Morphology Of Nanoarrays Research Articles

In-situ synthesis of MEMS compatible Al/Cu2HIO6/PVDF Metastable composites film with high combustion performance

To address the challenges related to significant pressure loss and weakened combustion performance of energetic materials when ignited on Micro-Electro-Mechanical Systems (MEMS), periodate-based MICs (Metastable Intermolecular Composites) have emerged as promising candidates due to their high energy density and combustion pressure. However, the integration of periodate-based MICs onto MEMS has not been effectively achieved thus far. Herein, we propose a simple, environmentally friendly, and cost-effective approach to fabricate a MEMS-compatible Al/Cu2HIO6/PVDF (polyvinylidene difluoride) energetic composite film. Our method involves utilizing a Cu(OH)2 array as a template and employing an in-situ and spin-coating process. The resulting Al/Cu2HIO6/PVDF film was characterized using various techniques including SEM, TEM, XRD, and XPS. These analyses reveal a tightly packed nano array morphology with a porous structure. DSC-TG analysis was conducted to investigate the thermal reaction of the Al/Cu2HIO6/PVDF composite film. The results demonstrate that the thermal reaction involved a complex multi-step process, with higher heat release (1121 J g-1), a faster reaction rate, and a lower initial reaction temperature (294.5 °C) compared to the Al/CuO/PVDF composite film. the reaction process of Al/Cu2HIO6/PVDF film was also been proposed by analyzing the products at different temperatures. combustion diagnostic tests were carried out to evaluate the combustion performance of the Al/Cu2HIO6/PVDF composite film. The results indicate that as CuO transformed into Cu2HIO6, the film exhibits a reduced ignition delay (8 ms) and combustion duration (50 ms), higher combustion temperature (3710 K), and stronger flame intensity (8630 a.u.).

Electrochemically inducing V2O5·nH2O nanoarrays vertically growth on VSx microrods for highly stable zinc ion battery cathode

The lack of suitable cathode materials greatly limits the potential applications of rechargeable aqueous zinc ion batteries (ZIBs), despite their great promise in terms of high safety, high energy density, and low cost. One promising cathode material is VOOH, which possesses high specific capacity and fast Zn2+ transport channels after a phase transition to V2O5·nH2O during electrochemical cycling. However, its susceptibility to structural disintegration and aggregation during charging and discharging leads to severe capacity decay. To address this issue, we construct a composite consisting of VOOH particles and VSx microrods by a one-step hydrothermal method using a vanadium-based metal-organic framework (MIL-88B(V)) as a sacrificial template. The VOOH particles undergo electrochemical activation and transform into V2O5·nH2O nanoarrays that vertically grow on the VSx microrods. This unique nano-composite effectively maintains the morphology of nanoarrays in electrochemical cycling, resulting in a significant enhancement of rate performance and long-term cycling stability. Moreover, the VSx itself provides considerable capacity and its high conductivity improves the rate performance of the composite. Consequently, the VOOH/VSx nanocomposite exhibits a superior capacity of 364 mA h g−1 at 0.2 A g−1 after activation. Notably, it maintains remarkable capacity retention of 99.6% after 700 cycles, even at a high current density of 10 A g−1. Based on these findings, we believe that the VOOH/VSx composite holds great promise as a cathode material for aqueous ZIBs.

Oxygen vacancy-rich nickel-iron hydroxides-derived phosphide with superaerophobic nanoarray morphology for robust overall water splitting

Multiscale engineering of efficient catalysts to optimize the adsorption energy of intermediates (atomic level) and achieve rapid mass transfer (three-dimensional (3D) bulk level) is crucial for boosting overall water splitting. In this work, we first create oxygen vacancies in nickel–iron hydroxide and then transform the hydroxide into NiFe-Vo-P having a nanoarray morphology via phosphorization. During the oxygen evolution reaction, Ni(Fe)OOH and phosphate anions can be in situ formed on the NiFe-Vo-P surface and optimize the adsorption strength of the intermediates. Consequently, NiFe-Vo-P could achieve a high current density of 1.5 A cm−2 at an overpotential of 289 mV. Moreover, the superhydrophilic/superaerophobic nanoarray morphology of NiFe phosphide effectively facilitates the mass transfer, and NiFe-Vo-P achieves current densities of 580 mA cm−2 and 1.0 A cm−2 at a cell voltage of ∼2.0 V at 25 and 70°C, respectively, over twice those of its counterpart without the superaerophobic morphology.

