Electrodeposition of Alloys and Compounds in the Era of Microelectronics and Energy Conversion Technology

Surface functionalization of hydroxyapatite nanoparticles for biomedical applications

This review completely covers the various aspects of hydroxyapatite (HAp) nanoparticles and their role in different biological situations, and provides the surface and interface contents on (i) hydroxyapatite nanoparticles and their hybridization with organic molecules, (ii) surface designing of hydroxyapatite nanoparticles to provide their biocompatibility and photofunction, and (iii) coating technology of hydroxyapatite nanoparticles. In particular, we summarized how the HAp nanoparticles interact with the different ions and molecules and highlighted the potential for hybridization between HAp nanoparticles and organic molecules, which is driven by the interactions of the HAp nanoparticle surface ions with several functional groups of biological molecules. In addition, we highlighted the studies focusing on the interfacial interactions between the HAp nanoparticles and proteins for exploring the enhanced biocompatibility. Such studies focus on how these interactions affect the hydration layers and protein adsorption. However, the hydration layer state involves diverse molecular interactions that can alter the shape of the adsorbed proteins, thereby affecting cell adhesion and spreading on the surfaces. We also summarized the relationship between the surface properties of the HAp nanoparticles and the hydration layer. Furthermore, we spotlighted the cytocompatible photoluminescent probes that can be developed by designing HAp/organic nanohybrid structures. We then emphasized the importance of photofunctionalization in theranostics, which involves the integration of diagnostics and therapy based on the surface design of the HAp nanoparticles. Furthermore, the coating techniques using HAp nanoparticles and HAp nanoparticle/polymer composites were outlined for fusing base biomaterials with biological tissues. The advantages of HAp/biocompatible polymer composite coatings include the ability to effectively cover porous or irregularly shaped surfaces while controlling the thickness of the coating layer, and the addition of HAp nanoparticles to the polymer matrix improves the mechanical properties, increases the roughness, and forms the morphologies that mimic bone nanostructures. Therefore, the fundamental design of hydroxyapatite nanoparticles and their surfaces was suggested from various aspects for biomedical applications.

Anodic Electrodeposition of IrO x Nanoparticles from Aqueous Nanodroplets

Electrodeposition has been used for centuries to create new materials. However, synthetic platforms are still necessary to enrich a variety of nanomaterials that can be electrodeposited. For instance, IrO x is a popular material for the water oxidation reaction, but electrodeposition strategies for the controlled growth of IrO x nanoparticles are lacking. Here, we demonstrate the anodic electrodeposition of IrO x nanoparticles from aqueous nanodroplets. Field emission scanning electron microscopy (FESEM) and scanning transmission electron microscopy (STEM) images confirm the macro- and microstructure of the resulting nanoparticles. IrO x nanoparticles of 43 ± 10 nm in diameter were achieved. X-ray photoelectron spectroscopy (XPS) showed the presence of Ir(III) and Ir(IV) hydrated oxyhydroxide species. The synthesis of IrO x nanoparticles under anodic conditions using water nanodroplets expands the capabilities of our technique and provides a tunable platform for IrO x nanoparticle electrodeposition.

Advanced Synthesis and Characterization of CdO/CdS/ZnO Heterostructures for Solar Energy Applications

This study introduces an innovative method for synthesizing Cadmium Oxide /Cadmium Sulfide/Zinc Oxide heterostructures (CdO/CdS/ZnO), emphasizing their potential application in solar energy. Utilizing a combination of electrochemical deposition and oxygen annealing, the research provides a thorough analysis of the heterostructures through scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy. The findings reveal a complex surface morphology and a composite structure with significant contributions from hexagonal CdS and cubic CdO phases. The study highlights the uniformity in the distribution of luminescent centers and the crystalline quality of the heterostructures, which is evident from the PL analysis. The redshift observed in the emission peak and the additional peaks in the excitation spectrum indicate intricate optical properties influenced by various factors, including quantum confinement and lattice strain. The research demonstrates these heterostructures' potential in enhancing solar cells' efficiency and applicability in optoelectronic devices. This comprehensive characterization and analysis pave the way for future optimization and application in efficient and sustainable solar energy solutions.

