Effect Of Electrolyte Concentration Research Articles

Analyses and optimization of electrolyte concentration on the electrochemical performance of iron-chromium flow battery

In order to improve the electrochemical performance of iron-chromium flow battery, a series of electrolytes with x M FeCl2 + x M CrCl3 + 3.0 M HCl (x = 0.5, 0.75, 1.0, 1.25) and 1.0 M FeCl2 + 1.0 M CrCl3 + y M HCl (y = 1.0, 2.0, 3.0, 4.0) are prepared, and the effect of electrolyte concentration on the electrochemical performance of iron-chromium flow battery are firstly investigated. The viscosity of electrolyte increases along with the increasing concentration of FeCl2, CrCl3 and HCl, however, the corresponding conductivity decreases with the increasing concentration of FeCl2 and CrCl3 but increases with the increasing HCl concentration. It is worth noting that the electrolyte with 1.0 M FeCl2, 1.0 M CrCl3 and 3.0 M HCl presents the best electrochemical performance due to the synergistic effect of viscosity, conductivity and electrochemical activity. Most importantly, iron-chromium flow battery with the optimized electrolyte presents excellent battery efficiency (coulombic efficiency: 97.4%; energy efficiency: 81.5%) when the operating current density is high up to 120 mA cm−2. This work can improve the battery performance of iron-chromium flow battery more efficiently, and further provide theoretical guidance and data support to its engineering application.

Effect of Electrolyte Concentration on the Solvation Structure of Gold/LITFSI–DMSO Solution Interface

The use of high-concentration electrolytes in lithium metal batteries enables the effective suppression of lithium dendrite growth at the lithium anode. The issue of the solvation structure at the ...

Effects of electrolyte concentration on the morphology control of gold nanotips in electrochemical etching

Gold nanotips fabrication with electrochemical etching has advantages of low cost, short processing time and easy operation, while the morphology control and related electrochemical etching mechanism remain to be explored. Through analyzing the cyclic voltammetry curves during the etching processes, it was found that HCl solution is more stable in fabricating nanotips as compared to KCl solution. The effects of electrolyte concentration on the etching process were also investigated. Based on the constant meniscus descending rate and radial etching rate, a model to explain the unique tip morphology formed at different electrolyte concentrations was established, which indicated that the cone angles of the tips gradually decreased with the increase of the HCl concentration, while the curvature radius was not sensitive to the concentration. This investigation demonstrated the controllability of tip cone angle during the etching process, which would be of great significance to low cost preparation and application of gold nanotips on the high-resolution detection of biological and medical molecules.

The Effect of Electrolyte Concentration and Electric Current on the Quality of Surface Coloring on Anodized Aluminum

The use of aluminum metal in daily life has widely used coloring techniques to enhance the aesthetic value of the metal. Aluminum anodizing process can produce porous on the metal surface. The formed porous can be used to store and hold the coloring agent to make them more durable. The research intends to observe the coloring characteristics on the aluminum surface influenced by several parameters of the anodizing process, including electrolyte concentration and electric current. In this study the current H2SO4 concentration was used as a variable to improve the quality of staining on anodized aluminum surfaces. The anodization process was carried out on H2SO4 electrolyte solution with variations in concentrations of 10% to 20% and the current density used was 3 A to 5 A. The tests were carried out using micro Vickers to observe the hardness value. The hardness was higher at lower concentration of electrolyte solution due to thinner layer of oxide film, scanning electron microscope to observe the structure and visual observations for anodized color quality. From the results given, the tendency of the lower current density the size and density of porous lower. With the same condition, the color was darker than higher current density.