Novel Superaerophobic Anode with Fern‐Shaped Pd Nanoarray for High‐Performance Direct Formic Acid Fuel Cell

AbstractDirect formic acid fuel cells (DFAFCs) possess the advantages of high power density and theoretical cell potential. Exploring robust catalysts for electrochemical formic acid electro‐oxidation (FAO) is greatly essential for the wide spread uptake of DFAFCs. However, many electrodes with attractive catalysts suffer limited mass transport due to sluggish CO2 bubble growth and departure steps on its surface. In this study, a superaerophobic electrode is developed by depositing fern‐shaped palladium nanostructured arrays on the carbon paper (Pd‐nanoarray@CP). Its unique superaerophobic feature successfully facilitates the CO2 bubble releasing from the catalyst surface in a significantly small size. With the merits of specific nanoarray morphology, superior under water superaerophobicity, and rapid gas bubble release, the Pd‐nanoarray@CP shows fast charge/mass transport rate, high electrocatalytic activity, and great stability for FAO. A direct formic acid fuel cell equipped with the Pd‐nanoarray@CP anode is successfully fabricated on a microfluidic platform. A peak power density of 35.8 mW cm−2 and limiting current density of 173.3 mA cm−2 are obtained, respectively, which are 49.2% and 33.0% higher than that of conventional Pd‐black anodes. The electrode with superaerophobic interface allows deeper insight into the mechanism of FAO efficiency and holds promise for possible applications of commercially viable DFAFCs.

Visible-light driven photocatalytic performance of eco-friendly cobalt-doped ZnO nanoarrays: Influence of morphology, cobalt doping, and photocatalytic efficiency

In order to remove the organic pollution from water environment, Co2+-doped ZnO nanoarray photocatalyst was prepared through a hydrothermal process. The influences of Co2+ doping amount and hydrothermal temperature on the nanostructure and photocatalytic performance of Co2+-doped ZnO nanoarray were discussed in detail. The standard ZnO structure and nanoarray morphology of Co2+-doped ZnO samples were achieved and the absorption of visible light was also realized through Co2+ doping. The 2% Co2+-doped ZnO nanoarray prepared at 95 °C exhibited excellent photocatalytic activity and could degrade 96% of methylene blue solution within 120 min under visible light. Furthermore, the as-prepared 2% Co2+-doped ZnO nanoarray still maintained 91% for removal rate after 3 cycles of photocatalytic degradation, showed good photocatalytic activity and recyclability. All results indicate that ZnO nanoarray with Co2+ doping has a potential application in visible light photocatalysis for environmental protection and pollution control.

Super‐Hybrid Transition Metal Sulfide Nanoarrays of Co3S4 Nanosheet/P‐Doped WS2 Nanosheet/Co9S8 Nanoparticle with Pt‐Like Activities for Robust All‐pH Hydrogen Evolution

AbstractHighly active and multifunctional non‐precious metal‐based hydrogen evolution reaction (HER) eletcrocatalysts have aroused great interest in the large‐scale conversion of sustainable electrical energy to fuels and feedstocks in different application scenarios. Here, a metal sulfide‐based super hybrid nanoarray composed of a metallic Co3S4 nanosheet, P doped WS2 nanosheet, and Co9S8 nanoparticles (Super‐Co3S4/P‐WS2/Co9S8) for all‐pH HER is reported. The Super‐Co3S4/P‐WS2/Co9S8 only requires 58, 70, and 129 mV in alkaline, acid, and neutral media, respectively, to reach 10 mA cm‐2, which also presents fast reaction kinetics and high long‐term stability. The experimental and density functional theory (DFT) results verify that the abundant active heterostructure in Super‐Co3S4/P‐WS2/Co9S8 can not only provide Pt‐like H*‐adsorption Gibbs free energy (ΔGH*) but also promote the H2O adsorption and dissociation kinetics for all‐pH HER. Moreover, the collaboration of favorable metallic components and special nanoarray morphology can also strengthen the electric conductivity for electron transfer and promote the maximum exposure of active heterointerfaces for mass transport in electrocatalysis. The interesting strategy herein is expected to inspire the future design of advanced metal sulfide‐based heterostructures for energy storage and conversion.

