Potentiostatic Deposition Research Articles

Electrochemical and structural investigation of BixTey thin films electrodeposited on ITO substrate

Bismuth telluride films with various stoichiometries BixTey have been successfully elaborated by potentiostatic deposition on indium tin oxide (ITO) substrate from an acidic solution containing a mixture of different concentrations of Bi3+ and HTeO2+ ions. The electrochemical study using cyclic voltammetry and chronoamperometry shows that the electrodeposition of bismuth telluride is a quasi-reversible reaction controlled by the diffusion process and the composition of the reaction mixture controls the BixTey stoichiometry. It was found, from electrochemical and EDS analysis, that a mixture in stoichiometric proportions leads to the formation of bismuth tellurium Bi2Te3, an excess of telluryl ion HTeO2+ gives a product rich in tellurium Bi2-xTe3+x, but a high concentration of Bi3+ (compared to the stoichiometry) gives rise to the electrodeposition of a compound rich in bismuth Bi2+xTe3-x. The chronoamperometric analysis of current density-time transients using Scharifker-Hills model showed that the mechanism of deposition and growth of BixTey on ITO substrate takes place according to a progressive 3D nucleation for low Bi3+ concentration and 3D instantaneous nucleation for higher concentration. The morphology of the BixTey films is strongly depending to the electrolytes composition. The X-ray diffraction characterization shows that the crystalline structure of bismuth tellurium BixTey produced is of the rhombohedral type.

The Electrodeposition of Derivatives of Pyrrole and Thiophene on Brass Alloy in the Presence of Dodecane-1-Sulfonic Acid Sodium Salt in Acidic Medium and Its Anti-Corrosive Properties

In this paper, potentiostatic and galvanostatic deposition (electrochemical deposition) processes have been used for the obtained of a new composite polymer: N-methylpyrrole-sodium 1-dodecanesulfonate/poly 2-methylthiophene (PNMPY-1SSD/P2MT) coatings over brass electrode for corrosion protection. The sodium 1-dodecanesulfonate as a dopant ion employed in the electropolymerization procedure can have a meaningful effect on the anti-corrosion protection of the composite polymeric film by stopping the penetration of corrosive ions. The composite coatings have been characterized by cyclic voltammetry, Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) procedures. The anti-corrosion performance of PNMPY-1SSD/P2MT coated brass has been investigated by potentiostatic and potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) practices in 0.5 M H2SO4 medium. The corrosion assessment of PNMPY-1SSD/P2MT coated brass was noticed to be ~9 times diminished than of uncoated brass, and the efficiency of these protective coatings of this coating is above 90%. The highest effectiveness is realized by the electrochemical deposition of PNMPY-1SSD/P2MT obtained at 1.1 V and 1.4 V potential applied and at 0.5 mA/cm2 and 1 mA/cm2 current densities applied in molar ratio 5:3. The outcomes of the corrosion tests denoted that PNMPY-1SSD/P2MT coatings assure good anti-corrosion protection of brass in corrosive media.

Hierarchical Design of CuO/Nickel-Cobalt-Sulfide Electrode by a Facile Two-Step Potentiostatic Deposition.

Herein, a scalable electrodeposition strategy is proposed to achieve hierarchical CuO/nickel-cobalt-sulfide (NCS) electrodes using two-step potentiostatic deposition followed by high-temperature calcination. The introduction of CuO provides support for the further deposition of NSC to ensure a high load of active electrode materials, thus generating more abundant active electrochemical sites. Meanwhile, dense deposited NSC nanosheets are connected to each other to form many chambers. Such a hierarchical electrode prompts a smooth and orderly transmission channel for electron transport, and reserves space for possible volume expansion during the electrochemical test process. As a result, the CuO/NCS electrode exhibits superior specific capacitance (Cs) of 4.26 F cm-2 at 20 mA cm-2 and remarkable coulombic efficiency of 96.37%. Furthermore, the cycle stability of the CuO/NCS electrode remains at 83.05% within 5000 cycles. The multistep electrodeposition strategy provides a basis and reference for the rational design of hierarchical electrodes to be applied in the field of energy storage.

