed hydrothermal method, with the assistance of a surfactant, sodium dodecyl benzene sulfonate. The crystalline structure and surface morphology of ZnCo2O4 were investigated by XRD, XPS, SEM, TEM, and BET analyses. The results of SEM and TEM suggest a clear nanocluster particle structure of cubic ZnCo2O4 (~100 nm in diameter), which consists of aggregated primary nanoparticles (~10 nm in diameter), is achieved. The electrochemical behavior of synthesized ZnCo2O4 NCPs was investigated by galvanostatic discharge/charge measurements and cyclic voltammetry. The ZnCo2O4 NCPs exhibit a high reversible capacity of 700 mAh g−1 over 100 cycles under a current density of 100 mA g−1 with an excellent coulombic efficiency of 98.9% and a considerable cycling stability. This work demonstrates a facile technique designed to synthesize ZnCo2O4 NCPs which show great potential as anode materials for lithium ion batteries.

Large surface area, high electrical conductivity, and abundant channels have been recognized to favor faradic capacitors, but their realization at the same time by a facile preparation process is still a great challenge. Here, we synthesized porous cadmium sulphide freely standing on nickel foam (CdS/NF) via a one-step hydrothermal method which possesses high specific capacitance, good rate capability and outstanding cycling stability. The CdS/NF microspheres present pores with a mean size of ∼3 nm, resulting in fast diffusion of ions, facile transportation of electrons and high activity, which make great synergistic contributions to reversible redox reactions. In the resulting supercapacitors, a specific capacitance of 909 F g−1 is achieved at a current density of 2 mA cm−2 with excellent rate capability that 88% of the original capacitance is retained at 50 mA cm−2. After 5000 charge–discharge cycles at current densities as large as 50 mA cm−2, 104% of initial capacitance is maintained. Finally, asymmetric supercapacitors with a high energy density of 28 W h kg−1 at a power density of 160 W kg−1 were obtained.

•Porous Ni(OH)2 nanoleaf is prepared by using ZnO as pore forming agent.•The mass loading of active material on binder-free Ni(OH)2/NF electrode is as high as 10 mg.•The porous Ni(OH)2/NF electrode displays high specific capacitance of 1142C g−1.Ni(OH)2 has been reported widely as one of the most promising supercapactior electrode materials due to its high specific capacitance, yet which were only based on low mass loading. Thus, it is desirable to promote supercapacitor performance for high mass loading Ni(OH)2 through optimizing microstructure. In this work, we first prepared crossed ultrathin Ni(OH)2/ZnO nanoleafs directly grown on nickel foam via hydrothermal method, and then we produced pores on the nanoleafs by dissolving ZnO in alkaline solution. Definitely, this unique structure design for high mass loading binder-free Ni(OH)2 electrode could benefit the penetration of electrolyte and the transportation of electrons, efficiently improving the supercapacitor performance. The obtained porous Ni(OH)2/NF electrode exhibits a mass specific capacity of 1142C g−1 based on 10 mg active materials, equating to a areal specific capaciy of 11.4C cm−2, and pleasant cycling stability with retention of 85% of initial capacity after 10000 charge-discharge cycles. The fabricated asymmetric device shows a high energy density of 42 Wh kg−1 (4.73 mWh cm−3) at power density of 105 W kg−1 (17 mW cm−3). These results demonstrate the optimized structure makes the high mass loading binder-free Ni(OH) 2/NF electrode could also display excellent supercapacitor performance.

•We synthesized copper sulfides via one-step, facile and controllable in-situ etching copper foam.•We investigated the influence of etching time on the morphology and electrochemical performance.•The electrode composed of nanorod Cu1.92S accompanying nanoribbon CuS displays high specific capacitance of 448.8 C g−1.Facile in-situ etching current collector prepares corresponding oxide or sulfide, which is directly used as faradic electrode material, supplying faster electron transportation and better connection, and thus displaying good supercapacitor performance. Here, we prepare CuxS via etching copper foam and investigate the influence of etching time on the morphology and electrochemical performance. The results show that compared with the nano-rod CuxS-1h/CF, nano-rod/wire CuxS-2h/CF and block/nanorod CuxS-4h/CF, the nano-rod/ribbon CuxS-3h/CF electrode exhibits the highest specific capacity (448.8C g−1 at current density of 5 mA cm−2). We fabricate asymmetric supercapacitor based on CuxS-3h/CF as positive electrode and AC as negative electrode to further evaluate the supercapacitor property and the device achieves a high energy density of 35 Wh kg−1 at power density of 266 W kg−1. Furthermore, the outstanding cycling stability of 88% capacitance retention after 5000 charge-discharge cycles more enable the CuxS-3h/CF become promising faradic electrode material.