Design of conical hollow ZnS arrays vertically grown on carbon fibers for lightweight and broadband flexible absorbers

High-performance electromagnetic (EM) absorbers are necessary for military and industry application in view of the extensive utilization of EM devices. Carbon fibers (CFs) have been considered as promising candidates in electromagnetic wave (EMW) absorption materials, while the single carbon fiber material cannot achieve satisfactory EMW absorption performance because of its limited impedance matching. Herein, electrodeposition and hydrothermal methods were used to fabricate vertical hollow ZnS nanoarrays on carbon cloth (CC) substrate, and then one kind of novel flexible EM composite absorbers with excellent performance was obtained through adjusting morphology of hollow ZnS nanoarrays by easily changing the synthesis parameters of the precursor. Noteworthy, the miniaturized cone-shaped hollow ZnS nanoarray composite absorber shows excellent EMW absorption performance of strong absorption and wide absorption band. The maximum reflection loss value is −52.5 dB and the effective absorption bandwidth reaches 5.1 GHz when the thickness is only 1.9 mm. At the same time, the composite possesses the characteristics of light weight and thin thickness. The excellent properties of the composite absorbers are mainly attributed to their morphological structure. The unique hollow ZnS nanoarray structure enhances the interface polarization and multiple reflections, meanwhile also giving it the properties of metamaterials with resonant absorption. Furthermore, the adjustment of the ZnS nanoarray morphology can not only change the transmission behavior of EMW but also affect the resonance frequency and intensity of the ZnS nanoarray unit. This study obtains high-performance absorbing materials with flexible characteristics as well as highlights the importance of the adjustment of the morphological structure to improve the EMW absorption performance.

Self‐Assembled Urchin‐Like CuWO4/WO3 Heterojunction Nanoarrays as Photoanodes for Photoelectrochemical Water Splitting

AbstractWith attractive visible‐light response and chemical stability, CuWO4 has emerged to be a promising candidate as a photoanode for photoelectrochemical (PEC) water oxidation. In this work, we report a one‐step hydrothermal method to prepare CuWO4‐based films directly grown on a conductive glass substrate from a stable precursor solution. By controlling the reaction duration, CuWO4/WO3 heterojunctions with urchin‐like nanoarray morphology are obtained. The CuWO4/WO3 film obtained with an optimized hydrothermal reaction time exhibits an onset potential of 0.6 V and a photocurrent density of 0.48 mA cm−2 at 1.23 V vs. RHE, which is almost five times that of bare CuWO4. The superior structure of the urchin‐like array with large surface area, optimizing film thickness for adequate light absorption and formation of heterojunctions for efficient charge separation conjointly, contributes to the improved performance as well as robust stability.

Flexible Supercapacitor Electrodes Based on Carbon Cloth-Supported LaMnO3/MnO Nano-Arrays by One-Step Electrodeposition.

La-based perovskite-type oxide is a new type of supercapacitor electrode material with great potential. In the present study, LaMnO3/MnO (LMO/MnO) nano-arrays supported by carbon cloth are prepared via a simple one-step electrodeposition as flexible supercapacitor electrodes. The structure, deposit morphology of LMO/MnO, and the corresponding electrochemical properties have been investigated in detail. Carbon cloth-supported LMO/MnO electrode exhibits a specific capacitance of 260 F·g−1 at a current density of 0.5 A·g−1 in 0.5 M Na2SO4 aqueous electrolyte solution. The cooperative effects of LMO and MnO, as well as the uniform nano-array morphology contribute to the good electrochemical performance. In addition, a symmetric supercapacitor with a wide voltage window of 2 V is fabricated, showing a high energy density of 28.15 Wh·kg−1 at a power density of 745 W·kg−1. The specific capacitance drops to 65% retention after the first 500 cycles due to the element leaching effect and partial flaking of LMO/MnO, yet remains stable until 5000 cycles. It is the first time that La-based perovskite has been exploited for flexible supercapacitor applications, and further optimization is expected.