Investigation on corrosion inhibition performance of polypyrrole coating on Q235 steel in civil structure

The use of conductive polymers with excellent electrochemical properties and environmental friendliness is becoming increasingly important in the field of metal corrosion inhibition. To this end, a polypyrrole anticorrosive coating was synthesized on the surface of structural steel Q235 via potentiostatic deposition. By altering the deposition potential value in a stirred ice bath, the best deposition performance was achieved. It was found that potentiostatic deposition could yield effective anticorrosive coatings over a wide voltage range. The electrochemically deposited films were all Ppy films with C2O42-. This proposed coating has extended the lifespan of metal materials in civil engineering applications.

Recovery of Rare Earth Elements from Spent NdFeB Magnets: Metal Extraction by Molten Salt Electrolysis (Third Part)

The results obtained from the work on a concept of a recycling process for NdFeB magnets to recover rare earth elements for remanufacturing similar magnets are presented. This paper investigates the viability of extracting rare earth metals from magnet recycling-derived oxide (MRDO) by means of molten salt electrolysis. The MRDO was produced from spent NdFeB magnets through oxidation in air and subsequently carbothermic reduction under an 80 mbar Ar gas atmosphere. This MRDO contained roughly 33 wt.% Nd and 10 wt.% Pr. The electrochemical reduction process of the MRDO on molybdenum electrodes in NdF3 + LiF and NdF3 + PrF3 + LiF fused salts systems was investigated by cyclic voltammetry and chronoamperometry measurements. The resulting electrolytes and electrodes were examined after potentiostatic deposition by scanning electron microscopy (SEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), and X-ray diffraction (XRD) analysis. The electrodeposited metals appeared to accumulate on the cathode and X-ray diffraction analysis confirmed the formation of metallic Nd and Pr on the working substrate. The suitability of the obtained alloy intended for the remanufacturing of NdFeB magnets was then evaluated.

Seedless electrodeposition of Cu thin films on ALD Ru diffusion barriers with different electrical properties

Seedless Cu electrodeposition was performed directly on 10 nm atomic-layer-deposited (ALD) Ru diffusion barrier layer for Cu interconnect application in microelectronic devices. N2 gas flow rate ratio of Ru ALD process was varied between 0.24 and 0.86 to manipulate the electrical property of resultant ALD Ru layers. The nucleation and growth characteristic of Cu on ALD Ru changed depending on the electrical resistivity of ALD Ru layer under the potentiostatic deposition of Cu in an additive-free Cu-ammonia-citrate (Cu-NH3-Cit) electrolyte. As a result, a less resistive ALD Ru layer, which was formed at a lower N2 gas flow rate ratio, led to a lower electrical resistivity of Cu thin film.

Direct electrochemical extraction of metallic Li from a molecular liquid–Based electrolyte under ambient conditions

The high chemical activity of metallic Li hinders its efficient electrochemical extraction at low temperatures, necessitating the use of energy- and cost-intensive methods such as vacuum thermal reduction or electrodeposition from ionic-liquid and molten-salt electrolytes. Herein, we report the direct room-temperature electrowinning of metallic Li from a simple low-cost electrolyte, namely a solution of LiCl in dimethylacetamide (DMAc), determine the optimal concentration of LiCl, and examine the redox processes in the optimized system. Potentiostatic deposition on high-purity Al is shown to induce solid-state cathode alloying and thus produce a uniform, flat, and dense coating of a LiAl master alloy comprising spherical clusters formed by LiAl alloy nanosheets. Finally, the direct smelting of electrodeposited films is proposed as a method of rapidly realizing the “thin film” to “bulk” transformation of electrodeposited materials to stabilize metallic Li and form bulk Li-based alloys. Thus, this study provides a basis for the continuous, low-cost, sustainable, and fast electrochemical production of bulk active metals or their alloys.

