Electrolyte Parameters Research Articles

SYNTHESIS OF ELECTROLYTIC TERNARY ALLOYS WITH HIGH MICROHARDNESS

Electrodeposition of electrolytic alloys consisting of metals of the iron subgroup and zirconium allows obtaining a coating with a unique combination of physical and chemical properties that cannot be achieved by other coating methods. One of the reasons limiting the use of electrolytic coatings based on such alloys is the complexity of process control process and composition forecasting. The properties of alloys of the iron subgroup containing refractory metals and their composites depend not only on the chemical composition, that is, the content of the refractory component, but also on the deposition conditions. Varying the polarization current density allows the deposition of coatings of different composition and, accordingly, different functional properties. The aim of the work was to study the influence of electrolysis parameters on the chemical composition, structure, surface morphology and physical and mechanical properties of CoNiZr ternary alloy coatings. The formation of CoNiZr ternary alloys from citrate electrolyte on the copper surface in pulse mode was studied. The influence of electrolyte pH, mixing and current density on the composition, surface morphology and current yield and microhardness of ternary electrolytic alloys of the iron and zirconium subgroup was determined. The resulting coatings are characterized by a uniformly developed surface without cracks and sufficiently high and reproducible microhardness. Based on the results of the experiments, it can be concluded that the zirconium content does not affect the microhardness of the CoNiZr coating, but depends on the conditions of electrolysis and the properties of the electrolyte. Based on the conducted studies to determine the influence of electrolysis parameters on the microhardness of electroplated coatings, it was found that the properties of ternary CoNiZr coatings depend on the pH of the electrolyte, temperature and pulse current density. The conducted studies allow us to determine the conditions for obtaining high-quality coatings with specified functional properties.

Eletrochemical evaluation of a sensor modified with tucumã biochar for analysis of environmental samples

In this study, a carbon paste electrode modified with tucumã biochar (EPCM/TB) was produced for the determination of pyridine in industrial effluents. To develop the methodology, different paste proportions were evaluated, and a proportion of 40:30:30 (m/m/m) of graphite:tucumã biochar:binder was selected. Cyclic voltammetry was used to characterize the charge and mass transfer process of the electrochemical system; the reaction occurred with the transfer of two electrons. The reaction was irreversible and controlled by diffusion. The experimental variables such as the supporting electrolyte, pH and instrumental parameters of the differential pulse voltammetry (DPV) technique were evaluated. After the optimization of these parameters, four analytical curves were constructed using DPV to calculate the matrix effect (ME). The analytical curves in the presence of the matrix showed good linearity for the three effluents, with R2 values of 0.991, 0.997 and 0995. The limits of detection (LODs) for effluents 1, 2 and 3 were 34.9, 5.5 and 36.8 nmol/L, respectively. The limits of quantification (LOQs) for effluents 1, 2 and 3 were 116.6 nmol/L, 18.4 nmol/L and 122.6 nmol/L, respectively. The MEs of the three effluent samples showed values above 50.0 %, indicating strong MEs; therefore, the quantification of pyridine was performed using the matrix curves. The method had recoveries close to 100 % for the three effluents. The repeatability and reproducibility studies of the method provided RSD% values below 5 %; therefore, the method has potential application in the quantification of pyridine in textile effluents.

Effects of heat stress on global DNA methylation and blood parameters of two strains of laying hens.

This study aimed to determine the global levels of DNA methylation and alterations in hematological and electrolytic parameters of two strains of laying hens subjected to heat stress and thermal comfort in climatic chambers. The experiment was conducted in two climate chambers with 192 laying hens of two strains: Dekalb White and Dekalb Brown. After the seven-day adaptation period, each climate chamber was programmed to a thermal condition for 28 consecutive days: Comfort (THI = 73.8) and Heat Stress (THI = 85.9). Blood samples were collected weekly. At each collection, a total of three milliliters of venous blood was collected from the ulnar wing or jugular vein. The experimental design was a randomized complete block design, with a 2 × 2 factorial scheme with split plots. Blood glucose, complete blood count, pH, ionized calcium, sodium, potassium, chloride, and global DNA methylation were evaluated. Stress increased chloride levels but did not affect the other evaluated blood parameters. At 28days of the experiment, the Dekalb Brown strain showed higher levels of leukocytes and hematocrit and lower concentrations of chloride and sodium compared to the Dekalb White strain. Leukocyte levels, plasma protein, sodium, and ionized calcium remained above reference values for both strains. There were no methylation differences between temperature treatments, but a significant difference was observed between strains at 28days of the experiment. Methylation patterns were independent of the evaluated blood parameters in this study but dependent on the bird strain, suggesting that strains respond with different biological mechanisms to heat adaptation. The absence of correlation does not completely exclude a causal relationship, and further studies are needed to investigate possible physiological and biological associations of blood and how strains respond to different heat adaptive mechanisms.

