Effect Of Cathode Material Research Articles

Capture and Electrochemical Conversion of CO2 into Carbon Nanotubes Using Molten Alkali Metal Borates

Molten alkali metal borates have recently shown promise as high-temperature sorbents for capture of CO2 and acid gases. These molten salt sorbents enable realization of thermodynamic enhancements offered by conventional solid high temperature sorbents while resolving practical challenges such as morphological degradation. Prior studies have focused on regeneration of alkali borates through steam sweeping and thermal cycling. In this work, we demonstrate that mixed sodium-lithium borate salts as CO2 sorbents can also be regenerated electrochemically, producing valuable multiwalled carbon nanotubes (MWCNT) via electroreduction of captured CO2. Effects of cathode materials and operating conditions in CO2 electroreduction in molten sodium-lithium borate are quantified. By varying relative starting compositions of alkali borates and alkali carbonates, an optimal composition of borates and carbonates is determined, achieving high coulombic efficiencies and significantly higher CO2 uptake capacities than traditionally employed carbonate salts used for conversion of CO2 into CNTs in the desirable 550-650°C range.

Effect of cathode material on the morphology and osseointegration of TiO2 nanotube arrays by electrochemical anodization technique

Titanium (Ti) has been one of the most widely used materials for biomedical implants owing to its suitable bulk and surface properties. To control the risk of tissue infection and implant failure, titanium dioxide nanotubes (TNTs) have been frequently grown on Ti surface via electrochemical anodization (EA), which is a cost-effective process offering tunable TNTs structures with ease. In the present work, the role of counter electrodes in affecting the microstructure and surface properties of TNTs was investigated. To study this less-highlighted parameter systematically, platinum (Pt), graphite (Gp), and stainless steel (SS) were selected as representatives. The use of Pt and Gp cathodes led to TNTs with typical circular morphology, while those produced with the SS cathode displayed hexagonal-shaped tubes. Moreover, TNTs fabricated with SS cathode exhibited particle debris on the surface at the expense of some portion of its tube length. This morphology, however, resulted in greater surface roughness and hydrophilicity. The highly complicated surface microstructure played a major role in facilitating the growth of bone-forming apatite during osseointegration.

Enhanced oxidation and recovery of phosphorous from hypophosphite wastewater: Key role of heterogeneous E-Fenton system with MOFs derived hierarchical Mn-Fe@PC modified cathode

Hypophosphite has high solubility and stable chemical structure, however, the effective oxidation of hypophosphite wastewater with high purity phosphate by-product recovery remains a big challenge. In this work, hypophosphite was oxidized by heterogeneous Electro-Fenton system (hetero-EF) with Metal organic Frameworks (MOFs) derived Mn-Fe co-doped porous carbon (Mn-Fe@PC) modified cathode. The effects of cathode material, current intensity and pH value were investigated. The results indicated that the Mn-Fe@PC modified cathode performed much better on hypophosphite oxidation than Fe doped porous carbon (Fe@PC) or Mn doped porous carbon (Mn@PC) modified cathodes, and the optimal Mn/Fe doping ratio was 1: 2. In the hetero-EF system, H2PO2− (10 mM) was completely oxidized within 240 min at 10 mA/cm2 of current density and 3 of pH. The radical quenching experiments results indicated that •OH was the main active species on the oxidation of H2PO2− into H2PO4−. In addition, the actual wastewater tests confirmed the feasibility of recycling high-purity lithium iron phosphate and struvite from the phosphate solution after the oxidation of hypophosphite in hetero-EF oxidation process, which would provide a new green approach for recycling phosphorus from hypophosphite wastewater.

Effect of cathode material on electrochemical reduction of levulinic acid to γ-valerolactone and valeric acid in aqueous and organic media

The electrochemical conversion of biobased levulinic acid (LA) into renewable chemicals and biofuel precursors represents an important and reasonable alternative to the high temperature conventional catalytic processes of great importance for the development of a sustainable and cost-effective biorefinery. The establishment of the mechanism of levulinic acid reduction is a promising strategy in choosing the optimal electrocatalyst for the redox-transformation of biobased substrates. Herein, we report a new approach to study an electrochemical reduction mechanism of levulinic acid using of proton-deficient non-aqueous reaction media. The electrochemical reduction of levulinic acid to γ-valerolactone (GVL) and valeric acid (VA) in aqueous and organic solutions on various electrodes (glassy carbon, graphite, Al, Pb) was studied. The mechanism of LA electrochemical reduction and major reaction products significantly was found to depend on the solvent, the presence of proton donors, the material of cathode, and the magnitude of the applied potential. In an aqueous solution the process proceeded with the formation of valeric acid on all the electrodes studied. In acetonitrile in the presence of protons, the electrochemical reduction of LA proceeded by various mechanisms, both with the participation of atomic hydrogen and the protonated form of LA, and led to the formation of GVL and/or VA. The difference (ΔE1/2) between the reduction half-wave potential of protons and levulinic acid was found to play an important role in the reduction pathway of LA carbonyl group. At a large ΔE1/2, as in the case of the GC electrode, the LA reduction resulted in the GVL formation. LA can be completely reduced to VA by transferring four electrons due to the close reduction potentials of protons and LA (a low ΔE1/2), as on a Pb electrode. The pathway depends on the conditions of the reduction process and can be estimated based on electrochemical data obtained in the study of reaction products in organic media.