Electrodeposited Pd nanoparticles on polypyrole/nickel foam for efficient methanol oxidation

The present work describes the Ni foam (Ni–F)/polypyrrole (PPy)/palladium (Pd) (Ni–F/PPy/Pd) multilayered catalysts via a facile electrochemical technique. Potentiostatic deposition of PPy on the surface of Ni–F is followed by galvanostatic deposition of Pd nanoparticles on Ni–F/PPy acted as supports for electrochemical deposition of Pd nanoparticles. The produced catalysts are utilized for electrocatalytic methanol oxidation in alkaline media. Chronoamperometry (CA), cyclic voltammetry (CVs), and electrochemical impedance spectroscopy (EIS) techniques are used to examine the electrocatalytic performance of Ni–F/PPy/Pd based electrodes for methanol oxidation. The polypyrrole modification on Ni–F leads to an improvement in the electrocatalytic activity of the Ni-F/PPY-Pd catalysts toward methanol oxidation. As an open-pored, porous metal with high electrical conductivity, nickel foam produces a substantial amount of active area during the modification of Pd and polypyrrole, which results in significant catalytic activity and a rapid rate charge transfer reaction kinetics on methanol oxidation. The Ni–F/PPy/Pd10 catalyst exhibits enhanced specific activity than its counterparts and a reduced onset potential for methanol oxidation, as well as a low Tafel slope. Based on these results, Ni–F/PPy/Pd10 is suggested as a good material for the anode in the electrocatalytic oxidation of methanol.

An electrochemical sensor for purine base detection with ZIF-8-derived hollow N-doped carbon dodecahedron and AuNPs as electrocatalysts

In this paper, a novel electrochemical sensor was constructed for the detection of purine bases. Ultrafine carbide nanocrystals confined within porous nitrogen-doped carbon dodecahedrons (PNCD) were synthesized by adding molybdate to ZIF-8 followed by annealing. With MoC-based PNCDs (MC-PNCDs) as the carrier, gold nanoparticles (AuNPs) were deposited on the electrode surface via potentiostatic deposition as the promoter of electron transfer, forming a AuNPs/MC-PNCDs/activated glassy carbon electrode (AGCE) sensor. MC-PNCDs had a large specific surface area, which combined with the excellent electrocatalytic activity of AuNPs, synergistically improved the electrocatalytic activity. The morphology and structure of the electrode surface modifier were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray photoelectron spectroscopy, infrared spectroscopy, X-ray diffraction, nitrogen adsorption-desorption analysis, and electrochemical characterization. Under the optimal conditions, the linear detection range of guanine (G) and adenine (A) was 0.5-160.0 μM, and the detection limits (S/N=3) were 72.1 and 69.6 nM, respectively. AuNPs/MC-PNCDs/AGCE was successfully constructed, and was used to simultaneously detect G and A with high sensitivity and selectivity. Moreover, the sensor was successfully used to detect G and A in herring sperm DNA samples.

Electrodeposition of high-quality Cr coatings with solid solution Al from Cr2+ electrolyte

Smooth and dense nanocrystallline Cr coatings with solid solution Al have been electrodeposited using the proposed Cr2+ electrolyte without any additives, i.e., AlCl3–1-ethyl-3-methyl-imidazolium chloride (AlCl3–EMIC) ionic liquid dissolving CrCl2. Systematic study demonstrates that 2 to 50 at.% Al is in solid solution with body-centered-cubic (BCC) Cr. The solid solution alloys deposited at relatively positive potentials are attributed to the underpotential deposition (UPD) of Al on Cr deposits, which is confirmed by cyclic voltammetry (CV), potentiostatic deposition and X-ray photoelectron spectroscopy (XPS). The coating microstructure, surface morphology and composition are dependent on the deposition potential. The Vickers hardness is 850HV0.01, which is comparable to that of Cr coatings electrodeposited from aqueous solution. The corrosion current density is as low as 2.8 × 10−8A/cm2, which is an order of magnitude lower than that of pure Cr sheet and pure Ni sheet. In addition, the formation process and mechanism of divalent chromium ions are discussed in detail. Our work will have significant impact on engineering application for the excellent performance and the avoidance in hydrogen embrittlement.

