Alloy Nanofibers Research Articles

Novel B-doped FeNi/C alloy nanofibers electrocatalyst for efficient oxygen evolution reaction from water splitting

Industrial-scale water splitting processes will require economical and efficient electrocatalyst materials. Many oxygen evolution electrocatalysts prepared with non-precious metals have been reported. However, transition metal-based nanomaterials experience unavoidable aggregation and low stability in corrosion environments, which substantially reduces their catalytic performance. Herein, we successfully used a simple electrospinning technique followed by carbonation to synthesize a porous B-doped carbon fiber electrocatalyst with embedded B-doped FeNi alloy nanoparticles. To prepare the optimal catalyst sample, 1.05 g PAN, 5.0 mmol H3BO3, 2.5 mmol Fe(NO3)3, and 2.5 mmol Ni(NO3)2 were used as precursors. The electrospun pristine fibers were annealed for 1 h at 800 °C in argon. Its overpotential for oxygen evolution at a current density of 10 mA cm−2 was only 231 mV, and a 60.99 mV·dec−1 Tafel slope was achieved. At this current density, this catalyst exhibits good performance for over 24 h or for more than 1000 CV cycles. This is due to the doping of non-metallic B atoms into the alloy nanoparticles, as well as the support and protection on them by carbon nanofibers. Insight This research provides a more thorough understanding of the preparation and practical application of low-cost and high-efficiency transitional metal alloy based water splitting catalysts.

Bimetallic Ru1−xVxO2 and trimetallic Ru1−x−yVxCryO2 alloy nanofibers for efficient, stable and pH-independent oxygen evolution reaction catalysis

We present ruthenium-vanadium mixed alloy metal oxide (Ru1−xVxO2) nanofibers as well as chromium (Cr) doped Ru1−x−yVxCryO2 nanofibers using electrospinning and subsequent thermal annealing procedures as cost-effective, highly active and stable electrocatalyst for oxygen evolution reaction (OER). Both Ru1−xVxO2 and Ru1−x−yVxCryO2 nanofibers exhibited tetragonal crystalline structure, confirming that Ru, V, and Cr ions randomly occupied the tetragonal lattice sites due to the similar ionic sizes. Both Ru1−xVxO2 and Ru1−x−yVxCryO2 nanofibers showed excellent OER electrocatalytic activity, characterized by low overpotentials and small Tafel slopes, in both acidic and alkaline conditions. Ru1−xVxO2 (x = 0.52) nanofibers demonstrated an enhanced elemental substitution effect, leading to an enlarged active surface area that contributed to their exceptional OER activity. Ru1−x−yVxCryO2 nanofibers, achieved through optimal doping with Cr4+ ions, not only displayed significantly improved stability but also exhibited high OER activity. Interestingly, both Ru1−xVxO2 and Ru1−x−yVxCryO2 nanofibers consistently catalyzed alkaline OER, even under conditions of reactant depletion. These nanofibers, containing noble Ru with less than half of the total metal content, are proposed as efficient and cost-effective OER catalysts for use in both acidic and alkaline media.

Fe-Cu-Rh ternary alloy nanofibers as an outstanding pH-universal electrocatalyst for hydrogen evolution reaction: The catalytic roles of Fe depending on pH

Fe-Cu-Rh ternary alloy nanofibers having various elemental compositions (x-Fe@Cu-Rh) were synthesized through the thermal hydrogen reduction of Fe-substituted CuRh2O4 nanofibers, which were prepared by electrospinning of a solution containing Cu and Rh precursors at a constant molar ratio (Cu:Rh = 1:2) with varying Fe precursor wt% (x = 6, 12, 24, 48 and 80). A series of x-Fe@Cu-Rh nanofibers were composed of the phases of metallic (fcc) and/or spinel CuRh2O4 where Fe ion substitutes primarily Rh ion in the octahedral site. x-Fe@Cu-Rh ternary alloy nanofibers showed higher pH-universal HER activity than pure Rh and Cu-Rh binary counterparts; and particularly, 12-Fe@Cu-Rh composed of 7.3, 27.2 and 65.5 atomic % of Fe, Cu and Rh, respectively, presented a superb activity (e.g., the most positive onset potential and the smallest Tafel slope) along with reasonable stability, even outperforming commercial Pt. The addition of Fe to Cu-Rh binary system improved alkaline HER activity substantially, proposing the crucial role of Fe-Cu-Rh interfaces for facilitating water molecule adsorption/dissociation. In acidic condition, Fe served as an excellent diluent reducing noble Rh content without deteriorating the acidic HER activity. Surprisingly, 80-Fe@Cu-Rh having only 18.5 atomic % of noble Rh exhibited decent HER activity during 24 h, demonstrating its potential as a stable and economic catalyst particularly for acidic HER.

