Anodic Current Density Research Articles

A clean and efficient route for extraction of vanadium from vanadium slag by electro-oxidation combined with ultrasound cavitation

Extracting vanadium (V) from vanadium slag (VS) by the traditional roasting-leaching process has disadvantages of high energy consumption and high poisonous gases emission. In this work, a green and efficient route was developed to extract V from VS without roasting by electro-oxidation combined with ultrasound cavitation (EOUC) intensification in sulfuric acid solution. The leaching parameters (e.g., leaching temperature, sulfuric acid concentration, anodic current density, ultrasound power, liquid to solid ratio, leaching time and particle size) were optimized. The leaching mechanism was explored by comparing the leaching behavior and mineralogical evolution of the direct sulfuric acidic leaching (DSL), electro-oxidation-assisted sulfuric acidic leaching (EOSL), ultrasound cavitation-assisted sulfuric acidic leaching (UCSL) and EOUC methods. The results show that introducing electric field strengthens the ultrasound cavitation effect on slag particles in sulfuric acid solution. Under the optimum parameter of EOUC method, the leaching rate of V from VS is as high as 94.64 %. Using EOUC method can open the silicate-wrapped structure of the spinel, increase pore volume of VS from 0.00127 cm3 g−1 to 0.01124 cm3 g−1, decrease slag particle size from 26.8 μm to 16.4 μm and improve specific surface area from 0.508 m2 g−1 to 10.855 m2 g−1, which significantly accelerate V leaching process. The exposed spinel was oxidized by both electrochemical route and chemical route, forming a mixture of V3+ ion and VO2+ ion after leaching.

Finite Modeling and Simulation of the Effects of Neutral Electrolytic Pickling Process Parameters on EN 1.4404 Steel Strips

Surface treatment via neutral electrolytic pickling (NEP) aims to remove oxide layers and scaling from stainless steel. The objective of this study was to investigate the factors that affect the energy efficiency of the process. This study developed a COMSOL Multiphysics model for the distribution of current across a bipolar steel strip by controlling the following parameters: Na2SO4 concentration, temperature, electrode-to-strip distance, and inter-electrode distance. Full factorial measurements of the electrolyte’s conductivity as well as the steel strip’s and the electrode’s polarization were conducted to provide data for the NEP model. Galvanostatic pulse measurements were performed to calculate transient times during pickling. According to the model, an applied voltage of less than 11 V was insufficient to polarize the steel strip to the potentials needed on both the anodic and cathodic sides. A higher voltage of 11–15 V resulted in anodic current densities of 600–1600 A m−2 and cathodic current densities of 700–2000 A m−2 on the steel strip. These current densities are within the range of previous experimental studies and industrial practices. The model showed that when a steel strip acts as a bipolar electrode, the current’s efficiency decreases, as only a fraction of the strip facing the anodes or cathodes is polarized sufficiently. The galvanostatic tests showed that anodic polarization of the steel strip is easier than cathodic polarization. The slow polarization in the cathodic direction can be improved by using a higher current density. The time needed to polarize stainless steel indicates that the strip’s velocity should be less than 1 m s−1 to give enough time for polarizing the steel strip.

Porous Tellurium-Doped Ruthenium Dioxide Nanotubes for Enhanced Acidic Water Oxidation.

Electrocatalysts with high activity and durability for acidic oxygen evolution reaction (OER) play a crucial role in achieving cost-effective hydrogen production via proton exchange membrane water electrolysis. A novel electrocatalyst, Te-doped RuO2 (Te-RuO2) nanotubes, synthesized using a template-directed process, which significantly enhances the OER performance in acidic media is reported. The Te-RuO2 nanotubes exhibit remarkable OER activity in acidic media, requiring an overpotential of only 171mV to achieve an anodic current density of 10mAcm-2. Furthermore, they maintain stable chronopotentiometric performance under 10mA cm-2 in acidic media for up to 50h. Based on the experimental results and density functional calculations, this significant improvement in OER performance to the synergistic effect of large specific surface area and modulated electronic structure resulting from the doping of Te cations is attributed.