Fabrication of High-Aspect-Ratio Microwire Electrodes Using a Vertical Liquid Membrane Electrochemical Etching Method

A vertical liquid membrane electrochemical etching method is proposed for the fabrication of high-aspect-ratio microwire electrodes. The potential and current density distributions are simulated using COMSOL software. The simulation results show that the unique potential distribution generated by the proposed method, combined with reciprocating linear motion of the wire electrode, can be used to fabricate microwire electrodes with large aspect ratio. These simulation results are verified experimentally. Different concentrations of electrolyte result in different reaction rates and thus different distributions of the diffusion layer and different bubble flows, resulting in different morphologies of the prepared wire electrodes. The effect of electrolyte concentrations is studied experimentally. At low electrolyte concentrations, the products of electrolysis are removed from the processing area under the action of gravity, and uniform electrodes with high aspect ratio can be prepared. At high electrolyte concentrations, intense bubble production destroys the diffusion layer around the electrode and leads to a dynamic equilibrium state, allowing the preparation of uniform wire electrodes in a rough machining process. The proposed method can prepare wire electrodes with different initial diameters. In this paper, uniform wire electrodes of length 1900 μm, diameter 7 μm, and aspect ratio 270 are fabricated by the proposed method from a tungsten wire of initial diameter 50 μm.

Effect of coated and geometrically modified tools on performance of electrochemical micromachining

ABSTRACT Micro-holes are the basic features which are found in various components of medical devices, electronics, and biotechnology devices. The existing machining methods in ECMM for making micro-holes are generally accompanied with higher overcut (OC). Therefore, it is important to suppress OC and improve the machining rate (MR) which predominantly depend on electrode size, electrical parameters, tool electrode insulation, and electrolyte type. Hence, in this research, the suitable tool geometry and coating for the tool electrode is proposed, namely, ceramic, hot melt adhesive (HMA), and hollow wedge, short solid tools, respectively. The effect of electrolyte concentration in g/L, machining voltage in V and duty cycle in % on the OC and MR was studied. The results show that the ceramic tool produces 43.1% lesser OC than normal tool at the parameter combination of 23 g/L, 15 V, and 85% and short solid tool produces 74.3% higher MR for former with same parametric combination. The scanning electron microscope pictures of micro-holes were analyzed to study the effect of tool geometry and its coating. The ceramic and HMA coated tools control the leakages of current and shape modified tools to enhance the flow of current in the inter-electrode gap.

Effect of electrolyte concentration on the tribological performance of MAO coatings on aluminum alloys

Micro-arc oxidation (MAO) is an efficient approach to improve the hardness, wear resistance, and other properties of aluminum alloys. In order to investigate the effect of the electrolyte concentration on the properties of MAO coatings for LY12 alloy, the voltage variation during the MAO process was recorded. The surface morphologies and phase compositions of the coatings produced with different electrolytes were investigated using scanning electron microscopy and X-ray diffraction, respectively. The roughness and thickness of the coatings were measured using a pocket roughness meter and an eddy-current thickness meter, respectively. The tribological performances of the coatings were investigated against GCr15 bearing steel on a ball-on-disc wear tester in open air. The results showed that with an increase in the Na2SiO3 content, the working voltage of the MAO process decreased, the roughness and thickness of the coatings increased significantly, and the relative content of the α-Al2O3 phase decreased. With an increase in the KOH content, the working voltage decreased slightly, the roughness and thickness of the coatings increased slightly, and the α-and γ-Al2O3 phase contents remained unchanged. The friction coefficient and wear rate of the coatings increased with an increase in the Na2SiO3 and KOH concentrations. A decrease in the porosity and roughness and an increase in the α-Al2O3 content of the coatings reduced their wear mass loss.

Colour and COD removal from aqueous solutions of direct yellow 86 textile dyestuff by electro-Fenton method

In this study, COD and colour removal were investigated by the electro-Fenton method from aqueous solutions of direct yellow 86 commercial textile dyes. The effects of electrolyte concentration (250-3,000 mg/L), H2O2 concentration (250-3,000 mg/L), the initial dye concentration (50-500 mg/L), the distance of anode-cathode (0.5-1.5 cm) on COD and colour removals were investigated. Under optimal experimental conditions (NaCl: 1,500 mg/L, H2O2: 1,500 mg/L, the initial dye concentration: 50 mg/L, the distance of anode-cathode: 1.5 cm), the maximum COD and colour removal efficiencies were 95.3% and 99.5%, respectively. It was determined that H2O2 concentration and dye concentration had the highest effect on the removal efficiencies. It was determined that pollutant removal efficiencies increased with increasing H2O2 concentration, and decreased with increasing initial dye concentration. The results showed that the electro-Fenton method can be effectively applied in COD and colour removal from aqueous solutions of direct yellow 86 commercial textile dyestuff.