Ternary PtRuTe alloy nanofibers as an efficient and durable electrocatalyst for hydrogen oxidation reaction in alkaline media

Sluggish kinetics of anodic hydrogen oxidation reaction (HOR) in alkaline media, which arises from the two orders of magnitude lower HOR activity in alkali than that in acid media for platinum group metals, hinders the commercial implementation of anion exchange membrane fuel cells (AEMFCs). Consequently, the development of platinum-based catalysts combined with high efficiency and durability is urgently required. Herein, we report a facile route for the synthesis of ternary PtRuTe alloy nanofibers with Pt atomic ratio of only 11% via a simple galvanic replacement reaction. We optimize the adsorption strength of platinum and ruthenium towards hydrogen and hydroxyl species by regulating the electron donation from tellurium to platinum and ruthenium. Hence, the obtained trimetallic alloy catalyst exhibits an impressive kinetic current density of 30.6 mA cm−2geo at 50 mV and an exchange current density of 0.426 mA cm−2metal, which shows 3.0- and 2.5-fold enhancement compared with the commercial Pt/C in alkaline electrolyte, respectively. Moreover, the catalyst also demonstrates excellent stability with merely 5% activity attenuation after 2000 potential cycles. This work offers new pathways to boost alkaline HOR by rationally designing multicomponent alloys.

Porous Pd-Sn Alloy Nanotube-Based Chemiresistor for Highly Stable and Sensitive H2 Detection.

While H2 is indispensable as a green fuel source, it is highly flammable and explosive. Because it is difficult to detect due to its lack of odor and color, a solution for proper monitoring of H2 leakage is essential to ensure safe handling. To this end, we have successfully fabricated hollow Pd-Sn alloy nanotubes (NTs) with a Brunauer-Emmett-Teller surface area of 223.0 m2/g through electrospinning and a subsequent etching method, which is the first demonstration of synthesizing Pd-based hollow alloy nanofibers with ultrafine grain sizes. We found that the alloying of Pd with Sn could effectively prevent degradation of the sensing performance upon the α-β phase transition during hydrogen detection. Besides, the highly porous structure with smaller nanograins offered more exposed active sites and higher gas accessibility to bulk materials. The resultant Pd-Sn NTs exhibited excellent sensitivity toward H2 (0.00005-3%). Notably, the limit of detection of 0.0001% is an outstanding achievement on H2 sensing among state-of-the-art H2 sensors. Moreover, when exposed to a high concentration of H2 (3%), Pd-Sn NTs showed excellent cycling stability with a standard deviation of 0.07% and a sensitivity of 9.27%. These obtained sensing results indicate that Pd-Sn NTs can be used as a highly sensitive and stable H2 gas sensor at room temperature (25 °C).

Fe-Cu-Rh Ternary Alloy Nanofibers as an Outstanding Ph-Universal Electrocatalyst for Hydrogen Evolution Reaction: The Catalytic Roles of Fe Depending on Ph

Fe-Cu-Rh Ternary Alloy Nanofibers as an Outstanding Ph-Universal Electrocatalyst for Hydrogen Evolution Reaction: The Catalytic Roles of Fe Depending on Ph

Au-Ru alloy nanofibers as a highly stable and active bifunctional electrocatalyst for acidic water splitting

