Template-assisted Electrodeposition Research Articles

Enhancing the Deposition Rate and Uniformity in 3D Gold Microelectrode Arrays via Ultrasonic-Enhanced Template-Assisted Electrodeposition.

In the pursuit of refining the fabrication of three-dimensional (3D) microelectrode arrays (MEAs), this study investigates the application of ultrasonic vibrations in template-assisted electrodeposition. This was driven by the need to overcome limitations in the deposition rate and the height uniformity of microstructures developed using conventional electrodeposition methods, particularly in the field of in vitro electrophysiological investigations. This study employs a template-assisted electrodeposition approach coupled with ultrasonic vibrations to enhance the deposition process. The method involves utilizing a polymeric hard mask to define the shape of electrodeposited microstructures (i.e., micro-pillars). The results show that the integration of ultrasonic vibrations significantly increases the deposition rate by up to 5 times and substantially improves the uniformity in 3D MEAs. The key conclusion drawn is that ultrasonic-enhanced template-assisted electrodeposition emerges as a powerful technique and enables the development of 3D MEAs at a higher rate and with a superior uniformity. This advancement holds promising implications for the precision of selective electrodeposition applications and signifies a significant stride in developing micro- and nanofabrication methodologies for biomedical applications.

Control of Crystallographic Growth Orientation and Twinning Structure in Copper Nanowires by Template-Assisted Electrodeposition

Synthesis and characterization of noble metal nanowires have been a popular topic in the field of microelectronic devices and catalysts. Nanotwinned copper nanowires (nt-CuNWs) possess high mechanical strength, excellent electromigration resistance and low electrical resistivity, which have been considered as a promising interconnect material in ultra-large scale integrated circuits (ICs). Here, we deposited nt-CuNWs in two different anodic aluminum oxide (AAO) templates with respective pore sizes of 70 nm and 35 nm pore by pulse electrodeposition. The influence of thermal treatment on the Cu seed layer deposited on AAO membranes prior to electrodeposition is investigated. Both coarse and thin nt-CuNWs mainly grew in <111> crystallographic direction with (111) texture coefficients (TC(111)) > 2.5, and an aspect ratio (AR) > 100 according to x-ray diffraction analysis. An addition of gelatin (14 ppm) in the copper sulfate electrolyte is found to suppress the growth of (220)-oriented Cu grains in the AAO by forming copper nanowires with large TC(111) > 2.65 and high-density nanotwin structure. This study provides a simple route to tailoring microstructure and physical properties of nanoscale copper wires, which is beneficial for the interconnect technology development in semiconductor IC devices.

