Single-step Electrodeposition Research Articles

3D hierarchical nanostructured NiCo-LDH/Cu electrode for efficient alkaline hydrogen evolution

The development of an efficient and cost-effective electrocatalyst for the Hydrogen Evolution Reaction (HER) that can be widely applied in industrial settings poses a multifaceted challenge. This research involved fabricating a NiCo-LDH/Cu electrode as a self-supported catalyst for hydrogen evolution on nickel foam using a solvothermal method and constant potential electrodeposition. In comparison to the NiCu electrocatalyst produced through a single-step electrodeposition, the NiCo-LDH/Cu hydrogen evolution electrode prepared via this combined approach exhibited significant electrocatalytic performance for HER in an alkaline electrolyte. The NiCo-LDH/Cu catalytic electrode requires only an overpotential of 78.0 mV to achieve a current density of 10 mA·cm−2 in 1 M KOH. The current density required to catalyze the hydrogenation reaction is reduced by 64 % compared to pure nickel foam. This reduction accelerates the hydrogenation catalytic reaction and enhances electrochemical stability. The remarkable HER efficiency of the NiCo-LDH/Cu catalytic electrode primarily stems from the increased active surface area facilitated by the LDH structure and the synergistic impact generated during the NiCu co-deposition process. This work shows an economical and practical method for developing efficient non-precious metal catalytic electrodes.

Preparation and capacitance performance of NiCo layered double hydroxide by multi-step constant current electrodeposition method

In comparison with single-step electrodeposition, multi-step electrodeposition for electrode preparation is more effective in releasing internal stresses, utilizing the highly efficient deposition time at the beginning of the electrodeposition, improving deposition efficiency, and producing adhesive-free high-performance electrodes with controllable mass. In this paper, NiCo layered double hydroxide (NiCo-LDH) with similar mass was successfully deposited by a two-electrode constant-current electrodeposition method using nickel foam as the substrate through different electrodeposition steps. A comparative study was conducted on the effects of NiCo-LDH deposition steps on the morphology, total deposition time, and electrochemical performance of NiCo-LDH samples. The results show that the mass of NiCo-LDH grown on foam nickel is similar when the number of deposition steps is from 1 to 6 at 12–13 mg, the coating of foam nickel substrate became more uniform. The total deposition time has decreased from 2550 s for 1-step deposition to 1542 s for 6-step deposition, reducing the occupation time of the electrodeposition equipment. As the number of deposition layers increases, the specific capacitance of NiCo-LDH shows a trend of first increasing and then stabilizing. The high mass specific capacitance of NiCo-LDH electrode material deposited in 6 steps is 953 F g−1 at a current density of 3 mA cm−2. The assembled asymmetric supercapacitor device achieved an energy density of 0.309 mWh cm−2 at a power density of 4.25 mW cm−2, and a capacitance retention rate of 94% after 10,000 cycles at a current density of 40 mA cm−2. This indicates that the NiCo-LDH material prepared by multi-step electrodeposition method has good capacitance performance, providing a simple and time-saving method for manufacturing large-scale multi-step electrodeposition of adhesive-free supercapacitor electrodes.

Silver Nanoparticle-Decorated Carbon Fiber Microelectrode for Imidacloprid Insecticide Analysis

The electrocatalytic activity of silver towards imidacloprid reduction was demonstrated at both macro- and nano-scales. Coupled with the advantages of microscopic electrodes, this has led to the development of a highly-sensitive and selective electrochemical sensor for imidacloprid detection. This sensor utilizes silver nanoparticle-decorated carbon fiber microelectrodes (AgNPs/CF) fabricated through a single-step electrodeposition. Employing AgNPs/CF, the linear range, sensitivity, and limit of detection (3SB/m) were determined to be 0.0–0.40 mM, 2.98 × 10−8 ± 0.10 × 10−8 A mM−1, and 60.4 nM, respectively. The sensor was successfully applied to detect imidacloprid directly in various water samples without the need for sample preparation, demonstrating ca. 100% recoveries. Moreover, the sensor was applied to analyze imidacloprid release from contaminated soil samples, revealing Langmuir characteristics of the desorption process.