NiO nanoplates for energy storage application: Role of electrolyte concentration on the energy storage property

Here in, synthesis of NiO nanoplates by employing a mixed solvent system under solvothermal method followed by calcining the obtained product nickel hydroxide in air is reported. Diffraction, microscopic, and spectroscopic results confirmed the formation of NiO phase. The as synthesized NiO nanoplates are tested as a robust material for energy storage applications. The effect of electrolyte concentration on the capacitive behavior of NiO is studied thoroughly. The outcome from the electrochemical analysis reveals that NiO nanoplates have a high specific capacity value of 108.4 C g−1 (270 F g−1) in 6 M KOH electrolyte and the value decreases to 85.0 C g−1 (212.5 F g−1) and 78.2 C g−1 (195.5 F g−1) for 4 M, and 2 M KOH electrolyte, respectively. The resistance values also decreased with increase in the KOH concentration. The better electrochemical performance depicted by the 6 M KOH electrolyte is mainly ascribed to the availability of plenty of OH− ions in the electrolyte solution, which helped in the proper wettability of the sample so that the OH− ions can participate to higher extent during the electrochemical redox reactions, due to which the observed charge storage capacity is more in higher electrolyte concentration and vice-versa. Thus, the results suggest the usefulness of this material for energy storage applications.

Effect of Electrolyte Concentration in Process Water on Flocculation

Abstract. The effect of electrolyte concentration and potential determining ions on the coagulation and flocculation of illite, dolomite, and illite-dolomite mixture suspensions was investigated. Electrokinetic measurements, settling rate tests, and viscosity measurements were performed to examine the stability of these mineral suspensions and to characterize flocculants under various physico-chemical conditions. Two flocculants: A-100 anionic polyacrylamide (PAM) and polyethylene oxide (PEO) were employed.
 The tests revealed that polyethylene oxide does not flocculate dolomite under any tested conditions. Viscosity results corroborated that the conformation of PAM macro- molecules in water is very sensitive to electrolyte concentration; on the other hand, the conformational state of PEO macromolecules is not affected by ionic strength. The intrinsic viscosity measurements suggest that the unattainable flocculation of dolomite suspensions with PEO must result from poor adsorption of this flocculant onto dolomite particles. In both tested cases, with PAM and PEO, the relationship between coagulation and flocculation was not confirmed.
 
 Resumen. Se investigó el efecto de la concentración electrolítica y iones determinantes de potencial en la coagulación y floculación de suspensiones de ilita, dolomita y mezcla de ilita-dolomita. Mediciones electrocinéticas, ensayos de velocidad de sedimentación, y mediciones de viscosidad fueron realizadas para examinar la estabilidad de estas suspensiones minerales y caracterizar floculantes bajo varias condiciones fisicoquímicas. Se empleó dos floculantes: A-100 poliacrilamida aniónica (PAM) y óxido de polietileno (PEO).
 Los experimentos revelaron que el óxido de polietileno no flocula la dolomita bajo ninguna condición empleada. Los resultados de viscosidad corroboraron que la conformación de las macromoléculas PAM en agua es sensible a la concentración electrolítica; por otro lado, el estado conformacional de las macromoléculas de PEO no se ve afectado por la fuerza iónica. Las mediciones de viscosidad intrínseca sugieren que la floculación inalcanzable de las suspensiones de dolomita con PEO debe ser resultado de una mala adsorción de este floculante en las partículas de dolomita. En ambos casos probados, con PAM y PEO, no se confirmó la relación entre coagulación y floculación.

