Ni Nanofibers Research Articles

CO2 to Value-Added Chemicals: Synthesis and Performance of Mono- and Bimetallic Nickel–Cobalt Nanofiber Catalysts

In an epoch dominated by escalating concerns over climate change and looming energy crises, the imperative to design highly efficient catalysts that can facilitate the sequestration and transformation of carbon dioxide (CO2) into beneficial chemicals is paramount. This research presents the successful synthesis of nanofiber catalysts, incorporating monometallic nickel (Ni) and cobalt (Co) and their bimetallic blend, NiCo, via a facile electrospinning technique, with precise control over the Ni/Co molar ratios. Application of an array of advanced analytical methods, including SEM, TGA–DSC, FTIR-ATR, XRD, Raman, XRF, and ICP-MS, validated the effective integration and homogeneous distribution of active Ni/Co catalysts within the nanofibers. The catalytic performance of these mono- and bimetallic Ni/Co nanofiber catalysts was systematically examined under ambient pressure conditions for CO2 hydrogenation reactions. The bimetallic NiCo nanofiber catalysts, specifically with a Ni/Co molar ratio of 1:2, and thermally treated at 1050 °C, demonstrated a high CO selectivity (98.5%) and a marked increase in CO2 conversion rate—up to 16.7 times that of monometallic Ni nanofiber catalyst and 10.8 times that of the monometallic Co nanofiber catalyst. This significant enhancement in catalytic performance is attributed to the improved accessibility of active sites, minimized particle size, and the strong Ni–Co–C interactions within these nanofiber structures. These nanofiber catalysts offer a unique model system that illuminates the fundamental aspects of supported catalysis and accentuates its crucial role in addressing pressing environmental challenges.

NiMo solid-solution alloy porous nanofiber as outstanding hydrogen evolution electrocatalyst

Developing a high-efficiency hydrogen evolution reaction (HER) electrocatalyst for the large-scale production of hydrogen is essential but challenging. In this study, we used NiMo solid-solution alloy porous nanofibers to develop a robust HER electrocatalyst through electrospinning, oxidization, and high-temperature reduction treatment. In 1 M KOH electrolyte, the fabricated NiMo solid-solution alloy porous nanofibers exhibited higher HER activity than Ni nanofibers, which required a low overpotential of 69, 208, and 300 mV at 100, 500, and 1000 mA cm−2, respectively, and had outstanding durability at 100 mA cm−2 over 60 h. We developed a promising candidate for a high-efficiency HER electrocatalyst, and our findings provided valuable information for fabricating highly robust alloy-based electrocatalysts.

Flexible and functional SiO2 nanofibers immobilized with nickel nanoparticles for nanocatalysis and protein adsorption

A high coverage of nickel nanoparticles (NPs) anchored on the surface of SiO2 nanofibers (SiO2NF) with one-dimensional (1D) structure was developed for nanocatalysis and protein adsorption by combining an extend Stöber method with a carbonization process. Firstly, a complex of polydopamine and nickel ion (PDA-Ni2+) was easily coated on SiO2NF in an extend Stöber condition. Subsequently, a high loading amount of nickel NPs anchored on SiO2NF via an annealing process in a nitrogen atmosphere. Notably, owing to the polydopamine-Ni2+ precursor, the generated Ni NPs could be well dispersed on SiO2NF without obvious aggregation. Additionally, the size and density of Ni NPs could be finely tuned by adjusting the pyrolysis temperature or the molar ratio between dopamine and nickel ion. Benefiting from the magnetism derived from Ni NPs, the cloth-like morphology and flexibility of SiO2NF, the resultant SiO2 @C-Ni nanofibers can be easily recycled and reused, facilitating practical applications. Thus, the as-prepared SiO2 @C-Ni nanofibers manifested excellent performance both on the reduction of 4-nitrophenol(4-NP) and the adsorption histidine-rich (His-rich) proteins.