Enhanced electrocatalytic activity of graphitic carbon nitride‐supported Ni/NiO microflower structures for urea electro‐oxidation

AbstractBACKGROUNDIn this study, a 3D heterostructure of Ni/NiO microflower‐decorated graphitic carbon nitride (g‐C3N4) with different ratios was synthesized using the hydrothermal method. The aim was to investigate the electrocatalytic activity of these materials toward urea electrochemical oxidation (UEO) and compare them with various Ni‐based catalysts in NaOH solution.RESULTSThe crystal structure and morphology of the synthesized electrocatalysts were characterized using X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. Among the different ratios studied, the Ni/NiO 30%/g‐C3N4 nanocomposites exhibited the highest electrocatalytic activity and stability. The anodic current density of Ni/NiO 30%/g‐C3N4 was approximately 1.5 times higher than that of NiO microflowers, indicating its superior capability for facilitating the electro‐oxidation of urea at its surface. Furthermore, the Ni/NiO 30%/g‐C3N4 composition showed a lower Tafel slope, low charge transfer resistance, and higher current density, making it a promising material for urea fuel cells.CONCLUSIONThe results of this study highlight the significance of the Ni/NiO 30%/g‐C3N4 composition in achieving efficient electrocatalytic activity for UEO. The 3D heterostructure design, combining the synergistic effects of Ni/NiO and g‐C3N4, offers enhanced performance and stability. These findings contribute to the development of advanced electrocatalysts for urea fuel cells, with potential applications in energy conversion systems. Further research should focus on optimizing the composition and exploring the underlying mechanisms to improve the performance of these electrocatalysts for practical applications. © 2023 Society of Chemical Industry (SCI).

Waterline corrosion behaviors of carbon steel covered by organic coating with artificial defects in seawater

The waterline corrosion behaviors of carbon steel covered by organic coating with artificial defects at and under the waterline simultaneously in simulated artificial seawater were studied by the wire beam electrode (WBE) and electrochemical impedance spectroscopy (EIS) technologies. It was first proposed that the corrosion process of the metal substrate covered by organic coating under the waterline was mainly divided into three stages: no significant corrosion reactions of the metal substrate occurred; the cathodic reaction occurred with relatively slight corrosion on the metal substrate; cathodic delamination of the coating occurred, and the metal substrate was further corroded. Due to the different concentrations of dissolved oxygen, the corrosion reactions of the two exposed electrodes at the waterline and under the waterline were dominated by cathodic and anodic reactions, respectively. For the electrodes under the waterline, on account of the anodic dissolution reaction of the metal substrate, the cathode to anode polarity reversal occurred. In addition, for the yellow corrosion products, the main components were α − Fe2O3, β − FeOOH and γ − FeOOH, while α − Fe2O3 and Fe3O4 were the main components of the black corrosion products. γ − FeOOH participated in the cathodic reaction to form Fe3O4, which resulted in the reduction of the anodic current density at the electrode surface.

Effects of electrolyte type and concentration on the anodic oxidation of 4H-SiC (0001) in slurryless electrochemical mechanical polishing

Slurryless electrochemical mechanical polishing (ECMP) is a promising polishing method for SiC wafers. To achieve a high polishing efficiency, low surface roughness, low cost, and low environmental load, the effects of the electrolyte type and concentration on the anodic oxidation and ECMP of the 4H-SiC (0001) surface were investigated. It is confirmed that the anodic oxidation rate is mainly affected by the conductivity but not the type of electrolyte, and the electric conductivity affects the oxidation current that determines the anodic oxidation rate and performance. The anodic oxidation rate of the SiC surface was restricted by the conductivity at low electrolyte concentrations, and the anodic oxidation rate increased with increasing electrolyte concentration in this stage. The anodic oxidation rate decreased with increasing electrolyte concentration after the conductivity exceeded ∼0.1 S/m, owing to the increasing resistance of the generated oxide layer. Overall, the anodic oxidation uniformity of the SiC surface increased with increasing electrolyte concentration owing to the increasing anodic oxidation current density. The changes in material removal rate of ECMP with increasing electrolyte concentration were consistent with those of the anodic oxidation rate, while the surface roughness obtained by ECMP always decreased with increasing electrolyte concentration. This study provides a new way to improve the performance of slurryless ECMP.