Recent Developments in Electrodeposition of Transition Metal Chalcogenides-Based Electrode Materials for Advance Supercapacitor Applications: A Review

High-performance supercapacitive electrode materials have received significant attention from researchers worldwide, thus aiming for comparable performance similar to the extensively used rechargeable batteries. For emerging energy storage technologies like flexible supercapacitors, transition metal chalcogenides (TMCs) have been in the spotlight due to their promising electrochemical features compared to other electrode materials. Among the synthesis techniques, electrodeposition-mediated preparation of thin films of TMCs offered an affordable binder-free approach for electrode fabrication that effectively improved the supercapacitor performance. Hence, this review mainly focussed on the electrodeposition-based syntheses of single/ multinary chalcogenides and their composites for supercapacitors applications. Further, the effects of different deposition parameters were discussed for boosting the supercapacitor performance. Finally, this review outlined the existing challenges and future perspectives in this research domain, which will assist the upcoming exploration in the energy storage field.

Growth of copper indium diselenide ternary thin films (CuInSe2) for solar cells: Optimization of electrodeposition potential and pH parameters

Herein, copper indium diselenide ternary (CuInSe2) thin film has been deposited on Indium Tin Oxide (ITO) coated glass substrate by electrochemical deposition technique with different potential and pH solutions. CuInSe2 thin films were deposited by one-step electrodeposition before post-depot selenization at 450 °C for 30 min. The effect of potential and pH on the structural and optical properties of CuInSe thin film have been studied using X-ray diffraction (XRD), Scanning electron microscopy (SEM), and UV-Visible spectrometer. According to the X-ray diffraction (XRD) measurements, it was observed that all samples exhibit prominent reflections (112), (204/220), and (312/116) of tetragonal CuInSe2. The films electrodeposited at -0.8 V potential shows growth and peak values increasing in the (204/220) crystal direction within a pH range of 2.2, whereas the films electrodeposited at pH 2.6 tend to favor an increase in (112) peaks. We also noticed an improvement in surface morphology and adherent of CuInSe2 thin films electrodeposited at -0.8 V applied potential from the solution having pH 2.6. The band gaps of samples electrodeposited at -0.8V potentials from pH 2.6, 2.4, and 2.2 solutions were 1.15 eV, 1.25 eV, and 1.21 eV, respectively. As part of our investigation, we used a Solar Cell capacitance simulator (SCAPS) to perform our electrodeposited films. The most effective Power conversion efficiency (PCE) was obtained for thin films electrodeposited at -0.8 V within the solution having pH 2.4.

Review Paper: Residual Stresses in Deposited Thin-Film Material Layers for Micro- and Nano-Systems Manufacturing

This review paper covers a topic of significant importance in micro- and nano-systems development and manufacturing, specifically the residual stresses in deposited thin-film material layers and methods to control or mitigate their impact on device behavior. A residual stress is defined as the presence of a state of stress in a thin-film material layer without any externally applied forces wherein the residual stress can be compressive or tensile. While many material properties of deposited thin-film layers are dependent on the specific processing conditions, the residual stress often exhibits the most variability. It is not uncommon for residual stresses in deposited thin-film layers to vary over extremely large ranges of values (100% percent or more) and even exhibit changes in the sign of the stress state. Residual stresses in deposited layers are known to be highly dependent on a number of factors including: processing conditions used during the deposition; type of material system (thin-films and substrate materials); and other processing steps performed after the thin-film layer has been deposited, particularly those involving exposure to elevated temperatures. The origins of residual stress can involve a number of complex and interrelated factors. As a consequence, there is still no generally applicable theory to predict residual stresses in thin-films. Hence, device designers usually do not have sufficient information about the residual stresses values when they perform the device design. Obviously, this is a far less than ideal situation. The impact of this is micro- and nano-systems device development takes longer, is considerably more expensive, and presents higher risk levels. The outline of this paper is as follows: a discussion of the origins of residual stresses in deposited thin-film layers is given, followed by an example demonstrating the impact on device behavior. This is followed by a review of thin-film deposition methods outlining the process parameters known to affect the resultant residual stress in the deposited layers. Then, a review of the reported methods used to measure residual stresses in thin-films are described. A review of some of the literature to illustrate the level of variations in residual stresses depending on processing conditions is then provided. Methods which can be used to control the stresses and mitigate the impact of residual stresses in micro- and nano-systems device design and fabrication are then covered, followed by some recent development of interest.

