Electrode Current Density Research Articles

Synthesis and characterization of Co3O4 ultra-nanosheets and Co3O4 ultra-nanosheet-Ni(OH)2 as non-enzymatic electrochemical sensors for glucose detection

The present study examines the synthesis of Co3O4 ultra-nanosheets (Co3O4 UNSs) and Co3O4 ultra-nanosheet-Ni(OH)2 (Co3O4 UNS-Ni(OH)2) via solvothermal process and their application as non-enzymatic electrochemical sensors for glucose detection. X-ray diffraction and transmission electron microscopy results confirmed the Co3O4 UNS deposition on Ni(OH)2 surface. The presence of Co3O4 UNSs on Ni (OH) 2 surface improved the sensitivity of glucose detection, from the increase of glucose oxidation peak current at the Co3O4 UNS-Ni(OH)2/glassy carbon electrode (current density: 2000μA·cm−2), compared to the Co3O4 UNSs. These results confirmed that Ni(OH)2 on glassy carbon electrode is a sensitive material for glucose detection, moreover the Co3O4 UNSs can increase the interaction and detection of glucose due to their high surface area. The estimated limit of detection (S/N=3) and limit of quantification (S/N=10) of the linear segment (5–40μM) are 1.08μM and 3.60μM respectively. The reproducibility experiments confirmed the feasibility of Co3O4 UNS-Ni(OH)2 for the quantitative detection of certain concentration ranges of glucose.

Catalytic activity of iridium dioxide with different morphologies for oxygen reduction reaction

Iridium dioxide with different morphologies (nanorod and nanogranular) is successfully prepared by a modified sol-gel and Adams methods. The catalytic activity of both samples for oxygen reduction reaction is investigated in an alkaline solution. The electrochemical results show that the catalytic activity of the nanogranular IrO2 sample is superior to that of the nanorod sample due to its higher onset potential for oxygen reduction reaction and higher electrode current density in low potential region. The results of Koutecky-Levich analysis indicate that the oxygen reduction reaction catalyzed by both samples is a mixture transfer pathway. It is dominated by four electron transfer pathway for both samples in high overpotential area, while it is controlled by two electron transfer process for both samples in low overpotential area.

Highly Dense Cu Nanowires for Low-Overpotential CO2 Reduction.

Electrochemical reduction of CO2, an artificial way of carbon recycling, represents one promising solution for energy and environmental sustainability. However, it is challenged by the lack of active and selective catalysts. Here, we report a two-step synthesis of highly dense Cu nanowires as advanced electrocatalysts for CO2 reduction. CuO nanowires were first grown by oxidation of Cu mesh in air and then reduced by either annealing in the presence of hydrogen or applying a cathodic electrochemical potential to produce Cu nanowires. The two reduction methods generated Cu nanowires with similar dimensions but distinct surface structures, which have provided an ideal platform for comparative studies of the effect of surface structure on the electrocatalytic properties. In particular, the Cu nanowires generated by electrochemical reduction were highly active and selective for CO2 reduction, requiring an overpotential of only 0.3 V to reach 1 mA/cm(2) electrode current density and achieving Faradaic efficiency toward CO as high as ∼60%. Our work has advanced the understanding of the structure-property relationship of Cu-based nanocatalysts, which could be valuable for the further development of advanced electrocatalytic materials for CO2 reduction.

Transcranial Direct Current Stimulation Post-Stroke Upper Extremity Motor Recovery Studies Exhibit a Dose-Response Relationship.

Transcranial direct current stimulation (tDCS) has shown mixed results in post-stroke motor recovery, possibly because of tDCS dose differences. The purpose of this meta-analysis was to explore whether the outcome has a dose-response relationship with various dose-related parameters. The literature was searched for double-blind, randomized, sham-controlled clinical trials investigating the role of tDCS (≥5 sessions) in post-stroke motor recovery as measured by the Fugl-Meyer Upper Extremity (FM-UE) scale. Improvements in FM-UE scores were compared between active and sham groups by calculating standardized mean differences (Hedge's g) to derive a summary effect size. Inverse-variance-weighted linear meta-regression across individual studies was performed between various tDCS parameters and Hedge's g to test for dose-response relationships. Eight studies with total of 213 stroke subjects were included. Summary Hedge's g was statistically significant in favor of the active group (Hedge's g = 0.61, p = 0.02) suggesting moderate effect. Specifically, studies that used bihemispheric tDCS montage (Hedge's g = 1.30, p = 0.08) or that recruited chronic stroke patients (Hedge's g = 1.23, p = 0.02) showed large improvements in the active group. A positive dose-response relationship was found with current density (p = 0.017) and charge density (p = 0.004), but not with current amplitude. Moreover, a negative dose-response relationship was found with electrode size (p < 0.001, smaller electrodes were more effective). Our meta-analysis and meta-regression results suggest superior motor recovery in the active group when compared to the sham group and dose-response relationships relating to electrode size, charge density and current density. These results need to be confirmed in future dedicated studies.