•3D RGNA was prepared by a “dipping, electroreduction and electrodeposition” process.•RGNA exhibits good stability and high electrocatalytic activity for NaBH4 oxidation.•The high specific surface area, electric conductivity, and hydrogen storage property of graphene lead to a super catalytic activity.Three-dimensional (3D) reduced graphene networks (RGN) were successfully fabricated on Ni foam without any conductive agents and polymer binders by dipping commercial Ni foam into graphene oxide (GO) suspension and subsequent a electroreduction process in a buffer solution. Au nanoparticles were then deposited on the RGN through an electrodeposition process to form a novel reduced graphene networks-Au (RGNA) electrode. The morphology and phase structure of the RGNA electrode are characterized by scanning electron microscope, transmission electron microscope and X-ray diffraction spectrometer. The NaBH4 electrooxidation performance on the RGNA electrode is investigated by means of cyclic voltammetry and chronoamperometry. The RGNA electrode owns special hierarchical porous structure, rapid electron and ion transport, and large electroactive surface area due to the intrinsic electronic conductivity, mesoporous nature of graphene. The RGNA electrode exhibits a good stability during the electrochemical process and the oxidation current density at RGNA electrode reached 500 mA cm−2 at 0 V in the solution containing 0.1 mol dm−3 NaBH4 and 2 mol dm−3 NaOH, which is higher than that at bare Au–Ni foam without graphene. The excellent structural stability and high catalytic performance for NaBH4 electrooxidation make the RGNA a promising material for future energy systems.

In this work, an FeOOH/Ag/ZnO shell/core array electrode was prepared by electro-depositing FeOOH on Ag decorated ZnO nanorod arrays. Some characterization methods, including X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy were used to study the structure and surface morphologies of FeOOH/Ag/ZnO. The results suggest that Ag particles are homogeneously distributed on ZnO nanorods, and FeOOH is well-distributed on the surface of Ag/ZnO nanorod arrays. When evaluated as a supercapacitor electrode material, the FeOOH/Ag/ZnO shell/core array electrode exhibits a high specific capacitance of 376.6 F g−1 at a charge/discharge current density of 1 A g−1, and 70.3% specific capacitance is retained after 1000 cycles. The superior pseudo-capacitive properties of FeOOH/Ag/ZnO shell/core arrays are attributed to the unique shell/core structure. First, the ZnO nanorod arrays as skeleton loading active materials can provide a large surface to volume for easy access of electrolyte ions. Second, the Ag decorated on ZnO nanorods can improve the electrical conductivity of the as-prepared electrode, which can provide fast electron transfer for faradaic reactions. The results confirm that FeOOH/Ag/ZnO shell/core arrays are advantageous as electrochemical energy storage materials.

•Willow catkin is effectively converted into cross-linked porous carbon nanosheets.•N,S-PCNs1-1 electrode shows excellent capacitive performance.•The assembled symmetric supercapacitor exhibits high energy density.A facile one-step pyrolysis and activation synthesis method is utilized to convert a common biomass of willow catkin into interconnected porous carbon nanosheets (PCNs), and then followed by effective nitrogen and sulfur co-doping. Owing to the unique hollow and multilayered structure of willow catkin fiber, the pore structure of obtained carbons can be controlled by adjusting the mass ratio of raw material to alkali. As a result, the nitrogen and sulfur co-doped PCNs demonstrate a high specific capacitance of 298 F g−1 at 0.5 A g−1 and 233 F g−1 at 50 A g−1, revealing excellent rate performance. In addition, the electrode demonstrates superb cycling stability with only 2% capacitance loss after 10,000 cycles. Furthermore, the assembled symmetric cell with a wide voltage range of 1.8 V yields a remarkable specific energy of 21.0 Wh kg−1 at 180 W kg−1. These exciting results exhibit a green and low-cost design of electrode materials for high performance supercapacitors.The willow catkin derived nitrogen and sulfur co-doped porous carbon nanosheets (N,S-PCNs1-1) are prepared by a facile one-step pyrolysis and activation synthesis method, and then followed by effective nitrogen and sulfur co-doping. As a result, the as-obtained carbon processes cross-linked graphene-like structure with high specific surface area and interconnected pore texture, resulting in high specific capacitance, excellent rate performance and cycling stability.

A facile hydrothermal synthetic method, followed by in situ reduction and galvanic replacement processes, is used to prepare PtCo-modified Co3O4 nanosheets (PtCo/Co3O4 NSs) supported on Ni foam. The prepared nanomaterial is used as an electrocatalyst for NaBH4 oxidation in alkaline solution. The morphology and phase composition of PtCo/Co3O4 NSs are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic performance of PtCo/Co3O4 NSs is investigated by cyclic voltammetry (CV) and chronoamperometry (CA) in a standard three-electrode system. Current densities of 70 and 850 mA·cm–2 were obtained at–0.4 V for Co/Co3O4 and PtCo/Co3O4 NSs, respectively, in a solution containing 2 mol·L–1 NaOH and 0.2 mol·L–1 NaBH4. The use of a noble metal (Pt) greatly enhances the catalytic activity of the transition metal (Co) and Co3O4. Besides, both Co and Co3O4 exhibit good B–H bond breaking ability (in NaBH4), which leads to better electrocatalytic activity and stability of PtCo/Co3O4 NSs in NaBH4 electrooxidation compared to pure Pt. The results demonstrate that the as-prepared PtCo/Co3O4 NSs can be a promising electrocatalyst for borohydride oxidation.

