Nanowire Array Electrode Research Articles

Underwater superaerophobic Ni nanoparticle-decorated nickel–molybdenum nitride nanowire arrays for hydrogen evolution in neutral media

Abstract Electrochemical water splitting into hydrogen and oxygen in neutral electrolytes has great significance for future energy supply security, potentially offering a pathway for H2 generation from seawater. However, the electrocatalytic hydrogen evolution reaction (HER) generally occurs at low rates in neutral solutions due to the low proton concentration in such media. Herein, we fabricated a novel HER catalyst capable of efficient H2 evolution in water at neutral pH, comprising a nickel-molybdenum nitride nanowire array modified with metallic Ni nanoparticles (Ni/NiMoN). The entire Ni/NiMoN array was supported on a Cu foam. The Ni nanoparticles promoted the dissociation of adsorbed water to enhance the supply of protons in the neutral electrolyte, whilst the nanowire array imparted the electrode surface with underwater superaerophobic properties, thus allowing H2 gas bubbles to detach from the electrode in a facile manner. On the basis of the synergies realized between the different electrode components, the Ni/NiMoN nanowire array electrode offered exceptional HER performance, with an overpotential of only 37 mV at a current density of 10 mA cm−2 in a neutral electrolyte. Results guide the development of next-generation earth-abundant element electrocatalysts for HER in neutral media.

Comparative Study of PtNi Nanowire Array Electrodes toward Oxygen Reduction Reaction by Half-Cell Measurement and PEMFC Test.

A clear understanding of catalytic activity enhancement mechanisms in fuel cell operation is necessary for a full degree translation of the latest generation of non-Pt/C fuel cell electrocatalysts into high-performance electrodes in proton-exchange membrane fuel cells (PEMFCs). In this work, PtNi nanowire (NW) array gas diffusion electrodes (GDEs) are fabricated from Pt NW arrays with Ni impregnation. A 2.84-fold improvement in the oxygen reduction reaction catalytic activity is observed for the PtNi NW array GDE (cf. the Pt NW array GDE) using half-cell GDE measurement in a 0.1 M HClO4 aqueous electrolyte at 25 °C, in comparison to only a 1.07-fold power density recorded in the PEMFC single-cell test. An ionomer is shown to significantly increase the electrochemically active surface area of the GDEs, but the PtNi NW array GDE suffers from Ni ion contamination at a high temperature, contributing to decreased catalytic activities and limited improvement in operating PEMFCs.

Tuning MnCo2O4 nanowire arrays on carbon cloth as an efficient cathode catalyst for Li–O2 batteries

Li–O2 batteries with higher theoretical specific capacity are a promising energy storage system. Designing an efficient cathode catalyst can alleviate the problem that derives from the sluggish dynamic process. In this study, morphologies of MnCo2O4 are easily tuned from square blocks to nanowire arrays by simple adjusting mole numbers of NH4F under hydrothermal conditions. The MnCo2O4 nanowire arrays on carbon cloth with a large specific surface area of 194.9 m2 g−1 are synthesized by 9 mmol NH4F, which as a cathode catalyst for Li–O2 batteries can maintain for 167 cycles with a cutoff capacity to 500 mA h g−1 at 340 mA g−1 (0.2 mA cm−2). And the MnCo2O4 nanowire array electrodes show the discharge capacities of 8364, 7544 and 5887 mA h g−1 at 200, 400 and 800 mA g−1, respectively, which show good rate performance.

Electron density modulation of GaN nanowires by manganese incorporation for highly high-rate Lithium-ion storage

Gallium nitride (GaN) has high theoretical capacity and low discharge platform. However, it still suffers from poor conductivity and unsatisfactory cycle performance in lithium-ion batteries (LIBs). In this work, the doped manganese (Mn) are realized in GaN nanowires through a simple and straight forward chemical vapor deposition (CVD) process. When the successful Mn doping was carefully examined in structural characterizations, it is discovered at the atomic level that the species of Mn dopants in GaN nanowires only exist in the feature of Mn+ rather than of metallic Mn, which can significantly promote the electrical conductivity and Li-ions transfer. The tested Mn doped GaN nanowire arrays electrode exhibit the capacity up to 780.3 mA h g−1 at 0.1 A g−1 after 100 cycles and 326.8 mA h g−1 at 5.0 A g−1 after 500 cycles, respectively. The tight and direct contact between Mn doped GaN nanowires and graphite layer provides ultrafast electronic transfer. Density functional theory (DFT) studies confirm that Mn covalent doping can generate the change of local atomic arrangement. Moreover, the electronic structure change significantly increase the electrical conductivity for the fast charge transfer efficiency. This covalent doping strategy for the electron densities regulation could boost the Li-ions storage performance for developing advanced electrode materials in energy storage and beyond.