Characterization and Functional Properties of Electroplated Silver and Silver Alloys from Cyanide Free Electrolytes

The reduction of tungstate ions in aqueous solution is often referred as induced codeposition. Those ions can only be reduced to a metallic state alongside another element which is mostly nickel. However, other metal such as cobalt and iron are reported in the literature. Various hypothesis have been made concerning the precise mechanism behind induced codeposition, but even if the exact role of the various chemical species isn’t fully understood, tungsten was successfully electrodeposited using more noble element such as copper and silver [1]. Silver electroplating is a widely used process in the connector industry. In fact, while silver coatings exhibit an extremely high thermal and electrical conductivity, they remain highly vulnerable to sulphuration and present poor mechanical properties both in hardness and wear resistances. For these reasons, electrodeposition of silver alloys has aroused a recent interest, relying on an alloying element addition that would compensate silver weaknesses. Alloy compounds inducing high mechanical and chemical resistances such as tungsten, are obvious candidates. Moreover, limitations in free cyanide use in electroplating processes is an active research subject. While gold-cyanide complexes are stable enough to be used without any cyanide ions in solution, silver complexation in alkaline baths is highly dependent on high free cyanide concentrations. Processes using thiosulfate, nitrogen heterocyclic compounds or methane sulfonate were proposed as replacement solutions, but they are still under investigations [2]. The present study is part of the SILAHPERF project, led by IRT-M2P and UTINAM Institute, which try to investigate the codeposition mechanism of various silver-based alloys of interest with a particular focus on silver-tungsten while seeking for environmental-friendly solutions. A cyanide-free silver-tungsten plating bath is proposed and resulting coatings are characterized by various techniques (SEM, XRD, GDOES...). Resolutely intended for connector applications, functional properties such as hardness, wear resistance and electrical conductivity of the deposit were evaluated depending on bath composition and electrolysis parameters. [1] A. Kola, X. Geng, and E. J. Podlaha, ‘Ag–W electrodeposits with high W content from thiourea–citrate electrolytes’, Journal of Electroanalytical Chemistry, vol. 761, pp. 125–130, Jan. 2016[2] B. Satpathy, S. Jena, S. Das, and K. Das, ‘A comprehensive review of various non-cyanide electroplating baths for the production of silver and gold coatings’, International Materials Reviews, vol. 68, no. 7, pp. 825–861, Oct. 2023

Investigation of the influence of electrolytic milling machining parameters on the machining accuracy of thin-walled parts

Aircraft parts are often designed as thin-walled structures to reduce the weight of the aircraft. However, thin-walled structures are prone to deformation during the milling process, leading to a decrease in machining accuracy. To address this problem, a method combining milling and electrochemical machining, known as electrolytic milling, is proposed to minimize deformation and enhance the accuracy of thin-walled parts. The factors that affect the machining accuracy of electrolytic milling were analysed, and a model for predicting the thickness of the material removed was established. Electrolytic milling experiments were designed, and the model was solved. Based on the built model, the influences of feed rate, spindle speed, radial cutting depth, voltage and electrolyte concentration on material removal thickness were investigated. Compared with the milling method, the electrolytic milling method can improve the machining accuracy of thin-walled parts. Electrolytic milling experiments were conducted on box-shaped parts to verify the reliability of the proposed method.