Eco-friendly method for construction of superhydrophobic graphene-based coating on copper substrate and its corrosion resistance performance

In this work, Ni and Ni-graphene, Ni-G, films were electrodeposited on copper substrate by potentiostatic deposition. To achieve superhydrophobicity, myristic acid, MA, was used to modify the surface of the electrodeposited coatings. The manufactured Ni film modified with myristic acid, Ni-MA, and the Ni-G film modified with myristic acid, Ni-G-MA, show excellent superhydrophobic, SHP, properties with a water contact angle of 159° and 162°, respectively. The surface morphology of the prepared SHP films was investigated using a Scanning Electron Microscope, and the results revealed micro-nano structures in both Ni-MA and Ni-G-MA films. The Fourier Transform Infrared Spectrophotometer data showed that the Ni-MA and Ni-G-MA films were successfully grafted on the copper metal. The Ni-G-MA film possessed higher chemical stability and mechanical abrasion resistance than Ni-MA. The Ni-MA and Ni-G-MA films exhibit long-term durability in the outdoor environment for more than four months. The potentiodynamic polarization and electrochemical impedance spectroscopy results demonstrated that the SHP films on the copper substrate exhibit remarkable corrosion resistance in 0.5 M NaCl.

Electrodeposition of Lithium Manganese Oxide Cathodes for Lithium-Ion Batteries

Lithium manganese oxides (LMOs) have drawn significant interest as cathode materials for lithium (Li)-ion batteries due to their high thermal stability, high energy density, and a longer cycle life at a lower cost than lithium cobalt oxides. A significant amount of research has been conducted to prepare cathode materials for Li-ion batteries ex-situ and then to integrate them into electrodes after forming a slurry with the binder and deposition onto the current collector. An alternative pathway to achieve active LMO cathodes is to directly synthesize them on the current collector via electrodeposition (ED). Using ED not only could improve active material utilization and electrode mechanical properties, but it may also reduce the cost of electrode fabrication as well as provide a pathway for facile recycling of spent manganese from a number of applications (e.g. alkaline batteries). To date, a few studies have reported the synthesis of LMOs by electrodeposition [1,2]. When doing this, the first step of the process is to deposit manganese oxide (s), MnxOy. Then, the oxide is lithiated to form the LMOs (i.e. LiMnxOy). Despite the fact that this process has been demonstrated, and active materials with reasonable capacity have been shown, it is presently unknown what LiMnxOy phase or phases are active. It is also not definitively known which MnxOy phase(s) is(are) involved in the transformation. To move the application of direct deposition of manganese oxide active phases closer to reality, a critical understanding of the solid-state chemistry for its conversion and energy storage is needed. In this study, Mn oxides were electrochemically prepared by potentiostatic deposition on multiple substrates and treated by lithium hydroxide. After that, the heat treatment of the lithiated deposits gave a mixture of LMOs as the cathode materials on the substrate. This talk will discuss the likely reactions for the formation of LMOs as well as their chemistry during charge/discharge. The morphology and the elemental composition of LMOs will be shown by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The composition and presence of crystalline Mn oxides and LMOs will be clarified by X-ray diffraction. Lastly, results will be shown regarding the cycle performance of the electrochemically prepared LMOs as well as the crystalline phases present after charge-discharge.

Electrochemical Detection of Nitrite Ions Using PEDOT Based Films

Poly (3,4-ethylenedioxythiophene) (PEDOT) is an important conducting polymer that is widely studied for applications in photovoltaic devices, thermoelectric materials, batteries, capacitors and sensors [1]. In the field of sensors, PEDOT and PEDOT composites synthesized by chemical and electrochemical methods have been used for the detection of organic and inorganic analytes [2]. In particular, the performance of the composites of PEDOT with nanomaterials (mono and bi-metallic nanoparticles, graphene and nanotubes) has been thoroughly investigated in the last years because the incorporation of those nanostructures can significantly improve the sensing properties of the pristine polymer [3,4]. However, to the best of our knowledge the effect of the content of hollow PdAu nanoparticles in PEDOT composites for the detection of nitrite, an important environmental pollutant, has not been reported before.In this work, PEDOT films were prepared by cyclic voltammetry and under amperometric and potentiostatic conditions from a solution of EDOT, LiClO4 and SDS (sodium dodecyl suphate). The films were characterized by scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX). 500 nm- and 300 nm-thick PEDOT films deposited on glassy carbon were used for the electrochemical detection of nitrite by differential pulse voltammetry. 500 nm-thick films shown a higher sensitivity towards NO2 - ions (0.027 μA μM-1). Hollow nanoparticles of gold and palladium were synthesized by a galvanic replacement reaction using Na2PdCl4. PEDOT films were codeposited with the hollow PdAu nanoparticles at constant potential. The performance of the composites with different contents of the bimetallic nanoparticles (3,6,12,15,24 and 30% of the total mass of nanoparticles) were evaluated for the detection of nitrite ions in the range of 50 to 250 μM nitrite. All composites exhibited a higher performance in comparison to PEDOT films mainly in the range of 50 to 112.5 μM.Figure 1.- SEM PEDOT films produced by (a) potentiostatic deposition, (b) constant current, (c) cyclic voltammetry and (d) DPV curves of nitrite detection with PEDOT + 15% mass percent of PdAu nanoparticles suspension Figure 1

