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Abstract: Nanowire arrays of mixed oxides of Co and Ni freely standing on Ni foam are prepared by a template-free growth method. The effects of Ni content on the morphology, structure and catalyst performance for oxygen evolution reaction are investigated by scanning electron microscopy, X-ray diffraction spectroscopy and electrochemical techniques including cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. A transformation from nanowire arrays to nanoplate arrays is found with the increase of the atomic ratio of Ni to Co in the preparation solution. The NixCo3−xO4 electrode obtained at 1:1 of Ni:Co in the preparation solution exhibits nanowire array structure and has better catalytic performance for oxygen evolution reaction than other NixCo3−xO4 and Co3O4 electrodes. The catalytic activities of the NixCo3−xO4 and Co3O4 electrodes are correlated with their surface roughness. Superior stability of the NixCo3−xO4 nanowire array electrode is demonstrated by a chronopotentiometric test. The reaction orders with respect to OH− on the NixCo3−xO4 electrode are close to 2 and 1 at low and high overpotentials, respectively. [Copyright &y& Elsevier]

Highlights • 3D porous CF is prepared using sponge as template and C 5 H 6 O 2 as carbon source. • PANI nanowires are deposited at the CF by a facile electrodeposition method. • CF-PANI exhibits good electrochemical performances. • The asymmetric supercapacitor assembled with CF-PANI and CF shows high energy and power densities. Abstract In this paper, three-dimensional (3D) porous carbon framework (CF) is prepared using commercial sponge as template and furfuryl alcohol (C 5 H 6 O 2) as carbon source, through polymerizing and solidifying by oxalic acid (H 2 C 2 O 4) followed by a carbonizing process at high temperature. Then, one-demensional (1D) polyaniline (PANI) nanowires are deposited on the CF substrate by a simple one-step electrodeposition method to obtain CF-PANI energy storage electrode. The CF-PANI maintains initial 3D porous structure as CF substrate with PANI layer, benefiting for the diffusion of electrolyte and the contact between active material and electrolyte. Besides, the carbon skeleton is surrounded by the PANI nanowires, which provide more transfer channels for electrons during the charge/discharge process. The loading mass of PANI on CF is as high as 21.3 mg cm−3, and the gravimetric and volumetric capacitances reach 866 F g−1 and 18.5 F cm−3, respectively, at the scan rate of 2 mV s−1. Moreover, the asymmetric supercapacitor based on CF-PANI as anode electrode and CF as cathode electrode exhibits a high energy density of 44 W h kg−1 at the power density of 800 W kg−1, indicating its promising applications as the electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The unique NiCo 2 S 4 nanowire arrays directly grown on Ni foam was prepared by two-step hydrothermal routes. • The synergistic effect between Ni and Co for urea electrooxidation has been discussed. • The effects of KOH and urea concentrations for urea electrooxidation were investigated. Abstract A 3D NiCo 2 S 4 nanowire arrays directly grown on Ni foam electrode (NiCo 2 S 4 /NF) is prepared by two-step simple hydrothermal process. The morphology and phase composition of NiCo 2 S 4 /NF are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). As expected, in the following electrocatalytic measurement, the binder-free, self-made NiCo 2 S 4 /NF electrode exhibits much higher catalytic activity, lower onset potential, better stability and greater tolerance towards urea electrooxidation compared with the Ni 3 S 2 /NF electrode synthesized under the same reaction conditions. The NiCo 2 S 4 /NF electrode delivers a current density of 720 mA cm−2 at 0.18 V (vs. Ag/AgCl) in a solution containing 5 mol L−1 KOH and 0.33 mol L−1 urea. The impressive electrocatalytic activity of the NiCo 2 S 4 /NF catalyst is largely ascribed to its distinctive structure, which exposes more electrochemical active sites at the electrode–electrolyte interface. Besides, the high intrinsic electronic conductivity also largely boosts the charge transfer rates for urea electrooxidation. The results demonstrate that the NiCo 2 S 4 /NF electrode showing a beneficial application prospect in the wastewater treatment and direct urea fuel cells. [ABSTRACT FROM AUTHOR]

Graphical abstract The super-ionic conductivity nanowire Cu 2 Se/Ni-foam electrode processes excellent cycling performance and the electrode is firstly assembled to asymmetric supercapacitor achieving high energy and power density. Abstract Transition metal selenide has stimulated much research interest in energy storage and conversion, due to its excellent electrical conductivity. β-Cu 2 Se with special crystal structure is considered as super-ionic conductor, of which the diffusion coefficient is as large as a liquid. The fast ions and electrons conductor β-Cu 2 Se with uniformly dense nanowire crossing with each other directly on nickel foam is prepared via simple one-step solvothermal grow method for 4 h, avoiding conductive agent and binder. The feature much benefitting for electrons and ions transfer enable the β-Cu 2 Se-4h electrode delivers specific capacity as high as 182.4 mA h g−1 at current density of 2 mA cm−2, which is still 105.6 mA h g−1 even at high current density of 50 mA cm−2, and excellent cycling stability of 85% after repetitively charge-discharge 10,000 times. The fabricated asymmetric supercapacitor (β-Cu 2 Se-4h//AC) achieves maximum energy and power density is 48 Wh kg−1 and 5500 W kg−1. [ABSTRACT FROM AUTHOR]