Bimetallic AuRu alloy nanofibers (NFs) with Au:Ru atomic ratios of 7.5:92.5 are constructed and characterized as a bifunctional electrocatalyst for electrochemical overall water splitting (OWS) of both oxygen (OER) and hydrogen evolution reaction (HER). First, composite NFs consisting of RuO2 fibrous mainframes adorned with tiny Au nanoparticles are synthesized by electrospinning and calcination. The following heat treatment of these composite NFs under H2 gas flowing induces the reduction of RuO2 mainframes to metallic Ru within which Au atoms are dispersed to form homogeneous AuRu alloy NFs regardless of their immiscibility. The OWS activities of prepared AuRu alloy NFs are investigated in 0.5 M H2SO4 aqueous solution; and compared to those of RuO2, Ru, Au, and commercial catalysts, M/C (20 wt% metal loading on Vulcan XC-72 with M = Pt, Ru and Ir). In particular, AuRu alloy NFs show outstanding activity for OER: the lowest overpotential at 10 mA cm−2 and the smallest Tafel slope among the tested catalysts. Of great importance, AuRu alloy NFs also present an excellent long-term stability in a sharp contrast to easily deteriorated Ru-based catalysts (e.g., Ru NFs and Ru/C). AuRu alloy NFs also exhibit good HER activity and stability better than most of tested materials. In a two-electrode system, AuRu NFs ∣∣ AuRu NFs is confirmed to have a lower overpotential for OWS than Ir/C ∣∣ Pt/C, a commercial standard. The OWS performance of AuRu alloy NFs is superior to those of Ru-based bifunctional catalysts found in the literature. HER at AuRu alloy is further studied with density functional theory calculation. The current study reveals Ru alloyed with a small amount of Au having a robust nanofibrous morphology improves the electroactivity and stability for both OER and HER in acidic environments. Given that stable bifunctional catalysts for acidic water splitting have been rarely reported, AuRu alloy NFs exhibit an outstanding feasibility as a practical electrocatalyst for overall water splitting with the high activity and stability.

Features of the Titanium Alloy Nanofibers Production for Neurosurgery and Ophthalmology

A method for manufacturing the titanium alloy NT-50 nanofibers (1-20) microns in a composite assembly is proposed. The undamaged nanofibers production conditions are determined. Nanofibers are used to create new products: diagnostic sensors for ophthalmology.

A fascinating pH independent catalyst for hydrogen evolution reaction: Crystalline bimetallic hcp-CoxRh1-x alloy nanofibers driven by thermally induced phase transition from a single phase of CoRh2O4

Two distinct crystalline phases of bimetallic CoxRh1−x alloy nanofibers were synthesized through the thermal H2-reduction of single-phase CoRh2O4 nanofibers that were prepared via calcination preceded by electrospinning. By varying the reduction temperature (T) and retention time (t), it was confirmed that the formation of a fully reduced crystalline metallic alloy required T ≥ 250 °C for t ≥ 2 h. During the reduction process, the single phase of CoRh2O4 was first transformed to an intermediate face centered cubic (fcc) phase where Rh element was principally reduce to Rh(0) and Co element was present as the oxide form. Then, a fully reduced CoxRh1−x alloy was obtained in hexagonal close-packed (hcp) phase. In particular, the hcp structured CoxRh1−x showed a fascinating hydrogen evolution reaction (HER) activity (e.g., the lowest overpotential at 10 mA cm−2 and the smallest Tafel slope) pH independently that was superior to those of commercial Pt and the pure single metal (Co and Rh) nanofibers. CoxRh1−x alloy also showed a robust stability during 10 000-s continuous HER and 1000-repetitive potential sweeps in alkaline (1.0 M NaOH), neutral (1.0 M PBS, pH 7.2) and acidic (0.5 M H2SO4) media. The pH-universal HER activity was ascribed to alloying effect: Co atoms in the alloy interact O atoms in H2O molecules and therefore assist neighboring Rh atoms in adsorbing H atoms readily in alkaline and neutral condition.