Electrochemical microfluidic immunosensor with graphene-decorated gold nanoporous for T-2 mycotoxin detection

T-2 is one of the most potent cytotoxic food-borne mycotoxins. In this work, we have developed and characterized an electrochemical microfluidic immunosensor for T-2 toxin quantification in wheat germ samples. T-2 toxin detection was carried out using a competitive immunoassay method based on monoclonal anti-T-2 antibodies immobilized on the poly(methyl methacrylate) (PMMA) microfluidic central channel. The platinum wire working electrode at the end of the channel was in situ modified by a single-step electrodeposition procedure with reduced graphene oxide (rGO)-nanoporous gold (NPG). T-2 toxin in the sample was allowed to compete with T-2-horseradish peroxidase (HRP) conjugated for the specific recognizing sites of immobilized anti-T-2 monoclonal antibodies. The HRP, in the presence of hydrogen peroxide (H2O2), catalyzes the oxidation of 4-tert-butylcatechol (4-TBC), whose back electrochemical reduction was detected on the nanostructured electrode at −0.15 V. Thus, at low T-2 concentrations in the sample, more enzymatically conjugated T-2 will bind to the capture antibodies, and, therefore, a higher current is expected. The detection limits found for electrochemical immunosensor, and commercial ELISA procedure were 0.10 μg kg−1 and 10 μg kg−1, and the intra- and inter-assay coefficients of variation were below 5.35% and 6.87%, respectively. Finally, our microfluidic immunosensor to T-2 toxin will significantly contribute to faster, direct, and secure in situ analysis in agricultural samples.

YÜKSEK ENTROPİLİ OKSİ-HİDROKSİTLERIN ÜRETİLMESİ, KARAKTERİZASYONU VE OKSİJEN ÇEVRİM REAKSİYONU ELEKTRO KATALİZÖRÜ OLARAK UYGULANMASI

The need for energy is rising quickly, and the usage of fossil fuels is contributing to the greenhouse effect and environmental pollution, both of which are raising public concerns. The development of novel electrochemical energy storage techniques as well as the creation of cleaner, more sustainable energies have both become highly researched topics as a result of this condition. New functional materials are being investigated for the advancement of energy storage. High entropy hydroxides (HEH) have lately been emerged as promising electrocatalyst for universal water splitting reactions, which are central for solid oxide fuel cells, hydrogen production and metal-air batteries. In this work, a cost-effective and scalable fabrication method was applied to fabricate several HEH on Nickel foam through single-step electrodeposition technique. Results showed that high-entropy FeCoNiMnOOH exhibits excellent OER activity with a low overpotential of 151 mV at current density of 100 mA cm−2, which is associated with it’s defective structure.

Bottom-Up Signal Boosting with Fractal Nanostructuring and Primer Exchange Reaction for Ultrasensitive Detection of Cancerous Exosomes.

Exosomes are emerging as promising biomarkers for cancer diagnosis, yet sensitive and accurate quantification of tumor-derived exosomes remains a challenge. Here, we report an ultrasensitive and specific exosome sensor (NPExo) that initially leverages hierarchical nanostructuring array and primer exchange reaction (PER) for quantitation of cancerous exosomes. This NPExo uses a high-curvature nanostructuring array (bottom) fabricated by single-step electrodeposition to enhance capturing of the target exosomes. The immuno-captured exosome thus provides abundant membrane sites to insert numerous cholesterol-DNA probes with a density much higher than that by immune pairing, which further allows PER-based DNA extension to assemble enzyme concatemers (up) for signal amplification. Such a bottom-up signal-boosting design imparts NPExo with ultrahigh sensitivity up to 75 particles/mL (i.e., <1 exosome per 10 μL) and a broad dynamic range spanning 6 orders of magnitude. Furthermore, our sensor allows monitoring subtle exosomal phenotypic transition and shows high accuracy in discrimination of liver cancer patients from healthy donors via blood samples, suggesting the great potential of NPExo as a promising tool in clinical diagnostics.