Combined electrocoagulation and electrochemical oxidation treatment for groundwater denitrification

Electrocoagulation (EC) with an aluminum electrode arrangement as anode-cathode was applied to denitrify groundwater and electrooxidation (EO) was examined as a post-treatment step to remove the produced by-products. Initially, EC experiments were performed under batch operating mode using artificially-polluted tap water to investigate the effects of initial pH (5.5, 7.5, 8.5), initial NO3−-N concentration (25, 35, 45, 55 mg L−1) and applied current density (10, 20 mA cm−2) on process efficiency. The effect of initial solution pH on ammonium cation concentration was also investigated as their generation (as a by-product) is the main drawback preventing wide-scale application of these treatment processes. Experimental results revealed high nitrate removal percentages (up to 96.3%) for initial pH 7.5 and all initial concentrations and current densities, while the final ammonium concentrations ranged between 5.3 and 9.2 mg NH4+-N L−1 (for initial NO3−-N of 25 mg L−1). Therefore, EO was examined to oxidize the ammonium cations to nitrogen gas on iridium oxide coated titanium electrodes (IrO2/Ti) anode surface. The effects of cathode material (aluminum, stainless steel), total current density and anode surface area (3.3–30 mA cm−2 and 12–36 cm2, respectively) were investigated, and lead to NH4+-N percentage removals of between 25% (10 mA cm−2, 12 cm2) and 100% (30 mA cm−2, 24 cm2) for an initial NH4+-N concentration of 10 mg L−1. The optimum EC (20 mA cm−2, natural initial pH 7.5–7.8) and EO parameters (30 mA cm−2, 24 cm2 surface area anode, Al cathode) were combined into a hybrid system to treat two real nitrate-polluted groundwaters with initial NO3−-N concentrations of 25 and 75 mg L−1. Results revealed that the proposed hybrid treatment system can be used to efficiently remove nitrate from groundwaters.

Effect of Cathode Material and Its Size on the Abundance of Nitrogen Removal Functional Genes in Microcosms of Integrated Bioelectrochemical-Wetland Systems

Constructed wetland-microbial electrochemical snorkel (CW-MES) systems, which are short-circuited microbial fuel cells (MFC), have emerged as a novel tool for wastewater management, although the system mechanisms are insufficiently studied in process-based or environmental contexts. Based on quantitative polymerase chain reaction assays, we assessed the prevalence of different nitrogen removal processes for treating nitrate-rich waters with varying cathode materials (stainless steel, graphite felt, and copper) and sizes in the CW-MES systems and correlated them to the changes of N2O emissions. The nitrate and nitrite removal efficiencies were in range of 40% to 75% and over 98%, respectively. In response to the electrochemical manipulation, the abundances of most of the nitrogen-transforming microbial groups decreased in general. Graphite felt cathodes supported nitrifiers, but nirK-type denitrifiers were inhibited. Anaerobic ammonium oxidation (ANAMMOX) bacteria were less abundant in the electrochemically manipulated treatments compared to the controls. ANAMMOX and denitrification are the main nitrogen reducers in CW-MES systems. The treatments with 1:1 graphite felt, copper, plastic, and stainless-steel cathodes showed higher N2O emissions. nirS- and nosZI-type denitrifiers are mainly responsible for producing and reducing N2O emissions, respectively. Hence, electrochemical manipulation supported dissimilatory nitrate reduction to ammonium (DNRA) microbes may play a crucial role in producing N2O in CW-MES systems.