The effect of electrolyte concentration and electric current on the quality of surface colouring on anodized aluminium

The use of aluminium metal in daily life has widely used colouring techniques to enhance the aesthetic value of the metal. Aluminium anodizing process can produce porous on the metal surface. The formed porous can be used to store and hold the colouring agent to make them more durable. The research intends to observe the colouring characteristics on the aluminium surface influenced by several parameters of the anodizing process, including electrolyte concentration and electric current. In this study the current H2SO4 concentration was used as a variable to improve the quality of staining on anodised aluminium surfaces. The anodization process was carried out on H2SO4 electrolyte solution with variations in concentrations of 10% to 20% and the current density used was 3 A to 5 A. The tests were carried out using micro Vickers to observe the hardness value. The hardness was higher at lower concentration of electrolyte solution due to thinner layer of oxide film, scanning electron microscope to observe the structure and visual observations for anodised colour quality. From the results given, the tendency of the lower current density the size and density of porous lower. With the same condition, the colour was darker than higher current density.

Constructing geometrically-ordered alumina nanoporous filters and alumina nanowire arrays by using ultrahigh voltage two step anodization

Abstract A simple ultrahigh voltage two-step anodization was developed to fabricate nanopore and nanowire arrays which can be utilized in various applications like water purification filter technology. Investigation of the electrolyte concentration effect on controlling the morphology and geometry of the alumina nanopore and nanowire (ANW) arrays has been done. The anodization was carried out in H2C2O4/H3PO4 mixture at about 0 °C to reach the best ordered nanopores array. In hard anodization step, the current density showed a peak shape profile so that its maximum was directly depended on the H3PO4 concentration. The SEM images of the arrays were studied by image histogram and fast Fourier transform (FFT). The model curves demonstrated direct dependency of the nanopores ordering on electrolyte concentration. The most ordered array was achieved by utilizing 0.3 M H2C2O4 and 0.35 M H3PO4. The SEM images showed that the pores became wider by etching the nanopores in an acidic solution. In addition, fast fabrication of nanowire arrays was achieved by managing the anodization process at 30 °C in a short time. The ANWs were obtained from nanopores etching through the anodization, without an extra etching step requirement. The studies on SEM images demonstrated succeeding high ordered ANWs bundle.

Effect of electrolyte concentration on morphological and photoluminescence properties of free standing porous anodic alumina membranes formed in oxalic acid

The free-standing porous anodic alumina membranes (AAM) were prepared in oxalic acid by varying electrolyte concentration from 0.1 to 0.9 M with a constant potential of 40 V at 8 °C. The influence of electrolyte concentration on the morphological and optical features of AAM has been studied. Regularity ratio (RR) of AAM was measured using WSxM software, highest RR obtained for AAM formed in 0.3 M. From X-ray diffraction (XRD) analysis, it was found that prepared AAM were amorphous in nature. UV–Vis absorbance spectra reveal that absorbance bands slightly moves towards the higher wavelength side with increasing electrolyte concentration. Photoluminescence (PL) of AAM has been studied and related with RR of AAM. PL measurements of AAM exhibit strong PL peak in blue region, having a slight change with increasing electrolyte concentration. PL bands were originating from two kinds of oxygen-deficient defects (F and F+), their distributions were discussed on the basis of PL spectrum.

Enhancement in Desalination Performance of Battery Electrodes via Improved Mass Transport Using a Multichannel Flow System.

Desalination technologies have heavily been investigated to utilize the abundant salt water on Earth due to the global freshwater shortage. During recent years, the desalination battery (DB) has attracted attention for its low-cost, eco-friendly, and energy-efficient characteristics. However, the current DB system is subject to inevitable performance degradation because of the mass-transfer limitation at the electrode-electrolyte interface, particularly when the system is used to treat brackish water. Here, we present a novel strategy to overcome the intrinsic mass-transfer limitation of DB in brackish water using an effective cell design based on a multichannel flow system. Compared to the conventional DB that consists of one feed channel, the multichannel desalination battery (MC-DB) is configured using two side channels introducing a highly concentrated solution to the electrodes and one middle feed channel for water desalination. The MC-DB showed a desalination capacity of 52.9 mg g-1 and a maximum salt removal rate of 0.0576 mg g-1 s-1 (production rate of 42.3 g m-2 h-1) when a salinity gradient between the feed streams in the middle (10 mM NaCl) and side (1000 mM NaCl) channels was present, which were 3-fold higher than those in the case with no salinity gradient. In addition, the high concentration solution in the side channel significantly enhanced the rate capability of MC-DB, allowing the system to operate under a high current density of 40 A m-2 with a desalination capacity of 34.1 mg g-1. Considering the effect of electrolyte concentration on the battery electrode performance through electrochemical characterization, the highly saline medium at the side channel in the MC-DB creates an optimal environment for the battery electrode to fully capitalize the high desalination capacity, salt removal rate, and capacity retention of the battery electrodes.