Novel Au@Ni nanoarrays electrode is facilely obtained by firstly template-assisted electro-deposition of Ni nanowire arrays (NAs), followed by galvanostatic deposition of Au catalysts onto the Ni NAs without any conductive agents and binders. The Au@Ni NAs electrode shows a rough surface and fringe with the diameter of ∼90 nm, which assures a high utilization of Au catalysts and provides a large specific surface area. The elemental distribution of Ni mainly exists in the inner layer of a single Au@Ni nanowire with the diameter ∼56 nm, while the elemental distribution of Au catalysts merely appears in the outer layer to form the unique core-shell nanowire structure. The Au@Ni NAs electrode reveals excellent electrochemical property and desirable stability for catalyzing NaBH 4 electro-oxidation in basic solutions. The Au@Ni NAs electrode in the 2.00 M NaOH and 0.24 M NaBH 4 solution demonstrates an oxidation current density of 2.35 A mg −1 at −0.5 V (vs. Ag/AgCl), which is much higher than that of the noble metal catalysts previously reported, indicating that this material may be hopefully used as anodic catalysts for applying in fuel cells. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The design of inexpensive bifunctional electrocatalysts with excellent catalytic activity is crucial for the cost reduction from water splitting. As a kind of biomass with hollow tubular structure, Metaplexis japonica fluff is expected to be a natural substrate for the growth of nanostructured electrocatalysts. Herein, nanowire-like NiCo precursors are grown on Metaplexis japonica fluff biomass substrates by hydrothermal method, which are then converted into carbon microtube supported NiCoP-NiS 2 composites (NiCoP-NiS 2 /CMT) by low-temperature phosphorization and sulfidation treatment. As expected, the biomass substrate provides a guiding role for the growth of NiCoP-NiS 2 nanowires, which is conducive to expose more active areas and promote charge transfer during the reaction. As a result, the obtained NiCoP-NiS 2 /CMT exhibits good electrocatalytic performance for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH, which only requires overpotentials of 134 and 308 mV at 10 mA cm−2, respectively. In addition, the constructed symmetric water splitting device exhibits a cell voltage of 1.62 V at 10 mA cm−2, and it also displays good stability during the 24 h test. [Display omitted] [ABSTRACT FROM AUTHOR]

The design of inexpensive bifunctional electrocatalysts with excellent catalytic activity is crucial for the cost reduction from water splitting. As a kind of biomass with hollow tubular structure, Metaplexis japonica fluff is expected to be a natural substrate for the growth of nanostructured electrocatalysts. Herein, nanowire-like NiCo precursors are grown on Metaplexis japonica fluff biomass substrates by hydrothermal method, which are then converted into carbon microtube supported NiCoP-NiS 2 composites (NiCoP-NiS 2 /CMT) by low-temperature phosphorization and sulfidation treatment. As expected, the biomass substrate provides a guiding role for the growth of NiCoP-NiS 2 nanowires, which is conducive to expose more active areas and promote charge transfer during the reaction. As a result, the obtained NiCoP-NiS 2 /CMT exhibits good electrocatalytic performance for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH, which only requires overpotentials of 134 and 308 mV at 10 mA cm−2, respectively. In addition, the constructed symmetric water splitting device exhibits a cell voltage of 1.62 V at 10 mA cm−2, and it also displays good stability during the 24 h test. [Display omitted] [ABSTRACT FROM AUTHOR]

Nickel-cobalt nanowire arrays (Ni-Co NWAs) electrode is prepared by one-step galvanostatic electrodeposition with a polycarbonate membrane as the template. By adjusting the Co proportion in the Ni and Co bath solution into 10%, the optimal Ni-Co NWAs electrode in terms of relatively lower onset potential and highest current density towards urea electro-oxidation is obtained. Its catalytic performance is investigated by constructing single direct urea/hydrogen peroxide (H 2 O 2 ) fuel cell. Results show that a peak power density of 7.4 mW cm −2 and an open circuit voltage of 0.92 V are achieved at room temperature when 9.0 mol L −1 KOH and 0.33 mol L −1 urea are used as the anolyte, H 2 SO 4 and H 2 O 2 as the catholyte. Additionally, the urea/H 2 O 2 fuel cell also demonstrates excellent stability during short term duration test. [ABSTRACT FROM AUTHOR]