Gold-Ruthenium Alloy Nanofibers As a Bifunctional Electrocatalyst for Overall Water Splitting in Acidic Environments

Hydrogen is widely regarded as an environmentally-friendly and practical alternative energy to reduce reliance on fossil fuels. Also, hydrogen has the outstanding advantages of high energy storage density and sustainable reaction products. The most promising technology to produce hydrogen from abundant renewable sources is water electrolysis. Electrochemical water splitting involves two reaction systems, namely, an anodic oxygen evolution reaction (OER) and a cathodic hydrogen evolution reaction (HER). In general, typical HER catalysts with good activity in acidic solutions, such as Pt, exhibit poor activity in OER. Therefore, it is important to study bifunctional catalyst with high activity, efficiency and stability in acidic solutions.In this presentation, we demonstrate the synthesis of AuRu alloy nanofibers as bifunctional electrocatalysts for water splitting. The Au/RuO2 nanocomposites are synthesized via electrospinning and calcination. After the subsequent reduction process, the AuRu alloy nanofibers are formed. The reduction process of Au/RuO2 nanocomposites to AuRu alloy nanofibers are investigated and the physical properties of AuRu alloy nanofibers in comparison to those of pure Au and Ru are analyzed with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The morphologies of the Au/RuO2 nanocomposites and AuRu alloy nanofibers are confirmed with field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The electrocatalytic activity of AuRu alloy nanofibers are studied toward both OER and HER in Ar-saturated 0.5 M H2SO4 aqueous solution with rotating disk electrode (RDE) voltammetry. The Tafel slopes which represent kinetics of the reaction for OER and HER are obtained based on the corresponding RDE curves. In summary, this study presents the AuRu alloy nanofibers as a better bifunctional electrocatalyst for overall water splitting than Au/RuO2, RuO2, Ru, Pt/C, Ir/C, Au/C and Ru/C.This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT& Future Planning (NRF-2017R1A2A2A14001137).

Au-Ir alloy nanofibers synthesized from Au-Ir/IrO2 composites via thermal hydrogen treatment: Application for glucose oxidation

This paper reports the facile formation of the alloy nanofibers of highly immiscible Au and Ir with diverse composition ratios (denoted as TH2_AuxIr1−x, x = 0.05, 0.10 or 0.33, relative molar content of Au precursor) and the application for direct glucose oxidation. First, the composite nanofibers consisting of Ir/IrO2 fibrous main frames decorated with Au nanoparticles (denoted as Pre_AuxIr1−xOy) were synthesized via electrospinning and calcination. Then, these composites were annealed under H2 gas flowing and successfully transformed to Au-Ir alloy nanofibers along with IrO2 reduction to Ir metal in the Ir/IrO2 fibrous frames. Thermal H2-treatments with varying temperatures and duration times confirmed that Au-Ir alloy production required an unusually low temperature ≥ 90 °C at which Au and Ir were completely alloyed within 1 min. This study suggests that the Au-Ir alloying and IrO2 reduction occur simultaneously and promote each other. TH2_Au0.33Ir0.67, with ∼50.4 % Au atomic %, was found to still have segregated Au phase, indicating the limited solubility (molar ratio of Au/Ir < 1). Alloyed TH2_Au0.10Ir0.90 exhibited high electroactivity for glucose oxidation: a surprisingly low onset potential (<< −0.4 V vs SCE) and greatly enhanced oxidation current levels compared with Pre_Au0.10Ir0.90Oy and pure Au nanoparticles. The high activity of TH2_Au0.10Ir0.90 was attributed to the higher surface area of Au and more favorable formation of catalytically active OHads in the Au-Ir alloy. Current study presents that Au-Ir alloys can be formed under moderate condition via thermal H2-treatment and possess a feasibility for nonenzymatic glucose oxidation.

NixRh1−x bimetallic alloy nanofibers as a pH-universal electrocatalyst for the hydrogen evolution reaction: the synthetic strategy and fascinating electroactivity

NixRh1–x bimetallic alloy nanofibers synthesized by H2-reduction of NiRh2O4 exhibited outstanding pH-universal HER electrocatalytic activity with high stability.

Smart reinforced nano/microscale plates for mass detection at ultrasmall levels: A nonlocal continuum-based approach

In the present study, a scale-dependent plate model is developed to examine the vibrational response of ultrasmall mechanical mass detectors applying nano/microscale plates with shape memory alloy (SMA) nanofibers. The nonlocal elasticity is utilized to capture the influence of being at ultrasmall levels on the performance of the ultrasmall mass detector. The present scale-dependent plate model has no limitation regarding the number of nanoparticles. The ultrasmall plate is resting on an elastic medium, which is described via the Pasternak model. The coupled differential motion equations are derived employing Brinson’s model together with the nonlocal elasticity. Galerkin’s scheme, as a solution technique, is then employed to determine the frequency shift of the ultrasmall mass detector. After indicating the validation of the present results, the influences of various system parameters including the recovery stress, scale coefficient, volume fraction and the location of nanoparticles on the frequency shifts are studied. It is found that SMA nanofibers can be utilized to enhance the performance of ultrasmall mass detectors using vibrating nanoplates.