•MP substrate was fabricated by adhering MWNTs on a piece of obsoleted plastic bag.•Co nano-thorns were prepared by a simple electrodeposition method on the MP surface.•MP owns a superior stability in strong alkaline environment.•CMP exhibits a high catalytic activity for NaBH4 electrooxidation.•The possible mechanisms of NaBH4 electrooxidation on CMP was discussed.A novel multi-walled carbon nanotubes (MWNTs)-Plastic (MP) substrate was first fabricated by adhering MWNTs on a piece of obsoleted plastic bag, and Co nano-thorns were subsequently prepared by a simple electrodeposition method on the MP surface. The morphology and phase structure of the as-prepared Co@MWNTs-Plastic (CMP) catalytic electrode are characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffractometer. The catalytic activity of the CMP electrode for NaBH4 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The employing of waste plastic bags reduces white pollution and the MP substrate exhibits superior stability in alkaline solution. The 3D CMP catalytic electrode owns a high electrochemical activity for NaBH4 oxidation. Moreover, we discussed the possible mechanisms of NaBH4 electrooxidation on the CMP.

•3D honeycomb-like NiS2/NiO were prepared via a green hydrothermal process.•The NiS2 reduces the electrochemical impedance of NiO.•The NiS2/NiO electrode exhibits exceptional electrochemical performance.Three dimensional (3D) honeycomb-like NiS2/NiO nano-multiple materials were successfully prepared by fabricating cribrate NiS2 on the surface of NiO nanosheets through simple hydrothermal process on nickel foam. The morphology and phase structure of the NiS2/NiO are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer, transmission electron microscope, X-ray diffractometer and the electrochemical properties are tested by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The NiS2/NiO electrode owns lower electrochemical impedance compared with bare NiO substrate and exhibits exceptional capacitance performance with a high specific capacitance of 2251 F g−1 delivered at current density of 1 A g−1, while 1192 F g−1 retained at 20 A g−1. What's more, after 2000 cycles, the specific capacitance remains 1275 F g−1 (at 5 A g−1) with a capacitance retention of 78%. Therefore, the NiS2/NiO electrode shows remarkable electrochemical performance and has a promising future for electrochemical supercapacitors.

•The unique bud morphology has large specific surface.•The Co(OH)2 buds/Ni foam electrode exhibits high specific capacitance.•The asymmetric supercapacitor has high energy density.In this work, Co(OH)2 buds direct growth on Ni foam (Co(OH)2 buds/Ni foam) is prepared via a hydrothermal method. Their structure and morphologies are characterized by using X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. Result shows that the Co(OH)2 buds are assembled by several nanorods and uniformly covered on the surface of Ni foam. Due to its unique structure, the Co(OH)2 buds/Ni foam electrode shows high capacitive performance and long cycle life. The specific capacitance of Co(OH)2 buds/Ni foam is as high as 2041 F g−1 at a current density of 3 mA cm−2 in 6 M KOH electrolyte, and 811 F g−1 even at a high current density of 60 mA cm−2. The capacitance of the Co(OH)2 buds/Ni foam electrode remained 72.4% after 1000 cycles at 18 mA cm−2. An asymmetric supercapacitor was successfully assembled, in which Co(OH)2 buds/Ni foam and AC used as positive and negative electrode, respectively. The energy density of the AC//Co(OH)2 buds/Ni foam supercapacitor reaches to 20.3 W h kg−1 at a power density of 90.6 W kg−1. Our result shows that the Co(OH)2 materials are promising candidate for electrochemical energy applications.

•A novel 3D Au nanoparticles electrode with good electron conductivity and high surface area is successfully fabricated.•Au nanoparticles are uniformly distributed on the surface of C@TiO2 nanowire array.•The electrode exhibits high performance and good stability for NaBH4 oxidation.In this work, Au nanoparticles directly grown on the surface of TiO2 core-C shell (Au/C@TiO2) has prepared by a simple electrodeposition method for the first time. The morphology is characterized by scanning electron microscope, and its structure is investigated by X-ray diffraction. Au nanoparticles are uniformly distributed on the surface of C@TiO2 nanowire array. Its catalytic performance for NaBH4 oxidation is evaluated by cyclic voltammetry and chronoamperometry measurement. The results indicate that Au/C@TiO2 shows a good and stable catalytic performance. In 2 mol cm−3 NaOH and 0.2 mol cm−3 NaBH4 the oxidation current density for the electrooxidation of BH4− can reach 475 mA cm−2 at 0 V. The electrons transfer number released by BH4− electrooxidation on Au/C@TiO2 electrode has been found to be a 6-electron process. The high performance is mainly attributed to its 3D structure which can promote the mass transport of NaBH4, electronic conductivity and Au utilization.

