Ultrathin Nanowires Research Articles

1D PtCo nanowires as catalysts for PEMFCs with low Pt loading

The high cost of platinum (Pt)-group metal (PGM)-based catalysts used in proton-exchange membrane fuel cells (PEMFCs) poses a critical roadblock to their widespread adoption. Although using low PGM loading PEMFCs can largely address this challenge, high current density performance will be severely compromised consequently. To overcome this dilemma, we report the development of ultra-thin platinum-cobalt nanowires (PtCoNWs) as the cathode catalysts for ultralow Pt loading and high-performance membrane electrode assembly (MEA). The PtCoNWs delivered a record-high mass activity (MA) of 1.06 ± 0.14 AmgPt−1 of Pt-alloy catalysts towards oxygen reduction reaction (ORR) in MEA, yielding an impressive total Pt utilization of 5.14 WratedmgPt−1. The PtCoNWs retained a respectable end-of-life MA of 0.45 A mgPt−1 after the 30,000 cycles square-wave accelerated stability test, which is still above the Department of Energy 2020 beginning-of-life target for catalysts. In-situ X-ray absorption spectroscopy studies suggest that the high degree of alloying in the PtCoNWs stabilizes the ultrathin structure and may contribute to the high ORR activity and power density performance in PEMFC.

Free-standing 3D Co3O4@NF micro-flowers composed of porous ultra-long nanowires as an advanced cathode material for supercapacitor

The development of smart structured cathode materials for supercapacitors (SCs) has sparked tremendous interest. However, the appropriate design to achieve high capacitance and energy density-based cathode materials remains a major problem for energy storage systems. This article describes the effective synthesis of self-supported 3D micro-flowers composed of ultrathin nanowires array of Co3O4 on Ni foam (NF) using hydrothermal conditions (Co3O4@NF). The mesoporous Co3O4@NF with a high surface area, providing a rich active state for the Faraday redox reaction and increasing the diffusion rate of the electrolyte ions. The optimized Co3O4@NF-16h electrode exhibited supreme electrochemical performance by delivering a high specific capacitance of 1878, (1127) and 1200 (720 C g−1) F g−1 at 1.0 and 20 A g−1, respectively. The Co3O4@NF electrode retained good capacitance stability of 91% over 10000 cycles at 20 A g−1 with excellent rate-performance of 67% at 20 folded high current values. The obtained results for the Co3O4@NF electrode are presented the enhanced pseudocapacitive performance, indicating the substantial potential for high-performance supercapacitor applications.

Ultrathin PtMo-CeOx hybrid nanowire assemblies as high-performance multifunctional catalysts for methanol oxidation, oxygen reduction and hydrogen oxidation

Although Pt-based alloy catalysts have been considered promising candidates for fuel cell applications, constructing highly efficient, multifunctional Pt-based catalysts that simultaneously boost the three key reactions (MOR, ORR and HOR) in proton exchange membrane fuel cells (PEMFCs) remains a huge challenge. Herein, PtMo-CeOx hybrids with interesting ultrathin and ultralong nanowire assemblies (NAs) structure are synthesized by a one-pot solvothermal method without templates. The PtMo-CeOx-NAs catalyst exhibits 5.2-fold, 6.9-fold and 2.4-fold higher mass activity than commercial Pt/C towards the MOR, ORR and HOR simultaneously and shows excellent durability and CO poisoning tolerance. Detailed experiments reveal that the enhancement should be due to strain and ligand effects. Most impressively, when PtMo-CeOx-NAs membrane electrode assemblies (MEAs) fabricated by a catalyst-coated method are used both as the anode and cathode in PEMFCs, the performance of fuel cells is dramatically boosted compared to those with Pt/C.

Surface-Stabilization of Ultrathin Gold Nanowires for Capacitive Sensors in Flexible Electronics

Surface-Stabilization of Ultrathin Gold Nanowires for Capacitive Sensors in Flexible Electronics

Sub-Monolayer YOx /MoOx on Ultrathin Pt Nanowires Boosts Alcohol Oxidation Electrocatalysis.

A crucial issue restricting the application of direct alcohol fuel cells (DAFCs) is the low activity of Pt-based electrocatalysts for alcohol oxidation reaction caused by the reaction intermediate (CO*) poisoning. Herein, a new strategy is demonstrated for making a class of sub-monolayer YOx /MoOx -surface co-decorated ultrathin platinum nanowires (YOx /MoOx -Pt NWs) to effectively eliminate the CO poisoning for enhancing methanol oxidation electrocatalysis. By adjusting the amounts of YOx and MoOx decorated on the surface of ultrathin Pt NWs, the optimized 22% YOx /MoOx -Pt NWs achieve a high specific activity of 3.35mA cm-2 and a mass activity of 2.10 A mgPt -1 , as well as the enhanced stability. In situ Fourier transform infrared (FTIR) spectroscopy and CO stripping studies confirm the contribution of YOx and MoOx to anti-CO poisoning ability of the NWs. Density functional theory (DFT) calculations further reveal that the surface Y and Mo atoms with oxidation states allow COOH* to bind the surface through both the carbon and oxygen atoms, which can lower the free energy barriers for the oxidation of CO* into COOH*. The optimal NWs also show the superior activities toward the electro-oxidation of ethanol, ethylene glycol, and glycerol.