Plating Utilization of Carbon Felt in a Hybrid Flow Battery

A hybrid flow battery is a type of flow battery that includes a deposition reaction at the negative electrode; therefore, the volume available in the negative electrodes of the stack limits the total energy that can be stored by such a battery. In this paper, the plating capacity of a porous carbon felt in a hybrid flow battery with a flow-through geometry was examined by copper deposition from a mixed Cu-Fe sulfate chemistry. Due to uneven current distribution across the porous electrode, at most only 23% of the available volume was actually usable for metal deposition before the battery failed. The percentage of volume able to be utilized varied with the applied current density. A model for predicting this plating utilization as a function of the porous electrode characteristics, electrolyte properties, and current density was developed, and ways of improving the current distribution to achieve higher plating utilization were examined. Even under non-optimized conditions, plating densities in excess of 560 mAh cm−2 were achieved.

Feasibility of electrocoagulation/flotation treatment of waste offset printing developer based on the response surface analysis

In the printing plate developing process, the offset printing developer undergoes changes, as well as enrichment by the various chemicals, i.e. metals, organic binders and photosensitive compounds. The objective of this study was to investigate the electrocoagulation/flotation (ECF) treatment efficiency for the removal of copper, turbidity and organic substances from the waste offset printing developer (WOPD). The effect of operational parameters, such as electrode materials, current density, interelectrode distance and operating time, was studied. Also, the response surface analysis was applied to evaluate the effect of main operational variables and to get a balanced removal efficiency of investigated WOPD parameters by ECF treatment. The removal efficiency increases significantly with the increasing of operating time and mainly increases with the increasing of current density. The obtained results show that the interelectrode distance and combinations of electrodes determine the removal efficiency of copper, turbidity and organic substances. Based on the obtained results, the optimized parameters for the ECF treatment removal of investigated WOPD parameters were identified as: Al(−)/Fe(+) electrode combination with interelectrode distance of 1.0cm, operating time of 5min and current density of 8mAcm−2. This study confirms the practical feasibility of ECF method for treating real printing industrial effluent under optimum conditions.

Electrochemical Degradation of Triketone Herbicides and Identification of Their Main Degradation Products

The aim of this paper was the development and optimization of an electrochemical method for the degradation of two triketone herbicides, mesotrione, and sulcotrione, in a two‐electrode undivided electrochemical cell equipped with commercially available, non‐modified, electrode materials. The electrochemical parameters studied included five different electrode systems (Zr/Pt, Pd/Pt, C/Pt, Nb/Pt, and Ti/Pt), current densities (27.66, 55.33, …, 110.66 mA · cm−2) and pH values (3, 7, and 9) in 0.05 M sodium sulfate as supporting electrolyte. The electrical energy consumption and chemical oxygen demand were calculated for optimal conditions. The degradation efficiency was determined by high performance liquid chromatography (HPLC) equipped with a diode array detector, while the degradation products for both pesticides were identified and compared by ultra‐high performance liquid chromatography (UHPLC)‐mass spectrometry. The results could lead to an accurate estimate of their effect on the environment. A real water sample was used to study the influence of organic matter on pesticide degradation. Based on the results obtained the electrochemical treatment could be used for the successful removal of triketone herbicides from contaminated water.

Effect of Electrode Patterning on PEM Fuel Cell Performance using Ink-Jet Printing Method