Electrodeposition of Cu Nanocubes in the Presence of Cl- and Br-

Electrodeposition is one of the simple methods for fabricating metal and alloy thin films. Electrodeposition is performed by applying external electrical energy to conductive substrates immersing in electrolytes containing metal precursors. Metal ions or complexes are reduced on a substrate surface and form metal films. The properties of metal thin films and surface morphology of the electrodeposit can be modulated by the parameters of electrodeposition, the composition of electrolytes, i.e., the concentrations of metal precursors and additives. Furthermore, the atomic composition of alloy films can also be easily controlled by electrochemical parameters in the electrodeposition process.1 As explained, the electrodeposition process has various advantages in producing metal thin films with desired properties. However, creating nanostructures with precisely controlling their shapes in the nm scale is relatively difficult. In colloidal syntheses, various nanocrystals, including nanowires, nanospheres, octahedrons, nanocubes, and nanoplates, can be obtained by introducing shape-directing agents.2-4 In the case of electrodeposition, the template-assisted electrodeposition method is the most common to form nanostructures,5,6 and relatively few examples of shape controlling by additives have been reported. Although the formation of metal nanowires in the presence of 3,5-diamino-1,2,4-triazole (DAT) has been recently reported,7 shape control of metal deposits by additives during the electrodeposition process is still limited to few nanostructures. Electrodeposition induces metal growth relatively faster than colloidal synthesis, and a precise nucleation step is not involved in the electrodeposition, which is critical in colloidal syntheses. In this study, we have adopted pulse-reverse electrodeposition to modulate metal nucleation at the initial stage of electrodeposition and also maximize the effects of additives. Pulse-reverse electrodeposition has been researched for controlling the properties of metal thin films and changing the adsorption of additives.8,9 Therefore, pulse-reverse electrodeposition can catch up with the shape control in colloidal syntheses. This presentation will introduce how the parameters in pulse-reverse electrodeposition and additives (halide ions) affect the shape of Cu nanocrystals. References 1) T. P. Moffat, J. J. Mallett, and S. M. Hwang, “Oxygen Reduction Kinetics on Electrodeposited Pt, Pt100− x Nix , and Pt100−xCox” J. Electrochem. Soc. 156, B238 (2009)2) Y. Xia, Y. Xiong, B. Lim, and S. E. Skrabalak, “Shape-Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?” Angew. Chem. Int. Ed. 48, 60 (2009)3) K. A. Fichthorn, Z. Chen, Z. Chen, R. M. Rioux, M. J. Kim, and B. J. Wiley, “Understanding the Solution-Phase Growth of Cu and Ag Nanowires and Nanocubes from First Principles” Langmuir 37, 4419 (2021)4) D. Huo, M. J. Kim, Z. Lyu, Y. Shi, B. J. Wiley, and Y. Xia, “One-Dimensional Metal Nanostructures: From Colloidal Syntheses to Applications” Chem. Rev. 119, 8972 (2019)5) K. R. Yeo, J. Y. Eo, M. J. Kim and S.-K. Kim, “Shape Control of Metal Nanostructures by Electrodeposition and their Applications in Electrocatalysis” J. Electrochem. Soc. 169, 112502 (2022)6) C. Liu, Z. Li, P. Yu, H. W. Wong, and Z. Gu, “Vertically Aligned and Surface Roughed Pt Nanostructured Wire Array as High Performance Electrocatalysts for Methanol Oxidation” ACS Appl. Energy Mater. 1, 3973 (2018)7) T. T. H. Hoang, S. Ma, J. I. Gold, P. J. A. Kenis, and A. A. Gewirth “Nanoporous Copper Films by Additive-Controlled Electrodeposition: CO2 Reduction Catalysis” ACS Catal. 7, 3313 (2017)8) M. J. Kim, T. Lim, K. J. Park, S. K. Cho, S.-K. Kim, and J. J. Kim “Characteristics of Pulse-Reverse Electrodeposited Cu Thin Films: I. Effects of the Anodic Step in the Absence of an Organic Additive” J. Electrochem. Soc. 159, D538 (2012)9) M. J. Kim, T. Lim, K. J. Park, O. J. Kwon, S.-K. Kim, and J. J. Kim “Characteristics of Pulse-Reverse Electrodeposited Cu Thin Film: II. Effects of Organic Additives” J. Electrochem. Soc. 159, D544 (2012) Figure 1

Magnetization processes in two-dimensional arrays of iron nanowires

Arrays of iron nanowires (NWs) obtained by template-assisted electrodeposition constitute a promising composite material characterized by a combination of high magnetization in the filler and perpendicular magnetic anisotropy. The properties of these composites arise from the interplay between the behavior of individual NWs and their magnetostatic interactions. In this study, we investigated NW arrays with identical wire diameters but varying spatial arrangements. Major hysteresis loops were studied under various field directions relative to the NW axis. Key parameters such as the slope of the magnetization curve, saturation magnetization, and coercive force were quantified. Additionally, FORC (First Order Reversal Curve) measurements were conducted with the field oriented longitudinally with respect to the NW, offering insights into the inhomogeneity of the demagnetizing field influenced by the NW array's configuration. In the sample with the highest NW density, we observed isotropic behavior of the effective demagnetizing field, and we proposed an explanation for this phenomenon using the effective media approach. Micromagnetic simulations revealed that the magnetic behavior of individual NWs with a 100 nm diameter can be described as an interchange between volumes characterized by vortex and uniform magnetization patterns. Calculations of the demagnetizing field using the effective medium model demonstrated excellent agreement with experimental data across arrays featuring different NW densities. Remarkably, the quantitative consistency of coercive field values obtained from micromagnetic simulations and experimental measurements in the range of angles from 0° to 45° for the studied samples underscores the structural homogeneity of the obtained NWs.