Flexible and binder-free multi-walled carbon nanotube (MWNT)-modified sponge-based nickel (Ni) is employed as the electrode material for methanol (CH3OH) electrooxidation. The nano-spherical Ni is electrodeposited on the surface of the MWNTs which are assembled on the skeleton of a commercial sponge. The as-prepared MWNT-modified sponge-based Ni electrode (MSNi) is characterized by scanning electron microscopy, transmission electron microscope, and X-ray diffractometer. The catalytic activity of the MSNi electrode for CH3OH electrooxidation is investigated by means of cyclic voltammetry, chronoamperometry, and electrochemical impedance spectra. The preparation process of the flexible MSNi electrode does not use any binder and it exhibits a unique three-dimensional (3D) network-porous structure. The MSNi exhibits a high electrocatalytic performance of 23 mA (cm2 mg−1) in 0.5 mol dm−3 CH3OH at 0.5 V.

•Co3O4 with different morphologies are synthesized via a simple solvothermal method.•The influences of solvent and probable growth mechanism are discussed.•The electrode exhibits high performance and good stability for H2O2 reduction.Hydrogen peroxide (H2O2) replaced oxygen (O2) as oxidant has been widely investigated due to its faster reduction kinetics, easier storage and handling than gaseous oxygen. The main challenge of using H2O2 as oxidant is the chemical decomposition. In this article, by using different C2H5OH/H2O volume ratio as the solvent, Co3O4 with different morphologies (nanosheet, nanowire, ultrafine nanowire net, nanobelts, and honeycomb-like) direct growth on Ni foam are synthesized via a simple solvothermal method for the first time. Results show that the introduction of ethanol could obviously improve the catalytic performance toward H2O2 electroreduction. The sample prepared in the solution with the C2H5OH/H2O volume ratio of 1:2 shows the best catalytic performance among the five samples and a current density of 0.214 A cm−2 is observed in 3.0 mol L−1 KOH + 0.5 mol L−1 H2O2 at −0.4 V (vs. Ag/AgCl KCl), which is much larger than that on the other metal oxides reported previously, almost comparable with the precious metals. This electrode of Co3O4 directly grown on Ni foam has superior mass transport property, which combining with its low-cost and facile preparation, make it a promising electrode for fuel cell using H2O2 as the oxidant.

•CuO/nitrogen-doped reduced graphene oxide (CuO/N-RGO) composites are synthesized via a facile and scalable method.•CuO nanoparticles anchor homogeneously on the nitrogen-doped reduced graphene oxide (N-RGO) nanosheets.•The composite of 10 mmol CuO/N-RGO shows excellent capacitive performance.CuO/nitrogen-doped reduced graphene oxide (CuO/N-RGO) composites are prepared by refluxing in ammonia solution and low temperature annealing. The as-prepared samples have been characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The loading of CuO has been measured by using inductively coupled plasma mass spectroscopy (ICP-MS). Results reveal that the CuO nanoparticles with ∼5 nm in diameter are anchored homogeneously on the nitrogen-doped reduced graphene oxide (N-RGO) nanosheets. Their electrochemical performances for supercapacitors are investigated by cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The CuO/N-RGO composite with 15.1 wt% CuO loading shows a high specific capacitance of 340 F g−1 at a charge/discharge current density of 0.5 A g−1 in 6 mol dm−3 KOH electrolyte, and with a wide potential window of 1.4 V. Importantly, 58% of capacitance is retained when the charge/discharge current density increases from 0.5 A g−1 to 5 A g−1. The capacitance retention can reach to 80% after 500 charge/discharge cycles. These findings demonstrate that the CuO/N-RGO material is a promising candidate for supercapacitor applications.

•A novel MWNTs–CC collector is prepared by dipping a piece of waste cosmetic cotton textile into MWNTs ink.•The Co–MWNTs–CC electrode shows a unique 3D hierarchical-network structure.•The Co–MWNTs–CC electrode exhibits remarkably high catalytic activity and good stability for the electrooxidation of NaBH4.Flexible and wearable cobalt electrode with a unique three-dimensional hierarchical-network structure is prepared by electrodeposition of spherical Co particles onto multiwalled carbon nanotubes (MWNTs) which are assembled on the skeleton of cosmetic cotton (CC). The morphology and phase structure of the cobalt–multiwalled carbon nanotubes–cosmetic cotton (Co–MWNTs–CC) electrode are characterized by scanning electron microscope, transmission electron microscope and X-ray diffraction spectrometer. The NaBH4 electrooxidation performance on the Co–MWNTs–CC electrode is investigated by means of cyclic voltammetry and chronoamperometry. Results show that the Co–MWNTs–CC electrode exhibits remarkably high catalytic activity and good stability for NaBH4 electrooxidation. The oxidation current density reaches as high as 170 mA cm−2 at −0.7 V in 1.0 mol dm−3 NaOH and 0.1 mol dm−3 NaBH4, which is higher than the most-related previous results.