Quantification of Structural Heterogeneities and Morphologies in Ultrathin Au-based Nanowire Systems using 4D STEM and Electron Tomography

Quantification of Structural Heterogeneities and Morphologies in Ultrathin Au-based Nanowire Systems using 4D STEM and Electron Tomography

Intrinsic Helical Twist and Chirality in Ultrathin Tellurium Nanowires

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Ultrathin Ti3C2 nanowires derived from multi-layered bulks for high-performance hydrogen evolution reaction

One-dimensional ultrathin nanowires (NWs) offer a great deal of promising properties for electrochemical energy storage and conversion due to their nanoscale confinement effect and high surface-to-volume ratios. It is highly desirable to precisely design and synthesize ultrathin Ti3C2 NWs in the aspect of size, crystalline structure and composition. Here, we report a simple alkalization strategy to design the ultrathin Ti3C2 NWs for hydrogen evolution reaction (HER) by modulating the surface-active sites. The design principle can well improve the amount of the defect sites and ion accessibility to increase the interactions between Ti3C2 NWs and H*. The optimized Ti3C2 NWs achieve an overpotential of 476 mV at the current density of 10 mA/cm2 and a Tafel slope of 129 mV/dec for HER catalysis, which are superior to that of Ti3C2 nanosheets and m-Ti3C2. It paves an avenue for the rational transformation of MXene bulks to one-dimensional NWs catalysts for HER.

Ultrathin Silicon Nanowires for Optical and Electrical Nitrogen Dioxide Detection.

The ever-stronger attention paid to enhancing safety in the workplace has led to novel sensor development and improvement. Despite the technological progress, nanostructured sensors are not being commercially transferred due to expensive and non-microelectronic compatible materials and processing approaches. In this paper, the realization of a cost-effective sensor based on ultrathin silicon nanowires (Si NWs) for the detection of nitrogen dioxide (NO2) is reported. A modification of the metal-assisted chemical etching method allows light-emitting silicon nanowires to be obtained through a fast, low-cost, and industrially compatible approach. NO2 is a well-known dangerous gas that, even with a small concentration of 3 ppm, represents a serious hazard for human health. We exploit the particular optical and electrical properties of these Si NWs to reveal low NO2 concentrations through their photoluminescence (PL) and resistance variations reaching 2 ppm of NO2. Indeed, these Si NWs offer a fast response and reversibility with both electrical and optical transductions. Despite the macro contacts affecting the electrical transduction, the sensing performances are of high interest for further developments. These promising performances coupled with the scalable Si NW synthesis could unfold opportunities for smaller sized and better performing sensors reaching the market for environmental monitoring.

Pseudo-Periodically Coupling NiO Lattice with CeO Lattice in Ultrathin Heteronanowire Arrays for Efficient Water Oxidation.

Transition metal oxides (TMOs) have been under the spotlight as promising precatalysts for electrochemical oxygen evolution reaction (OER) in alkaline media. However, the slow and incomplete self-reconstruction from TMOs to (oxy)hydroxides as well as the formed (oxy)hydroxides with unmodified electronic structure gives rise to the inferior OER performance to the noble metal oxide ones. Herein, a unique dual metal oxides lattice coupling strategy is proposed to fabricate carbon cloth-supported ultrathin nanowires arrays, which are composed of pseudo-periodically welded NiO with CeO2 nanocrystals (NiO/CeO2 NW@CC). When served as an OER precatalyst in 1.0 m KOH, the NiO/CeO2 NW@CC shows an ultralow overpotential of 330mV at 50mA cm-2 , along with an impressive cycle durability of more than 3 days even at 50mA cm-2 , surpassing CC-supported NiO and commercial IrO2 catalysts. The combined experimental and theoretical investigations unveil that the atomic coupling of CeO2 can not only appreciably trigger the generation of oxygen vacancies and expedite phase transformation of NiO into active NiOOH, but also in situ create a chemical bond with the formed NiOOH and enable the electron injection, thus effectively inhibiting the aggregation of the accessible NiOOH nanodomains and optimizing their reaction free energy towards oxygen-containing intermediates.