Synthesis and electrochemical performance of hollow-structured NiO + Ni nanofibers wrapped by graphene as anodes for Li-ion batteries

Hollow-structured NiO + Ni nanofibers wrapped by graphene were designed and successfully fabricated via a simple method. First, solid NiO + Ni nanofibers were prepared by electrospinning followed by calcination. Here, a portion of the metallic Ni was retained to improve the electrochemical performance of NiO by adjusting the calcination temperature. Next, the nanofibers were thoroughly mixed with different amounts of graphene and calcinated once more to form hollow-structured NiO + Ni nanofibers with an extremely high specific surface via the reaction between graphene and NiO on the nanofiber surface and subsequent migration of NiO into the nanofibers. Results showed that the obtained hollow-structured NiO + Ni electrode demonstrates optimal electrochemical performance when the graphene content is controlled to 3 wt%. The first cycle discharge/charge specific capacity of the electrode peaked (1596/1181 mAh · g−1 ) at 100 mA · g−1, with a coulombic efficiency of approximately 74% (60% for 0 wt% graphene, 65% for 1 wt% graphene, and 51% for 4 wt% graphene). It also presented excellent cycling stability after 100 cycles at 100 mA · g−1 on account of its high retained discharge specific capacity (251 mAh · g−1 for 0 wt% graphene, 385 mAh · g−1 for 1 wt% graphene, 741 mAh · g−1 for 3 wt% graphene, and 367 mAh · g−1 for 4 wt% graphene). Moreover, the synthesized electrode possessed outstanding rate capability owing to its large average discharge specific capacity of approximately 546 mAh · g−1 (45 mAh · g−1 for 0 wt% graphene, 256 mAh · g−1 for 1 wt% graphene, and 174 mAh · g−1 for 4 wt% graphene) from 100 mA · g−1 to 2000 mA · g−1. The observed improvement in electrochemical performance could be attributed to the increase in active sites and decrease in charge transport distance in the hollow-structured NiO + Ni nanofibers. Excessive introduction of graphene caused a sharp loss in electrochemical performance due to the agglomeration of graphene sheets on the nanofiber surfaces.

Fabrication of a Low-Coercivity, Large-Magnetoresistance PVA/Fe/Co/Ni Nanofiber Composite Using an Electrospinning Technique and Its Characterization.

A nanofiber composite is a unique engineered material, which can impart new physical, chemical, and electrical properties. Among existing polymer composites, the metallic nanofiber composite has a significant role in biomedical applications. In this study, a metallic nanofiber composite was fabricated using poly vinyl alcohol [PVA-(C₂H₄O)n] reinforced with ferric nitrate [Fe(NO₃)₃·9H₂O], cobalt nitrate [Co(NO₃)₂·6H₂O], and nickel acetate [C₄H6NiO₄·4H₂O] using a low-cost electrospinning process. The process parameters were optimized for fabricating uniform, bead-free, and substratefree fibers. The morphological features of the composite were evaluated using a scanning electron microscope (SEM). Hysteresis of the heat-treated composite was studied using a vibrating sample magnetometer (VSM). This study showed that the composite behaved as a ferromagnetic (intermediate) material with coercivity in the range 318-671 G for different wt.% of nickel. Pellets (8-mm diameter and 250-μm thickness) of this composite changed the resistance by 18% when dispensed in a magnetic field of 1200 G at an ambient temperature. Based on a thermogravimetric analysis, the thermal stability and magnetoresistance property showed that the fabricated composite was suitable for developing a highly sensitive magnetic sensor, which could be used in bio-sensing applications.

Increasing self-sensing capability of carbon nanotubes cement-based materials by simultaneous addition of Ni nanofibers with low content

This paper aims to increase self-sensing capability of carbon nanotubes cement-based materials by simultaneous addition of Ni nanofibers with low content. The carbon nanotubes cement-based composites with a low content of Ni nanofibers and without Ni nanofibers were fabricated. The microstructures of as-fabricated cement-based composites were observed with transmission electron microscopy (TEM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Besides, the conductivity and pressure sensitivity of as-fabricated cement-based composites were studied by four electrode voltammetry. The results show that the Ni nanofibers and carbon nanotubes were well dispersed in the as-fabricated cement-based composites. The resistivities of as-fabricated cement-based composites show typical percolation phenomenon with the increases of carbon nanotube contents. The addition of Ni nanofibers with a low content induces the increase in the conductivity of cement-based composites, but not change the percolation threshold of carbon nanotubes. Moreover, the addition of Ni nanofibers with a low content increases the sensitivity, linearity and repeatability of cement-based composite with carbon nanotubes.