Magnetic Properties of GaAs/NiFe Coaxial Core-Shell Structures.

Uniform nanogranular NiFe layers with Ni contents of 65%, 80%, and 100% have been electroplated in the potentiostatic deposition mode on both planar substrates and arrays of nanowires prepared by the anodization of GaAs substrates. The fabricated planar and coaxial core-shell ferromagnetic structures have been investigated by means of scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). To determine the perspectives for applications, a comparative analysis of magnetic properties, in terms of the saturation and remanence moment, the squareness ratio, and the coercivity, was performed for structures with different Ni contents.

Electrochemical formation and stability of copper selenide thin films in the choline chloride-urea deep eutectic solvent at gold electrode

The electrodeposition of copper-selenium binary compounds on gold electrode was investigated in the choline chloride – urea (ChCl-U) deep eutectic solvent at 110 °C. Cyclic voltammetry and potentiostatic deposition followed by stripping voltammetries were employed to gain thermodynamic insights pointing to the formation of Cu2Se, which is supported by X-Ray Photoelectron Spectroscopy. The electrochemical stability domain of the compound is about 900 mV (from ≈−0.81 V to ≈+0.07 V vs. a silver quasi-reference electrode) and is consistent with the thermodynamics of induced co-deposition. The domain is limited at positive potentials by the oxidation to Se(0) and at negative potentials by the reduction to Cu(0). While copper is readily deposited on the gold electrode, the electrodeposition of selenium requires a significant overpotential. As a consequence, copper is kinetically favoured in the co-deposition and is present in its pure form at short deposition times. This is circumvented by using longer deposition times or more negative potentials. Photoelectrochemical measurements show that the as-deposited compound behaves as a p-type semiconductor.

Active Sulfur-Host Material VS4 with Surface Defect Engineering: Intercalation-Conversion Hybrid Cathode Boosting Electrochemical Performance of Li-S Batteries.

Transition-metal sulfides as late-model electrocatalysts usually remain inactive in lithium-sulfur (Li-S) batteries in spite of their advantages to accelerate the rapid conversion of lithium polysulfides (LiPSs). Herein, a series of cobalt-doped vanadium tetrasulfide/reduced graphene oxide (x%Co-VS4/rGO) composites with an ultrathin layered structure as an active sulfur-host material are prepared by a one-pot hydrothermal method. The well-designed two-dimensional ultrathin 3%Co-VS4/rGO with heteroatom architecture defects (defect of Co-doping and defect of S-vacancies) can significantly improve the adsorption ability on LiPSs, the electrocatalytic activity in the Li2S potentiostatic deposition, and the active sulfur reduction/oxidation conversion reactions and greatly boost the electrochemical performances of Li-S batteries. On the one hand, the ultrathin 3%Co-VS4/rGO possesses good conductivity inheriting from rGO which contributes to the capacity of internal redox reactions on lithiation from VS4. On the other hand, the hybrid architectures provide strong adsorption and excellent electrocatalytic ability on LiPSs, which benefit from the surface defects caused by heteroatom doping. The S@3%Co-VS4/rGO cathode displays a high specific capacity of 1332.6 mA h g-1 at 0.2 C and a low-capacity decay of only 0.05% per cycle over 1000 cycles at 3 C with a primary capacity of 633.1 mA h g-1. Furthermore, when the sulfur loading (single-side coating) reaches 4.48 mg cm-2, it still can deliver 756.2 mA h g-1 after the 100th cycle at 0.2 C with 89.5% capacity retention. In addition, the in situ X-ray diffraction test reveals that the sulfur conversion mechanism is the processes of α-S8 → Li2S → β-S8 (first cycle) and then β-S8 ↔ Li2S during the subsequent cycles. The designing strategy with heteroatom doping and self-intercalation capacity adopted in this work would provide novel inspiration for fabricating advanced sulfur-host materials to achieve excellent electrochemical capability in Li-S batteries.