Eco-friendly fabrication of nonenzymatic electrochemical sensor based on cobalt/polymelamine/nitrogen-doped graphitic-porous carbon nanohybrid material for glucose monitoring in human blood

The design and development of eco-friendly fabrication of cost-effective electrochemical nonenzymatic biosensors with enhanced sensitivity and selectivity are one of the emerging area in nanomaterial and analytical chemistry. In this aspect, we developed a facile fabrication of tertiary nanocomposite material based on cobalt and polymelamine/nitrogen-doped graphitic porous carbon nanohybrid composite (Co-PM-NDGPC/SPE) for the application as a nonenzymatic electrochemical sensor to quantify glucose in human blood samples. Co-PM-NDGPC/SPE nanocomposite electrode fabrication was achieved using a single-step electrodeposition method under cyclic voltammetry (CV) technique under 1 M NH4Cl solution at 20 constitutive CV cycles (sweep rate 20 mV/s). Notably, the fabricated nonenzymatic electroactive nanocomposite material exhibited excellent electrocatalytic sensing towards the quantification of glucose in 0.1 M NaOH over a wide concentration range from 0.03 to 1.071 mM with a sensitive limit of detection 7.8 μM. Moreover, the Co-PM-NDGPC nanocomposite electrode with low charge transfer resistance (Rct∼81 Ω) and high ionic diffusion indicates excellent stability, reproducibility, and high sensitivity. The fabricated nanocomposite materials exhibit a commendable sensing response toward glucose molecules present in the blood serum samples recommends its usage in real-time applications.

Evolution of novel nanostructured MoCoFe-based hydroxides composites toward high-performance electrochemical applications: Overall water splitting and supercapacitor

Metal hydroxides are versatile and appealing electrode materials owing to their merits such as easy room-temperature synthesis, nanostructures formation, higher conductivity, crystallite or non-crystallite formation, porous structures, etc. Herein, nanostructured ternary transition metal (M = Mo, Co, Fe) hydroxides (TTMHs) are successfully grown on nickel foams via template-free single-step electrodeposition for overall water splitting and supercapacitor applications. Interestingly, numerous element ratios of Mo5+, Co2+, and Fe3+ in the electrodeposition precursor solutions manifested novel nanostructures viz nanosheets, nanoflakes, nanoparticles, and nanograss-like structures were evolved for different precursor solutions. For water splitting, a negative electrode prepared using aqueous Mo:Co:Fe (4.0:4.0:2.0 M ratio) metal salt solution that exhibited excellent hydrogen evolution activity with 98 mV overpotential, whereas a positive electrode (Mo:Co:Fe = 3.0:3.5:3.5) shows efficient oxygen evolution with 227 mV overpotential, and a full cell assembled from these active electrodes exhibited lower 1.56 V cell voltage at 10 mAcm−2. For the supercapacitor, a working electrode with composition Mo:Co:Fe = 6.0:2.0:2.0 showed 3354.7 mFcm−2 high areal capacitance at 1.0 mAcm−2 with excellent retention (91% after 3000 cycles). An asymmetric supercapacitor (ASC) device was fabricated that exhibited enormous energy and power densities of 1.27 × 10−3 Whcm−3 and 3.75 Wcm−3, respectively. The high-performances of both devices (water splitting full cell and supercapacitor) are due to the unique composition of hybrid electrodes (with nanostructured morphology) and synergistic effects. The present investigation demonstrates a simple strategy for preparing potential TTMHs composite electrodes with the evolution of different morphologies for multiple electrochemical applications.

Inter-Electronic Interaction between Ni and Mo in Electrodeposited Ni-Mo-P on 3D Copper Foam Enables Hydrogen Evolution Reaction at Low Overpotential.

Electrocatalytic hydrogen evolution reaction (HER) via water electrolysis has been considered the most effective and sustainable route to produce clean hydrogen. Designing and structure optimization are the two important parameters to develop an affordable, easy to fabricate, and stable non-noble metal electrocatalyst for the production of hydrogen as a clean, sustainable, and green fuel. Herein, we have synthesized Ni-Mo-P on copper foam (Cuf) via a facile single-step electrodeposition method, which can show stratospheric efficiency toward HER with a Tafel slope of 67 mV dec-1 and a very low overpotential of only 53 mV at a current density of 20 mA cm-2. Cuf acts as a conducting substrate support and the existence of the inter-electronic effect between Ni and Mo results in substantial catalytic activity toward hydrogen generation. In addition to this, the catalyst shows long time stability of around 97.5 h with almost negligible degradation under the applied overpotential for HER in alkaline media. This work features the significance of structure design and construction of non-noble metal catalysts via a simple method for efficient hydrogen generation.