Nickel Nanofibers Manufactured via Sol-Gel and Electrospinning Processes for Electrically Conductive Adhesive Applications

The electrospun fibers of poly(vinyl pyrrolidone) (PVP)-nickel acetate (Ni(CH3COO)2·4H2O) composite were successfully prepared by using sol-gel processing and electrospinning technique. Nickel oxide (NiO) nanofibers were obtained afterwards by high temperature calcinations of the precursor fibers, PVP/Ni acetate composite nanofibers, at 700 °C for 10 h. Following with the reduction of NiO nanofibers at 400 °C using hydrogen gas (H2) under inert atmosphere, the metallic nickel (Ni) nanofibers were subsequently produced. In addition, as-prepared Ni nanofibers were chemically coated with silver (Ag) nanoparticles to enhance their electrical property and prevent the surface oxidation. The characteristics of as-prepared fibers, such as surface morphology, fiber diameters, purity, the amount of NiO nanofibers, and metal crystallinity, were determined using a scanning electron microscope (SEM), a Fourier transform infrared spectrometer (FT-IR), a thermogravimetric analyzer (TGA), and a wide-angle x-ray diffractometer (WAXD). The volume resistivity of epoxy nanocomposite filled with Ag-coated short Ni nanofibers was lower than the one containing short Ni nanofibers with no coating due to the synergetic effect of Ag nanoparticles created during the coating process. We also demonstrated that the volume resistivity of epoxy nanocomposite filled with Ni nanofibers could be dramatically decreased by using Ni nanofibers in the non-woven mat form due to their small fiber diameter and high fiber aspect ratio, which yield a high specific surface area, and high interconnecting network.

Multifunctional nickel nanofiber for effective air purification: PM removal and NO reduction from automobile exhaust

Particulate matter and NO pollution caused by automobile exhaust cause severe air pollution and respiratory diseases. Traditional gasoline particulate filter and three-way catalysts face the problem of high cost and no resistance to high temperature. Development of multifunctional filtration purification media with low cost and temperature resistance is necessary. In this paper, Ni nanofibers filter is easily fabricated by electrospinning, suitable for working environment with variable temperature. Moreover, between adjacent nanofibers, the preferable fused junction was formed which is beneficial to mechanical properties of the filter. The Ni nanofibers filter exhibits outstanding PM1 and NO gas removal ability. The PM1 filtration efficiency up to 99.86% @300 nm was achieved under wing speed of 5.3 cm/s. Moreover, the Ni nanofibers also achieve impressive NO-to-N2 and NO adsorption ability owing to the high specific surface area and activity of Ni nanofiber itself. As such, the multifunctional Ni nanofibers filter equips the potential for the actual application in automobile exhaust purification converter.

In-situ growth of carbon nanotubes on Ni/NiO nanofibers as efficient hydrogen evolution reaction catalysts in alkaline media

Abstract A novel hierarchical structure of carbon nanotubes grown on Ni/NiO composite nanofiber has been in-situ fabricated by electrospinning and following low-temperature (500 °C) vacuum thermal treatment. During vacuum thermal treatment, decomposition of electrospun nickel acetate/polyvinylpolypyrrolidone precursor nanofibers generate gases as a function of both reducing agents and carbon sources for NiO reduction and carbon nanotubes growth. The thermal treatment processing parameter, i.e. heating rate, controls the morphology and composition of the resulting Ni nanofibers or Ni/NiO‑carbon nanotubes composite nanofibers. This proposed method avoid the usual extra introduction of reducing agents and carbon source. It is a low cost, high yield and safe no-hazard technique. Then, these non-noble metal-based nanofibers are applied as efficient electrocatalysts for the hydrogen evolution reaction in alkaline solution. The Ni/NiO‑carbon nanotubes (10 °C min−1) can drive 10 mA cm−2 at an overpotential of 98 mV in 1 M KOH, which is 52 mV less than for Ni nanofibers. This work offers promising novel catalyst materials in water-splitting devices for large-scale production of hydrogen fuel.

Anchoring carbon nanotubes and post-hydroxylation treatment enhanced Ni nanofiber catalysts towards efficient hydrous hydrazine decomposition for effective hydrogen generation.

For effective hydrogen generation with remarkable durability, carbon nanotubes (CNTs) grown on Ni nanofibers and their post hydroxylation treatment engendered active Ni nanofiber catalysts an efficient decomposition of hydrous hydrazine with a turnover frequency (TOF) of 19.4 h-1 and an activation energy down to 51.05 KJ mol-1.