Ni Hierarchical Structures Supported on Titania Nanowire Arrays as Efficient Nonenzymatic Glucose Sensor.

Developing new advanced nonenzymatic electrochemical nano-sensors for glucose detection has attracted intensive attraction. In this work, we designed a novel nanocomposite nonenzymatic glucose sensor by fabricating hierarchically nanostructured metal nickel on titania nanowire arrays, which was loaded on a transparent conductive substrate (i.e., fluorine-doped tin oxide, FTO) surface by mild hydrothermal method. Due to the large surface area of the hierarchically nanostructured Ni and fast electron transfer of the TiO₂ nanowire arrays electrode, the nanocomposite electrode shows excellent electrochemical activity toward the oxidation of glucose. The electrode exhibits high sensitivity in detecting glucose concentration (1472 μA mM-1 cm-2) with a wide linear range from 2×10-4 M to 2×10-3 M, fast response time (within 5 s), and small detection limit (10 μM) (S/N = 3). The good analytical performance, low cost and simple preparation method make this novel electrode material promising for the development of effective glucose nonenzymatic glucose sensor.

Manipulating dehydrogenation kinetics through dual-doping Co3N electrode enables highly efficient hydrazine oxidation assisting self-powered H2 production

Replacing sluggish oxygen evolution reaction (OER) with hydrazine oxidation reaction (HzOR) to produce hydrogen has been considered as a more energy-efficient strategy than water splitting. However, the relatively high cell voltage in two-electrode system and the required external electric power hinder its scalable applications, especially in mobile devices. Herein, we report a bifunctional P, W co-doped Co3N nanowire array electrode with remarkable catalytic activity towards both HzOR (−55 mV at 10 mA cm−2) and hydrogen evolution reaction (HER, −41 mV at 10 mA cm−2). Inspiringly, a record low cell voltage of 28 mV is required to achieve 10 mA cm−2 in two-electrode system. DFT calculations decipher that the doping optimized H* adsorption/desorption and dehydrogenation kinetics could be the underlying mechanism. Importantly, a self-powered H2 production system by integrating a direct hydrazine fuel cell with a hydrazine splitting electrolyzer can achieve a decent rate of 1.25 mmol h−1 at room temperature.

Co3O4 nanowire@ultrathin Ni-Co layered double hydroxide core-shell arrays with vertical transfer channel for high-performance supercapacitor

High electrochemical performance of supercapacitor electrodes largely rely on the heterostructure of different active component materials. Furthermore, the integration of Co3O4 nanowire (internal conductive highway) to bridge the Ni-Co layered double hydroxides nanosheets (provided high specific capacity), which is favorable for fast charge transfer, as well as improved conductivity. Thus, the Co3O4@Ni-Co LDH core-shell nanowire arrays electrodes exhibit a remarkable specific capacitance (1318 F·g−1 at 0.5 A·g−1) and also a relatively low resistance. Due to synergistic interaction of porous NiCo-LDH nanosheets and inner Co3O4 nanowire, an asymmetric supercapacitor (ASC) is assembled with Co3O4@Ni-Co LDH as the anode and active carbon as cathode. The as-fabricated ASC shows high energy density of 46.3 Wh·kg−1 and exhibit superior cyclic stability of 92% retention after 5000 cycles, suggesting this electrode is promising for efficient electrochemical capacitors.

Hierarchical core-shell electrode with NiWO4 nanoparticles wrapped MnCo2O4 nanowire arrays on Ni foam for high-performance asymmetric supercapacitors

Rational construction of MnCo2O4-based core-shell nanomaterials with distinctive and desirable architectures possesses great potential in the advanced electrode material of high-performance supercapacitors. Here, a new class of hierarchical core-shell nanowire arrays (NWAs) with a shell of NiWO4 nanoparticles and a core of MnCo2O4 nanowires is reported, which can significantly improve the electrochemical energy storage properties of supercapacitors. The unique core-shell structure endows the MnCo2O4@NiWO4 NWAs electrode with a high areal specific capacitance of 5.09 F cm−2 at a current density of 1 mA cm−2 and a superior cyclic retention of 96% after 5000 charge-discharge cycles, which are more preferable than those of MnCo2O4 NWAs electrode. More importantly, an aqueous electrochemical energy storage device (core-shell MnCo2O4@NiWO4 NWAs as the positive electrode and active carbon as the negative electrode, MnCo2O4@NiWO4//AC ASC) was assembled and shows a high energy density of 0.23 mWh cm−2 at a power density of 2.66 mW cm−2, and 0.09 mWh cm−2 at 16.00 mW cm−2, indicating hopeful potential for practical applications. This work highlights the significance of NiWO4 as a shell for hierarchical core-shell nanostructures, which can further improve the electron transport characteristic of the electrode material, thereby achieving performance breakthroughs in energy storage devices.