Performance of a polymer electrolyte membrane (PEM) fuel cells depends upon several electrode parameters such as platinum loading, micro-structure and ionomer content. These parameters can be varied by changing the catalyst ink formulation and electrode fabrication technique [1]. In this work, inkjet printing is investigated as an electrode fabrication technology. Our results show that with this technique, it is possible to have an electrode thickness of less than 2 µm with an evenly distributed micro-structure and a platinum loading of around 25 µg/cm2 [2]. The platinum mass activity of these electrodes is seen to be up to 8 times higher that a conventionally fabricated electrode at high current densities, mainly due to the reduction in macro-scale transport losses due to the reduced thickness (Figure 1). Electrode current density at low overpotentials was improved with increasing Pt loading by increasing the number of deposited layers. However, this resulted in an increased electrode thickness which increased the mass-transport losses thereby reducing the platinum mass activity at high current densities.It was hypothesized that patterning of electrodes would help reducing mass-transport losses at the macro-scale by having through-plane pathways for the reactant gases and water. It has also been shown that patterning of the electrodes influences the electrochemical active area of the cell [3]. This work studies the fabrication process of patterned electrodes and their performance when compared to a normal electrode. First, the resolution of our inkjet printer technology was studied. Various patterns were tested using two printer cartridges having drop volumes of 1 pL and 10 pL corresponding to a nozzle diameter of 9 µm and 21 µm respectively. It is shown that distinguishable patterns as small as 200 µm x 200 µm could be fabricated. The maximum resolution is shown to be a function of the nozzle diameter, substrate used, number of active nozzles during the fabrication process, droplet spacing, and number of printed layers. Figure 2 shows sample spacing resolutions between the patterns fabricated. Smaller nozzle size helps in increasing the pattern resolution. Minimum distinguishable spacing between the patterns was found to be 100 µm when using the 1 pL cartridge and 500 µm with the 10 pL cartridge. Figure 3 shows a performance comparison at 70% RH and a cell temperature of 80 C between two catalyst coated membranes with a 5 cm2 cathode layer obtained using: a) a patterned electrode, and b) a conventional electrode (15 layers). The estimated cathodic Pt loading for both the CCMs is approximately 0.175 mg/cm2. It can be seen that patterning significantly improves the cell performance at high current densities due to reduction in the mass-transport losses as there is lower resistance to the flow of gases through the electrode. This effect will be more prominent once the performance plots are obtained when using cathodic reactant gas with lower oxygen concentration. The effects of cell performance on the type of patterns and the substrate used for ink deposition is underway.

Production of reducing sugars from corn stover by electrolysis

In this study, an electrochemical system composed of a Ti/IrO2–Pt plate as the anode and a Ti plate as the cathode was employed for the treatment of corn stover to afford reducing sugars. The optimum conditions, following the experimental design methodology of Taguchi, were electrode spacing, current density, and NaCl addition of 10 mm, 30 mA cm−2, and 2000 mg L−1, respectively. The recovery of reducing sugars under optimum conditions reached 0.610 mg mL−1 at 180 min, demonstrating the greater efficacy of this process compared to ozone pretreatment (0.297 mg mL−1 at 180 min). Indirect oxidation by hypochlorous acid generated in the bulk solution was a significant contributor to lignocelluloses oxidation. An increase in temperature and variation in pH during electrolysis enhanced the oxidation. After electrochemical treatment, the lignocellulosic structure was destroyed and became disordered, the crystalline index decreased from 0.4396 to 0.3493, indicating the efficacy of the described electrochemical method for converting lignocelluloses to reducing sugars. After the electrolysis, the structure of lignocelluloses became disordered, and the crystalline index decreased from 0.4396 to 0.3493, indicating that the electrolysis was an effective method for converting the lignocelluloses to the reducing sugars.

Treatment of Coal Stockpile Wastewater by Electrocoagulationusing Aluminum Electrodes

The performance of electro coagulation system with aluminum and iron electrodes to remove heavy metals from actual wastewater of coal's stockpile which has studied. The effects of process variables such as electrode material, current density and operation time for electro coagulation process are investigated on ferrous and manganese removal efficiencies. Preliminary results show that the electro coagulation process is able to enhance the removal of heavy metal contents. The batch experiment results showed that the high heavy metals which is contained wastewater coal's stockpile can be effectively treated by electro coagulation system using aluminum electrodes. The overall removal efficiencies of heavy metals have been obtained at 89.7% for ferrous and 94.6% for manganese, respectively. The removal rates of those elements were increase with operation time. Therefore, electro coagulation technique to remove high content of heavy metal and TSS from wastewater of coal's stockpile is found effective and friendly with the environment.

Productivity of chemical-electrochemical gold leaching from rebellious ore

The authors describe experimental research findings on chemical-electrochemical leaching of gold from rebellious minerals. A laboratory-scale plant has been designed for studying the leaching kinetics. Rational parameters of chemical-electrochemical leaching are specified (duration of the process, electrode current density, NaCl concentration). The researchers analyze the changed microstructure and phase composition of arsenopyrite surface after the leaching and substantiate the leaching improving practices.