Stationary and pulsed electrodeposition of silicon in LiCl–KCl–CsCl–K2SiF6 melt

Silicon and its materials are widely used in metallurgy, micro- and nano-electronics, solar energy, and are also promising materials for anodes of lithium-ion power sources with increased specific capacity. The expansion of application areas of silicon with controlled morphology necessitates the development of new energy–efficient methods of its production. In the present work, the influence of the mode as well as parameters of electrolysis of the LiCl–KCl–CsCl–K2SiF6 melt with a temperature of 545 оC on the morphology of electrolytic precipitation of silicon on glassy carbon has been studied. The galvanostatic mode of electrodeposition, widely used in industry, as well as the pulsed mode, which is actively investigated at present, were used for the electrolysis. Silicon electrodeposition was carried out by varying such parameters as cathodic current density (from 3 to 50 mA/cm2) and electrolysis duration (from 30 to 180 min) in the galvanostatic mode, as well as by varying the density and duration of the cathodic current pulse, the duration of current pauses and the total duration of electrolysis in the pulsed mode. It is shown that electrodeposition of silicon on glassy carbon is accompanied by the formation of a continuous sediments of hemispherical nuclei with a diameter of about 1 micron on the electrode surface. An increase in the cathodic current density and an increase in the cathodic current pulse pause frequency contribute to the disruption of the sediment continuity and the growth of dendrites of ordered or arbitrary shape. At the same time, the pulsed mode allows to increase the cathode current density at silicon electrodeposition (from 25–30 to 250–500 mA/cm2) and stabilize the value of the cathode potential during electrolysis.

Electrochemical production of zirconium silicides from KCl–K<sub>2</sub>SiF<sub>6</sub>–ZrO<sub>2</sub> melt

The unique properties of zirconium silicides attract the attention of a large number of authors from various scientific fields. Expansion of application methods also poses the challenge of developing new, more environmentally friendly and affordable methods of production. The most environmentally friendly method without equipment requirements is the electrolysis of the molten salt. The work proposes a method for producing zirconium silicides by electrolysis of the KCl–K2SiF6–ZrO2 melt. In order to substantiate the electrolysis parameters, the kinetics of cathodic reduction was studied and the limiting stage of the process was determined. The structure and phase composition of the cathode deposit were studied using X-ray diffraction and electron scanning microscopy. In the course of the work, conclusions were drawn about the change in the content of the ZrO2 additives on the morphology of the sediment, and it was also suggested that it was possible to obtain zirconium silicides from more accessible raw materials, such as zircon.

Simultaneous desalination and removal of organic pollutants in a novel bifunctional FCDI system: The enhancement by in-situ reutilization of chloride ions

A new system of flow electrode capacitive deionization coupled with in situ electro-oxidation (FCDI-EO) was constructed to achieve the degradation of organic pollutants while maintaining high desalination efficiency. The effects of different parameters of potential difference, electrolyte, and pH on the chloride removal performance of FCDI-EO and the removal performance of rhodamine B (RhB) were investigated. Under the optimal conditions of potential difference = 4 V, [Cl−] = 500 mg/L, and pH = 4, the removal of chloride ions, RhB and total organic carbon (TOC) was as high as 88.74 %, 99.02 %, and 87.82 %, respectively. The quenching experiments showed that hydroxyl radicals (OH) and reactive chlorine species (RCS) were involved in the FCDI-EO system. The liquid chromatography-mass spectrometry (LC-MS) analysis suggested the possible mineralization pathway of RhB. Furthermore, toxicity assessment analysis showed that the toxicity of the degradation intermediates of RhB decreased during the treatment. Overall, this study provides a promising process that reducing the generation of high-concentration saline water in desalination and in situ utilizing the Cl− gathered from the feed water. The findings of this study could provide useful guidance for the development of flow electrode capacitive deionization technology and organic pollutant control.