Development of MnO 2 based electrode materials for supercapacitor application with high comprehensive electrochemical performance, such as high capacitance, superior reversibility, excellent stability, and good rate capability, is still a tremendous challenge. In this work, a distinctive interwoven three-dimensional (3D) structure electrode with ultra-thin 2D graphene nanosheet decorated on the surface of 1D C/TiC nanowire array is built as the support to immobilize MnO 2 nanoflakes (MnO 2 -Graphene nanosheet-C/TiC nanowire array, denoted as MGCT). Compared with the normal 1D core/shell structure, this novel 3D architecture can dramatically not only increase the surface area for MnO 2 loading but also facilitate the ion and electron transfer. The electrochemical performance of the as-prepared 3D MnO 2 electrode is evaluated by cyclic voltammetrys, galvanostatic charging-discharging tests and electrochemical impedance spectroscopy, high specific capacitance (856 F g −1 at 2 A g −1 ), good rate capability (69.1% capacitance retention at 40 A g −1 vs 2 A g −1 ), superior reversibility, and cycling stability (85.7% capacitance retention after 10,000 cycles at 10 A g −1 ) are obtained, suggesting that this novel structure can offer a new and appropriate idea for obtaining high-performance supercapacitor electrode materials. [ABSTRACT FROM AUTHOR]

Urea peroxide as a solid-state fuel instead of liquid hydrogen peroxide is electro-catalytic oxidized by nickel nanowire arrays (NWAs) electrode. Nickel NWAs electrode is prepared by galvanostatically electrodepositing nickel into the pores and over-plating on the surface of polycarbonate template (PCT) from nickel bath solution. The NWAs are obtained after dissolving PCT in methylene chloride. Results show that urea peroxide decomposes into hydrogen peroxide and urea in aqueous solutions, then is electro-oxidized via two processes: i, hydrogen peroxide electro-oxidation at lower potential region; ii, both hydrogen peroxide and urea electro-oxidation at higher potential region. The onset oxidation potential and current density of urea peroxide electro-oxidation in 6.0 mol L −1 KOH and 1.0 mol L −1 urea peroxide are ca. -0.2 V and 700 mA cm −2 at 0.6 V, respectively. The nickel NWAs electrode demonstrates excellent stability for urea peroxide electro-oxidation under different polarization potentials. [ABSTRACT FROM AUTHOR]

Nanoporous palladium supported on the carbon coated titanium carbide (C@TiC) nanowire arrays (Pd NP/C@TiC) are successfully prepared by a facile chemical vapor deposition of three-dimensional (3D) C@TiC substrate, followed by electrochemical codeposition of Pd–Ni and removal of Ni via dealloying. The structure and morphology of the obtained Pd NP/C@TiC electrodes are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) are used to examine the catalytic performances of the electrodes for H 2 O 2 electroreduction in H 2 SO 4 solution. The Pd NP/C@TiC electrode exhibits a largely effective specific surface area owing to its open nanoporous structure allowing the full utilization of Pd surface active sites. At the potential of 0.2 V in 2.0 mol L −1 H 2 O 2 and 2 mol L −1 H 2 SO 4 solutions, the reduction current density reaches 3.47 A mg −1 , which is significantly higher than the catalytic activity of H 2 O 2 electroreduction achieved previously with precious metals as catalysts. [ABSTRACT FROM AUTHOR]

A novel three-dimensional carbon- and binder-free nickel nanowire arrays (Ni NAs) electrode is successfully fabricated by a facile galvanostatic electrodeposition method using polycarbonate membrane as the template. The Ni NAs electrode achieves a oxidation current density (divided by the electroactive surface areas of Ni) of 25.1 mA cm −2 in 4 mol L −1 KOH and 0.9 mol L −1 H 2 O 2 at 0.2 V (vs. Ag/AgCl) accompanied with a desirable stability, which is significantly higher than the catalytic activity of H 2 O 2 electro-oxidation achieved previously with precious metals as catalysts. The impressive electrocatalytic performance is largely attributed to the superior 3D open structure and high electronic conductivity, which ensures the high utilization of Ni surfaces and makes the electrode have higher electrochemical activity. The apparent activation energy of H 2 O 2 electro-oxidation on the Ni NAs catalyst is 13.59 kJ mol −1 . A direct peroxide–peroxide fuel cell using the Ni NAs as anode exhibits a peak power density of 48.7 mW cm −2 at 20 °C. The electrode displays a great promise as the anode of direct peroxide–peroxide fuel cell due to its low cost, high activity and stability. [ABSTRACT FROM AUTHOR]