Ubiquitous organic molecule-based free-standing nanowires with ultra-high aspect ratios

The critical dimension of semiconductor devices is approaching the single-nm regime, and a variety of practical devices of this scale are targeted for production. Planar structures of nano-devices are still the center of fabrication techniques, which limit further integration of devices into a chip. Extension into 3D space is a promising strategy for future; however, the surface interaction in 3D nanospace make it hard to integrate nanostructures with ultrahigh aspect ratios. Here we report a unique technique using high-energy charged particles to produce free-standing 1D organic nanostructures with high aspect ratios over 100 and controlled number density. Along the straight trajectory of particles penetrating the films of various sublimable organic molecules, 1D nanowires were formed with approximately 10~15 nm thickness and controlled length. An all-dry process was developed to isolate the nanowires, and planar or coaxial heterojunction structures were built into the nanowires. Electrical and structural functions of the developed standing nanowire arrays were investigated, demonstrating the potential of the present ultrathin organic nanowire systems.

Sensitive H2 gas sensors based on SnO2 nanowires

Sensitive H2 gas sensors are highly desirable for the prediction and early-warning of H2 leakage. Low-dimensional nanostructures of metal oxide semiconductor emerge as promising materials candidates, but it remains a challenge to preserve the nanostructures in the real sensors. In this work, we demonstrated highly sensitive H2 gas sensors based on porous network of SnO2 nanowires that exhibited ultrasmall diameter ∼ 2 nm. Colloidal SnO2 nanowires synthesized via a solvothermal process were drop-coated onto the commercial alumina substrates, followed by in-situ annealing treatment at 350 °C to remove the surface ligands. The sensors exhibited sensitive response with linear dependence on the H2 gas concentration ranging from 2 ppm to 100 ppm when operated at 250°C. Typically, the sensor had a response of 13 toward 40 ppm of H2, with the response and recovery time being 15 s and 31 s, respectively. To further improve the sensor performance, Palladium doped SnO2 nanowires were thoroughly investigated. It’s shown that, the operating temperature of the sensor decreased from 250 °C to 150 °C after Pd doping, and the response and recovery time decreased to 6 s/3 s. The superb sensitivity was attributed to the enhanced gas reception, electron transport as well as utility factor owing to the network nanostructure of ultrathin SnO2 nanowires and catalytic activity of Pd, according to theoretical calculation and adsorption kinetics studies. Combined with the excellent solution processability, the colloidal SnO2 nanowires are potentially attractive for next-generation gas sensors with lower power consumption and integration with silicon-based substrates.

Enhanced photocatalytic activity of ultrathin InOOH nanowires

Uniform ultrathin InOOH nanowires are selected to demonstrate the unique properties and special characters of one-dimensional semiconductor nanomaterials. Their photocatalytic properties are evaluated with the results indicating that InOOH nanowires exhibit higher activity than P25-TiO2 in the photocatalytic degradation of rhodamine B (RhB) under ultraviolet light irradiation. Furthermore, the photocatalysis kinetics are also discussed at varying catalyst contents. The results demonstrate that the second-order kinetic model shows a better fit to the experimental data at the higher InOOH contents of 0.4 and 0.8 g/L.

Surfactant assisted electrochemical growth of ultra-thin CuSCN nanowires for inverted perovskite solar cell applications

In this report, a simple surfactant-assisted electrodeposition method is developed to obtain ultra-thin CuSCN nanowires with controlled thickness and diameter. The morphology and thickness of the CuSCN nanowires are controlled by changing the electrochemical potential and deposition time. The phase pure β-CuSCN is confirmed from XRD and Raman analysis. The packing fraction and diameter of the CuSCN nanowires are confirmed using FESEM micrographs. The formation of tetragonal shaped ultra-thin CuSCN nanowire is observed at 3 min deposition time for all the applied potentials. The chemical composition and oxidation state of the grown CuSCN nanowires are confirmed from XPS spectra. The maximum short circuit current of 21.09 mA/cm2 and power conversion efficiency of 16.99% is achieved for the thickness of 186 nm and packing fraction of 3067 nanowires/μm2. The low hysteresis and high charge transfer nature of the CuSCN nanowire boost the device efficiency more than 60% comparing with CuSCN nanowire grown at short deposition time and low applied potential. The large-area (0.75 cm2) device showed excellent stability up to 1400 h with CuSCN nanowires and carbon back contact. It is observed that the packing fraction and thickness of the CuSCN nanowire significantly influences the photovoltaic performance of the device. The present investigation provides a pathway for the application of CuSCN nanowire and carbon back contacts for efficient large-area solar cell fabrication.