(Digital Presentation) Electrodeposition of Free-Standing Porous Cu Frameworks for Energy Applications

Recently, a convenient method has been suggested to produce a highly porous metal structure such as Cu using a single-step electrodeposition method [1]. In this approach, hydrogen bubbles are used as dynamic templates during the metal electrodeposition process to create the micro-porous structure. However, the pore walls of the porous layers often grow in ramified dendritic structure, which results in limited mechanical stability and creates challenged for applications in compact devices.In this contribution, a novel approach will be discussed to improve the mechanical stability of these porous structures by employing a second electrodeposition step. This process greatly reduces the number of dendrites within the pore walls making the porous layer more compact and thus improving the mechanical stability significantly. Furthermore, a complete separation of the porous layer from the flat substrate can be achieved by ultrasonication to obtain a free-standing porous Cu framework. Some parameters such as the layer thicknesses and pore sizes can be tuned easily by changing the current density and the electrodeposition time, respectively.The use of thus prepared free-standing porous Cu frameworks will be discussed for photoelectrochemical (PEC) water splitting and CO2 reduction. For the PEC water splitting application, a photoactive Cu2O layer is electrodeposited on the free-standing porous Cu framework. A homogenous coating of the Cu2O can be achieved and the PEC performance shows a significant increase of photocurrents by more than 80 % at 0 V vs. RHE in comparison to the Cu2O planar substrate [2]. For the CO2 reduction application, a large sample with10 cm2 geometric surface area was successfully prepared. The sample was used in a custom-made electrochemical cell with a cation exchange membrane as a separator. CO2 gas in a high humidity environment is transported to the free-standing porous Cu working electrode via a membrane pump in a closed-loop system. Our preliminary results show formation of ethylene and ethane gas using gas chromatography which indicates a successful reduction reaction of the CO2.[1] H.C. Shin., M. Liu. Chem Mater 16:5460–5464 2004. Doi:10.1021/cm048887b[2] M. Kurniawan, M. Stich, M. Marimon, M. Camargo, R. Peipmann, T. Hannappel, A. Bund, J. Mater. Sci. 2021, Doi:10.1007/s10853-021-06058-y

Nickel nanobrush platform for a magnetic field-assisted electrochemical response enhancement

A single-step electrochemical procedure to synthesize a brush-like platform, which composed of a nickel nanowire array attached to a nickel continuous layer acting as a solid base, is described. Room temperature hysteresis properties of this brush-like architecture (nanobrush) and those of the individual components (nanowires and layer) are determined. It is shown that the direction of the nanobrush magnetic easy axis may be tailored, being also possible to control the magnetic system's coercivity and remanence. The electrochemical response and the catalytic activity of a Ni nanobrush towards the redox probes [Fe(CN) 6 ] 4-/3- and ethanol were evaluated in the presence and absence of an applied magnetic field. The external field strongly affects the system's behavior by enhancing the electrode charge-transfer response, even at fields as low as 6 mT. This improvement was further investigated by Electrochemical Impedance Spectroscopy and Electrochemical Capacitance Spectroscopy studies. It is concluded that the enhanced electrochemical charge-transfer process of the Ni nanobrush electrode, with a magnetic field applied along the Ni nanowires axis, arises from a larger electroactive area. • A Ni nanobrush electrode is obtained by a single step electrodeposition route. • Nanobrush architecture consists of Ni NWs perpendicularly attached to a Ni layer. • The whole platform easy axis orientation is controlled by the brush shape and crystalline texture. • Catalytic activity towards redox probes Fe(CN) 6 −4/−3 and ethanol are evaluated. • A small magnetic field drastically reduces the nanobrush impedance.