Methodology for Determining Point of Zero Salt Effect of Clays in Terms of Surface Charge Properties

Surface charge properties of colloids can be studied from their point of zero charge (PZC) measurements. The point of zero salt effect (PZSE), a category of PZC, indicates the pH value at which the effect of electrolyte concentration on a pH-dependent charge is zero. In the present study, it was mathematically deduced that for clay minerals, the rate change of pH and zeta potential with ionic concentration approaches zero at a pH value corresponding to the PZSE of the soil. The procedure is based on applying the constraint of electroneutrality to the charge-balance equation for colloids in equilibrium with an electrolyte. The theoretical observations were corroborated experimentally by obtaining the pH and zeta potential variations of three mineralogically diverse soils and comparing the values with the standard salt titration results. The study identifies PZSE from pH measurement as a more suitable approach for soil exhibiting variable charge. In the case of highly reactive soils, PZSE measurement using a divalent electrolyte medium yielded comparable results. In view of the obtained results, the proposed method can be an alternative for PZSE determination of clay minerals.

Mathematical Modelling of Material Removal Rate and Diameter of overcut for Sodalime glass through pressurized flow ECDM Process by Response Surface Methodology

The effect of electrolyte concentration, voltage, duty factor and electrolyte flow rate on material removal rate (MRR) and diameter of overcut (DOC) of the micro-hole machining of sodalime has been studied. The experimental values changed with the theoretical calculation in the range of 3 – 10 %. This mathematical model showed that decreasing electrolytic concentration reduces MRR and DOC. Pressurized flow Electrochemical DischargeMachining (pf-ECDM) can meet these differences. In order to put this phenomenon to use many experiments were experimented to machine holes on glass. Since parameters like electrolyte concentration, voltage, duty factor and electrolyte flow rate play an important role in MRR and DOC it needs to be calculated in order to improve the capability of this technology in machining difficult and high aspect ratio features. A mathematical model has been extensively developed to know the role of electrolyte concentration, voltage, duty factor and electrolyte flow in MRR and DOC of the process. However, machining excessive component ratio elements on ceramics like glass stays an ambitious challenge due to overcut. Although, electrical discharge machining (EDM) and electrochemical machining (ECM) are properly set up non-traditional strategies to meet these challenges, they are restrained to electrically conductive materials. In order to execute functionalities like excessive power and sustainability with minimal use of space, the raw substances used need to possess desirable mechanical, chemical and physical properties. Experimental research has been conducted, and the model was proven below various machining parameters. Demand for miniaturized merchandise is ever growing as they accomplish the venture of supplying the preferred functionalities with high efficiency using minimalistic raw material. These researches proved that growing the voltage in pf-ECDM plays a primary function in growing the MRR of the machined features.

Effects of electrolyte concentration on the microstructure and properties of plasma electrolytic oxidation coatings on Ti-6Al-4V alloy

In this investigation, the effect of electrolyte concentration parameters on the plasma electrolytic oxidation (PEO) coatings on Ti-6Al-4V alloy were investigated by an orthogonal experiment involving four factors with three levels by changing the concentration of Ca(CH3COO)2·H2O, NaH2PO4·2H2O, Ethylene-diamine-tetra-acetic acid (EDTA) and NaOH, respectively. The self-corrosion current density, Ca/P, bond strength, phase composition and microstructure of the coatings were studied in detail. The results indicate that the nine PEO coatings had unevenly distributed porous structures comprising different ratios of titanium, rutile, and anatase phase. The effect of electrolyte concentration parameters on the properties and performance of coatings are sequenced hierarchically as follows: EDTA > NaOH > Ca(CH3COO)2·H2O > NaH2PO4·2H2O for corrosion resistance, NaOH > EDTA > Ca(CH3COO)2·H2O > NaH2PO4·2H2O for Ca/P, Ca(CH3COO)2·H2O > NaH2PO4·2H2O > NaOH > EDTA for bond strength. The highest bond strength of the PEO coatings can reach as high as 60 MPa. The optimized electrolyte composition for the Ti-6Al-4V is: CCa(g/L) = 11.44 g/L, CP(g/L) = 5.72 g/L, CEDTA(g/L) = 10 g/L, CNaOH(g/L) = 15 g/L and the corresponding PEO coating had adequate thickness (11.78 μm), satisfactory bond strength (33.69 MPa) and a fitting Ca/P ratio of 1.68.