A nitrogen-doped graphene oxide/copper oxide (N-GO/CuO) nanocomposite is prepared through a modified Hummers method followed by heat treatment. The composite is characterized by scanning electron microscopy and transmission electron microscopy, and the results show crumpled and curved graphene oxide nanosheets with uniformly distributed CuO nanoparticles. The composition of N-GO/CuO is further studied by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The electrochemical behaviors of N-GO/CuO as an anode material for lithium ion rechargeable batteries are investigated by galvanostatic discharge–charge measurements and cyclic voltammetry. N-GO/CuO exhibits a high reversible capacity of 472 mA h g−1 under the current density of 372 mA g−1 with excellent capacity retention of 99.7% over 100 cycles and improved rate capacities. This work demonstrates that N-GO/CuO is a promising anode material for lithium ion batteries.

A simple method involving dyeing and electrodeposition is introduced to fabricate a three-dimensional Ni@multi-walled carbon nanotubes flexible electrode on wearable fabric. The as-prepared Ni@multi-walled carbon nanotubes/Fabric (Ni@MWNTs/Fabric) electrode was characterized by scanning electron microscopy and X-ray diffraction spectrometry. The catalytic activity of the Ni@MWNTs/Fabric electrode for hydrogen peroxide electrooxidation was tested by means of cyclic voltammetry and chronoamperometry. Such a three-dimensional hybrid electrode structure allows a large specific surface area and a large mass loading, which lead to a high areal current density of 720 mA cm−2 at 0.5 V in 2 mol dm−3 NaOH and 2.5 mol dm−3 hydrogen peroxide. The electrode shows great promise as the anode of a direct peroxide fuel cell due to its being flexible, wearable, and environmentally friendly.

A low-cost and binder-free cobalt electrode is prepared by the electrodeposition of Co nanoplates onto a flexible conductive substrate, which is prepared simply by scratching a piece of A4 paper with a common 8B pencil. The morphology and phase structure of the cobalt–graphite–paper (CGP) electrode are characterized by scanning electron microscopy, transmission electron microscopy and an X-ray diffractometer. The catalytic activity of the CGP electrode for NaBH4 electro-oxidation is investigated by cyclic voltammetry and chronoamperometry. The catalyst combines tightly with the paper and exhibits a good stability. The oxidation current density reaches up to 180 mA cm−2 in 1 mol dm−3 NaOH and 0.10 mol dm−3 NaBH4 at −0.4 V.

•The novel Ni-MWNTs-textile electrode is prepared by the facile “dipping and drying” and electrodeposition process.•The Ni-MWNTs-textile electrode exhibits a special three dimensional network structure.•The Ni-MWNTs-textile electrode exhibits excellent performance for N2H4 electrooxidation.A new composite Ni electrode is simply prepared by electrodeposition of nano-scaled Ni particles onto multi-walled carbon nanotubes (MWNTs)-enabled conductive textile fiber (cosmetic cotton) which owns an especial three-dimensional (3D) network structure. The morphology and phase structure of the Ni-MWNTs-textile electrode are characterized by scanning electron microscope, transmission electron microscope and X-ray diffraction spectrometer, and the catalytic performance for the N2H4 electrooxidation is tested by linear sweep voltammetry and chronoamperometry. The results show that the Ni-MWNTs-textile electrode exhibits a remarkably high catalytic activity and good stability for N2H4 electrooxidation. The onset potential stays at around −0.9 V and the oxidation current density reaches as high as 12 mA cm−2 in the solution containing 1 mol dm−3 NaOH and 20 mmol dm−3 N2H4 at around −0.80 V, both of which outstrip the previous reports.

Al-doped β-Ni(OH)2 nanosheets are prepared by a simple hydrothermal process onto nickel foam by using a mixed aqueous solution of nickel nitrate, aluminum nitrate and ammonia. Their structure and surface morphology are studied by using X-ray diffraction analysis, energy-dispersive X-ray spectroscopy and scanning electron microscopy. The SEM images show changes in the microstructure of β-Ni(OH)2 by the addition of Al. The XRD results show that the α-phase Ni(OH)2 appeared by the addition of Al. The effects of Al content on the electrochemical behaviors of β-Ni(OH)2 are investigated by cyclic voltammetrys, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results show a drastic improvement in the capacitive characteristics of β-Ni(OH)2 with a specific capacitance increase from 941.7 to 2122.6 F g−1 by the addition of just 3.4 mol% Al. This work suggests that the as-prepared Al0.034Ni0.966LDH electrode has a promising future as higher charging/discharging rate materials for pseudo-supercapacitors.Highlights► Al-doped β-Ni(OH)2 nanosheets were prepared by a simple hydrothermal process. ► The effect of Al content on the electrochemical behaviors was investigated clearly. ► The as-prepared Al0.034Co0.966LDH electrode exhibited highest specific capacitance of 2122.6 F g−1 at 1 A g−1.