Effect of High Current Density in Electrocoagulation Process for Sewage Treatment

Treatment of sewage wastewater by electrocoagulation with high cell current densities (605 A/m2, 908 A/m2, 1211 A/m2, 1513 A/m2 and 1816 A/m2) using stainless steel, iron and aluminum electrodes were studied. High current densities applied were very effective for the removal of chemical oxygen demand, biochemical oxygen demand and suspended solid in 0.5 h. In the electrocoagulation of sewage wastewater, the effect of electrode material, current densities, electrocoagulation time, inter-electrode distance and initial pH were examined. The optimum operating range for each operating variable was experimentally determined in order to provide an economical and effective treatment for the sewage wastewater. Therefore, the optimum condition for this treatment is in 0.5 h, by using stainless steel electrode, at 1816 A/m2, in pH 7 and 10 mm electrode distances. The optimum treatment condition reduced chemical oxygen demand by 98.07 %, biochemical oxygen demand by 98.07 % and suspended solid by 97.64 % and the anode loss during the experiment was 9.2 × 102 g.

Corrosion Currents in the Cathodic and Anodic Sections of a Circular Stress Concentrator

A quantitative relationship between the mechanical stress field and local distribution of the shifts of electrode potentials and corrosion current densities in the metal containing a circular stress concentrator filled with corrosive medium is analytically determined. The dependences of the sizes of cathodic and anodic sections on the applied forces and the contents of Na + and Cl − ions in the medium are analyzed. The boundaries of the cathodic and anodic sections on the surface of the circular hole are determined. In order to evaluate the serviceability and durability of structural elements in the course of long-term opera- tion under the action of static loads and working media, it is important to establish the relationship between the stress-strain state of the metal and its electrochemical interaction with the medium, which substantially affects the strength, load-carrying ability, and fracture processes in the products. The force loading and the correspond- ing inhomogeneous stress field induce the space redistribution of current carriers in metallic bodies. In the pro- cess of tension of this body, the zone of the highest concentration of stresses turns into the anode, whereas the remaining part of the surface plays the role of cathode. Even small-size anodic and cathodic regions cause the motion of charges and, hence, the local electrochemical corrosion of the surface, where the metal body contacts with the corrosive medium. However, the mutual influence of the stress-strain state and the electrochemical in- teraction of media with metals is studied insufficiently. Fr this reason, we estimate the shifts of the electrode potentials and current density on the boundary of a circular hole in the metal placed in a corrosive medium in the process of deformation.

The treatment of zinc-cyanide electroplating rinse water using an electrocoagulation process

This paper investigates the treatment of zinc-cyanide electroplating rinse water using an electrocoagulation process (ECP). The effects of operating parameters such as electrode material, current density (2.5-40 A/m(2)), operating time (0-60 min), initial pH (5-12) and electrode connection mode (monopolar parallel (MP-P), monopolar series and bipolar series) on the ECP were evaluated to find the optimum operating conditions. At 20 A/m(2), 60 min, the highest removal efficiencies were obtained with 85 and 99% for Fe and 64 and 33% for Al electrodes, for cyanide and zinc, respectively. The optimum operating conditions were found to be 30 A/m(2) and 40 min, for the Fe electrode at the original pH (9.5) of the rinse water. Considering efficiency and economy, the MP-P connection mode was determined as the optimum connection mode.

The effect of thiourea, l(−) cysteine and glycine additives on the mechanisms and kinetics of copper electrodeposition

The influence of thiourea, l(−) cysteine and glycine on the mechanisms and kinetics of copper electrodeposition from aqueous solution at pH 1.00 ± 0.05 and 25 °C was investigated using several complementary techniques. Rotating disc electrode current density measurements and the kinetic parameters calculated from Koutecký–Levich analysis indicated that at 5 × 10−3 M thiourea and l(−) cysteine addition the electro-reduction of Cu(II) was significantly inhibited. By contrast, upon similar addition of glycine, the reduction current density increased and the equilibrium potential moved towards more positive values. Microscopic imaging studies of the resulting Cu films showed that thiourea and l(−) cysteine led to fine-grained deposits, whilst glycine addition resulted in a coarser deposit. It is suggested the additives substantially altered the electron and mass transfer processes during electrodeposition. Both thiourea and l(−) cysteine appear to act by specific chemical interactions that lead to CuS co-crystallization. On the other hand, glycine is believed to act by mediating the Cu(II) to Cu(I) reduction process.