Electrochemical Synthesis of Nanocrystalline CuAg Coatings on Stainless Steel from Cyanide-Free Electrolyte

Herein we demonstrate a novel plating bath, free from cyanide, to plate a highly adherent nanocrystalline copper-silver (ncCuAg) coating on a stainless-steel substrate and its application as an antimicrobial coating. The microstructures, such as the grain size, texture, microstrain, and the crystalline preferential orientation of CuAg deposits, are systematically investigated by X-ray diffraction analysis. The range of 13.4–16.6 nm was discovered to be the crystallite size determined from the X-ray peak broadening (Scherrer’s formula). Both HRTEM, FESEM-EDS, XPS, and mapping analysis revealed that the ncCuAg coatings are composed of both Ag and Cu atoms. Electrochemical processes occurring during CuAg co-deposition were investigated by using linear sweep voltammetry (LSV), cyclic voltammetry (CV), and anodic linear stripping voltammetry (ALSV). Additionally, the coatings made of ncCuAg produced by these baths work well as antibacterial agents against gram-positive (Staphylococcus) and gram-negative bacteria (Escherichia coli).

Influence of Bath Hydrodynamics on the Micromechanical Properties of Electrodeposited Nickel-Cobalt Alloys

The influence of bath hydrodynamics on the resultant micromechanical properties of electrodeposited nickel-cobalt alloy system is investigated. The bath hydrodynamics realized by magnetic stirring is simulated using COMSOL Multiphysics and a region of minimum variation in velocity within the electrolytic cell is determined and validated experimentally. Nickel-cobalt alloy and nickel coating samples are deposited galvanostatically (50 mA/cm²) with varying bath velocity (0 to 42 cm/s). The surface morphology of samples gradually changed from granular (fractal dimension 2.97) to more planar (fractal dimension 2.15) growth type, and the according average roughness decreased from 207.5 nm to 11 nm on increasing the electrolyte velocity from 0 to 42 cm/s for nickel-cobalt alloys; a similar trend was also found in the case of nickel coatings. The calculated grain size from the X-ray diffractograms decreased from 31 nm to 12 nm and from 69 nm to 26 nm as function of increasing velocity (up to 42 cm/s) for nickel-cobalt and nickel coatings, respectively. Consecutively, the measured Vickers microhardness values increased by 43% (i.e., from 393 HV0.01 to 692 HV0.01) and by 33% (i.e., from 255 HV0.01 to 381 HV0.01) for nickel-cobalt and nickel coatings, respectively, which fits well with the Hall–Petch relation.

On the resistivity, temperature coefficient of resistance, and ampacity of Cu–CNT and Ni–CNT composites

The annealing (at 1073 K under Ar) of Ni–CNT composite, featuring CNT being fully embedded in Ni, leads to a highly interconnected system (by Ni nodules) with a decreased resistivity, as opposed to Cu–CNT composite.

Supercapacitor performance of porous nickel cobaltite nanosheets

In this work, nickel cobaltite (NiCo2O4) nanosheets with a porous structure were fabricated on nickel foam as a working electrode for supercapacitor applications. The nanosheets were fabricated by electrochemical deposition of nickel-cobalt hydroxide on the nickel foam substrate at ambient temperature in a three-electrode cell followed by annealing at 300 °C to transform the coating into a porous NiCo2O4 nanosheet. Field emission scanning electron microscopy and transmission electron microscopy revealed a three-dimensional mesoporous structure, which facilitates ion transport and electronic conduction for fast redox reactions. For one cycle, the NiCo2O4 electrodeposited nickel foam has a high specific capacitance (1734.9 F g-1) at a current density (CD) of 2 A g-1. The electrode capacitance decreased by only approximately 12.7% after 3500 cycles at a CD of 30 A g-1. Moreover, a solid-state asymmetric supercapacitor (ASC) was built utilising the NiCo2O4 nanosheets, carbon nanotubes, and a polyvinyl alcohol-potassium hydroxide gel as the anode, cathode, and solid-state electrolyte, respectively. The ASC displayed great electrochemical properties with a 42.25 W h kg-1 energy density at a power density of 298.79 W kg-1.