Facile synthesis of electrospun C@NiO/Ni nanofibers as an electrocatalyst for hydrogen evolution reaction

Hydrogen evolution reaction (HER) is considered to be one of the most important electrochemical reactions from both fundamental and application perspective to produce hydrogen. Polyacrylonitrile (PAN) based carbon (C)@NiO/Ni nanofibers were fabricated via simple electrospinning method. The as-prepared C@NiO/Ni nanofibers were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy Energy Dispersive X-ray Spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectra. The SEM and TEM analyses revealed that NiO/Ni nanoparticles distributed on the PAN based carbon nanofibers. EDS, XPS and XRD results confirm the presence of the nanoparticles. The catalytic activity and durability of C@NiO/Ni nanofibers containing different weight ratio of Ni salt content (2%, 3%, & 4%) were examined for HER in 1 M KOH solution. It has been observed that C@NiO/Ni nanofibers containing Ni content (4%) showed the highest catalytic activity. It indicates that the catalytic activity of electrocatalyst can be enhanced by increasing the effective active sites. Noteworthy to mention here that the nanofibers catalyst reached a current density of 60 mA/cm2. The as-prepared catalyst showed remarkable stability up to 22 h and retained 99% of its initial activity even after 16 h of reaction.

In situ synthesis of Ni nanofibers via vacuum thermal reduction and their efficient catalytic properties for hydrogen generation

Ni nanofibers have been prepared by a vacuum thermal reduction method, and further used as efficient catalysts for hydrogen generation from hydrous hydrazine decomposition reaction.

Ni-core CuO-shell fibers produced by electrospinning and electroplating as efficient photocathode materials for solar water splitting.

Charge recombination in CuO photocathodes inhibits efficient electron flow and limits the photo-electrochemical performance of these cathodes for solar water splitting. To circumvent this shortcoming, we introduce highly conductive Ni/CuO core-shell structured fibers. The photocurrent density (PCD) achieved with these core-shell fibers exceeded that of fibers without a Ni core by a factor of 2.6. The PCD enhancement arises from increased acceptor concentration and electron-hole recombination time, as measured by electrochemical impedance spectroscopy. These core-shell nanofibers were fabricated via electrospinning and electroplating. First, a polyacrylonitrile fiber was electrospun and then seeded with metal via sputtering. Second, electroplating was used to encase and metalize the fiber with Ni and Cu. Finally, the outermost Cu shell was oxidized to CuO, which is an effective photocathode for solar water splitting. The Ni-CuO, core-shell layers were characterized by scanning electron microscopy, elemental mapping, X-ray diffraction, and X-ray photoelectron spectroscopy. The core Ni content and number of core-shell fibers per area were optimized through parametric studies.

NiO and CrO3 double surface-decorate Ni nanofibers for hydrogen evolution reduction

Electrocatalysts are of great importance for water splitting to produce hydrogen. Here, NiO and CrO3 double surface-decorate Ni (Ni@NiO@CrO3) nanofibers were prepared by electrospinning as highly effective and stable electrocatalysts for hydrogen evolution reaction. It shows high electrocatalytic activity (100mAcm−2 at a low overpotential versus RHE at 228mV) and superior stability (after 120h without decay). The excellent electrocatalytic activity of Ni@NiO@CrO3 nanofibers is account for the well distribution of CrO3 nanoparticles and the good conductivity of Ni nanowires. As CrO3 nanoparticles are partly embedded in the nanofibers, they are difficult to peel off from the Ni@NiO nanofibers, enabling a good stability of the hybrid materials.

Graphene/Nickel Nanofiber Hybrids for Catalytic and Microbial Fuel Cell Applications.

The present work deals with the preparation of fcc-nickel (Ni) nanofibers and Graphene/Ni hybrids. The analysis of XRD, FTIR and Raman data confirms the formation of pure Ni, graphite oxide, reduced graphene and their hybrids. SEM micrographs clearly show the decoration of Ni nanofibers on the graphene flakes. The synthesized Ni-based hybrid systems can have applications in areas ranging from: magnetism, catalysis to microbial fuel cells. The vibrating sample magnetometer (VSM) investigations reveal that the hybrid structure shows hysteresis loop similar to that expected from a superparamagnetic system. When the same hybrid structure is used as catalyst for decolourization of 4-nitrophenol, the maximum rate constant of 0.1 min⁻¹ can be obtained. The catalytic activity also shows dependence on the loading concentration of Ni. The enhanced performance can be explained on the basis of synergistic effect between graphene and nickel nanofibers. The developed hybrids have also been applied as catalyst for cathode in microbial fuel cells and the studies showed improved power density compared to conventional microbial fuel cells (MFCs).