Electrical Resistivity Modification of Electrodeposited Mo and Mo–Co Nanowires for Interconnect Applications

Achieving historically anticipated improvement in the performance of integrated circuits is challenging, due to the increasing cost and complexity of the required technologies with each new generation. To overcome this limitation, the exploration and development of novel interconnect materials and processes are highly desirable in the microelectronics field. Molybdenum (Mo) is attracting attention as an advanced interconnect material due to its small resistivity size effect and high cohesive energy; however, effective processing methods for such materials have not been widely investigated. Here, we investigate the electrochemical behavior of ions in the confined nanopores that affect the electrical properties and microstructures of nanoscale Mo and Mo–Co alloys prepared via template-assisted electrodeposition. Additives in an electrolyte allow the deposition of extremely pure metal materials, due to their interaction with metal ions and nanopores. In this study, boric acid and tetrabutylammonium bisulfate (TBA) were added to an acetate bath to inhibit the hydrogen evolution reaction. TBA accelerated the reduction of Mo at the surface by inducing surface conduction on the nanopores. Metallic Mo nanowires with a 130 nm diameter synthesized through high-aspect-ratio nanopore engineering exhibited a resistivity of (63.0 ± 17.9) μΩ·cm. We also evaluated the resistivities of Mo–Co alloy nanowires at various compositions toward replacing irreducible conventional barrier/liner layers. An intermetallic compound formed at a Mo composition of 28.6 at%, the resistivity of the Mo–Co nanowire was (58.0 ± 10.6) μΩ·cm, indicating its superior electrical and adhesive properties in comparison with those of conventional barriers such as TaN and TiN. Furthermore, density functional theory and non-equilibrium Green’s function calculations confirmed that the vertical resistance of the via structure constructed from Mo-based materials was 21% lower than that of a conventional Cu/Ta/TaN structure.

Hydride formation and dynamic phase changes during template-assisted Pd electrodeposition

We investigated the structural evolution of electrochemically fabricated Pd nanowires in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and two-dimensional surface optical reflectance (2D-SOR). This shows how electrodeposition and the hydrogen evolution reaction (HER) compete and interact during Pd electrodepositon. During the bottom-up growth of the nanowires, we show that β-phase Pd hydride is formed. Suspending the electrodeposition then leads to a phase transition from β-phase Pd hydride to α-phase Pd. Additionally, we find that grain coalescence later hinders the incorporation of hydrogen in the Pd unit cell. GTSAXS and 2D-SOR provide complementary information on the volume fraction of the pores occupied by Pd, while XRF was used to monitor the amount of Pd electrodeposited.

Photothermal superhydrophobic copper nanowire assemblies: fabrication and deicing/defrosting applications

Ice and frost buildup continuously pose significant challenges to multiple fields. As a promising de-icing/defrosting alternative, designing photothermal coatings that leverage on the abundant sunlight source on the earth to facilitate ice/frost melting has attracted tremendous attention recently. However, previous designs suffered from either localized surface heating owing to the limited thermal conductivity or unsatisfied meltwater removal rate due to strong water/substrate interaction. Herein, we developed a facile approach to fabricate surfaces that combine photothermal, heat-conducting, and superhydrophobic properties into one to achieve efficient de-icing and defrosting. Featuring copper nanowire assemblies, such surfaces were fabricated via the simple template-assisted electrodeposition method, allowing us to tune the nanowire assembly geometry by adjusting the template dimensions and electrodeposition time. The highly ordered copper nanowire assemblies facilitated efficient sunlight absorption and lateral heat spreading, resulting in a fast overall temperature rise to enable the thawing of ice and frost. Further promoted by the excellent water repellency of the surface, the thawed ice and frost could be spontaneously and promptly removed. In this way, the all-in-one design enabled highly enhanced de-icing and defrosting performance compared to other nanostructured surfaces merely with superhydrophobicity, photothermal effect, or the combination of both. In particular, the defrosting efficiency could approach ∼100%, which was the highest compared to previous studies. Overall, our approach demonstrates a promising path toward designing highly effective artificial deicing/defrosting surfaces.