•A novel 3D Pd-porous Ni/Ni foam electrode is successfully fabricated.•Pd is uniformly distributed on the surface of porous Ni film supported on Ni foam.•The electrode exhibits high performance and good stability for NaBH4 oxidation.A novel three-dimensional electrode consisting of Pd doped porous Ni film supported on Ni foam (Pd-porous Ni/Ni) is successfully prepared. The porous Ni film is synthesized by electrodeposition of Ni nanoparticles using hydrogen bubbles as a dynamic template. Pd doping is carried out via a chemical replacement reaction between Ni film and Na2PdCl4 solution. The obtained electrode exhibits a three-dimensional (3D) porous structure allowing the full utilization of catalyst surface active sites. The morphology of the electrode and the distribution of Pd on Ni particle surfaces are characterized by scanning electron microscope and energy dispersive X-ray spectrometer. The structure is analyzed using an X-ray diffractometer. The catalytic performance of the porous 3D electrode is evaluated by voltammetry and chronoamperometry. Results show that the electrode displays high catalytic activity and good stability for NaBH4 electrooxidation. The oxidation current density of NaBH4 on the Pd-porous Ni/Ni in 3.0 mol L−1 NaOH containing 0.1 mol L−1 NaBH4 at −0.6 V reaches 2.2 A mg−1, which is about 22 times of that on Pd/C (0.1 A mg−1) reported previously.A novel, simple 3D electrode with high performance for NaBH4 oxidation is prepared. The oxidation current density on the Pd-porous Ni/Ni foam electrode at a potential of −0.6 V (2.2 A mg−1) is about 22 times of that for Pd/C (0.1 A mg−1) reported previously.

•Al-substituted β-Ni(OH)2 were prepared by a simple template-free growth method.•The effect of Al contents on the electrochemical performances was investigated.•The specific discharge capacity was greatly enhanced by the addition of Al.Al-substituted β-Ni(OH)2 nanosheets are directly grown on nickel foam by a simple template-free growth process. Their microstructure and surface morphology are studied by X-ray diffraction spectroscopy, scanning electron microscopy and transmission electron microscopy. The SEM and TEM images show changes in the microstructure of β-Ni(OH)2 by the addition of Al. The XRD results show that the α-phase Ni(OH)2 appeared in Al-substituted Ni(OH)2 electrodes. The effects of Al content on the electrochemical behaviors are investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results demonstrate that the 7 mol% of Al in Ni(OH)2 has better electrochemical performance, such as better reaction reversibility, higher proton diffusion coefficient, lower electrochemical impedance, higher specific capacity, and better cyclic stability. The as-prepared 7%-Al-Ni(OH)2 electrode exhibits a specific discharge capacity of 324.5 mAh g−1 at 0.2 C, 220.6 mAh g−1 at 10 C, and 198.6 mAh g−1 at 30 C. The specific capacity loss is less than 8% after 200 charge/discharge cycles at 0.2 C and with columbic efficiency higher than 90%. This work suggests that the as-prepared 7%-Al-Ni(OH)2 electrode has a promising future as higher charging/discharging rate materials for nickel metal hydride power battery.

•MgFe2O4 nanoparticles are prepared by a sol–gel method.•The initial discharge specific capacity under the current density of 180 mA g−1 reaches 1404 mAh g−1.•The high specific capacities and good stability were due to its small particle size and the good electrochemical activity.Magnesium ferrite nanoparticles are prepared by a sol–gel method and characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The electrochemical behavior as anode materials of lithium-ion rechargeable batteries is investigated by galvanostatic discharge/charge measurements and cyclic voltammetry. The average diameter of the MgFe2O4 particles is around 11 nm. MgFe2O4 shows better performance than the traditional carbon material. The initial discharge specific capacity under the current density of 180 mA g−1 reaches 1404 mAh g−1, which is higher than that reported in literatures. After 50 cycles, the discharge and charge capacity of the MgFe2O4 under 90 mA g−1 is 493 and 473.6 mAh g−1, and the irreversible capacity loss is less than 5.2%.

•Cd(OH)2 nanowires was directly grown on nickel foam via a simple template-free method.•Cd(OH)2 nanowires exhibits a high specific capacitance of is 1164.8 F g−1 at 1 A g−1 in 6 mol dm−3 KOH solution.•The as-prepared Cd(OH)2 nanowires has potential applications in electrochemical capacitors.Cd(OH)2 nanowires have been synthesized on nickel foam by a simple template-free growth method. Structural characterization by SEM and TEM indicated that the Cd(OH)2 formed a porous film on the surface of the nickel foam skeletons. The thickness of the film reached approximately 25 μm and the nanowires have diameters of around ∼100 nm. The nanowires is confirmed to be pure phase hexagonal Cd(OH)2 by X-ray diffraction. The electrochemical capacitance behaviors of the Cd(OH)2 nanowires electrode are investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy tests. The Cd(OH)2 electrode performed in different electrolyte demonstrates that nanowires possess supercapacitance properties in the presence of high concentration OH− ion. The specific capacitances as high as 1164.8 F g−1 at 1 A g−1 and 257.6 F g−1 at 10 A g−1 are obtained in 6 mol dm−3 KOH solution. The remarkably high capacitance of the Cd(OH)2 nanowire electrode might be attributed to its unique 3D open structure for easy access of electrolyte ions, large surface area and high electrochemical activity. This work demonstrates that Cd(OH)2 nanowires electrode has potential application in electrochemical capacitors.