EFFICIENCY OF TREAD ALLOYS FOR VERTICAL STEEL TANKS

The article discusses the use of various protector alloys made of magnesium and aluminum to protect vertical steel tanks when storing oil and oil products. Characteristics of protector alloys made of magnesium or aluminium and their alloys are shown. Data on the rate of selfdissolution of protector alloys depending on the degree of mineralization of bottom water are given. Gravimetric tests were used to calculate the mass index of the corrosion rate and electrochemical tests were used to calculate the efficiency of the anode current density. An empirical equation is shown by which the self-dissolution rate of protector alloys made of aluminum and magnesium alloys can be calculated, and empirical coefficients are given for the case of using protector alloys considered in the work. The obtained empirical dependence will make it possible to predict the rate of self-dissolution of aluminum and magnesium protector alloys. The efficiency of magnesium and aluminum protector alloys was analyzed and the dependence of the efficiency factor on the anode current density for magnesium and aluminum protector alloys was shown. Shows the effectiveness of using aluminum protector alloys to protect vertical steel tanks. It was concluded that the use of aluminum protector alloys is more efficient, since their efficiency is higher than that of magnesium alloys, this is clearly seen in the graph presented in the work on the dependence of the efficiency on the total mineralization of bottom water. The results of the work can be used in the design of protector protection for vertical steel tanks pre-designated for storage of oil and oil products containing produced water of various salinity.

Corrosion Behavior of the Cu24Zn5Al Alloy in Sodium Sulfate Solution in the Presence of 1-Phenyl-5-mercaptotetrazole

The results of this research on the electrochemical behavior of Cu24Zn5Al alloy in a 0.1 mol/dm3 sodium sulfate (Na2SO4) solution containing 1-phenyl-5-mercaptotetrazole (PMT) are presented in this paper. The influence of PMT concentration, chloride ion concentration, and pre-treatment were examined. The influence of pre-treatment was studied in terms of the effect of the immersion time of the electrode in the appropriate inhibitor solution. After selecting the optimal immersion time, its effect on the behavior of the Cu24Zn5Al alloy was tested in a 0.1 mol/dm3 solution of sodium sulfate in the presence of different concentrations of chloride ions. Research shown that with the increase of PMT concentration, the anodic current density around the corrosion potential decreases, indicating that PMT behaves as a corrosion inhibitor for Cu24Zn5Al alloy.

Rapid Formation of Epitaxial Oxygen Evolution Reaction Catalysts on Dendrites with High Catalytic Activity and Stability.

Oxygen evolution reaction is an essential but kinetically sluggish step in many energy storage and conversion processes and therefore is in pursuit of highly efficient and stable catalysts. Although nanosized transition-metal-based oxides/hydroxides exhibit high catalytic activity toward the oxygen evolution reaction (OER), many of them suffer from low stability at an anode current density in industrial scale. Herein, by combining a rapid epitaxial formation method with dynamic bubble-templated electrodeposition, we successfully developed single crystalline NiFeCu oxide catalysts with a hierarchical porous structure. It was found that the structure can facilitate fast electron transportation for the catalysts and retard the diffusion of the O atoms to the inner metallic current collector. The hierarchical pores inherited from the hydrogen bubble templates built ideal channels for the massive and rapid release of oxygen bubbles. As a consequence, the NiFeCu oxides catalyzed the OER more efficiently and steadily than the commercial RuO2 catalyst at an anode current density in industrial scale (300 mA/cm2). This work, by resolving the durability concerns for nanosized oxides, offers a series of highly efficient and stable catalysts for OER and a structure building strategy to boost the catalytic activity and stability for nonconductive catalysts.