In this work, Au nanoparticles directly grown on the surface of TiO 2 core-C shell (Au/C@TiO 2 ) 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@TiO 2 nanowire array. Its catalytic performance for NaBH 4 oxidation is evaluated by cyclic voltammetry and chronoamperometry measurement. The results indicate that Au/C@TiO 2 shows a good and stable catalytic performance. In 2 mol cm −3 NaOH and 0.2 mol cm −3 NaBH 4 the oxidation current density for the electrooxidation of BH 4 − can reach 475 mA cm −2 at 0 V. The electrons transfer number released by BH 4 − electrooxidation on Au/C@TiO 2 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 NaBH 4 , electronic conductivity and Au utilization. [ABSTRACT FROM AUTHOR]

Fully metallic nickel nanowire arrays (NWAs) electrode is prepared by electrodepositing nickel within the pores and over-plating on the surface of polycarbonate template (PCT) with subsequent dissolution of the template in dichloromethane. The as-prepared electrode is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Urea electro-oxidation reaction in KOH solution on the nickel NWAs electrode is investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The results show that the nickel NWAs electrode achieves an onset oxidation potential of 0.25 V (vs. Ag/AgCl) and a peak current density of 160 mA cm −2 in 5 mol L −1 KOH and 0.33 mol L −1 urea accompanied with considerable stability. [ABSTRACT FROM AUTHOR]

Abstract: A facile and green method is developed to fabricate Fe3O4–Fe nanowires with a large amount of nanoholes directly grown on highly conductive nanofiber arrays. By electrodeposition of Fe clusters on C/TiC nanofiber array, followed by in-situ chemical conversion of Fe to FeC2O4–Fe nanowires and the thermal decomposition of FeC2O4–Fe to Fe3O4–Fe, a Fe3O4–Fe nanocomposite electrode with unique architecture is successfully prepared. The electrode is characterized by means of X-ray diffractometer, scanning electron microscope and transmission electron microscope. Electrochemical properties of the nanowire arrays electrode as the anode of lithium-ion batteries are examined by cyclic voltammetry and galvanostatic charge/discharge test. The electrode displayed remarkably high capacity, excellent high rate performance and superior cycling stability. The reversible capacity of the electrode reached 1012 mAh g−1 at 1C and retained to be 500 and 255 mAh g−1 at 10 and 20C, respectively. It can still deliver a specific capacity of 100 mAh g−1 even at 50C (72 s charge–discharge). The electrode also has a satisfactory cycling performance with capacity retention of 93.9% after 100 cycles at 1C. The magnificent performance can be attributed to the distinct configuration resulting from the novel fabrication process. [Copyright &y& Elsevier]

Highlights: [•] MnO2/C/TiO2 shell/shell/core arrays electrode has been prepared by simple thermal reaction and electrodeposition method. [•] The unique shell/shell/core structure has easy access of electrolyte ions, large surface to volume and high electrochemical activity. [•] The MnO2/C/TiO2 shell/shell/core arrays exhibits high specific capacitance of 639 F g−1 at a charge/discharge current density of 1 A g−1. [ABSTRACT FROM AUTHOR]

Abstract: Co3O4 nanowire arrays freely standing on Ti foil (Co3O4/Ti) are prepared via a template-free growth method. Pd nanoparticles are electrochemically deposited by cyclic voltammetry method on Co3O4 nanowires to obtain a nanocomposite electrode (Pd@Co3O4/Ti). The morphology and phase structure of the Pd@Co3O4/Ti electrode are characterized by scanning electron microscope and X-ray diffraction spectrometer. The catalytic activity of H2O2 electroreduction on the Pd@Co3O4/Ti electrode in alkaline medium is evaluated by means of linear scan voltammetry and chronoamperometry. The Pd@Co3O4/Ti electrode exhibits high performance and good stability to H2O2 electroreduction with a current density of 145.8 mA cm−2 at −0.4 V in 3.0 mol dm−3 KOH and 0.4 mol dm−3 H2O2 electrolyte, which outperforms the bare Co3O4 nanowire arrays without Pd doping. [Copyright &y& Elsevier]

Highlights: [•] 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 1164.8Fg−1 at 1Ag−1 in 6moldm−3 KOH solution. [•] The as-prepared Cd(OH)2 nanowires has potential applications in electrochemical capacitors. [Copyright &y& Elsevier]

Abstract: 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 6moldm−3 KOH solution. The results show that the Co3O4 nanowires have diameters of around 100nm and the lengths up to 1–2μm. The specific capacitance of Co3O4 nanowires is 1019.58Fg−1 at 3.38Ag−1 and 466.06Fg−1 at 33.80Ag−1. The capacitance loss is less than 5% after 1000 charge/discharge cycles at 3.38Ag−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. [Copyright &y& Elsevier]