Atomic-scale combination of germanium-zinc nanofibers for structural and electrochemical evolution

Alloys are recently receiving considerable attention in the community of rechargeable batteries as possible alternatives to carbonaceous negative electrodes; however, challenges remain for the practical utilization of these materials. Herein, we report the synthesis of germanium-zinc alloy nanofibers through electrospinning and a subsequent calcination step. Evidenced by in situ transmission electron microscopy and electrochemical impedance spectroscopy characterizations, this one-dimensional design possesses unique structures. Both germanium and zinc atoms are homogenously distributed allowing for outstanding electronic conductivity and high available capacity for lithium storage. The as-prepared materials present high rate capability (capacity of ~ 50% at 20 C compared to that at 0.2 C-rate) and cycle retention (73% at 3.0 C-rate) with a retaining capacity of 546 mAh g−1 even after 1000 cycles. When assembled in a full cell, high energy density can be maintained during 400 cycles, which indicates that the current material has the potential to be used in a large-scale energy storage system.

Influences of non-uniform initial stresses on vibration of small-scale sheets reinforced by shape memory alloy nanofibers

In the present paper, an attempt is made to investigate the influences of biaxial preload on the vibrational behavior of small-scale composite sheets reinforced by shape memory alloy nanofibers. Three small-scale reinforced sheets are employed to form the system. In order to cover more practical cases, the biaxial preload and the compression ratio are assumed to be non-uniform. In addition, the three-layered composite sheet is embedded in a matrix with elastic properties. The Brinson model, nonlocal elasticity and Pasternak foundation model are used to take into account shape memory alloy effects, the influences of being size-dependent and the effects of the elastic matrix on the vibrational behavior, respectively. Performing a work/energy balance via Hamilton's principle yields the differential equations of motions. Finally, the natural frequencies are calculated via Galerkin's procedure. It is found that the natural frequencies of reinforced sheets under a preload of quadratic variation are higher than those of uniform and linear variations.

The Synthesis of Ni–Cu Alloy Nanofibers via Vacuum Thermal Co-reduction Toward Hydrogen Generation from Hydrazine Decomposition

A safe and reductant-free method based on co-reduction of nickel and copper oxides via vacuum thermal treatment has been developed for the synthesis of Ni–Cu alloy nanofibers, which includes electrospinning of a nickel acetate/copper acetate/polyvinylpolypyrrolidone (NiAc/CuAc/PVP) precursor solution, followed by vacuum thermal reduction. On account of the synergistic effect between Cu and Ni, the Ni–Cu alloy nanofibers catalyst with an optimal composition exhibits good catalytic performance for the decomposition of hydrous hydrazine in NaOH solution. Ni–Cu alloy nanofibers have been prepared by a vacuum thermal co-reduction method, and further used as catalysts for hydrous hydrazine decomposition.

Synthesis, microstructure and magnetic properties of Fe2CoAl nanofibers

In this work, Fe2CoAl Heusler alloy nanofibers were first synthesized via an electrospinning method. It was found that the crystal structure, fiber diameter and magnetic properties of the samples varied with the metal salt concentration in the precursor solution. Magnetic measurement reveals that the obtained Fe2CoAl nanofibers exhibit ferromagnetic with a high Curie temperature and large coercivity. The saturation magnetic moment of the Fe2CoAl nanofibers at 5[Formula: see text]K is estimated to be 4.5–5.1[Formula: see text][Formula: see text]. The Fe2CoAl nanofibers synthesized using the low-cost electrospinning method in our work are magnetically superior and economically feasible for technological applications.

Glassy Metal Alloy Nanofiber Anodes Employing Graphene Wrapping Layer: Toward Ultralong-Cycle-Life Lithium-Ion Batteries.