Nickel ferrite/polypyrrole core-shell composite as an efficient electrode material for high-performance supercapacitor

In the present work, we report the high-performance supercapacitive behavior of NFO/PPy core–shell composite. The composite electrode was prepared by adopting simple and inexpensive in-situ chemical oxidation route in an aqueous medium containing sodium dodecyl sulfate (SDS) as a surfactant and characterized for the spectral, structural, electrical, thermal and morphological studies. The electrochemical properties were recognized by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy. The supercapacitive performance of NFO/PPy electrode was studied in an aqueous 0.1N H2SO4 electrolyte solution. The effect of electrolyte concentration on specific capacitance and the stability of electrode were studied. The highest specific capacitance (Cs) achieved with NFO/PPy electrode was 721.66 Fg−1. The specific energy (Es), specific power (Ps) and coulomb efficiency (η%) were observed to be 51.95 Whkg−1, 6.18 kWkg−1 and 99.08% respectively. This electrode shows the outstanding electrochemical stability over 1000th continuous charging–discharging cycles and emerged as an efficient electrode material for energy storage devices as a supercapacitor.

Improving the cycle life of cryptomelane type manganese dioxides in aqueous rechargeable zinc ion batteries: The effect of electrolyte concentration

Rechargeable aqueous zinc ion batteries (ZIBs) have many advantages such as high abundance and low cost of Zn, as well as safer battery chemistry in aqueous electrolytes. Cryptomelane-type manganese dioxides (α-MnO2s) are promising cathodes for ZIBs due to their high theoretical capacity, voltage, and abundance. However, α-MnO2 suffers from severe capacity fading as the battery is put through extended charge-discharge cycles. Here, we show that galvanostatic cycling performance of α-MnO2 can significantly be improved at ZnSO4 concentrations below 0.2 M. Low-electrolyte concentrations demonstrated higher discharge capacities and capacity retentions at long battery cycling tests. At 0.1 M ZnSO4, α-MnO2 delivered 62 and 103 mAh/g capacities with 0.3 A/g rate at the 1st and 100th cycles, respectively (166% retention). At a higher charge/discharge rate of 0.9 A/g, α-MnO2 delivered 85 mAh/g capacity at the 500th cycle, where the retention was 167% with respect to the 1st cycle in 0.1 M ZnSO4. On the other hand, at high electrolyte concentrations (>1.0 M), the capacity retentions were below 30% and discharge capacities were below 60 mAh/g after 100 cycles. Better electrochemical performance of α-MnO2 at low electrolyte concentrations is attributed to the suppression of cathode dissolution and the mitigation of the formation of impurity phases such as ZnMn2O4 and ZnMn3O7·xH2O.

Parametric analysis of water electrolysis by dual electrolytes and cells

ABSTRACTIn this study, sulfuric acid and potassium hydroxide are used as the electrolytes, separated by proton exchange membrane, to produce hydrogen. The effects of electrolyte concentrations, applied voltage, single or dual cells, and temperature on the hydrogen production rate and energy efficiency are investigated. Experimental results show that the amount of hydrogen production increases with voltage, and the dual electrolytes and cells can yield the best hydrogen production rate and energy efficiency. With 1-M KOH plus 1-M H2SO4 as electrolytes in separated cells, the highest hydrogen production rate is about 0.95 L/hr. Results also show that the rise of electrolyte temperature can significantly increase the hydrogen production rate up to 50%, and the energy efficiency up to 20%. Keeping a low PH value in cathodeand high anode PH value in anode indeed enhances the efficiency of hydrogen production rate.