Graphite‐Aligned Ni/Ni(OH)2 Nanowire‐Based Aqueous Asymmetric Supercapacitors Exhibiting Excellent Cycle Stability, High Rate Performance, and Wide Operation Voltage

AbstractWe present a new design for an asymmetric supercapacitor combining a vertically aligned Ni/Ni(OH)2 nanowire array electrode and a graphite‐based electrode. The arrangement of these two electrodes in a sandwiched fashion allows the device to function at a high operating voltage window of 2.0 V in an aqueous electrolyte. A thin layer of Ni(OH)2 can be readily formed on Ni nanowires (NiNWs) to yield a Ni/Ni(OH)2 structure. The redox reaction of Ni(OH)2 formed on the surface of NiNWs was crucial in achieving improved capacitance over this wide voltage window. The modification of the graphite electrode using graphene flakes was found to provide a more stable response at high current densities. The shape of the voltammogram can be retained up to high values and thus the device can operate at very rapid charge/discharge rates at an enhanced voltage window. Furthermore, the capacitance was found to be unchanged after 10000 continuous potential cycles.

Vertical nanowire electrode array for intracellular electrical stimulation to enhance neurogenesis of human neural stem cells

Vertical nanowire electrode array for intracellular electrical stimulation to enhance neurogenesis of human neural stem cells

Electrochemical Cycling-Induced Spiky Cu x O/Cu Nanowire Array for Glucose Sensing.

The glucose level is an important biological indicator for diabetes diagnosis. In contrast with costly and unstable enzymatic glucose sensing, oxide-based glucose sensors own the advantages of low fabrication cost, outstanding catalytic ability, and high chemical stability. Here, we fabricate a self-supporting spiky CuxO/Cu nanowire array structure by electrochemical cycling treatment. The spiky CuxO/Cu nanowire is identified to be a Cu core passivated by a conformal Cu2O layer with extruded CuO petals, which provides abundant active sites for electrocatalytic reaction in glucose detection. An interruptive potential sweeping experiment is presented to elucidate the growth mechanism of the spiky CuxO/Cu nanostructure during the potential cycling treatment. The spiky CuxO/Cu nanowire array electrode exhibits a sensitivity of 1210 ± 124 μA·mM–1·cm–2, a wide linear detection range of 0.01–7 mM, and a short response time (<1 s) for amperometric glucose sensing. The study demonstrates a route to modulate oxide phase, crystal morphology, and electrocatalytic properties of metal/oxide core–shell nanostructures.

Nanowire-array-based gene electro-transfection system driven by human-motion operated triboelectric nanogenerator

Electro-transfection serves as a promising non-viral gene delivery approach, but its performance faces several drawbacks associated with the high-voltage electrical pulses involved, which may adversely affect the cell viability. Here we developed a novel TENG (triboelectric nanogenerator)-driven nanowire electrode array (T-NEA) platform to facilitate the electroporation-based siRNA delivery into both adhesive and non-adhesive mammalian cells. Unlike conventional electroporation technology, the T-NEA system is powered by a TENG working in a vertical contact-separation mode, harvesting energy from simple human tapping motion. Since lower voltage is involved in the T-NEA system as compared to conventional electroporation method, high (>90%) cell viability was achieved for all of the six kinds of cell lines used in the experiments. Highly efficient siRNA electro-transfection was achieved at a tiny amount of energy consumption. The results exhibit that siRNA molecules could be successfully delivered into more than 95% of MiaPaCa-2 cell. Even for K562 cells, which is well-known as difficult-to-transfect cell, the delivery efficiency of siRNA reaches 84%. With the T-NEA system, the K-ras gene expression in MiaPaCa-2 cells was down-regulated by 46 ± 6.29%, and the bcr-abl gene expression was reduced by 31.6 ± 6.67% in K562 cells. When the expressions of the targeted mutation genes were significantly down-regulated, the cell proliferation and anti-apoptosis ability were significantly inhibited. Overall, the T-NEA system is demonstrated as an effective and versatile platform for high-throughput gene delivery in biological research and clinical cancer treatments due to its versatility, efficiency, and uniformity.