Electrocrystallization of Metals in Channels of Porous Films of Anodic Aluminum Oxide: The Real Template Structure and the Quantitative Model of Electrodeposition

A method is proposed for analytical description of current transients at the template-assisted electrodeposition of metal into porous films in anodic aluminum oxide (AAO). The template-assisted electrodeposition of copper and gold is accomplished. For the copper electrodeposition, it is shown that the experimental data are in quantitative agreement with the calculated values of current without any fitting parameters. The parameters of the AAO film structure including the conicity of pores and the number of dead-end channels are measured and their effect on the process of template-assisted electrodeposition is studied .

Bottom-up self-assembly of macroporous ZnO nanostructures for photovoltaic applications

The present study utilized a template-assisted electrodeposition route for the bottom-up epitaxial growth of macroporous zinc oxide nanostructures. To this end, the ZnO seed layer was coated on the p-type silicon substrates using a radio frequency magnetron sputtering technique to form a p-n heterojunction. Then, polymer microspheres were implanted on ZnO/Si substrates to act as a template. Subsequently, ZnO nanostructures were electrodeposited through the interstitial spaces between the microspheres. After the deposition, the microspheres were removed by dissolving in chloroform solvent, forming a porous structure. The planar and cross-sectional electron microscopy analyses exhibited a uniform macroporous morphology with an average pore diameter of ∼1 μm. The pores were homogeneously distributed on the surface of the electrodeposited ZnO layer. The advantage of this technique over the top-down approaches, such as electrochemical etching, is that the porosity and size of pores can be easily adjusted by varying the concentration and diameter of microsphere templates. The optical investigations revealed enhancement in photon absorption and photoluminescence (PL) intensity due to multiple light scattering in the pore walls of the deposited ZnO nanostructures. For the templated sample, a PL blue shift was observed due to the reduction in crystallite size of ZnO nanostructures. A heterojunction thin film solar cell was designed by the metallization of ZnO/p-Si samples to study the power conversion capability of macroporous ZnO nanostructures. The photovoltaic performance of the developed devices was evaluated under a solar light simulator. The device based on the templated sample showed increased shunt resistance and reduced series resistance compared to the flat sample. The optoelectrical results indicated an efficiency improvement for the fabricated solar cells based on the macroporous ZnO sample due to its higher exposed area and increased rate of electron-hole generation.

Template-assisted electrodeposition of metals: A method for determining the fraction of active nanopores

Template-assisted electrodeposition is a versatile technique for preparing metal nanostructures, e.g. nanowires and nanotubes, in anodic aluminium oxide (AAO) templates with cylindrical channels. However, the fraction of pores in which the electrochemical process occurs is not known in advance, which makes coulometric control of the deposition process nontrivial. In this paper, we propose a simple method for determining the fraction of active nanopores, i.e., pores in which metal is deposited. This is based on the analysis of current transients registered during templated electrodeposition. The developed method makes it possible to estimate the density of deposited nanowires and their average length by coulometric control without using scanning electron microscopy.

Electrodeposition of One-Dimensional Nanostructures: Environmentally Friendly Method