Extending the understanding of Shannon’s safe stimulation limit for platinum electrodes: biphasic charge-balanced pulse trains in unbuffered saline at pH = 1 to pH = 12

Objective.In neural electrical stimulation, safe stimulation guidelines are essential to deliver efficient treatment while avoiding neural damage and electrode degradation. The widely used Shannon's limit,k, gives conditions on the stimulation parameters to avoid neural damage, however, underlying damage mechanisms are not fully understood. Moreover, the translation from bench testing toin vivoexperiments still presents some challenges, including the increased polarisation observed, which may influence charge-injection mechanisms. In this work, we studied the influence on damage mechanisms of two electrolyte parameters that are differentin vivocompared to usual bench tests: solution pH and electrolyte gelation.Approach.The potential of a platinum macroelectrode was monitored in a three-electrode setup during current-controlled biphasic charge-balanced cathodic-first pulse trains. Maximum anodic and cathodic potential excursions during pulse trains were projected on cyclic voltammograms to infer possible electrochemical reactions.Main results.In unbuffered saline of pH ranging from 1 to 12, the maximum anodic potential was systematically located in the oxide formation region, while the cathodic potential was located the molecular oxygen and oxide reduction region whenkapproached Shannon's damage limit, independent of solution pH. The results support the hypothesis that Shannon's limit corresponds to the beginning of platinum dissolution following repeated cycles of platinum oxidation and reduction, for which the cathodic excursion is a key tipping point. Despite similar potential excursions between solution and gel electrolytes, we found a joint influence of pH and gelation on the cathodic potential alone, while we observed no effect on the anodic potential. We hypothesise that gelation creates a positive feedback loop exacerbating the effects of pH ; however, the extent of that influence needs to be examined further.Significance.This work supports the hypothesis of charge injection mechanisms associated with stimulation-induced damage at platinum electrodes. The validity of a major hypothesis explaining stimulation-induced damage was tested and supported on a range of electrolytes representing potential electrode environments, calling for further characterisation of platinum dissolution during electrical stimulation in various testing conditions.

Ischemia‐Free Kidney Transplantation From Deceased Donor Kidneys: The First Retrospective Cohort Study

ABSTRACTBackgroundThe study aimed to evaluate the safety and effectiveness of ischemia‐free kidney transplantation (IFKT) in preventing ischemia‐reperfusion injury (IRI), a common complication associated with organ transplantation.MethodsTwelve kidneys were obtained from six donors and divided into two groups: the IFKT and the conventional kidney transplantation (CKT) group. The left kidneys underwent conventional cold perfusion and storage, while the right kidneys were procured using normothermic machine perfusion (NMP) to maintain uninterrupted blood supply. Perfusion parameters, metabolic and electrolyte parameters in the perfusate and urine, along with post‐transplant clinical data of the recipients, were collected for subsequent analysis.ResultsPerfusion flow rates varied from 100 to 300 mL/min under a pressure of 65 mmHg across different donor kidneys. Biochemical parameters such as the pH value, oxygen partial pressure, and electrolyte levels, including Na+ and K+ concentrations in the perfusate, remained stable within physiological ranges during NMP. Urine samples demonstrated significantly lower pH values, reduced Na+ concentrations, and elevated K+ concentrations compared to the perfusate, indicating effective kidney function in acid excretion, sodium retention, and potassium excretion during NMP. All patients survived, and the kidney grafts showed satisfactory function during the 12‐month follow‐up period. Clinical outcomes for recipients in the IFKT group were comparable to those in the CKT group, including similar rates of patient and graft survival at 1 year, as well as equivalent serum creatinine levels and eGFR at 1, 3, 6, and 12 post‐transplantation. Delayed graft function (DGF) occurred in one case (16.67%) from the same donor in both groups. One patient in the IFKT group experienced acute rejection, while no instances of primary graft nonfunction or other complications were observed in either group.ConclusionsOur findings indicate that the kidneys maintained in a physiological environment through NMP exhibit stable function, and post‐transplant allograft function is comparable between IFKT and CKT. The IFKT procedure demonstrates both feasibility and safety, presenting a promising approach to effectively mitigating IRI in kidney transplantation.

Properties and Applications of Supersaturated Metastable Alloys Obtained via Electrodeposition

Supersaturated alloys can exhibit superior properties and electrodeposition is a cost-effective and versatile technique to produce them. In this review, the chemical, mechanical and structural properties of supersaturated alloys are discussed, and connections with metallic glasses and high entropy alloys are also exposed. After discussing mechanisms causing supersaturation in electrodeposited alloys, an overview of the most important electrodeposited metastable alloys is provided, showing that they are mainly used as protective coatings able to improve corrosion resistance and tribological performance of a large variety of industrial components. Composition of the electrolytic baths and deposition parameters are also considered and discussed.