Oxygen-vacancy-rich nickel-cobalt layered double hydroxide electrode for high-performance supercapacitors

The introduction of oxygen vacancies into electrode materials has been proven to be a valid way to enhance the electrochemical performance. However, the traditional methods to introduce oxygen vacancies require severe conditions that may be harmful to hydroxides. Herein, the oxygen vacancy-rich nickel-cobalt (NiCo) layered double hydroxide (denoted as Vo-NiCo LDH) nanowire array electrode is synthesized using the chemical reduction method. Owing to the reduction of NaBH4 solution, we can create oxygen vacancies under milder conditions, thus avoiding any damage to the hydroxide. The as-synthesized electrode shows a specific capacitance of 1563.1 F g−1 at 1 A g−1, which is much higher than that of the pristine electrode (995.4 F g−1 at 1 A g−1). Moreover, the cycling performance and rate performance are also enhanced. The as-fabricated asymmetric supercapacitor (Vo-NiCo LDH//Fe2O3) is able to deliver a maximum energy density of 56.2 W h kg−1 at a power density of 800 W kg−1 with a voltage window of 1.6 V.

Template-assisted fabrication of Ni nanowire arrays for high efficient oxygen evolution reaction

Architecture construction of electrode is one key factor for hydrogen generation from electrochemical water splitting. To enhance the efficiency of oxygen evolution reaction (OER) at high current density, the architecture construction must be designed skillfully to prevent the surface blanketed by gas bubbles. In this work, we developed a three-level hierarchical surface with cluster-like nickel (Ni) nanowire array. The contact angle measurement indicates the surface having excellent hydrophilicity. The OER performance characterization reveals that after the surface is loaded with NiFe-based catalyst the Ni nanowire array electrode can deliver 500 mA cm−2 at an overpotential of 297 mV in 1 M KOH solution and can survive for over 24 h under 500 mA cm−2 operation. All the results demonstrate that the cluster-like nanowire array is beneficial for the spatial pathway separation for electrolyte supply and gas bubbles departure and the enhancement of OER efficiency.

Electrodes: Antimicrobial Peptide Functionalized Conductive Nanowire Array Electrode as a Promising Candidate for Bacterial Environment Application (Adv. Funct. Mater. 23/2019)

Electrodes: Antimicrobial Peptide Functionalized Conductive Nanowire Array Electrode as a Promising Candidate for Bacterial Environment Application (Adv. Funct. Mater. 23/2019)

Electrochemical properties of the interaction between cytochrome c and a hematite nanowire array electrode

We investigate the interaction of horse heart cytochrome c (cyt c) with hematite nanowire array electrodes by cyclic voltammetry to study the electron transfer between redox active proteins and mineral surfaces. Using this model system, we quantify electron transfer rates between cyt c and hematite under varying electric potential and pH conditions. The results are consistent with two cyt c conformations adsorbed at the hematite surface: the native and a partially unfolded form. The partially unfolded protein maintained redox activity, but at a lower redox potential than the native protein. Adsorption of cyt c allowed direct electron transfer between cyt c and hematite, with an interfacial electron transfer rate, k°ET, of 0.4 s−1 for the native form and 0.55 s−1 for the partially unfolded protein at pH 7.07. At pH 4.66, protein adsorption decreased compared to neutral pH and the fraction of partially unfolded protein increased. Additionally, the diffusion controlled electron transfer rate between hematite and the electron shuttling compound anthraquinone-2,6-disulfonate (AQDS) was determined to be k°ET = 8.0·10−3 cm·s−1 at pH 7.07. Modulation of electron transfer rates as a result of conformational changes by redox active proteins has broad implications for describing chemical transformations at biological-mineral interfaces.

NiFe/(Ni,Fe)3S2 Core/Shell Nanowire Arrays as Outstanding Catalysts for Electrolytic Water Splitting at High Current Densities

AbstractNiFe/(Ni,Fe)3S2 core/shell nanowire arrays, fabricated with an anodic aluminum oxide membrane templated electrodeposition followed by sulfur ion exchange, are developed as an outstanding catalyst for electrolytic water splitting. Ni nanowire arrays achieve low overpotentials of 112 and 347 mV for the hydrogen evolution reaction at current densities of 10 and 400 mA cm−2, respectively, whereas ultralow overpotentials of 224 and 305 mV for the oxygen evolution reaction at current densities of 10 and 400 mA cm−2, respectively, are achieved by NiFe/(Ni,Fe)3S2 core/shell nanowire arrays. The pairing of the Ni nanowire array electrode as the cathode and the NiFe/(Ni,Fe)3S2 core/shell nanowire array electrode as the anode, delivers current densities of 10 and 400 mA cm−2 at ultralow cell voltages of 1.56 and 1.9 V, respectively, for the overall water splitting. The stability of the electrodes is also excellent, exhibiting only minor chronoamperometric decay after 24 h continuous operation at 400 mA cm−2. The nanowire array‐based electrodes, offering extended reaction surface areas and 1D guided charge transport and mass transfer, prove to be a promising new catalyst architecture design for electrocatalytic processes.