During the past decade, nanotechnology has become an active field of research because of its huge potential for a variety of applications. When the size of many established, well-studied materials is reduced to the nanoscale, radically improved or new surprising properties often emerge. There are mainly four types of nanostructures: zero, one, two and three dimensional structures. Among them, one-dimensional (1D) nanostructures have been the focus of quite extensive studies worldwide, partially because of their unique physical and chemical properties. Compared to the other three dimensional structures, the first characteristic of 1D nanostructure is its smaller dimension structure and high aspect ratio, which could efficiently transport electrical carriers along one controllable direction; as a consequence they are highly suitable for moving charges in integrated nanoscale systems. The second characteristic of 1D nanostructure is its device function, which can be exploited as device elements in many kinds of nanodevices. Indeed it is important to note that superior physical properties including superconductivity, enhanced magnetic coercivity and the unusual magnetic state of some 1D nanostructures have been theoretically predicted and some of them have already been confirmed by experiments. In order to attain the potential offered by 1D nanostructures, one of the most important issues is how to synthesize 1D nanostructures in large quantities with a convenient method. Many synthetic strategies, such as solution or vapor-phase approaches, template-directed methods, electrospinning techniques, solvothermal syntheses, self-assembly methods, etc., have been developed to fabricate different classes of 1D nanostructured materials, including metals, semiconductors, functional oxides, structural ceramics, polymers and composites. All the methods can be divided into two categories: those carried out in a gas phase (i.e., “dry processes”) and those carried out in a liquid phase (i.e., “wet processes”). The dry processes include, for example, techniques such as chemical vapor deposition (CVD), physical vapor deposition (PVD), pulse laser deposition (PLD), metal-organic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE). In general, these gas phase processes require expensive and specialized equipments. The wet processes include sol-gel method, hydrothermal method, chemical bath deposition (CBD) and electrodeposition. Among the above mentioned methods, electrodeposition has many advantages such as low cost, environmentally friendly, high growth rate at relatively low temperatures and easier control of shape and size. Generally, there are two strategies to produce the 1D nanostructures through the electrochemical process. They are the template-assisted electrodeposition, and the template-free electrodeposition. In this chapter, we will approach the recent progress and offer some prospects of future directions in electrodeposition of 1D nanostructures. Electrodeposition is a simple and flexible method for the synthesis of one-dimensional (1D) nanostructures and has attracted great attention in recent years.

Tailoring the structural and magnetic properties of self-ordered nickel nanowires created by template-assisted electrodeposition route

Thin films of vertically oriented self-ordered nickel nanowires were fabricated using the template-assisted electrodeposition method. Magnetic measurements of as-formed nanowires revealed the presence of an axial easy magnetization direction due to the shape of the nanowires. At moderate annealing temperatures, the magnetic anisotropy changed from positive to negative. This indicated easy magnetization direction flipping from axial to radial configuration. A nickel oxide phase started to grow at higher annealing temperatures with a distinct reduction in saturation magnetization due to its antiferromagnetic character. In addition, an exchange bias was observed owing to the coexistence of ferromagnetic and antiferromagnetic phases. Single-phase nickel oxide nanowires were generated at elevated annealing temperatures and exhibited an unexpected ferromagnetic behavior attributed to the incorporation of nickel ions and oxygen vacancies as suggested by ferromagnetic resonance measurements. Diffuse reflection measurements indicated an effective energy gap of 4.2 eV for nickel oxide nanowires.

Rhodium Oxide Nanorod Motors Powered by Light across the Full Visible Spectrum

We report nanorod motors made of gold (Au) and rhodium oxide (Rh2O3) that move in UV and visible light (purple, blue, green, or red). These nanorods are synthesized in large quantities (109/batch) by template-assisted electrodeposition, followed by annealing, and are uniformly distributed and resist strong acids or bases. Rh2O3 forms a heterojunction with Au so that a Rh2O3–Au nanorod moves toward Au under visible light via self-electrophoresis. Its speed increases with light intensities and fuel [e.g., hydrogen peroxide (H2O2)] concentrations, reaching 28.5 μm/s in 10% H2O2 under 365 nm light of 320 mW/cm2. These nanorod motors also form dynamic and reversible clusters under light.

Interwire and Intrawire Magnetostatic Interactions in Fe-Au Barcode Nanowires with Alternating Ferromagnetically Strong and Weak Segments.

Metallic barcode nanowires (BNWs) composed of repeating heterogeneous segments fabricated by template-assisted electrodeposition can offer extended functionality in magnetic, electrical, mechanical, and biomedical applications. The authors consider such nanostructures as a 3D system of magnetically interacting elements with magnetic behavior strongly affected by complex magnetostatic interactions. This study discusses the influence of geometrical parameters of segments on the character of their interactions and the overall magnetic behavior of the array of BNWs having alternating magnetization, because the Fe and Au segments are made of Fe-Au alloys with high and low magnetizations. By controlling the applied current densities and the elapsed time in the electrodeposition, the dimension of the Fe-Au BNWs can be regulated. This study reveals that the influence of the length of magnetically weak Au segments on the interaction field between nanowires is different for samples with magnetically strong 100 and 200 nm long Fe segments using the first-order reversal curve (FORC) diagram method. With the help of micromagnetic simulations, three types of magnetostatic interactions in the BNW arrays are discovered and analy. This study demonstrates that the dominating type of interaction depends on the geometric parameters of the Fe and Au segments and the interwire and intrawire distances.