Electrodeposited Binder-free Mn-Co-S Nanosheets toward High Specific-Energy Aqueous Asymmetric Supercapacitors

A simple single-step electrodeposition technique was followed for the three-dimensional (3D)-interconnected binary metallic manganese-cobalt sulfide nanosheets on nickel foam (MnCoS@NF). The architecture and chemical composition of the as-synthesized binder-free electrodes were analyzed by field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The MnCoS@NF achieves exceptionally high specific capacitance (1952.8 F g–1 at 2 A g–1) along with high cycle stability in a three-electrode cell measurement. Furthermore, an aqueous asymmetric supercapacitor (AAS) device was designed using electrodeposited MnCoS@NF in combination with reduced graphene oxide-coated NF (rGO@NF) as a positrode and negatrode, respectively. This device was able to provide very high specific energy (105.1 W h kg–1) at a specific power (7.25 kW kg–1) along with high cyclic stability (93.9% of specific capacitance retained after 3000 consecutive GCD cycles), which demonstrates its excellent candidature in supercapacitor applications.

Oxygen reduction reaction and proton exchange membrane fuel cell performance of pulse electrodeposited Pt–Ni and Pt–Ni–Mo(O) nanoparticles

Proton exchange membrane fuel cells (PEMFCs) are an important alternative to fossil fuels and a complement to batteries for the electrification of vehicles. However, their high cost obstructs commercialization, and the catalyst material, including its synthesis, constitutes one of the major cost components. In this work, Pt–Ni and Pt–Ni–Mo(O) nanoparticles (NPs) of varying composition have been synthesized in a single step by pulse electrodeposition onto a PEMFC's gas diffusion layer. The proposed synthesis route combines NP synthesis and their fixation onto the microporous carbon layer in a single step. Both Pt–Ni and Pt–Ni–Mo(O) catalysts exhibit extremely high mass activities at oxygen reduction reaction (ORR) with very low Pt loadings of around 4 μg/cm2 due to the favorable distribution of NPs in contact with the proton exchange membrane. Particle sizes of 40–50 nm and 40–80 nm were obtained for Pt–Ni and Pt–Ni–Mo(O) systems, respectively. The highest ORR mass activities were found for Pt67Ni33 and Pt66Ni32–MoOx NPs. The feasibility of a single-step electrodeposition of Pt–Ni–Mo(O) NPs was successfully demonstrated; however, the ternary NPs are of more amorphous nature in contrast to the crystalline, binary Pt–Ni particles, due to the oxidized state of Mo. Nevertheless, despite their heterogeneous nature, the ternary NPs show homogeneous behavior even on a microscopic scale.

Single-step electrodeposition of CZTS thin film: Influence of complexing agent concentration

Single-step electrodeposition of CZTS thin film: Influence of complexing agent concentration

Study on electrodeposited CuFe film on Cu electrode as an efficient catalyst for electrochemical reduction of nitrate

In this research, a novel CuFe catalyst was fabricated using a simple, single-step electrodeposition method on a traditional Cu electrode. CuFe films from various electrodeposition baths with different Cu and Fe ratios were prepared by chronopotentiometry and characterised by X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray analysis (EDX), and Pb underpotential deposition (Pb-UPD). The Cu electrode coated with CuFe8020 (from electrodeposition bath containing 80% Cu and 20% Fe) showed the highest reduction current among the film produced. The Cu electrode coated with CuFe8020 exhibited three times higher nitrate reduction efficiency and less undesired products like NO2− và NH4+ than the traditional Cu.

Growth of Cu2ZnSnS4 thin film absorber layer on transparent conductive oxides and molybdenum substrates by electrodeposition for photovoltaic application

Cu2ZnSnS4 (CZTS) absorber layer for the photovoltaic application was successfully deposited on different substrates, indium tin oxide (ITO), fluorine-doped tin oxide (FTO) and molybdenum (Mo) using a single step electrodeposition process. The structural, morphological and optical properties of the CZTS films were analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and photoluminescence (PL). The present study was designed to determine the effect of the substrate on the kesterite thin film properties grown by electrodeposition. The results confirm that the CZTS properties depend on the substrate nature. Furthermore, the CZTS films deposited on Mo substrate was found more appropriate for CZTS based solar cells due to their crystallinity and good morphology as well as their suitable energy bandgap around 1.6 eV.