Latent Fingerprint Enhancement on Metallic Surfaces Using Electroactive Film Deposition Combined with Electrochemically Driven Dye Encapsulation

Criminal investigations require establishment of the identities of suspects, victims and witnesses. The most common physical evidence that accomplishes this is a fingermark: it is unique to an individual and time-invariant. Its presence can establish contact between an individual and an object or place the individual at a crime scene. In practice, most such marks are latent (non-visible) fingermarks: these require chemical or physical treatment to render a visible image. Typical chemical treatments involve interaction of a reagent (powder, cyanoacrylate, dye) with the fingerprint residue. Deterioration or loss of residue due to environmental exposure limits the efficacy of these treatments. The success rate for developing a latent mark to a standard permitting a legally acceptable identification is only ca. 10%; this motivates new chemical approaches.In a complementary strategy, we have used the fingerprint residue as a template (“mask”) to direct electrochemically generated reagent to the bare surface between the deposited ridges, thereby creating a negative image of the fingerprint. On metallic substrates the deposition and viewing processes may be controlled electrochemically. This offers the promise of application to a range of objects forensically relevant to both violent crime (knives, guns, bullet casings) and volume crime (tools, handles at points of entry and metal theft). This templating concept was originally demonstrated using electrodeposited polyaniline [1] and PEDOT [2] films, whose electrochromic properties were used to optimize the visual contrast within the fingerprint image. We subsequently extended this concept through the use of electrodeposited poly(pyrrole-co-3,4-ethylenedioxythiophene) copolymers of varying composition to provide wider and more subtle variation of optical properties (simplistically, colour) [3]. Through deliberate selection of co-monomer feedstock, polymer deposition potential and subsequent “viewing” potential, one could then pre-select bespoke material characteristics optimized to a specific substrate.Here we further extend the concept by the inclusion of the dyes Methyl Red (MR), Methyl Orange (MO), Indigo Carmine (IC) or Basic Yellow 40 (BY) into electrodeposited polypyrrole (PPy) films by a combination of electrostatic and/or physical entrapment. The substrates were stainless steel electrodes, upon which a latent fingerprint had been deposited. The deposition medium was an aqueous pyrrole (0.05 mol L-1) / dye (0.005 mol L-1) solution. In the case of MR, sodium dodecylsulphate (0.005 mol L-1) was employed to improve dye solubility. We compare the effectiveness of potentiostatic (0.90 – 1.00 V vs. Ag/AgCl) and galvanostatic (2.5 – 5.0 mA cm-2) deposition control functions. The extent of polymer deposition was varied via deposition time (60 to 300 s) and coulometrically assayed.Dye encapsulation was qualitatively apparent as the polypyrrole films presented the colour of the dye used as dopant: PPy/MR and PPy/MO films were reddish-brown, and PPy/IC was blue. Complementary to these colours seen via absorbance, the emission properties of BY (widely used in conjunction with cyanoacrylate) are also apparent via fluorescence when irradiated with UV light. We will present and interpret images demonstrating how these all these composite electroactive materials yield excellent colour contrast between the surface and the fingerprint. Specifically, one can readily identify the so-called second level features that, in conjunction with dactyloscopy images, unambiguously identify individuals or establish connections between crime scenes. The advantages of this approach, alone and in combination with conventional visualization techniques, will be discussed.