Correction to Temperature Controlled Fragmentation and Ripening: Synthesis of ZnSe Nanorods with Variable Dimensions and Crystal Structure Starting from Ultrathin ZnSe Nanowires

Correction to Temperature Controlled Fragmentation and Ripening: Synthesis of ZnSe Nanorods with Variable Dimensions and Crystal Structure Starting from Ultrathin ZnSe Nanowires

Bimetal Au-Pd decorated hierarchical WO3 nanowire bundles for gas sensing application

This study has developed a simple but effective synthesis method to deposit bimetal Au-Pd nanoparticles onto WO3 hierarchical bundle nanowires through an in-situ redox reaction in a reducing aqueous medium. Hydrothermal method was used for the synthesis of WO3 hierarchical bundles ultrathin nanowire subunits, and the mechanisms controlling the segregation behavior and growth based on Na2SO4, citric acid, and ethylene glycol are discussed. It was found that the Pd-WO3 and/or Au-Pd-WO3 nanocomposites decorated with Au 2.4 wt% and Pd 0.48 wt% showed exemplary sensitivity (S) for 50 ppm n-butanol as S = 91 at 200 °C, approximately 14 and 1.4 times better than pristine WO3 (S = 5.7) and Pd-WO3 (S = 59), respectively. Moreover, the Pd-WO3 sensing results demonstrated that the Pd decoration could significantly reduce the operating temperature, similarly to the Au-Pd-WO3 sensor, which is particularly effective for n-butanol gas among common volatile organic compounds (VOCs). The analysis demonstrates that the bimetal Au-Pd decoration have resulted a synergistic effect in boosting the sensitivity of the WO3-based sensor toward n-butanol gas. The underlying sensing mechanism of such an Au-Pd-WO3 hybrid nanostructure is further discussed, based on chemical and electronic sensitizations in promoting the spillover of oxygen species and rectifying Schottky barriers at the interface of noble metal(s) and semiconductor oxide (e.g., WO3). This work may be beneficial for designing a unique Au-Pd-WO3 sensor with great potential to develop oxide-based sensors for detecting other hazardous gases at low temperature.

Recent Advances in Pt‐Based Ultrathin Nanowires: Synthesis and Electrocatalytic Applications†

AbstractElectrochemical energy conversion devices, with typical examples of fuel cells, are the centers in building a sustainable energy system that avoids environmental pollution and lowers the dependence on fossil fuels. Platinum (Pt)‐based catalysts are among the most potential candidates to drive these reactions due to their superior catalytic performance. Among the various Pt‐based catalysts, Pt‐based ultrathin nanowires exhibit remarkable catalytic performance due to the unique structural merits (i.e., high Pt atom utilization and strong interaction with supports). In this review, we attempt to summarize the recent advances in the synthesis of Pt‐based ultrathin nanowires, as well as their applications in various kinds of electrocatalytic reactions. We conclude this review with an emphasis on the current challenges in terms of synthesis and applications of Pt‐based ultrathin nanowires. Perspectives on further development are also proposed, which is expected to guide the related research in the future.

A Stretchable Gold Nanowire Sensor and Its Characterization Using Machine Learning for Motion Tracking

Motion analysis techniques are well-known for quantitative and objective human skills evaluation in various applications, including sport and medical skills training and development procedures. Such analysis invariably requires reliable data acquisition and analytical tools that can effectively monitor the human body movements. This paper introduces a novel soft and stretchable strain sensor for joint angle measurement applications. The strain sensor is made of ultrathin gold nanowires, which is highly stretchable, and sensitive. However, the electrical response of the sensor involves nonlinearity and hysteresis. To tackle this problem, we propose to use a machine learning algorithm to characterise the sensor for enhancing the predictability of the sensing response. A sensor embedded hinge system is developed for automated measurement of bending angle to validate the characteristics of the developed sensing system. The sensor has a high gauge factor of about 12 and shows high durability during a repeated stress-and-release test. It could measure the bending motion with an error of less than 2°. The developed sensor, combined with the proposed machine learning algorithm, can accurately monitor the bending motion. We believe that our sensing technology has great potential to be used for the evaluation and improvement of human skills proficiency.

PdAu alloy nano wires for the elevated alcohol electro-oxidation reaction

In the search of a satisfactory electrocatalyst for fuel cells, herein, we are reporting Au rich PdAu nano wires with excellent electro-catalytic activity towards methanol and ethanol oxidation. Ultrathin one-dimensional PdAu nanowires were prepared rapidly through a simple one step process. Among the prepared catalysts, the 10% Pd incorporated PdAu nano wire catalyst imparted greater catalytic activity, which exhibited ten times enhancement higher activity towards methanol as well as six times higher activity towards ethanol than that of the pure Pd catalyst. Eventually, the amount of Pd metal reduced to 90% without compromising its catalytic efficiency. Distinctive properties of one-dimensional Au were attributed to the improved catalytic activity.

Hybrid Bioelastomer Reinforced by Ultrathin Nanowires of Lanthanide Hydroxycarbonates for Promising Biomedical Applications

Hybrids composed of biocompatible polymers reinforced with inorganic nanomaterials are useful for many biomedical applications including implantation and tissue regeneration and engineering. In thi...