CHARACTERIZATION OF CORROSION BEHAVIOR OF INCONEL 617 WELDED JOINTS USING CMT-GMAW MULTI-CONTROL WELDING

This work addressed the effect of CMT-GMAW multi-control welding of Inconel 617 alloy with different wire feed rates (8.9, 9.4, and 9.9 m/min) on the microstructure, hardness, and electrochemical properties. The weld joints are composed of columnar dendritic structure with cellular crystals. Electron backscattered diffraction (EBSD) study showed equiaxed dendrite at the center of weld metal with growth direction perpendicular to the fusion boundary. The weldments showed diffraction peaks at 43.53[Formula: see text], 50.12[Formula: see text], and 74.82[Formula: see text], and these peaks mainly represent gamma ([Formula: see text]) and gamma prime ([Formula: see text]) phases along with the carbide peaks of Ti (C, N), M[Formula: see text]C6 and M6C. The Base metal (BM) had a lower hardness (232 ± 10 HV[Formula: see text]) and lower corrosion rate (0.212 mpy) than the weld joints. The increase in wire feed rate (WFR) results in the decrease of microhardness (267 ± 5 − 251 ± 6 HV[Formula: see text]) and increase in corrosion rate (1.833-28.140 mpy). The base metal exhibited higher potential ([Formula: see text]) and lower current density ([Formula: see text]) than the weld joints. As wire feed rate (WFR) increases, heat input increases; solidification time increases, grain boundaries coarsen, resulting in a lower grain boundary (GB) density, and hence increased carbide precipitation and segregation in weld zone leading to higher stable anodic current density, which caused corrosion resistance to deteriorating. The BM was more corrosion resistant than the weld joints. The metallurgical and physical changes caused by the welding process affect the corrosion resistance of the weld joints. This leads to the weld metal corroding faster than the base metal.

Behavior of biocide-free foul control paints for ships’ hulls in the immediate proximity of ICCP anodes

AbstractImpressed current cathodic protection systems are used in combination with organic coatings to prevent corrosion of hulls. The reaction species which are formed in the proximity of the anodes, like chlorinated compounds and acidity, can stress the antifouling paints of the protective coating system. A 3 × 3 matrix was defined to drive the tests aiming to investigate the behavior of novel biocide-free foul release (FR) and self-polishing (SP) paints under this kind of attack. The matrix was featured by different pH and free chlorine (free-Cl) values derived by a galvanostatic test performed at an anodic current density required for the protection of paints roughly at their mid age. Chemical/physical characterization was performed through visual analysis, thickness measurements, profilometry, contact angle measurements, and FTIR-ATR analysis. Both FR and SP paints underwent adhesive failure only in the harshest conditions, pH = 3/free-Cl 3–6 ppm, with unmodified chemistry of the polymers. Both paints exhibited no detachment in milder pH/free-Cl conditions, but thickness and contact angle reduction were observed. Finally, results were discussed inferring possible behaviors of the tested paints in real applications.

Corrosion Resistance of Titanium Dental Implant Abutments: Comparative Analysis and Surface Characterization.

Metals subjected to the oral environment are prone to corrosion over time and this can be harmful. Metallic restoration components such as dental subgingival implant abutments are exposed to pH changes and different ions while in contact with saliva. The aim of the study was to evaluate the corrosion resistance of titanium dental implant abutments and to compare and contrast the surface characteristics of these alloys before and after corrosion. The corrosion examination (Ecorr, jcorr, OCP, polarization curve) of two implant abutments (TiDesign EV, Astra Tech, Dentsply, York, PA, USA; Individual Titanium Abutment, Apollo Implants Components, Pabianice, Poland) was performed in 0.9% NaCl and 5% HCl. Moreover, specimens were investigated using SEM-EDS before and after the corrosion test. The value of jcorr in NaCl was higher for Astra (34.2 × 10-8 ± 2.5 × 10-8 A/cm2) than for Apollo (8.8 × 10-8 ± 2.5 × 10-8 A/cm2). Whereas, in HCl, the opposite relationship was observed (Astra 2.9 × 10-4 ± 0.8 × 10-4 A/cm2 and Apollo 62.7 × 10-4 ± 9.3 × 10-4 A/cm2). An average reactive anodic current density in NaCl for Astra amounted up to ~0.2 × 10-5-1.5 × 10-5 A/cm2, while for Apollo-up to ~3.3-9.7 × 10-7 A/cm2. The composition of both alloys after corrosion in NaCl demonstrated some changes: a decrease in the Ti, and Al and an increase in oxygen content. Hence, both alloys after corrosion in HCl demonstrated some minor changes in the elemental composition. Based on the results it can be concluded that: 1. Astra and Apollo abutments revealed good corrosion resistance and a passivation layer on the surface. 2. Apollo abutments exhibited better corrosion resistance in a neutral environment, suggesting that Astra abutments were found to be more resistant to corrosion in an acidic medium.