Hierarchical Design of Co(OH)2/Ni3S2 Heterostructure on Nickel Foam for Energy Storage

In this study, we rationally designed a facile stepwise route and successfully synthesized a Co(OH)2/Ni3S2 heterostructure supported on nickel foam (NF) as a binder-free electrode for energy storage. Galvanostatic deposition was first applied to produce uniform Co(OH)2 nanoflakes on NF. Then, Ni3S2 was applied to its surface by potentiostatic deposition to form a Co(OH)2/Ni3S2 heterostructure at room temperature. The added Co(OH)2 not only functions as a practical electrochemically active component but also provides support for the growth of Ni3S2, and the deposition amount of Ni3S2 is controlled by adjusting the electrodeposition duration of Ni3S2. Then, the electrochemical behaviors of the Co(OH)2/Ni3S2 composite can be optimized. A maximum areal specific capacitance (Cs) of 5.73 F cm−2 at 2 mA cm−2 was achieved, and the coulombic efficiency was as high as 94.14%. A capacitance retention of 84.38% was measured after 5000 charge–discharge cycles.

Corrosion performance of a steel surface modified by a robust graphene-based superhydrophobic film with hierarchical roughness

Potentiostatic deposition of cobalt film and cobalt-graphene, Co-G, composite, followed by modification with low surface energy stearic acid (SA), was used to fabricate superhydrophobic films on a steel substrate successfully. A scanning electron microscope was used to analyze the surface morphology of the prepared superhydrophobic cobalt film modified by stearic acid, Co-SA, and the cobalt-graphene film modified by stearic acid, Co-G-SA. The findings show that both the fabricated films have micro-nanostructures. The Co-G-SA film shows a higher roughness due to the network structures of graphene and so exhibits higher superhydrophobicity. The Fourier transform infrared spectrophotometer, FTIR, results confirm the formation of Co-SA and Co-G-SA films on the steel surface. The wettability of the prepared films shows that they exhibit superhydrophobicity, where the Co-SA and Co-G-SA films have contact angles of 155° and 158°, respectively. The Potentiodynamic polarization results show that the value of the corrosion current density for steel coated with Co-SA (0.7094 µA) is lower than that of bare steel (0.1457 mA), while the coated steel with Co-G-SA film has the lowest value (0.1732 µA). The electrochemical impedance spectroscopy, EIS, results show that the charge transfer resistance for steel coated with Co-SA is 38 times that of bare steel, while steel coated with Co-SA is 57 times that of bare steel. Potentiodynamic polarization and EIS results show that the prepared Co-G-SA film superhydrophobic films exhibit higher corrosion resistance. Co-G-SA film has higher mechanical stability (maintains superhydrophobicity until 900 abrasion cycles), chemical stability (has superhydrophobicity in the pH range 1–13), and long-term stability (retains superhydrophobicity after 30 days in a 0.5 M NaCl solution) in 0.5 M NaCl solution.

Hybrid polypyrrole/copper/graphene oxide nanocomposite films synthesized via potentiostatic deposition with enhanced photovoltaic properties

Novel ternary nanocomposites films of Polypyrrole/copper/graphene oxide (PPy/Cu/GO) showed enhanced optical and electronic properties. In this study, PPy/Cu/GO films were synthesized with different GO load (0.0, 0.4, 0.6, and 0.8 wt%) using electrochemical deposition technique. The structural, optical and electrical properties of the composites were evaluated using X-Ray Diffraction (XRD) spectroscopy, UV–visible spectroscopy, Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), and four-point probe methods. XRD results reveal that the GO was completely intercalated and dispersed uniformly in the nanocomposites. The results also revealed that the nanocomposite films are crystalline in nature, with distinct peaks corresponding to indexed miller indices. UV-visible analysis revealed that all of the nanocomposites showed good UV absorbance which was significant in the UV–Vis region of ≈450 nm. The energy band gap decreased with increase in GO load and was found within 3.46 to 2.25 eV, across the range of GO load which fall within the range of energy band gap for photovoltaic applications. The SEM results revealed that the nanocomposite films showed unevenly shaped structures with porous surface which increases with increasing GO loading, while the EDX result revealed the presence of carbon, oxygen nitrogen and copper as fundamental elements deposited. The nanocomposites' four-point probe analysis revealed slight increase in conductivity with low GO content. The incorporation of Cu and GO nanoparticles in PPy matrix provides a better balance and thus improved the photovoltaic properties of PPy/Cu/GO making them suitable for photovoltaic applications.