Parameterization Of Electrolysis For The Thickening Of Sludge From Wastewater Treatment Plant: Taguchi Method Approach

The buildup of sludge is a significant issue for wastewater treatment facilities, and this study focuses on thickening it by electrolysis. The main objectives are to identify the factors influencing the sludge characteristics and to determine the optimal levels of these factors for efficient thickening. The Taguchi method with an L8(2^4) orthogonal array was used to conduct the tests, which showed that electrolysis is effective in thickening the sludge, as evidenced by the increase in dryness rate from 2.97% to 34.37% and the mass loss of 0.23 kg or 2.3%. Analyses of the carbon, chlorine, nitrogen, and sodium levels indicate that the process does not pose significant environmental risks. Minitab analysis identified the most influential factors: the electrolytic additive (NaOH) and the settling effect (without settling) for sludge thickening, the current intensity (12.6 A) for sludge quality, and the concentration of the electrolytic additive (0%) for energy consumption and electrolysis efficiency. This data is crucial for optimizing the electrolytic parameters, thereby enhancing the process efficiency and minimizing environmental and energy impacts.

Electrochemical synthesis of vanadium boride powders from their oxide salts

A novel environmentally friendly electrochemical method for synthesizing vanadium boride powders from oxide-based electrolytes was introduced. During this process, co-depositions of vanadium and boron atoms took place on the surface of the low alloyed steel substrates at various stoichiometries, VxBy (x≥1; y≥1). The effects of critical electrolysis parameters namely current density (70, 100, 200, 500 mA/cm2), and temperature (900, 950, 1000 °C) were investigated systematically. The X-ray diffraction (XRD) analyses revealed that at low current density (70 mA/cm2) VB is the main phase; whereas, VB2 became a dominant structure at 100 and 200 mA/cm2. However, at high current densities like 500 mA/cm2 mixed borides containing VB- V3B4- V2B3 -VB2 were detected. The electrolysis temperatures did not cause major variations in the composition of synthesized borides. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) as well as grain size investigations indicated that there is no significant influence of electrolysis conditions on the particle size and it is possible to manufacture high-quality, stoichiometric VB, and VB2 powders with ≈ 4 µm particle size. The best parameters for producing powders containing primarily VB and VB2 powders were determined as 1000 °C, 70 mA/cm2, and 900 °C, 200 mA/cm2, respectively.

Investigation of electrolyte parameters on the performance of gadolinium-doped ceria–based solid oxide fuel cell: an analytical study

Investigation of electrolyte parameters on the performance of gadolinium-doped ceria–based solid oxide fuel cell: an analytical study

Review of Cathode Plasma Electrolysis Treatment: Progress, Applications, and Advancements in Metal Coating Preparation.

Cathodic plasma electrolytic treatment (CPET) is an emerging surface modification and coating preparation technology. By utilizing plasma discharge induced through electrolysis and the cooling impact of electrolyte, metal cleaning, saturation, and coating preparation are efficiently achieved. In this review, the principle, application, and development of the CPET process are briefly summarized based on the past literature. Detailed insights are provided into the influence of electrolyte parameters (pH, metal salt concentration, and temperature), electrical parameters (voltage, duty cycle, and frequency), and process parameters (electrode area ratio, material, roughness, and deposition time) on plasma discharge and coating formation for metal coatings. The interaction mechanism between plasma and material surfaces is also investigated. Recommendations and future research avenues are suggested to propel CPET and its practical implementations. This review is expected to provide assistance and inspiration for researchers engaged in CPET.