Influence Mechanism of Cathode Materials on the Transition Process of Arc Modes in Drawn Vacuum Arcs Under External AMF

The objective of this article is to determine the influence mechanism of the cathode materials on the transition process of the arc modes in high-current drawn vacuum arcs under the external axial magnetic field (AMF). Six kinds of pure metal of Cu, W, Mo, Fe, Cr, and Al were selected as the cathode materials. A high-speed charge-coupled device (CCD) video camera was selected to record the arc appearance. The experimental results indicate that the cathode materials had a great effect on the arc modes in the high-current vacuum arcs with the application of AMF. Under the cathode of W and Mo, the arc modes turned to the constriction arc mode and the anode spot arc mode more easily than that under the cathode of Cu, Fe, Cr, and Al, with the increase of the arc current. For various cathode materials and same anode, the critical current density inputting to anode surface for the transform of vacuum arc modes was different. This should be caused by the differences in the constricted characteristics and the ion energy of the vacuum arcs, which took a significant effect on the transition process of the arc modes in the vacuum arcs under AMF. The higher ion energy would lead to a more active anode, which resulted in the positive ion and metal vapor from the anode. Moreover, the cathode materials played different roles in the various stages of the discharging process of the drawn vacuum arcs. The effect of cathode material on the transition process of the arc modes in the high-current vacuum arc mainly took in Stage II, which sustained from the end of the bridge arc column to the arc current peak and dominated the transition process of the arc modes.

Effect of cathode material and charge loading on the nitrification performance and bacterial community in leachate treating Electro-MBRs

Electro-MBR technology, which combines an electrocoagulation process inside the mixed liquor of a membrane bioreactor, was studied for the treatment of a high-strength ammonia leachate (124 ± 4 mg NH4-N L−1). A lab-scale aerobic Electro-MBR was operated with a solid retention time of 45 days, hydraulic retention times of 24h and 12h, and charge loading ranging from 100 to 400 mAh L−1. At 400 mAh L−1, with a combination of a Ti/Pt cathode and a sacrificial iron anode, removal percentages for ammonia nitrogen, total organic carbon, and total phosphorus were 99.8%, 38%, and 99.0%, respectively. At 400 mAh L−1, the estimated ferric ion dosage was 325 mg Fe3+ L−1. Experiments conducted with different cathode materials showed that previously reported inhibition phenomena may result from a cathodic nitrate reduction into ammonia nitrogen. Conventional cathode materials, such as graphite, have electrochemical nitrate reduction rates of −0.03 mg NO3-N mAh−1. By comparison, when using Ti/Pt, the rate was −0.0045 mg NO3-N mAh−1(85% lower than graphite due to its low hydrogen overpotential). Charge loading tested in this study had no significant impact on both nitrification performance and microbial population diversity. However, the relative abundance of the mixed liquor’s Nitrosomonas increased from 4.8% to 8.2% when the charge loading increased from 0 to 400 mAh L−1. Results from this study are promising for future applications of the Ti/Pt - Iron Electro-MBR in various high-strength ammonia wastewater treatment applications.

The effect of cathode material, current density and anode–cathode gap on the COD and color removal from leachate by the electro-Fenton method

The effect of cathode material, current density and anode–cathode gap on the COD and color removal from leachate by the electro-Fenton method

Effect of cathode material on electro-Fenton process efficiency for electrocatalytic mineralization of the antibiotic sulfamethazine

Cathode material plays a crucial role in electro-Fenton process since its efficiency depends to the ability of the cathode material to generate H2O2 which controls the production rate of hydroxyl radicals, the main oxidizing agent for destruction of organic pollutants. Therefore, this study focused on the role of different cathode materials (i.e., carbon sponge (CS) of five different porosities, carbon felt (CF), and stainless steel (SS)) on the electrochemical oxidation and mineralization of sulfamethazine (SMT) in aqueous solution. Prior to studying the degradation and mineralization power of the cathodes under examination, we performed a systematic study of the production of H2O2. It was found that all the carbon sponge cathodes give high amounts of H2O2 in the solution, the most effective being the 45 ppi (pore per linear inch) porosity followed by carbon felt cathode. Stainless steel only gives poor amounts of H2O2 for current of 50 and 100 mA. The degradation and mineralization experiments were consistent with the yield of H2O2 for all electrolytic systems; electrolytic cells with higher H2O2 production capacity showed better performance on SMT degradation/mineralization. The most effective electrolytic system for SMT removal from polluted water was Pt/CS 45 ppi reaching a mineralization rate of 91.1% at 300 mA while the less effective was Pt/SS with only 41% mineralization.