Electrodeposition Fabrication of Chalcogenide Thin Films for Photovoltaic Applications

Electrodeposition, which features low cost, easy scale-up, good control in the composition and great flexible substrate compatibility, is a favorable technique for producing thin films. This paper reviews the use of the electrodeposition technique for the fabrication of several representative chalcogenides that have been widely used in photovoltaic devices. The review focuses on narrating the mechanisms for the formation of films and the key factors that affect the morphology, composition, crystal structure and electric and photovoltaic properties of the films. The review ends with a remark section addressing some of the key issues in the electrodeposition method towards creating high quality chalcogenide films.

Direct-Write Printing Copper-Nickel (Cu/Ni) Alloy with Controlled Composition from a Single Electrolyte Using Co-Electrodeposition

Although various processes for metal printing at the micro- and mesoscale have been demonstrated, printing functional devices such as thermocouples, thermopiles, and heat flux sensors that function based on interfaces between an alloy and another alloy/metal demands processes for printing alloys. Furthermore, a high-quality and crystalline alloy is required for acceptable function of these devices. This article reports for the first time co-electrodeposition-based printing of single-phase solid solution nanocrystalline copper/nickel (Cu/Ni) alloy with various controllable compositions (Cu100Ni0 to Cu19Ni81) from a single electrolyte. The printed alloy is nanocrystalline (<35 nm), continuous, and dense with no apparent porosity, with remarkable mechanical and magnetic properties, without any postprocessing annealing such as heat treatment. In addition, a functional thermocouple fabricated using this process is demonstrated. Such a process can not only be used for fabrication of functional devices, it may also facilitate fundamental studies on alloys by printing a continuous library of alloy composition for material characterization.

Silicon Electrochemistry in Molten Salts

Silicon electrochemistry has the potential to advance sustainable energy solutions by offering environmentally friendly and secure technologies that can contribute to the low-carbon economy. Electrochemical methods use electrons directly as reducing agents, eliminating the need for harmful chemicals and offering simpler, one-step, process control. Silicon itself is the second most abundant element in the earth's crust, is nontoxic, and is a robust material offering high efficiencies in solar photovoltaics. As such, silicon currently dominates the solar energy market and could continue to do so for the next few decades. This review summarizes recent achievements in the molten salt electrochemistry of silicon, highlighting subjects of technological significance such as the production of silicon by silica electro-deoxidation, the formation of photoactive layers, silicon electrorefining, and the synthesis of semiconductors as well as nanostructures for energy storage applications. The review highlights future opportunities and challenges such as the production of highly pure silicon, the creation of carbon-free anodes for oxygen production, and silicon electrodeposition from gaseous precursors.

Electrosynthesis of high-entropy metallic glass nanoparticles for designer, multi-functional electrocatalysis

Creative approaches to the design of catalytic nanomaterials are necessary in achieving environmentally sustainable energy sources. Integrating dissimilar metals into a single nanoparticle (NP) offers a unique avenue for customizing catalytic activity and maximizing surface area. Alloys containing five or more equimolar components with a disordered, amorphous microstructure, referred to as High-Entropy Metallic Glasses (HEMGs), provide tunable catalytic performance based on the individual properties of incorporated metals. Here, we present a generalized strategy to electrosynthesize HEMG-NPs with up to eight equimolar components by confining multiple metal salt precursors to water nanodroplets emulsified in dichloroethane. Upon collision with an electrode, alloy NPs are electrodeposited into a disordered microstructure, where dissimilar metal atoms are proximally arranged. We also demonstrate precise control over metal stoichiometry by tuning the concentration of metal salt dissolved in the nanodroplet. The application of HEMG-NPs to energy conversion is highlighted with electrocatalytic water splitting on CoFeLaNiPt HEMG-NPs.

High-entropy metallic glasses are an unexplored class of nanomaterials and are difficult to prepare. Here, the authors present an electrosynthetic method to design these materials with up to eight tunable metallic components and show multifunctional electrocatalytic water splitting capabilities.