A newly designed and fabricated electrode with three-dimensional structures is reported. The electrode consists of a conducting nanoarray substrate and Pd nanoparticles. The substrate is an array of TiO2 nanowires with a carbon coating layer prepared via a thermal evaporation method. Pd nanoparticles were electro-deposited on the substrate surfaces by the potentiostatic pulse method. The morphology of the electrode is observed by scanning electron microscopy and transmission electron microscopy, and its structure is analyzed using an X-ray diffractometer. The catalytic performance is evaluated by cyclic voltammetry and chronoamperometry. The electrode exhibited excellent catalytic performance for NaBH4 electro-oxidation. The current density for NaBH4 electro-oxidation at the electrode reported in this work (524 mA mg−1) is about 5 times of that at conventional Pd/C (100 mA mg−1). This enhanced performance is likely to be due to the improved mass transport of NaBH4, good electronic conductivity and high Pd utilization of the electrode.

Co3O4 nanowires have been successfully synthesized on nickel foam by a hydrothermal method. The morphology of Co3O4 is examined by scanning and transmission electron microscopy and the phase structure of Co3O4 nanowires is confirmed by X-ray diffraction. The electrochemical capacitance behavior of the Co3O4 nanowires electrode is investigated by cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy in 6 mol dm−3 KOH solution. The results show that the Co3O4 nanowires have diameters of around 100 nm and the lengths up to 1–2 μm. The specific capacitance of Co3O4 nanowires is 1019.58 F g−1 at 3.38 A g−1 and 466.06 F g−1 at 33.80 A g−1. The capacitance loss is less than 5% after 1000 charge/discharge cycles at 3.38 A g−1 and with columbic efficiency higher than 98%. The enhancement of pseudocapacitive properties at a higher charging/discharging rate is due to the porous nanostructure and the high utilization of active material.

The electrode of array of CuO nanosheet is prepared via a template-free growth method, and it is doped by Ag via the silver mirror reaction. The morphology of Ag-doped CuO nanosheet is examined by scanning electron microscopy. The phase structure of the Ag-doped CuO nanosheet is analyzed by X-ray diffraction spectroscopy. The supercapacitance behavior of Ag-doped CuO nanosheet is investigated by cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy. The results show that the thickness of a single nanosheet is up to around 150 nm. The specific capacitance of the Ag-doped CuO nanosheet electrode is 689 F g−1 at 1 A g−1 and 299 F g−1 at 10 A g−1, respectively, much higher than that of the unmodified CuO nanosheet arrays (418 F g−1 at 1 A g−1 and 127 F g−1 at 10 A g−1). The improved capacitance is explained in terms of the presence of dispersed Ag particle coated the CuO nanosheet arrays having good electrical conductivity.

Spherical clusters of Ni(OH)2 nanosheets are directly grown on skeletons of nickel foam via a facile template-free spontaneous growth method. The obtained electrode (β-Ni(OH)2/Ni-foam) is characterized by X-ray diffractometry, scanning and transmission electron microscopy and thermal analysis. Results show that Ni(OH)2 has a β-phase structure and presents on the nickel foam skeleton mostly as spherical clusters with a diameter of ∼10 μm. The spheres are composed of nanosheets with thickness of ∼60 nm, width of ∼230 nm and length up to ∼2 μm, and the nanosheets are assembled by nanoparticles with diameter of ∼20 nm. The electrochemical performance of the β-Ni(OH)2/Ni-foam electrode is evaluated by cyclic voltammetry and galvanostatic charge–discharge tests. The difference between the oxygen evolution reaction onset potential and the anodic peak potential for this electrode (∼100 mV) is larger than that for β-Ni(OH)2 nanosheets and nanotubes powder electrode (∼65–77 mV) and much larger than that for commercial spherical β-Ni(OH)2 powder electrode (∼25–47 mV), indicating that the β-Ni(OH)2/Ni-foam electrode can be fully charged. The specific discharge capacity of β-Ni(OH)2 in the β-Ni(OH)2/Ni-foam electrode reaches 275 mAh g−1, which is close to the theoretical value, lower than that of β-Ni(OH)2 nanotubes (315 mAh g−1), but higher than that of nanosheets (219.5 mAh g−1), commercial micrometer grade spherical powders (265 mAh g−1) and microtubes (232.4 mAh g−1).Highlights• Facile one-step preparation of Ni foam supported β-Ni(OH)2 nanosheets. • Nanosheets have porous structure and large electrochemical active surface area. • Nanosheets have large high rate discharge capacity and superior cycling stability.