Effects of cathode materials on H2O2 production in microbial fuel cells

Effects of cathode materials on H2O2 production in microbial fuel cells

Effect of cathode material on the electrorefining of U in LiCl-KCl molten salts

The influence of cathode materials on the U electrorefining process is examined using electrochemical measurements and SEM-EDX observations. Stainless steel (STS), Mo, and W electrodes exhibit similar U reduction/oxidation behavior in 500 °C LiCl-KCl-UCl3 molten salts, as revealed by the cyclic voltammograms. However, slight shifts are observed in the cathodic and anodic peak potentials at the STS electrode, which are related to the fast reduction/oxidation kinetics associated with this electrode. The U deposits on the Mo and W electrodes consist of uniform dendritic chains of U in rhomboidal-shaped crystals, whereas several U dendrites protruding from the surface are observed for the STS electrode. EDX mapping of the electrode surfaces reveals that simple scraping of the U dendrites from W electrodes pretreated in dilute HCl solutions to dissolve the residual salt, results in clear removal of the U deposits, whereas a thick U deposit layer strongly adheres to the STS electrode surface even after treatment. This result is expected to contribute to the development of an effective and continuous U recovery process using electrorefining.

Effects of Electrically Activated Silver–Titanium Implant System Design Parameters on Time-Kill Curves Against Staphylococcus aureus

Implant-associated infections pose serious threats to patients in terms of morbidity, mortality, and medical costs. This paper focuses on the quantitative assessment of the antimicrobial efficacy of a silver-based prophylactic system for orthopaedic implant applications. The implant system is configured to induce controlled local administration of silver ions via low intensity direct current activation (1–14 µA). We developed a broth-based in vitro testing model to evaluate the effects of important design parameters on the antimicrobial efficacy of the system over a 48-h interval. The time-kill curves obtained with various parameter levels were analyzed through a longitudinal model. Five parameters were investigated independently through one-way factorial experiments (n = 12) against Staphylococcus aureus. In phase 1 of the study, we investigated the effect of cathode material on system performance. We also determined the linear structure of the longitudinal model based on the Akaike information criterion by fitting the empirical data to multiple candidate model structures. The results show that substituting the silver cathode with titanium does not weaken the antimicrobial efficacy of the system (p = 0.9946). In phase 2, a detailed analysis with four design parameters was conducted using the silver–titanium configuration. The performance of the system was found to be independent of the electrode separation distance (p = 0.9926) and the pulsating current frequency (p = 0.9956). However, the anode surface area (p < 0.0001) and the current intensity (p < 0.0001) influenced the antimicrobial efficacy in an interactive manner. Overall, this study characterizes the in vitro antimicrobial efficacy of the proposed system and provides a reference of design parameters for future product engineering.

Effects of cathode design parameters on in vitro antimicrobial efficacy of electrically-activated silver-based iontophoretic system.

Post-operative infection is a major risk associated with implantable devices. Prior studies have demonstrated the effectiveness of ionic silver as an alternative to antibiotic-based infection prophylaxis and treatment. The focus of this study is on an electrically activated implant system engineered for active release of antimicrobial silver ions. The objective was to evaluate the effects of the cathode design, especially the cathode material, on the in vitro antimicrobial efficacy of the system. A modified Kirby-Bauer diffusion technique was used for the antimicrobial efficacy evaluations (24 h testing interval). In phase-1 of the study, a three-way ANOVA (n = 6, α = 0.05) was performed to determine the effects of cathode material (silver, titanium, and stainless steel), cathode surface area and electrode separation distance on the efficacy of the system against Staphylococcus aureus. The results show that within the design space tested, none of these parameters had a statistically significant effect on the antimicrobiality of the system (P > 0.15). Subsequently, one-way ANOVA (n = 6, α = 0.05) was conducted in phase-2 to validate the inference regarding the non-significance of the cathode material to the system efficacy using a broader spectrum of pathogens (methicillin-resistant S. aureus, Escherichia coli, Streptococcus agalactiae and Aspergillus flavus) responsible for osteomyelitis. The results confirmed the lack of statistical difference between efficacies of the three cathode material configurations against all pathogens tested (P > 0.58). Overall, the results demonstrate the ability to alter the cathode material and related design parameters in order to minimize the silver usage in the system without adversely affecting its antimicrobial efficacy.

The effect of cathode material on nitric acid reduction kinetics

The combined effect of potential and temperature on the mechanism of autocatalytic reduction of nitric acid is analyzed. The change of solubility of nitrogen oxides with temperature allows separation of potential intervals with predominant contribution of homogenous autocatalysis. Heterogeneous autocatalysis dominates in concentrated media, while homogenous catalysis is more real in totally disassociated solutions. The presence of nickel in steels catalyzes the formation of ammonia ions.