Preparation of BiFeO3-overcoated TiO2 nanorod arrays for the enhanced visible-light activity

In this work, a multiferric photosensitizer BiFeO3-coupled TiO2 nanorod arrays was synthesized by loading BiFeO3 on TiO2-NRs using a two-step process. The BiFeO3 was first prepared by a sol-gel precursor method and then spin-coated onto TiO2 nanorod arrays, which were grown on an FTO substrate by the hydrothermal method. The prepared BiFeO3/TiO2 photoelectrode was photoactive under visible light illumination, which exhibited higher photocurrent and excellent photochemical stability compared with bare TiO2 nanorod arrays. The feasibility of photogenerated charge transfer in BiFeO3/TiO2 was confirmed by electrochemical-impedance-spectroscopy. The BiFeO3/TiO2 nanorod arrays exhibited an enhanced photocatalytic performance in the degradation of methylene blue aqueous solution, likely due to the loading of the BiFeO3 photosensitizer, the formation of a heterostructure between the BiFeO3 and TiO2, and the nano-array morphology of the photocatalysts.

Circular Double‐Patterning Lithography Using a Block Copolymer Template and Atomic Layer Deposition

AbstractA novel and feasible methodology is developed to fabricate well‐ordered, freestanding 1D n‐ZnO/p‐Si nanotube (NT) and nanorod (NR) arrays via double‐patterning technology with block copolymer (BCP) self‐assembly, atomic layer deposition (ALD), and inductively coupled plasma (ICP) dry etching. To obtain the well‐ordered NT pattern, a self‐assembled, Si‐containing poly(styrene‐block‐4‐(tert‐butyldimethylsilyl)oxystyrene) BCP on an SU‐8/p‐Si wafer is employed as a template. After n‐ZnO deposition on the self‐assembled BCP template by ALD, an ICP etching process is performed to produce well‐defined, independent n‐ZnO/p‐Si NT arrays. The insights into the nanoarrays presented here are directly applicable to the fabrication of n‐ZnO/p‐Si NT/NR patterns and Si NT/NR patterns by precisely controlling the ALD cycles and ICP etching time. The electrical properties of a single n‐ZnO/p‐Si NT are measured by conductive atomic force microscopy, and the results show the typical rectifying behavior of a nanodiode with superior electrical properties. This simple and useful approach provides a very convenient route for fabricating high‐density nanodiode patterns. Additionally, the possibility of various applications is confirmed by simple analyses, including examinations of contact angle and reflectance. Furthermore, the wettability and antireflection properties can be controlled by changing the nanoarray morphology.

Morphology engineering of nickel molybdate hydrate nanoarray for electrocatalytic overall water splitting: from nanorod to nanosheet.

The morphology of nano-arrays plays an important role in their applications for catalysis, energy, environment. However, the morphology modulation of nano-arrays generally involves complex optimization of synthetic conditions including surfactants, pH, and solvent. In this work, we synthesize a NiMoO4·H2O nano-array by a simple hydrothermal method under mild conditions (pH = 6.47, aqueous solution, and without the aid of surfactants). The morphology modulation of the NiMoO4·H2O nano-array is realized by simply changing the hydrothermal temperature. When the hydrothermal temperature below 150 °C, a NiMoO4·H2O nanorod array is obtained. While the hydrothermal temperature is as high as 180 °C, the array on Ni foam is nanosheet instead of nanorod. The NiMoO4·H2O nanorod array synthesized at 150 °C shows a superior water splitting activity compared to the NiMoO4·H2O nanosheet array, affording a large current density of 10 mA cm−2 at an overpotential of <240 and 200 mV toward oxygen evolution reaction and hydrogen evolution reaction, respectively. Furthermore, the electrolyzer using NiMoO4·H2O nanorod array as both anode and cathode electrodes for catalyzing overall water splitting exhibits great performance, obtaining a current density of 10 mA cm−2 at 1.67 V, comparable to the integration of commercial noble-metal Pt/C and IrO2 electrodes.

Freeze Drying as a Novel Approach to Improve Charge Transport in Titanium Dioxide Nanorod Arrays

AbstractOrdered TiO2 nanostructure arrays, such as hydrothermal nanorod arrays (NRAs) and anodic nanotube arrays, have attracted great attention in solar cells, photocatalysis, and so on, mainly owing to their vertically aligned 1D architectures. However, the device performances are limited by their poor electronic properties, owing to the morphology collapse and surface adsorbates. In this work, a novel freeze‐drying technique has been used to post‐treat hydrothermal TiO2 NRAs. The freeze‐drying treatment not only leads to a well‐preserved nanoarray morphology, but also induces complete removal of adsorbed chlorine on the TiO2 surface. The light‐scattering feature and the energy band structure have thus changed after freeze drying as compared to common air drying. As a result, the charge transfer at the TiO2/electrolyte interface and the collection efficiency of photo‐excited electrons through the TiO2 NRAs are substantially improved, leading to the performance enhancement of model solar cells.