Treatment of aniline-containing wastewater by electrochemical oxidation using Ti/RuO2 anode: the influence of process parameters and reaction mechanism.

Aniline detected in many industrial wastewater is a refractive organic pollutant with strong biological toxicity to aquatic organisms and humans. In this research, electrochemical oxidation process with Ti/RuO2 as the anode has been used to degrade aniline-containing wastewater on a laboratory scale. The influence of anode materials, electrolyte, NaCl concentration, current density, and aniline initial concentration on COD removal, ICE, and Ep were studied. The results showed that Cl- addition in the electrolyte is essential to promote aniline degradation efficiency and avoid the anode being passivated. Furthermore, decreasing the current density, increasing Cl- concentration, and initial aniline concentration are beneficial to increase current efficiency and reduce energy consumption. Although the addition of SO42- has a restriction on the active chlorine evolution process, the conductivity increased, which resulted in the reduction of energy consumption. At last, the aniline degradation mechanism in the presence of chloride ions was summed up and proposed based on the literature.

Evaluation of the electroflotation efficiency for the oil-containing shipping waters treatment

The article describes the problems of formation and purification of ship oil-containing waters. The effectiveness of electroflotation using aluminum and iron anodes for the extraction of oil from water-oil emulsions with different mineralization was assessed.
 Electroflotation treatment of water-oil solutions provides 98.6–99.9 % oil removal using aluminum or iron electrodes at an anodic current density of 1.65–7.39 A/dm2 for highly mineralized waters and 0.07–0.50 A/dm2 for fresh water.
 Water treatment during the first 15 minutes provides a sharp decrease in oil content from 100 mg/dm3 to 1.31–2.52 mg/dm3, almost regardless of the type of anode metal. The efficiency of oil extraction from water mainly depends on its mineralization. In mineralized (salty) water, the treatment process is more efficient. In fresh waters, aluminum anode provides higher water purification efficiency compared to iron anode. However, in the case of pre-treatment of the iron anode with an alkali solution with the formation of a magnetite layer on it, this anode is characterized by the highest purification efficiency for low-salt waters, providing a degree of water purification at the level of 99.9 %.

Study of the Process of Electrochemical Oxidation of Active Pharmaceutical Substances on the Example of Nitrofurazone ((2E)-2-[(5-Nitro-2-furyl)methylene]hydrazine Carboxamide)

The effective mineralization of nitrofurazone (10–100 mg L−1) was performed in aqueous solutions in the presence of chloride ions by electrochemical treatment. The destruction of the organic pollutant molecules was due to their interaction with active oxygen- and chlorine-containing species forming at the inert anode (Pt/Ti or BDD) during electrolysis. Measurements of nitrofurazone concentration, chemical oxygen demand (COD) and total organic carbon (TOC) were used to estimate the removal efficiency of the pollutant. Both the pollutant oxidation rate and the degree of its mineralization were higher for the BDD anode due to the higher anode potentials on it in the course of electrolysis, which provides a high rate of active oxidizer species generation. As a result, practically full nitrofurazone molecule destruction (>99%) was achieved in 30 min at an anodic current density of 0.1 A cm−2, a volume current density of 1.33 A L−1 and pH 2 using BDD anodes. On the other hand, the nitrafurazone degradation efficiency was about 95% for Pt/Ti anodes under the same conditions. Additionally, byproducts of nitrofurazone electrooxidation were investigated by means of liquid chromato-mass-spectrometry (LC/MS). It was found that the initial decolorization of nitrofurazone solution, which occurs during the first 5 min of electrolysis, is due to the formation of a dichloro derivative of nitrofurazone, which causes the destruction of the π−conjugated bond system. Further electrolysis resulted in the almost complete destruction of the dichloro derivative within 30 min of electrochemical treatment.