Bilayered soft/hard magnetic nanowires as in-line writing heads

Multi-segmented cylindrical nanowires (NWs) are the most promising systems for 3D racetrack memory devices, where information is stored as in-line magnetic domains. However, reading and writing information is still a challenge, as external reading/writing heads have to be implemented near the tracks. The writing component should be made of a bilayered soft/hard coupled magnetic system, so that information could be easily written by external magnetic fields. Here, we demonstrate the feasibility of using a Ni90Cu10/Fe20Co80 segmented NW as the writing element, in which magnetic information is written by applying external magnetic fields. Using low-cost template-assisted electrodeposition methods, single, bi- and multi-segmented NW hexagonal arrays of NiCu and FeCo/Au were fabricated. A throughout magnetic characterization using magnetic hysteresis loops, ferromagnetic resonance and first-order reversal curves (FORCs) revealed that the soft segment (NiCu) induced the reversal of the hard segment (FeCo) in a two-step process, reducing its coercive and effective anisotropy fields when coupled. Finally, micromagnetic simulations certified the experimental observations of a multi-step reversal process. This work demonstrates the important role of interface interactions for the future implementation of an in-line writing component in a 3D racetrack memory device, enhancing their potential applicability.

Constructing hollow nanorod arrays by nickel–cobalt phosphide nanosheets as high-performance electrocatalysts for urea-assisted energy-efficient hydrogen generation

The slow kinetics of oxygen evolution reaction (OER) severely limits electrocatalytic water cracking for hydrogen (H2) generation. Replacing sluggish OER with thermodynamically favorable urea oxidation reaction holds great promise for energy-efficient H2 generation while also addressing the issue of urea-rich water contamination. In this paper, novel hollow nanorod arrays made of NiCoP nanosheets (denoted as NiCoP NSs@HNRAs) are created using an environmentally friendly and simple template-assisted electrodeposition and subsequent phosphorization method. The distinct HNRAs enable fast transport and short diffusion paths for electroactive species, as well as the high catalysts availability. Because of these structural advantages, NiCoP NSs@HNRAs have excellent electrocatalyst activity, requiring only a potential of 1.35 V (vs. RHE) to achieve a current density of 50 mA cm−2 with robust durability. Furthermore, an overall urea electrolysis system is constructed using commercial Pt/C as the cathode and NiCoP NSs@HNRAs as the anode, with an outstanding activity of 1.43 V and excellent stability at 50 mA cm−2. This paper presents a novel structural strategy for designing an electrocatalyst for urea-assisted energy-efficient H2 generation.

Dynamic cryo-mechanical properties of additively manufactured nanocrystalline nickel 3D microarchitectures

Template-assisted electrodeposition is a promising microscale additive manufacturing technique allowing to deposit pure metals with high resolution. To allow the application-relevant design of metamaterials, it is necessary to establish microstructure-mechanical property relationships under extreme conditions. In this work, a novel process based on two-photon lithography was used to synthesize arrays of nanocrystalline nickel micropillars and complex microlattices. This allowed high throughput mechanical testing using a newly developed in situ nanoindenter at unprecedented combination of cryogenic temperatures (160 to 300 K) and strain rates (0.001 to 500 s−1). Strain rate sensitivity was found to increase from ∼ 0.004 at 300 K to ∼ 0.008 at 160 K. Thermal activation analysis showed a decrease in activation volume from 122b3 at 300 K to 45b3 at 160 K and an activation energy of 0.59 eV in line with collective dislocation nucleation as the rate limiting mechanism. Transmission Kikuchi Diffraction allowed quantifying microstructural changes during deformation. As such, a deformation map along with the responsible deformation mechanisms has been ascertained for additively micromanufactured nanocrystalline nickel at unique combinations of extreme temperatures and strain rates. Further, rate-dependent compression of microlattices and complementary finite element simulations using the results from micropillars as constitutive models exemplified the promise of such metal microarchitectures in space and aviation applications.