Electrochemical and Kinetic Analysis of Manganese Electrolytes for Redox Flow Batteries

The hybrid hydrogen-manganese redox flow battery (H2-Mn RFB) is a promising and sustainable electrochemical system for long-duration energy storage. One strong reason is the excellent features of manganese, such as low cost, abundance, environmental friendliness, and relatively high standard potential (+1.51 V). Nevertheless, the electrochemical and kinetic parameters of manganese electrolytes have not been studied in detail for flow batteries. In the present work, the kinetics of the Mn2+/Mn3+ redox species in an electrolyte composed of 1M TiOSO4 and 1M MnSO4 in 3M H2SO4 were studied on carbon paper electrodes. The kinetic analysis of manganese redox species (Mn2+/Mn3+) in the presence of TiO2+ was performed using cyclic voltammetry and electrochemical impedance spectroscopy techniques within the H2-Mn RFB set-up. The results were compared to reference redox species vanadium (VO2+/VO2 +) within H2-V RFB system. The results showed that the heterogeneous electron transfer rate constant (8.6 × 10−7 cm s−1) of manganese is comparable to that of vanadium (4.8 × 10−6 cm s−1), with less than an order of magnitude difference between them.

Anti-diarrheal effects of ethanol leaf extract of Eleusine Indica in Castor Oil induced diarrhea using mice model

Ancient civilizations employed medicinal herbs to treat ailments. Medicinal herbs are essential for treating chronic disorders. Different medicinal plants can treat comparable ailments, depending on the country. In many rural communities in developing countries, particularly in Africa, therapeutic medicines and remedies derived from indigenous plants are almost invariably the only readily available and cost-effective alternatives to traditional diarrhea medicines. The study aims to evaluate the anti-diarrheal activity of the Eleusine indica ethanol extract in mice. The study used fresh Eleusine indica leaves. The extracts were administered at concentrations of 250, 500, and 1000 mg/kg for 28 days. On the 29th, the rats were induced with diarrhea, and blood samples were collected through the retro-orbital plexus before being sacrificed. The serum from the collected blood was used to run hematological and electrolyte tests. The liver and kidney function tests were analyzed using standard methods. The determination of antidiarrheal activity was done using the following models: Castor oil (CO) induced diarrhea, CO induced enteropooling activity, and CO induced gastrointestinal motility. The 80% ethanol extract produced significant (p<0.001) antidiarrheal activity in all three models tested. The hematological, renal, hepatic, and electrolyte parameters of extract-treated mice were not significantly (p > 0.05) different from those of the control group. There was no statistically significant difference (p > 0.05) in the chloride, sodium, potassium, calcium, and bicarbonate levels of the extract-treated groups when compared to the control group. The findings of the studies demonstrated the antidiarrheal activities of Eleusine indica leaves, which could be a therapeutic option against diarrhea.

Towards a scalable production of β-Li3PS4-based all-solid-state batteries: Optimizing pressing parameters of the tape-casted solid electrolyte and composite cathode films

Pressing of all-solid-state batteries (ASSBs) components is one of the most important processes for scalable production. Henceforth, pressing parameters (pressure and temperature) for β-Li3PS4 (β-LPS) solid electrolyte (SE) separator films and LiNi0.6Co0.2Mn0.2 (NCM622)/β-LPS composite cathode films prepared by a slurry-based process were investigated and optimized. Compression of the β-LPS film at a temperature of 100 °C led to higher ionic conductivity than cold-pressed films. Raman and X-ray photoelectron spectroscopic analyses revealed no changes in the chemical nature of β-LPS material after hot pressing. Interestingly, time-of-flight secondary ion mass spectrometric (ToF-SIMS) analyses indicated a binder enrichment in the upper layers of the hot-pressed film. In a similar trend, increasing compression and temperature resulted in higher densification of NCM622/β-LPS composite cathode films. Based on galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) measurements, hot-pressed composite cathode at 200 MPa/100 °C exhibited a higher coverage percent of catholyte on cathode active material and a greater Li+ diffusion coefficient (DLi+) than cold-pressed one at 200 MPa/20 °C. Cycling tests of “Li–In│β-LPS│NCM/β-LPS” ASSBs with hot-pressed films displayed better cycling performance than that with cold-pressed ones, attributed to the higher concentration of electrochemically active NCM in close contact with β-LPS catholyte.