Biodegradation of Oxide Nanoparticles in Apoferritin Protein Media: A Systematic Electrochemical Approach

AbstractFunctional oxide nanoparticles are extensively utilized in the last decades for biomedical purposes due to their unique functional properties. Nevertheless, their biodegradation mechanism by biological species, particularly by proteins at oxide/protein interfaces, still remains limited. Here, a systematic approaches is provided to investigate electrochemical behavior, electronic properties, and biodegradation mechanism of cobalt ferrite (CFO) and cobalt ferrite‐bismuth ferrite (CFO‐BFO) core‐shell nanoparticles in apoferritin‐containing media. Scanning Kelvin probe force microscopy results indicate that the presence of a thin shell (≈5 nm) of BFO on CFO causes a significant increase in surface potential. The potentiodynamic polarization measurements in different solutions showed higher anodic current densities for both samples when decreasing pH and increasing apoferritin concentration. Notably, CFO‐BFO exhibits lower anodic current densities than CFO due to a slightly higher flat band potential and lower donor density distribution on CFO‐BFO than on CFO, which results in lower electrochemical activity. Long‐term monitoring reveals that biodegradation of both nanoparticles is accelerated by high apoferritin concentrations and acidic media, resulting in the decrease of electrochemical potentials and impedance values, and enhancement of metal ion release. Thus, this systematic biodegradation study can help to predict the lifespan and toxicity of these functional nanoparticles in biological environments.

Electrodeposited CZTS loaded titania nanotubes for photocatalytic water splitting

Copper Zinc Tin Sulphide (Cu2ZnSnS4 (CZTS)) is a promising semiconductor material with optimum direct band gap of 1.4-1.6 eV, large light absorption coefficient (> 104 cm-1) and p-type electrical conductivity. In addition, its earth abundant and non-toxic elemental constituents make it a good candidate to replace the CdTe and CIGS absorber layers used in thin film solar cells. Also, it has properties that make it useful as a buffer layer that helps to reduce the effective band gap of TiO2 when used as an anode for photocatalytic splitting of water. We prepared titania nano tube (TNT) arrays by anodization of titanium foil. Raman spectrum of TNT confirmed the presence of pure anatase phase of TiO2. Field emission scanning electron microscopy images were obtained to analyse the surface morphology of TNT. CZTS sensitized titania nano tube arrays were then prepared by the electrodeposition of CZTS thin films over TNT arrays. FESEM images of the CZTS sensitized titania nano tube arrays showed that the electrodeposited CZTS layer had a fibrous structure. A photo electro chemical (PEC) cell was set up with CZTS sensitized titania nanotubes as anode. An anodic current density of 0.19 mA/cm2 was shown by the PEC cell when the anode was irradiated with blue light of wavelength 430 nm at power 50 mW/cm2. The incident photon to current conversion efficiency was 1.1 %.

Anodic Behaviour of NixFeyCu5 and NixFeyCu20 in Potassium-Rich Naf-KF-AlF3-Al2O3 Melts