Design of porous metal collector via bubble template-assisted electrochemical deposition using numerical simulation

Reduction of resistances in next-generation secondary batteries, which considerably affects battery performance under high-rate conditions, is essential to increase their output density. In particular, lithium-ion batteries (LiBs) require sufficient contact between the collector and the composite electrode layer. However, contact is often disrupted due to the absence of strong bonding. This issue can be redressed using a porous metal to fabricate the collector. In this study, a porous metal structure is theoretically designed and optimized for this purpose. To this end, a numerical model is developed to simulate the formation of the structure via the hydrogen bubble template-assisted electrodeposition method. With the model, the effects of electrodeposition on the process of formation were examined. Via simulation, the performance of the proposed porous metal structure is estimated corresponding to each deposition potential, and the validity of the architecture is confirmed based on experimental results. In addition, a gradient structure is designed to serve as a highly conductive collector during particle packing. The effectiveness of the overall architecture is evaluated via numerical simulation and a multi-step process is proposed to fabricate the gradient structure. Experimental results reveal that the optimal proposed structure exhibits 30% higher conductivity compared to conventional alternatives.

Metal oxide nanotubes via electrodeposition for battery-electrochemical capacitor hybrid device

Charge accessibility in nanotube electrodes and consequent electrochemical properties exploitable for energy storage and sensing device is higher due to their dual surfaces than solid nanowires; however, their controlled growth is often challenging. This article demonstrates synthesis of metal nanowires of cobalt and nickel using a template-assisted electrodeposition technique and its transformation into cobalt oxide (Co3O4) and nickel oxide (NiO) nanotubes by controlled annealing. The materials are characterized for their phase, surface, and morphology. The Co3O4 nanotubes has a spinal-type crystal structure, an inner diameter of ~100 nm and wall thickness of ~220 nm with uniform micropores centered at ~21 nm, whereas NiO has a face centered cubic crystal structure, inner diameter ~90 nm and wall thickness ~330 nm with uniform micropores centered at ~21 nm. The electrochemical charge storability of the nanotubes is evaluated in an aqueous alkaline electrolyte (6 M KOH) using a three-electrode system measurement. The Co3O4 and the NiO nanotubes delivered discharge specific charges of ~324 and ~263 C g−1, respectively, the difference charge storability is attributed to the surface and electrochemical properties. Further, a battery – electrochemical capacitor hybrid device is developed with desirable charge storage performance indicators using the Co3O4 nanotubes and reduced graphene oxide as positive electrode and negative electrode, respectively. This research thereby provides a method for developing scalable, reproducible, and efficient battery-electrochemical capacitor hybrid device using NiO and Co3O4 nanotubes.

Template-assisted electrodeposited cupric oxide nanotubes and hierarchical nanospikes for tailoring electrode-electrolyte interfacial charge transfer

Morphological modification in materials aids multi-channel electron access sites for easier electrolyte ion access for many electrochemical devices including energy storage devices. Controlled synthesis of such multichannel morphologies of metal oxides offers significant challenges. Herein, we report a template-assisted electrodeposition technique for the synthesis of Cu nanowires, which are transformed into either CuO nanotubes by controlled annealing or CuO hierarchical nanospikes using a simple hydroxyl ion impregnation technique and subsequent annealing. These materials are tested as electrodes in charge storage systems in 6 M KOH electrolyte in a three-electrode system; both electrodes have shown battery-type charge storage behaviour. Despite the chemical similarity between the two materials, the CuO nanospikes electrodes showed improved charge transport between electrode-electrolyte interface compared to the CuO nanotubes. With the cost-effectiveness, easy availability, and multi-channel morphology of CuO nanospikes along with the promising performance of the electrode in a three-electrode system, the present research offers future potential in developing low cost and high performing energy storage devices.