FeCoNiS Nanoparticles Integrated with Nitrogen−Doped Vertically Oriented Graphene via Single−Step Electrodeposition: An Efficient Bifunctional Catalyst for Overall Water Splitting

The development of transition metal electrocatalysts to replace precious metal electrocatalysts is essential for the development of sustainable water splitting technology for the mass production of clean hydrogen. FeCoNiS/NVG (N-doped vertically oriented graphene) is fabricated via single-step electrodeposition. Benefiting from the vertical structure of FeCoNiS/NVG and intrinsic catalytic activity of FeCoNiS, FeCoNiS/NVG displays excellent catalytic activities toward the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), with overpotentials of 126 and 347 mV at 10 mA cm−2, respectively. The overpotentials of FeCoNiS/NVG are similar to those of commercial Pt/C (100 mV) and IrO2 (329 mV). The Faraday efficiency of FeCoNiS/NVG for overall water splitting is about 95%. FeCoNiS/NVG also exhibits long-term stability for HER and OER. This work demonstrates the great potential of iron-group metal sulfides for overall water splitting.

One-step electrodeposition of CuSCN/CuI nanocomposite and its hole transport-ability in inverted planar perovskite solar cells

The synthesis of CuSCN/CuI nanocomposite by single-step electrodeposition is developed. The surface morphology and film thickness are controlled by changing the electrochemical potential and deposition time. The mixed-phase formation of CuSCN/CuI is confirmed through x-ray diffraction and Raman spectral analysis. Nanopetal (NP) like morphology of CuSCN/CuI is observed in FESEM micrographs. Interestingly, the NPs density and thickness are increased with increasing the deposition potential and time. The device fabricated using CuSCN/CuI nanocomposite as a hole transport layer (HTL) which is grown for 2 min delivers the best photovoltaic performance. The maximum power conversion efficiency of 18.82% is observed for CuSCN/CuI NP with a density of 1153 μm−2 and thickness of 142 nm. The charge transfer ability of the CuSCN/CuI NP HTL is analyzed by electrochemical impedance spectroscopy. Based on the observation, moderate charge transport resistance and optimum film thickness are required for achieving maximum photovoltaic performance in perovskite solar cells (PVSCs). Thus, the developed CuSCN/CuI NP HTL is a potential candidate for PVSCs.

Quantized electronic transitions in electrodeposited copper indium selenide nanocrystalline homojunctions

Pairing semiconductors with electrochemical processing offers an untapped opportunity to create novel nanostructures for practical devices. Here we report the results of one such pairing: the in-situ formation of highly-doped, interface-matched, sharp nanocrystalline homojunctions (NHJs) with single step electrodeposition of two copper-indium-selenide (CISe) compounds on flexible foil. It produces a homogenous film, comprising inherently ordered, 3-dimensional interconnected network of pn-CISe NHJs. These CISe NHJs exhibit surprising non-linear emissions, quantized transitions, large carrier mobility, low trap-state-density, long carrier lifetime and possible up-conversion. They facilitate efficient separation of minority carriers, reduce recombination and essentially function like quantum materials. This approach mitigates the material issues and complex fabrication of incumbent nanoscale heterojunctions; it also overcomes the flexibility and scale-up challenges of conventional planar pn junctions. The self-stabilized CISe NHJ film can be roll-to-roll processed in ambient atmosphere, thus providing a promising platform for a range of optoelectronic technologies. This concept exemplified by CISe compounds can be adapted to create nano-scale pn junctions with other inorganic semiconductors.