Using inert anode technology to produce aluminium would substantially reduce the aluminium industry's carbon footprint. Replacing the Hall-Héroult process with an alternative process based on vertical electrode cell (VEC) design using inert anodes and wettable cathodes is a promising alternative, but must be developed to be economically viable at scale. Three material types have been explored as inert anodes: metals, cermets and ceramics. Metallic anodes have been widely studied for their attractive properties, such as superior mechanical strength, high electrical conductivity and ease of fabrication. Of metallic anodes, Cu-Al, Ni-Fe and Ni-Fe-Cu-based alloys are the most commonly examined alloy systems for anode applications. It is also necessary to use low-temperature melts during the electrolysis process to ensure that the anodes are not damaged. In NaF-KF-AlF3 melts, increasing the KF content in the mixture would reduce the liquidus temperature and increase the alumina solubility in the melt.In this work, we examine the anodic behaviour of NixFeyCu5 and NixFeyCu20 electrodes, without prior surface treatment, in potassium-rich NaF-KF-AlF3 melts at 770°C. The cryolite ratio (xNaF+xKF/xAlF3) and potassium ratio (xKF/xKF+xNaF) of the melt used for the studies are 1.3 and 0.7, respectively. Electrochemical techniques such as chronopotentiometry, chronoamperometry and linear sweep voltammetry were performed to examine the anodic behaviour of these metallic anodes under an N2 atmosphere.Figure 1 shows the steady-state anodic polarisation curves on NixFeyCu5 and NixFeyCu20 anodes before and after galvanostatic polarisation with an applied current density of 0.5 Acm-2 for 120 minutes. It can be noted that the anodic potential at the same current density is more for the polarised anode compared to the non-polarised in both cases. This is due to the formation of a stable oxide layer during the galvanostatic polarisation of the anode. Oxidation of the anode is expected instead of fluoridation when the melt is saturated with alumina. The stabilisation of anodic current can be seen between 1.9 and 2.4 V. This stabilisation corresponds to the passivation of anodes due to the oxide layer formation. A rapid increase in the current after 2.4 V is due to the oxygen evolution reaction. The anodic current density in the passive region is much lower in anodes with Cu 20%, meaning a more protective layer is formed. After the galvanostatic polarisation of the anode, anodes were examined using scanning electron microscopy to understand the oxide layer composition. Anodes performed stably in potassium-rich melts, and Cu content plays a vital role in the anode's performance. Figure 1. Stationary state polarisation curves of NixFeyCu5 and NixFeyCu20 anodes before and after the polarisation at 0.5 A cm-2 Figure 1

High Performance Metal Oxide–Reduced Graphene Oxide Electrocatalyst for All Vanadium Redox Flow Batteries

Vanadium redox flow battery (VRFB) is one of the most favorable technologies for large-scale energy storage applications owing to its numerous gorgeous features, such as flexible design, high safety, and long cycle life. In this study, metal oxide (MOx)–reduced graphene oxide (rGO) nanohybrid was successfully synthesized via a facile hydrothermal route followed by annealing and employed as an electrocatalyst to modify the graphite felt (GF) electrode material for all-vanadium redox flow batteries (VRFBs) application. The as-synthesized MOx–rGO nanohybrid reveals good electrocatalytic reversibility and higher anodic and cathodic peak current density for V3+/V2+ and VO2 +/VO2+ redox couples compared with those of rGO and MOx samples. The voltage efficiency of the VRFB using MOx–rGO nanohybrid reaches 84% at 80 mA cm−2, which is 4% and 13% higher than the VRFBs using the rGO-loaded GF electrode and the pristine GF electrode, respectively. It still shows the voltage efficiencies of 76% and 70% at relatively high current densities of 120 mA cm−2 and 140 mA cm−2, respectively, but other samples have no effective discharge. This improvement is accredited to the uniform distribution of MOx nanoparticles on the rGO surfaces, avoiding the restacking of the rGO sheets and conquering nanoparticles aggregation, which might boost the effective active surface area and improve mass transport at the electrode-electrolyte interfaces. Besides, the existence of oxygen vacancies on MOx, the high electrical conductivity of rGO, and the high content of oxygen functional groups play the prodigious roles to facilitate the reversibility of vanadium ions redox reactions.

Effect of Cathode Rotation Speed on Mechanical Properties of Abrasive-Assisted Copper Electroforming with High Anode Current Density

Effect of Cathode Rotation Speed on Mechanical Properties of Abrasive-Assisted Copper Electroforming with High Anode Current Density