Influence of operating parameters on treatment of egg processing effluent by electrocoagulation process

The treatment of egg processing effluent was investigated in a batch electrocoagulation reactor using aluminum as sacrificial electrodes. The influence of operating parameters such as electrode distance, stirring speed, electrolyte concentration, pH, current density and electrolysis time on percentage turbidity, chemical oxygen demand and biochemical oxygen demand removal were analyzed. From the experimental results, 3-cm electrode distance, 150 rpm, 1.5 g/l sodium chloride, pH of 6, 20 mA/cm2 current density, and 30-min electrolysis time were found to be optimum for maximum removal of turbidity, chemical oxygen demand and biochemical oxygen demand. The removal of turbidity, chemical oxygen demand and biochemical oxygen demand under the optimum condition was found to be 96, 89 and 84 %, respectively. The energy consumption was varied from 7.91 to 27.16 kWh/m3, and operating cost was varied from 1.36 to 4.25 US $/m3 depending on the operating conditions. Response surface methodology has been employed to evaluate the individual and interactive effects of four independent parameters such as electrolyte concentration (0.5–2.5 g/l), initial pH (4–8), current density (10–30 mA/cm2) and electrolysis time (10–50 min) on turbidity, chemical oxygen demand and biochemical oxygen demand removal. The results have been analyzed using Pareto analysis of variance to predict the responses. Based on the analysis, second-order polynomial mathematical models were developed and found to be good fit with the experimental data.

Electrochemical Treatment of Oilfield Produced Wastewater on Ni-Sb- SnO2/Ti Electrodes

AbstractNickel and antimony doped tin dioxide (NATO) coated titanium electrodes were used for electrochemical treatment of oilfield produced wastewater. The effects of electrode distance, current density and electrolysis time on COD removal ratio, current efficiency, energy efficiency and BOD to COD ratio were investigated. The optimized electrode distance of 5 mm and current density of 6 mA cm

Enhanced Reduction of Fe(II)EDTA-NO/Fe(III)EDTA in NOx Scrubber Solution Using a Three-Dimensional Biofilm-Electrode Reactor

A promising technique called chemical absorption-biological reduction (CABR) integrated approach has been developed recently for the nitrogen oxides (NO(x)) removal from flue gases. The major challenge for this approach is how to enhance the rate of the biological reduction step. To tackle the challenge, a three-dimensional biofilm-electrode reactor (3D-BER) was utilized. This reactor provides not only considerable amount of sites for biofilm, but also many electron donors for bioreduction. Factors affecting the performance of 3D-BER were optimized, including material of the third electrode (graphite), glucose concentration (1000 mg·L(-1)), and volume current density (30.53 A·m(-3) NCC). Experimental results clearly demonstrated that this method significantly promotes the bioreduction rate of Fe(II)EDTA-NO (0.313 mmol·L(-1)·h(-1)) and Fe(III)EDTA (0.564 mmol·L(-1)·h(-1)) simultaneously. Experiments on the mechanism showed that Fe(II)EDTA serves as the primary electron donor in the reduction of Fe(II)EDTA-NO, whereas the reduction of Fe(III)EDTA took advantage of both glucose and electrolysis-generated H(2) as electron donors. High concentration of Fe(II)EDTA-NO or Fe(III)EDTA interferes the bioreduction of the other one. The proposed methodology shows a promising prospect for NO(x) removal from flue gas.

Kinetic study of slaughterhouse wastewater treatment by electrocoagulation using Fe electrodes

In this study, treatment of slaughterhouse wastewater by electrocoagulation was investigated in batch system using Fe electrodes. The effect of various variables such as electrode number, current density and operating time was tested. Pollutant removal efficiency increased with increasing electrode number and operating time. The biochemical oxygen demand (BOD(5))(,) chemical oxygen demand (COD), total suspended solid (TSS), and total nitrogen (TN) removal efficiencies using eight electrodes at a contact time of 50 min and a current density of 10 A/m(2) were 66, 62, 60, and 56%, respectively. Higher electrode numbers will allow shorter operating times to achieve certain removal efficiencies. Also, removal efficiencies increased by increasing the current density; the highest removal efficiencies of BOD(5,) COD, TSS, and TN at a contact time of 50 min and a current density of 25 A/m(2) were 97, 93, 81, and 84%, respectively. The results also show that the reactor pH varies directly with the current density; at 25 A/m(2), the reactor pH increased from an initial value of 7.1 to 7.7 after 50 min. The experimental results showed that the kinetics of BOD(5), COD, TSS and TN removal could be fitted adequately using a first order kinetic model (higher R(2)).

A Feasibility Study of Hydrogen Peroxide Electrogeneration in Seawater for Environmental Remediation

The electrogeneration of hydrogen peroxide in seawater by oxygen reduction on a gas diffusion cathode was investigated considering the feasibility of this process in an undivided reactor. The possible co-presence of different oxidants and the possibility of their synergistic action was evaluated. The loss of hydrogen peroxide due to direct anodic oxidation and to reaction with anodically electrogenerated species was evidenced. To optimize the production efficiencies of both active chlorine and hydrogen peroxide, the influence of electrode materials and current density was studied.An investigation of the possible analytical interferences was also provided.