Efficient Water Splitting Catalyzed by Cobalt Phosphide-Based Nanoneedle Arrays Supported on Carbon Cloth.

Efficient and low-cost electrocatalysts for water splitting are essential for solar fuel production. Herein, we report that nanoarrays of CoP supported on carbon cloth are an efficient bifunctional catalyst for overall water splitting. The catalyst exhibits remarkable activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media, delivering a current density of 10 mA cm(-2) at an overpotential of 281 mV for OER and 95 mV for HER. During electrocatalysis, the surface of the CoP catalyst was covered with a layer of CoOx , which was the active species. However, the CoP core and the nanoarray morphology contributed significantly to the activity.

Under‐Water Superaerophobic Pine‐Shaped Pt Nanoarray Electrode for Ultrahigh‐Performance Hydrogen Evolution

A pine‐shaped Pt nanostructured electrode with under‐water superaerophobicity for ultrahigh and steady hydrogen evolution reaction (HER) performance is successfully fabricated by a facile and easily scalable electrodeposition technique. Due to the lower bubble adhesive force (11.5 ± 1.2 μN), the higher bubble contact angle (161.3° ± 3.4°) in aqueous solution, and the smaller size of bubbles release for pine‐shaped Pt nanostructured electrode, the incomparable under‐water superaerophobicity for final repellence of bubbles from submerged surface with ease, is successfully achieved, compared to that for nanosphere electrode and for Pt flat electrode. With the merits of superior under‐water superaerophobicity and excellent nanoarray morphology, pine‐shaped Pt nanostructured electrode with the ultrahigh electrocatalytic HER performance, excellent durability, no obvious current fluctuation, and dramatically fast current density increase at overpotential range (3.85 mA mV−1, 2.55 and 13.75 times higher than that for nanosphere electrode and for Pt flat electrode, respectively), is obtained, much superior to Pt nanosphere and flat electrodes. The successful introduction of under‐water superaerophobicity to in‐time repel as‐formed H2 bubbles may open up a new pathway for designing more efficient electrocatalysts with potentially practical utilization in the near future.

Morphology control and electron field emission properties of high-ordered Si nanoarrays fabricated by modified nanosphere lithography

High-ordered silicon nanoarrays were prepared using direct nanosphere lithography combined with thermal oxidation. Atomic force microscope (AFM) images of the silicon arrays show that the patterns of polystyrene (PS) template are well transferred to the silicon surface. The size and morphology of the nanoarrays can be controlled effectively by varying the plasma-therm reactive ion etching (RIE) or thermal oxidation parameters. The field emission studies revealed that the typical turn-on field was about 7–8 V/μm with emission current reached 1 μA/cm 2. It is also found that the field emission current is highly dependent on the morphology of these Si nanoarrays.

Interaction of CO, O, and S with metal nanoparticles on Au(111): A theoretical study

Density functional theory and slab models are used to study the unusual behavior of Mo, Ni and Ru nanoparticles on a Au(111) substrate. After considering several different structures and compositions for the metal nanoparticles on the Au(111) interface, the calculations show that the metal particles energetically prefer to be embedded into the surface or form Au/metal particles/Au(111) sandwich like structures. The calculations also indicate that the observed deactivation of the Mo/Au interface to CO, ${\mathrm{O}}_{2},$ and ${\mathrm{S}}_{2}$ adsorption is due to the passivation of Mo as a result of the intermixing between Mo and Au. Mo atoms in the substrate can be pulled out to the surface by interacting with oxygen or sulfur adatoms, eventually forming molybdenum oxides or sulfides. This process depends on a delicate balance between the adsorbate-Mo and Mo-Au interactions, and usually requires high coverages of the adsorbate. It can lead to big changes in the morphology of nanoarrays. Ru/Au(111) and Ni/Au(111) exhibit a similar behavior to that of Mo/Au(111). Thus, the phenomena described above must be taken into consideration when preparing nanoparticles on a Au template.