The Effect of Cathode Materials on Indirect Electrochemical Oxidation of Methyl Orange, Malachite Green and Methylene Blue

The influence of cathode material on the electrochemical degradation of methyl orange (MO), methylene blue (MB) and malachite green (MG) dyes was investigated. The cathode materials used were platinum (Pt), copper (Cu), zinc (Zn) and aluminum (Al). The electrochemical activity of the selected dyes on the metal cathodes was examined by cyclic voltammetry (CV). The electrochemical treatment was carried out in both divided and undivided cells. The degradation process was monitored by UV-Visible spectroscopy and chemical oxygen demand (COD) measurement. The influence of pH on discoloration and degradation of dyes was studied. The power consumption and current efficiency of the treatment process involving different cathode materials was computed and compared. The role of cathode material in the degradation of dyes has been established.

Effects of cathode materials on the characteristics of electrolyte supported micro-tubular solid oxide fuel cells

The effects of the GDC–LSCF (Ce0.8Gd0.2O0−δ–La0.6Sr0.4Co0.2Fe0.8O3−δ) cathode layer and the GDC interlayer on the electrochemical performance of the ScSZ (Zr0.8Sc0.2O2−δ) electrolyte supported (≈270 μm) micro-tubular SOFC cells are investigated in this study. Material formulation and sintering profile for fabricating the micro-tubular SOFC cells are developed to avoid physical defects caused by the large sintering shrinkage mismatch among the layers. Cell B (with the LSCF–GDC composite cathode layer and the GDC interlayer) reports an ohmic resistance slightly higher than that of Cell A (with the GDC–La0.8Sr0.2MnO3−δ, i.e. LSM, composite cathode), while its polarization resistance emerges to be significantly smaller than that of Cell A. In terms of cell performance, Cell B demonstrates an OCV value (>1.07 V) similar to that of Cell A and a maximum power density (0.26 W cm−2) 44.4% greater than that of Cell A (0.17 W cm−2) at 850 °C. It can thus be concluded that using the LSCF–GDC composite-cathode layer and inserting the GDC interlayer help reduce the total cell impedance, thereby improving the power density of the tubular cells.

Numerical Simulation of the Effect of Cathode Materials on the Displacement in a 350 KA Aluminum Reduction Cell

A three dimensional mathematical model was developed to calculate the displacement of a 350 kA cell with graphitized cathode during preheat and early operation, and the calculated results have been compared and discussed with the measurements. The displacement has been studied for three typical kinds of aluminum reduction cells (semi-graphitic, graphitic and graphitized) after 30 days start-up. First, the sodium concentration distribution after 30 days start-up in cathode carbon blocks was calculated by one FE model of a cathode block. And numerical simulation was utilized to study the displacement fields of the above three typical kinds of the cell, which took the stress caused by chemistry and temperature gradient into account. The results indicate that the value of the cell displacement decreases with time during 30 days start-up and reaches a constant value.

Effect of Cathode Materials on Electrochemical Degradation of Luganil Blue N and Acid Red I

The degradation of Acid Red I dye (ARI) and Luganil Blue N (LBN) has been studied by electrochemical treatment methods. The efficiency of cathode materials such as platinum, copper, zinc, lead, graphite, nickel, steel and titanium metals on the degradation of Luganil Blue N and Acid Red I dyes were investigated. The suitable cathode material was chosen and other parameters such as current density, and NaCl and dye concentrations were optimized. The electrolysis process was monitored by UVVis spectrophotometer and measuring chemical oxygen demand of the electrolyzed solutions. The overall COD removal efficiencies reached as high as 74.24% and 87% for ARI and LBN, respectively.

Synthesis of micro and nanostructured MnO2 and their comparative study in lithium battery

Micro and nanostructured γ-MnO2 are synthesized to investigate the size effect of cathode active materials in battery performance. MnSO4 and (NH4)2S2O8 were used as starting materials to prepare micro and nanostructured samples in the presence of stirring and ultrasonic irradiation, respectively. Structure optimization is done by changing values for temperature and manganese sulphate concentration. The MnO2 micro and nanoparticles are characterized by scanning electron microscopy and X-ray diffraction (XRD). The XRD results reveal that only γ-MnO2 is formed under the reaction conditions. Under the optimized conditions, manganese dioxide nanoparticles, with an average particle size of 56 nm, are obtained. Both micro and nanostructured MnO2 is used as the cathode active material in Li/MnO2 battery. Discharge profiles of stirrer-based cathode material (micro) and ultrasonic instrument-based one (nano) compared with each other in constant discharge currents of 50 and 100 mA g−1. The results demonstrated that nanosized materials show higher specific capacities and energies. Electrochemical impedance spectroscopy is used to investigate the size effect of cathode material on battery resistance and the results show a copious decrease in total resistance.