The Study of Electron Transfer at the Interface of Cytochromes and Iron Oxide Minerals

Molecular-scale protein-mineral interactions are central to understanding electron transfer mechanisms and microbial processes in subsurface environments. Although, the electron transfer between c-type cytochrome and hematite has been investigated many factors impacting the electron transfer rate have not been determined. We investigated the interactions of horse heart cytochrome c (cyt c) with hematite nanowire array electrodes by cyclic voltammetry to study the electron transfer between redox active proteins and mineral surfaces. Using this model system, specific interactions of cyt c with hematite as a function of electrical potential and pH were examined. We observed direct electron transfer between cyt c and hematite with an interfacial electron transfer rate of kº ET = 0.6 s-1. show buffer pH has an apparent effect on the conformational and adsorption-induced change on the cyt c. Moreover, in the presence of the electron shuttling compound, anthraquinone-2,6-disulfonate (AQDS), electron transfer rate between cyt c and hematite increased to kº ET = 2 s-1, which is more than three times of the rate determined in absence of AQDS. This study provides into biomolecular factors controlling the complex interactions and electron transfer processes between redox-active proteins and minerals, which has broader implications for describing chemical transformations at biological-mineral interfaces at the molecular scale.

Polypyrrole⁻Nickel Hydroxide Hybrid Nanowires as Future Materials for Energy Storage.

Hybrid materials play an essential role in the development of the energy storage technologies since a multi-constituent system merges the properties of the individual components. Apart from new features and enhanced performance, such an approach quite often allows the drawbacks of single components to be diminished or reduced entirely. The goal of this paper was to prepare and characterize polymer-metal hydroxide (polypyrrole-nickel hydroxide, PPy-Ni(OH)2) nanowire arrays demonstrating good electrochemical performance. Nanowires were fabricated by potential pulse electrodeposition of pyrrole and nickel hydroxide into nanoporous anodic alumina oxide (AAO) template. The structural features of as-obtained PPy-Ni(OH)2 hybrid nanowires were characterized using FE-SEM and TEM analysis. Their chemical composition was confirmed by energy-dispersive x-ray spectroscopy (EDS). The presence of nickel hydroxide in the synthesized PPy-Ni(OH)2 nanowire array was investigated by X-ray photoelectron spectroscopy (XPS). Both FE-SEM and TEM analyses confirmed that the obtained nanowires were composed of a polymer matrix with nanoparticles dispersed within. EDS and XPS techniques confirmed the presence of PPy-Ni(OH)2 in the nanowire array obtained. Optimal working potential range (i.e., available potential window), charge propagation, and cyclic stability of the electrodes were determined with cyclic voltammetry (CV) at various scan rates. Interestingly, the electrochemical stability window for the aqueous electrolyte at PPy-Ni(OH)2 nanowire array electrode was remarkably wider (ca. 2 times) in comparison with the non-modified PPy electrode. The capacitance values, calculated from cyclic voltammetry performed at 20 mV s−1, were 25 F cm−2 for PPy and 75 F cm−2 for PPy-Ni(OH)2 array electrodes. The cyclic stability of the PPy nanowire array electrode up to 100 cycles showed a capacitance fade of about 13%.

Antimicrobial Peptide Functionalized Conductive Nanowire Array Electrode as a Promising Candidate for Bacterial Environment Application

AbstractConductive polymer electrodes are widely used for electrical signal detection owing to their unique mechanical, redox, and impedance characteristics. However, the performance of electrodes is compromised due to the interference of adhered bacteria and most of the scientists have not taken the microbial environment into consideration during electrode design. Here, a facile approach to construct antimicrobial peptide (AMP) functionalized polypyrrole nanowire array conductive electrodes (PNW‐AMP) is reported. Instead of compromising the electrochemical properties as the other antibacterial agents do, the PNW‐AMP electrodes exhibit excellent redox and low interfacial impedance properties. More importantly, the PNW‐AMP can eliminate bacterial adhesion and maintain electrochemical stability simultaneously in the microbial microenvironment for a long time. The antibacterial rate of the PNW‐AMP electrode reaches 95.8% after exposing the electrode to air for one month, while the charge transfer resistance ( Rct) value only increases by 9% at a bacterium (Escherichia. Coli ) concentration of 1 × 104 colony forming unit (CFU) mL−1. This research makes it possible to construct highly stable conductive polymer electrodes for bacterial environment electrical signal detection.