Thermoelectric Properties of Ultralong Silver Telluride Hollow Nanofibers

Ultralong AgxTey nanofibers were synthesized for the first time by galvanically displacing electrospun Ni nanofibers. Control over the nanofiber morphology, composition, and crystal structure was obtained by tuning the Ag+ concentrations in the electrolytes. While Te-rich branched p-type AgxTey nanofibers were synthesized at low Ag+ concentrations, Ag-rich nodular AgxTey nanofibers were obtained at high Ag+ concentrations. The Te-rich nanofibers consist of coexisting Te and Ag7Te4 phases, and the Ag-rich fibers consist of coexisting Ag and Ag2Te phases. The energy barrier height at the phase interface is found to be a key factor affecting the thermoelectric power factor of the fibers. A high barrier height increases the Seebeck coefficient, S, but reduces the electrical conductivity, σ, due to the energy filter effect. The Ag7Te4/Te system was not competitive with the Ag2Te/Ag system due to its high barrier height where the increase in S could not overcome the severely diminished electrical conductivity. ...

Formation and Characterization of Ni Nanofiber Catalysts on Nickel Metallic Foam by Electrospinning Process.

We report the fabrication of nickel nanofiber catalysts supported on nickel metallic foam using a modified electrospinning with a grounded rotor and sequential reduction process. The robust deposition of aligned Ni nanofibers with a uniform morphology on the highly porous surfaces of the metallic foam could be achieved by controlling electrospinning parameters such as applied voltage, tip-collector-distance (TCD), concentration of polymer, and humidity. The diameters of the obtained nanofibers decreased with increasing voltage and TCDs. The uniform and thinnest Ni nanofibers on the Ni foam were obtained at a humidity of less than 30%, 15 kV applied voltage, and 17 cm TCD when using a precursor composed of nickel nitrate salt and poly(vinyl) pyrrolidone. The Ni foam catalyst support exhibited the superior thermal conducting property than other supports of MgO-MgAl2O4, Al2O3, and SiC, enabling to a higher heat transfer during catalytic reaction. As a result, the Ni nanofiber catalyst with a high surface area and superior heat transfer performance, which is supported on the metallic foam, were successfully fabricated via a modified electrospinning for potential application of XTL process converting anything to liquids, such as for Gas-to-Liquid (GTL), Coal-to-Liquid (CTL), and Biomass-to-Liquid (BTL).

Porous Ni nanofibers with enhanced catalytic effect on the hydrogen storage performance of MgH2

Porous Ni nanofibers (NFs) were synthesized via a single-nozzle electrospinning technique with subsequent calcination and reduction.

Research Update: Nickel filling in nanofeatures using supercritical fluid and its application to fabricating a novel catalyst structure for continuous growth of nanocarbon fibers

A novel catalyst structure for continuous growth of nanocarbon fibers is proposed. In this structure, catalyst nanofibers are embedded in a membrane that separates the growth ambient into carbon-supplying and carbon-precipitating environments. The catalyst nanofibers pierce through the membrane so that carbon source gas is supplied only to one end of the catalyst fibers and nanocarbon fibers grow continuously at the other end. To realize this structure, self-supporting anodized alumina was used as a membrane, and its nano-through-holes were filled with catalyst Ni in supercritical CO2 fluid. Direct carbon growth from the Ni nanofibers was confirmed using this catalyst structure.

Galvanically Displaced Ultralong PbxSeyNiz Hollow Nanofibers with High Thermopower

A cost-effective process that combines electrospinning and a galvanic displacement reaction was utilized to synthesize ultralong hollow PbxSeyNiz nanofibers with controlled dimensions, morphology, composition, and crystal structure. Ni nanofibers were electrospun with an average diameter of 150 nm and were used as the sacrificial material for the galvanic displacement reaction. The composition and morphology of the PbxSeyNiz nanofibers were controlled during the reaction by tuning the concentration of HSeO2+ in the electrolytes. Hollow PbxSeyNiz nanofibers with smooth surfaces were obtained from the low-concentration HSeO2+ solution (i.e., 0.01 and 0.05 mM), but the hollow nanofibers synthesized from the high-concentration HSeO2+ solution (i.e., 1 mM) have rough outer surfaces with nanocrystal protrusions. The Pb content of the nanofibers’ composition was varied from 3 to 42% by adjusting the HSeO2+ concentration. The thermoelectric properties of the nanofiber mats were characterized, and the highest Seeb...