Template assisted preparation of high surface area macroporous supports with uniform and tunable nanocrystal loadings

The incorporation of catalytic nanocrystals into macroporous support materials has been very attractive due to their increased catalyst mass activity. This increase in catalytic efficiency is attributed in part to the increased surface area to volume ratio of the catalysts and the use of complementary support materials that can enhance their catalytic activity and stability. A uniform and tunable coating of nanocrystals on porous matrices can be difficult to achieve with some techniques such as electrodeposition. More sophisticated techniques for preparing uniform nanocrystal coatings include atomic layer deposition, but it can be difficult to reproduce these processes at commercial scales required for preparing catalyst materials. In this study, catalytic nanocrystals supported on three dimensional (3D) porous structures were prepared. The demonstrated technique utilized scalable approaches for achieving a uniform surface coverage of catalysts through the use of polymeric sacrificial templates. This template assisted technique was demonstrated with a good control over the surface coverage of catalysts, support material composition, and porosities of the support material. A series of regular porous supports were each prepared with a uniform coating of nanocrystals, such as NaYF4 nanocrystals supported by a porous 3D lattice of Ti1-xSixO2, Pt nanocrystals on a 3D porous support of TiO2, Pd nanocrystals on Ni nanobowls, and Pt nanocrystals on 3D assemblies of Au/TiO2 nanobowls. The template assisted preparation of high surface area macroporous supports could be further utilized for optimizing the use of catalytic materials in chemical, electrochemical, and photochemical reactions through increasing their catalytic efficiency and stability.

Electroplating for Decorative Applications: Recent Trends in Research and Development

Electroplating processes are widely employed in industrial environments for a large variety of metallic coatings, ranging from technological to decorative applications. Even if the galvanic electrodeposition is certainly a mature technology, new concepts, novel applications, environmental legislation and the new material requirements for next-generation devices make the scientific research in this field still very active. This review focuses mostly at the decorative and wearable applications, and aims to create a bridge between the past knowledge and the future direction that this process, i.e., electrodeposition, is taking. Both the theoretical fundamentals as well as some of the most widespread practical applications—limited to metallic and alloy coatings—are explored. As an integral part of the industrial process, we take a look at the main techniques thought which the quality control of deposits and surfaces is carried out. Finally, global industrial performance and research directions towards sustainable solutions are highlighted.

Morphological stabilization and KPZ scaling by electrochemically induced co-deposition of nanostructured NiW alloy films

We have assessed the stabilizing role that induced co-deposition has in the growth of nanostructured NiW alloy films by electrodeposition on polished steel substrates, under pulsed galvanostatic conditions. We have compared the kinetic roughening properties of NiW films with those of Ni films deposited under the same conditions, as assessed by Atomic Force Microscopy. The surface morphologies of both systems are super-rough at short times, but differ at long times: while a cauliflower-like structure dominates for Ni, the surfaces of NiW films display a nodular morphology consistent with more stable, conformal growth, whose height fluctuations are in the Kardar-Parisi-Zhang universality class of rough two-dimensional interfaces. These differences are explained by the mechanisms controlling surface growth in each case: mass transport through the electrolyte (Ni) and attachment of the incoming species to the growing interface (NiW). Thus, the long-time conformal growth regime is characteristic of electrochemical induced co-deposition under current conditions in which surface kinetics is hindered due to a complex reaction mechanism. These results agree with a theoretical model of surface growth in diffusion-limited systems, in which the key parameter is the relative importance of mass transport with respect to the kinetics of the attachment reaction.

Nanowire formation is preceded by nanotube growth in templated electrodeposition of cobalt hybrid nanostructures

Cobalt fluted nanowires, novel nanostructures with a diameter of 200 nm consisting of a solid nanowire base and a thin, nanotubular flute shape, were grown in track-etched polycarbonate membranes via templated electrodeposition. The structures were characterized electrochemically via cyclic voltammetry, chronoamperometry, and charge stripping, and structurally via  scanning electron microscopy, transmission electron microscopy, and focused ion beam cross-sectioning. Electrochemical and structural analysis reveals details of their deposition kinetics, structure, and morphology, and indicate possible mechanisms for their formation and control. These unique structures provide inspiration for an array of possible applications in electronics, photonics, and other fields.

Nanoscale electrodeposition of low-dimensional metal phases and clusters

The present status of the problem of electrochemical formation of low-dimensional metal phases is reviewed. The progress in this field achieved in the last two decades is discussed on the basis of experimental results obtained in selected electrochemical systems with well defined single crystal substrates. The influence of crystallographic orientation and surface inhomogeneities of foreign substrates on the mechanism of formation and the atomic structure of two-dimensional (2D) metal phases in the underpotential deposition range is considered. The localized electrodeposition of metal nanoclusters on solid state surfaces applying the STM-tip as a nanoelectrode is demonstrated.