Directing Reaction Paths to Electrodeposit Cu-In-Se Films with Alternate Morphologies

Electrodeposition approach has been widely explored for CuInSe2 and its alloys as a low cost, scalable alternative to vacuum methods. Achieving device quality electrodeposited films of ternary compounds requires a profound knowledge of the intricate reaction mechanisms and the possible alternate paths that determine the film composition and electronic properties. Various studies of the Cu-In-Se (CISe) system have enabled unraveling the rather complicated reaction mechanisms and ultimately electrodeposit stoichiometric CuInSe2 [1-7].The complexity of the reaction mechanism for the ternary system CuSe system arises mainly from the multiple oxidation states of its component elements. Single step electrodeposition (SSE) from a Cu+/In3+/Se4+ electrolyte is challenging due to many competing chemical (C) and electrochemical (E) reactions that invariably create multiple solid phases, as partly illustrated in the Fig. 1R schematic. Experimental investigations reveal the simultaneous reduction of Cu2+ and Se4+ ions (E1 ) and chemical assimilation of In (C1 ) to form CuSe(In) within the first minute [6,7]. The CuSe(In) further reduces to Cu2Se and Se2- (E2 ). The Se2- ions may react with Se4+ ions to form Se0 (C2 ) or with In3+ ions to form In2Se3 (C3 ). Subsequent chemical reactions of In3+ ions with the Cu2Se, In2Se3 and Se2- reaction products form CuInSe2 (C4 ) and further CuIn3Se5 (C5 ) if sufficient flux of In3+ is available, Fig. 1R.The reactions leading to the formation of the CISe compounds are thermodynamically driven, which enables SSE of self-stabilized stoichiometries from a single solution, at a single potential, ED. Manipulation of process parameters (temperature, electrolyte composition, pH, mass transport and deposition potential) allows controlling the kinetics of competing reactions for SSE of stoichiometric CuInSe2, CuIn3Se5, or a mixture of the two compounds, Fig. 1M. A brief post-anneal enhances crystallinity without altering the film composition [7, 8]. Surface analytical microscopies and spectroscopies support the fortuitous formation of surprisingly ordered, interlinked, space-filling CISe nanocrystals forming interconnected network of sharp, abrupt 3-dimensional p-CuInSe2/n-CuIn3Se5 nanocrystalline homojunctions (NHJs). This approach generates CISe NHJ films with homogeneous composition on large foil, facilitating easy scale-up via roll-to-roll processing.Besides the processing advantages, the CISe NHJ films exhibit extraordinary electro-optical attributes that can potentially maximize spectral absorption and reduce recombination losses. The specific NHJ structure enables efficient separation and transport of free carriers, and essentially performs the same functions as standard planar pn junctions. The CISe nanocrystals are very different from colloidal nanocrystals, used in state-of-the-art bulk homojunction devices; they exhibit high doping densities, mixed conductivity and multiple bandgaps. These distinctive innate attributes of CISe films naturally create ordered morphology and facilitate interconnections between the nanocrystals to form optimum NHJ structures. The CISe pn NHJ layer can be directly inserted between 2 band-aligned contact electrodes to produce high performance practical 3G devices, Fig, 1L.The direct deposition of CISe pn NHJ resolves problems with current approaches for device fabrication based on conventional planar pn junctions, organic/colloidal bulk heterojunctions or inorganic ordered heterojunctions. The totality manifests a highly significant advance in semiconductor processing, providing a generally accessible, low-cost electrochemical method to fabricate high quality pn NHJs in simple flexible thin-film form factor with inorganic material systems. The films can be directly used for harvesting solar energy on a large scale for photoelectrochemical or photovoltaic applications and other devices applications, including light emitting diodes. References K. Mishra and K. Rajeshwar, J. Electroanal. Chem., 271 279 (1989).Pottier and G. Maurin, J. Appl. Electrochem. (1991).Massaccesi, S. Rouquette-Sanchez, J. Vedel, J. Electrochem. Soc., 140, 2540 (1993).Froment, M. C. Bernard, R. Cortes, B. Mokili, D. Lincot, J. Electrochem. Soc, 142 (1995) 2642.Thouin and J. Vedel, J. Electrochem. Soc. 142, 2996 (1995)Menezes, Mat. Res. Soc. Symp. Proc., S. Francisco, 426, 189 (1996).Li, S. S. Shaikh, S. Menezes, Thin Solid Films, 524, 20-25 (2012).Menezes and A. Samantilekke, Scientific Reports, https://rdcu.be/3AD7 (2018). Figure 1. Schematics of (R) Reaction Mechanism (M) SSE of p-CuInSe2/n-CuIn3Se5 NHJ thin film and (L) CISe NHJ device Figure 1