One-Step Electrochemical Synthesis of Molybdenum-Disulfide-Based Materials for Enhanced Supercapacitor Performance

Molybdenum disulfide (MoS2)-based two-dimensional materials were produced in one-step at room temperature using cyclic voltammetry technique. These materials were then used as electrode materials in supercapacitors. Concentration of supporting electrolyte, precursor, and cycle number parameters, which were the factors affecting the success of the synthesis, were optimized as 0.5 M, 0.15 M,and 10 cycles, respectively. The produced MoS2-coated electrodes were characterized using spectroscopic and microscopic methods. The chemical characterizations of the produced materials were examined by X-ray photoelectron spectroscopy, X-ray diffraction diffractometry, and scanning electron microscopy-energy-dispersive X-ray analysis. Surface morphologies of the composite materials were investigated using scanning electron microscopy. Finally, the produced MoS2-based materials were used as electrode materials in supercapacitors. The produced supercapacitors were characterized using cyclic voltammetry and electrochemical impedance spectroscopy methods, and the changes in the capacitive behavior of these systems over cycles were investigated using the cyclic charge-discharge technique. The highest areal capacitance value was determined as 251 mF.cm−2 at 0.2 mA.cm−2 charge-discharge current rates in 1.0 M H2SO4 by using of MoS-AD1 as the electrode material. Capacitance retention of this electrode was over 100% after 4000 cycles.

Insights into the Optimization of Catalytic Active Sites in Lithium-Sulfur Batteries.

ConspectusLithium-sulfur batteries (LSBs), recognized for their high energy density and cost-effectiveness, offer significant potential for advancement in energy storage. However, their widespread deployment remains hindered by challenges such as sluggish reaction kinetics and the shuttle effect of lithium polysulfides (LiPSs). By the introduction of catalytic materials, the effective adsorption of LiPSs, smooth surface migration behavior, and significantly reduced conversion energy barriers are expected to be achieved, thereby sharpening electrochemical reaction kinetics and fundamentally addressing the aforementioned challenges. However, driven by practical application targets, the demand for higher loadings and reduced electrolyte parameters inevitably exacerbates the burden on catalytic materials during their service. Additionally, given that catalytic materials contribute negligible electrochemical capacity, their incorporation inevitably increases the mass of nonactive components for reducing the energy density of LSBs. A meticulous insight into the lithium-sulfur catalytic reaction reveals that the conversion of LiPSs is dominated by active sites on the surfaces of catalytic materials. These microregions provide the necessary electron and ion transport for the conversion reaction of LiPSs, with their efficacy and quantity directly impacting the conversion efficiency. In light of these considerations, the strategic optimization of active sites emerges as a paramount pathway toward promoting the performance of LSBs while concurrently mitigating unnecessary mass. Here, we outline three strategies developed by our group to optimize active sites of catalytic materials: (1) Augmenting active sites by customizing structural modulation and precise dimensional control to maximize exposure. Emphasis has been placed on the approaches for material synthesis and the essence of reactions for achieving this strategy. (2) Regulating the microenvironment of active sites by integrating the coordination refinement, long-range atomic interactions, metal-support interactions, and other electronic regulation strategies, thereby providing an elevation in the intrinsic catalytic performance. (3) Implementing a self-cleaning mechanism for active sites to counteract deactivation by designing a tandem adsorption-migration-transformation pathway of sulfur contained within the molecular domain. Throughout this process, the intrinsic mechanisms driving performance enhancement through active site optimization strategies have been prominently emphasized, which encompass aspects such as electronic structure, atomic composition, and molecular configuration and significantly expand the comprehension of Li-S catalytic chemistry. Subsequently, considerations demanding heightened attention in future processes of active site optimization for catalytic materials have been delineated, including the in situ evolution patterns and resistance to the poisoning of active sites. It is noteworthy that given the similarity between Li-S catalysis chemistry and traditional electrocatalytic processes, this Account elucidates the concept of active site optimization by drawing insights from representative works and our own works in the field of electrocatalysis, which is relatively rare in previous reviews of LSBs. The proposed insights contribute to uncovering the intrinsic mechanisms of Li-S catalysis chemistry and introducing innovative ideas into active site optimization, ultimately advancing energy density and stability in LSBs.