Amorphous silicon (a-Si) has been intensively explored as one of the most attractive candidates for high-capacity and long-cycle-life anode in Li-ion batteries (LIBs) primarily because of its reduced volume expansion characteristic (∼280%) compared to crystalline Si anodes (∼400%) after full Li(+) insertion. Here, we report one-dimensional (1-D) electrospun Si-based metallic glass alloy nanofibers (NFs) with an optimized composition of Si60Sn12Ce18Fe5Al3Ti2. On the basis of careful compositional tailoring of Si alloy NFs, we found that Ce plays the most important role as a glass former in the formation of the metallic glass alloy. Moreover, Si-based metallic glass alloy NFs were wrapped by reduced graphene oxide sheets (specifically Si60Sn12Ce18Fe5Al3Ti2 NFs@rGO), which can prevent the direct exposure of a-Si alloy NFs to the liquid electrolyte and stabilize the solid-electrolyte interphase (SEI) layers on the surfaces of rGO sheets while facilitating electron transport. The metallic glass nanofibers exhibited superior electrochemical cell performance as an anode: (i) Si60Sn12Ce18Fe5Al3Ti2 NFs show a high specific capacity of 1017 mAh g(-1) up to 400 cycles at 0.05C with negligible capacity loss as well as superior cycling performance (nearly 99.9% capacity retention even after 2000 cycles at 0.5C); (ii) Si60Sn12Ce18Fe5Al3Ti2 NFs@rGO reveals outstanding rate behavior (569.77 mAh g(-1) after 2000 cycles at 0.5C and a reversible capacity of around 370 mAh g(-1) at 4C). We demonstrate the potential suitability of multicomponent a-Si alloy NFs as a long-cycling anode material.

Low temperature growth of graphene on Cu-Ni alloy nanofibers for stable, flexible electrodes.

Here, we report a facile approach to grow graphene on Cu-Ni alloy NFs at a temperature as low as 450-500 °C, in which solid polystyrene (PS) carbon source and two-temperature-zone furnace were used to prepare graphene. The graphene coated Cu-Ni (designated as G-coated Cu-Ni) NFs were fully characterized by Raman spectra, XPS, FESEM and TEM. The G-coated Cu-Ni NFs exhibited excellent anti-oxidation, anti-corrosion and flexibility properties. The anti-corrosion of G-coated Cu-Ni NFs was examined through cyclic voltammetry measurements by using sea water as the electrolyte solution. Finally, using crossed arrays of G-coated Cu-Ni NF composite electrode thin films (sheet resistance is ∼10 Ω sq(-1)) as the flexible electrode, an alternating current (AC) electroluminescent (EL) device with a configuration of G-coated Cu-Ni/active layer (ZnS : Cu phosphor)/dielectric layer (BaTiO3)/front electrode (CNT) has been fabricated. Under an AC voltage of 200 V and frequency of 1300 Hz, the ACEL device emitted blue light at 496 nm with a brightness of 103 cd m(-2).

Low temperature preparation and characterization of (Ga1−xZnx)(N1−yOy) alloy nanostructures using electrospun nanofibers as source materials

By nitriding electrospun ZnO/ZnGa2O4 composite nanofibers with ammonia gas under different temperatures, (Ga1−xZnx)(N1−yOy) alloy nanostructures (GZNO A-NSs) were obtained. With increasing the nitriding temperature (TN) from 650°C to 850°C, the morphologies of the products transformed from nanofibers to short fibers and then nanoparticles, while the compositions of gallium and nitrogen (zinc and oxygen) in the products were increased (decreased). Both X-ray diffraction and Raman spectra confirmed the formation and evolvements of the GZNO A-NSs. The formation temperature of alloys was remarkably decreased due to the nanosize effect. At low TN of 650°C, zinc loss was very small and Ga0.5Zn0.5N0.3O0.7 alloy nanofibers were obtained. It indicated that nitriding electrospun nanofibers at low temperature is a new method to prepare zinc rich GZNO A-NSs. Interestingly, the Raman spectra exhibited one mode and two modes behaviors under the excitation of 488 and 325nm lasers, respectively. Our results also indicated that Raman spectra excited by 325nm laser can also be applied to evaluate the compositions of (Ga1−xZnx)(N1−yOy) alloys.