A novel plastic/multi-walled carbon nanotube (MWNTs)-nickel (Ni)-platinum (Pt) electrode (PMNP) is prepared by chemical-reducing Pt onto the surface of Ni film covered plastic/MWNTs (PM) substrate. The MWNTs are adhered by a piece of commercial double faced adhesive tape on the surface of plastic paper and the Ni film is prepared by a simple electrodeposition method. The morphology and phase structure of the PMNP electrode are characterized by scanning electron microscopy, transmission electron microscope and X-ray diffractometer. The catalytic activity of the PMNP electrode for NaBH4 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The catalyst combines tightly with the plastic paper and exhibits a good stability. MWNTs serve as both conductive material and hydrogen storage material and the Ni film and Pt are employed as electrochemical catalysts. The PMNP electrode exhibits a high electrocatalytic performance and the oxidation current density reaches to 10.76 A/(mg·cm) in 0.1 mol/dm3 NaBH4 at 0 V, which is much higher than those in the previous reports. The using of waste plastic reduces the discarding of white pollution and consumption of metal resources.A novel MWNTs modified plastic paper supported Ni–Pt electrode serves as an efficient electrocatalyst for NaBH4 oxidationDownload high-res image (91KB)Download full-size image

•Co/Co3O4 Ps reveal higher catalytic activity than Co3O4.•Co/Co3O4 Ps show unique 3D structure on Ni foam with a large surface area.•Co/Co3O4 Ps exhibit good catalytic activity and stability for H2O2 electroreduction.Petal shaped Co/Co3O4 composite electrocatalyst with a special structure used as a cathode for H2O2 electroreduction is obtained by a route of hydrothermal synthesis and in-situ chemical reduction. The phase composition and microstructure of the electrocatalyst are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical performance of H2O2 electroreduction on the Co/Co3O4 petals (Ps) is explored by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectrometry (EIS). The Co/Co3O4 Ps exhibits a higher conductivity than single Co3O4, which leads to a better catalytic activity and stability toward H2O2 electroreduction. In a solution of 3 mol L− 1 NaOH and 0.5 mol L− 1 H2O2, the current density of H2O2 electroreduction on Co/Co3O4 Ps is 440 mA cm− 2 at − 0.8 V, higher than that on Co3O4, which make the obtained Co/Co3O4 Ps an excellent alternative catalyst for H2O2 fuel cell.

•The in-situ etched Cu(OH)2 nanowire core structure efficiently shortened the pathway for electrons transport.•The novel shell materials NiOOH uniformly wraps each Cu(OH)2 nanowire.•The hybrid Cu(OH)2@ NiOOH/copper-foil electrode displays excellent specific capacity of 1300 C g−1.The 1D nanowire is prepared by in-situ etching current collector displaying faster electron transportation and better connection, plusing the directional charge transport properties, which could enable it become one of the most appropriate core of 3D core@shell structure. We apply novel nanowire-like Cu(OH)2, which is synthesized by etching copper foil, as core structure to be coated by novel NiOOH with high theoretical capacity. The fast electronic conductive core structure and promising faradic electrode material candidate material enable the Cu(OH)2@NiOOH/copper-foil electrode deliver high specific capacity of 1300 C g−1 at current density of 10 mA cm−2 and outstanding cycling stability of capacity retention of 88% after 10000 charge-discharge cycles, indicating the as-prepared Cu(OH)2@NiOOH/copper-foil electrode has potential application in electrochemical capacitors.

A newly designed and fabricated electrode with three-dimensional structures is reported. The electrode consists of a conducting nanoarray substrate and Pd nanoparticles. The substrate is an array of TiO2 nanowires with a carbon coating layer prepared via a thermal evaporation method. Pd nanoparticles were electro-deposited on the substrate surfaces by the potentiostatic pulse method. The morphology of the electrode is observed by scanning electron microscopy and transmission electron microscopy, and its structure is analyzed using an X-ray diffractometer. The catalytic performance is evaluated by cyclic voltammetry and chronoamperometry. The electrode exhibited excellent catalytic performance for NaBH4 electro-oxidation. The current density for NaBH4 electro-oxidation at the electrode reported in this work (524 mA mg−1) is about 5 times of that at conventional Pd/C (100 mA mg−1). This enhanced performance is likely to be due to the improved mass transport of NaBH4, good electronic conductivity and high Pd utilization of the electrode.

Large surface area, high electrical conductivity, and abundant channels have been recognized to favor faradic capacitors, but their realization at the same time by a facile preparation process is still a great challenge. Here, we synthesized porous cadmium sulphide freely standing on nickel foam (CdS/NF) via a one-step hydrothermal method which possesses high specific capacitance, good rate capability and outstanding cycling stability. The CdS/NF microspheres present pores with a mean size of ∼3 nm, resulting in fast diffusion of ions, facile transportation of electrons and high activity, which make great synergistic contributions to reversible redox reactions. In the resulting supercapacitors, a specific capacitance of 909 F g−1 is achieved at a current density of 2 mA cm−2 with excellent rate capability that 88% of the original capacitance is retained at 50 mA cm−2. After 5000 charge–discharge cycles at current densities as large as 50 mA cm−2, 104% of initial capacitance is maintained. Finally, asymmetric supercapacitors with a high energy density of 28 W h kg−1 at a power density of 160 W kg−1 were obtained.