Concentrations In Electrolyte Research Articles

Effects of Sodium Vacancies and Concentrations in Na3SO4F Solid Electrolyte.

The sodium-rich solid electrolyte, Na3SO4F (NSOF), holds promise for eco-friendly and resource-abundant energy storage. While the introduction of heterovalent dopants has the potential to enhance its suitability for battery applications by creating Na vacancies, the effect of vacancies and sodium concentrations on sodium conduction remains unclear. In this work, Mg2+ was introduced into Na+ sites in Na3SO4F, generating sodium vacancies with different contents by using solid-state synthesis method. Among the resulting materials, Na2.96Mg0.02SO4F exhibited an ionic conductivity that is two-order-of-magnitude higher than NSOF at 298 K. Notably, as the sodium concentration decreased, the ionic conductivity also declined, revealing an equilibrium between Na vacancies and concentrations. To further investigate the influence of sodium concentration, excess Na+ was introduced into NaMgSO4F, which inherently possesses a lower sodium content by using solid-state synthesis method. However, this adjustment only led to an approximately one-order-of-magnitude enhancement in optimal ionic conductivity at 298 K. Combined with an in situ X-ray diffraction analysis, our findings underscore the greater sensitivity of sodium conduction to variations in sodium vacancies. This study paves the way for the development of ultrafast sodium ion conductors, offering exciting prospects for advanced energy storage solutions.

Synergistic Impact of Electrolyte Components: Interplay between the Novel Phosphorus-Based Additives and Conducting Salt Advancing NMC811||SiC Cell Performance

A lithium-ion battery (LIB) typically consists of an anode, a lithiated transition metal oxide cathode, and an electrolyte formulation containing inorganic lithium conducting salt in aprotic organic solvents/co-solvents, and functional additives. In-depth research is being conducted in order to develop novel chemistries for the next-generation LIBs. Within the line, silicon-based anodes and nickel-rich cathodes are recognized as two feasible next-generation electrode materials. The long-term galvanostatic cycling performance of resulting cell chemistries relies on the effectivity and robustness of solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) formed during the initial cycles and originate from the galvanostatic cycling conditions, as well as the complex interplay between electrolyte and corresponding electrodes .[1] To enhance the SEI and CEI properties, implementing functional electrolyte additives into baseline electrolyte has been shown to be one of the most effective and cost-favorable strategies. Film-forming additives sacrificially reduce and/or oxidize at corresponding electrodes to form protective layers (SEI and CEI).Previous research has shown that phosphorus-based additives improve electrode |electrolyte interfaces stability and simultaneously enhance cell flame-retardant capability advancing the overall cell performance.[2,3] In this report, we indicated part of the above-mentioned properties originate from the synergy between lithium hexafluorophosphate (LiPF6) which is the state-of-the-art (SOTA) electrolyte conducting salt in LIBs and considered functional additives. Here, we demonstrated the functionality of 2-phenoxy-1,3,2-dioxaphospholane (PhEPi) as a novel film-forming additive[4] and 2,2,4,4,6-pentafluoro-6-(2,2,2-trifluoroethoxy)-1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine (CF3PFFPN) as a new flame-retardant additive, synthesized for the first time by our group. The presence of PhEPi and CF3PFPN at the optimum concentrations in the baseline electrolyte (1 M LiPF6 in EC: EMC 3:7 + 8 % VC) enhances the performance and safety of the resulting NMC811||Si-graphite (20% Si) cell chemistry. Impact of phospholane-based additive was confirmed by substituting LiPF6 with LiBF4 conducting salt and complementary post mortem analysis. This study along with improved cell chemistry, provided a better understanding and deeper insights into the synergistic interplay and impact of considered electrolyte components on the resulting NMC811||Si-graphite cell chemistry. [1] C. Wölke, B. A. Sadeghi, G. G. Eshetu, E. Figgemeier, M. Winter, I. Cekic-Laskovic, Advanced Materials Interfaces 2022, 9, DOI 10.1002/admi.202101898.[2] N. Von Aspern, D. Diddens, T. Kobayashi, M. Börner, O. Stubbmann-Kazakova, V. Kozel, G. V. Röschenthaler, J. Smiatek, M. Winter, I. Cekic-Laskovic, ACS Applied Materials and Interfaces 2019, 11, 16605–16618, DOI 10.1021/acsami.9b03359.[3] N. von Aspern, C. Wölke, M. Börner, M. Winter, I. Cekic-Laskovic, Journal of Solid State Electrochemistry 2020, 24, 3145–3156, DOI 10.1007/s10008-020-04781-1.[4] B. A. Sadeghi, C. Wölke, F. Pfeiffer, M. Baghernejad, M. Winter, I. Cekic-Laskovic, Journal of Power Sources 2023, 557, 232570, DOI 10.1016/j.jpowsour.2022.232570.

Electrochemical Investigations of Ag and Bi in Choline Chloride-Ethylene Glycol DES Electrolyte

Electrodeposition for silver and bismuth is currently carried out in alkaline solutions, e.g., by use of cyanide, and by electroplating these metals, by themselves or together. The electroplated products have important uses, e.g., in semiconductors [1].Choline Chloride (ChCl)-Ethylene Glycol (EG) DES mixtures, often referred to as ethaline, have been shown to have superior electrochemical properties compared to many other DES systems [2]. This system is considered a green solvent [3]. In this work, the electrochemical behaviour of Ag and Bi in ethaline electrolyte has been investigated to obtain the necessary parameters to extract them by electrochemical methods, either separately or together, when both are present in the DES electrolyte. The presence of Cu and Sb in the electrolyte, has also been studied, and its effect in the metal obtained has been evaluated. Ethaline solutions were fabricated by mixing together ChCl and EG at 1:2 ChCl:EG molar ratio by stirring at 60 °C until a clear liquid was formed. Model electrolyte solutions were then produced by dissolving AgCl and BiCl3, as well as SbCl3 and CuCl2, in the DES. Electrochemical investigations were carried out at 60 °C by cyclic voltammetry (CV), chronoamperometry (CA) and potentiostatic electrolysis using a 3-electrode setup.The CVs obtained using Pt-wire or GC-rod as working electrodes in the DES with 10 mM Ag(I) and Bi(III), showed two distinguished peaks in the cathodic scan. The CV and CA results showed that the Bi deposition starts at approximately 0.15-0.20 V more cathodic than the Ag deposition. Two or more electrochemical signals were observed in the reverse anodic scan, correlating to the dissolution of the metals, alloys and possible electrolyte reactions. Example of CV curve obtained on a Pt wire at a scan rate of 200 mV/s is included.The results indicated that it could be possible to electrochemically extract only Ag or both Ag and Bi simultaneously, when present at identical concentrations in the DES electrolyte, by carefully choosing the deposition potential. This was confirmed after analysis of the cathodic deposits on Pt and stainless steel (316L) substrates by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS).Experiments with Sb(III) and Cu(II), in addition to Ag(I) and Bi(III) present in the DES electrolyte showed that the cathodic deposition of the different metals appears in the order Ag<Sb<Bi<Cu. Significant co-deposition might occur, enhanced by favourable alloy formation, when metallic elements may deposit at activities lower than 1. Still, at 10 mM of each of the four metal salts present in the DES electrolyte, it was possible to obtain deposits with one, two, three or four metals present, by choosing the proper cathodic deposition potential.AcknowledgementsThis project has received funding from the EU’s Horizon 2020 research and innovation program under Grant Agreement 815748. The content in this presentation reflects only the views of the authors. The European Commission is not responsible for any use that may be made of the information it contains.

Understanding the Energetics of Ion Intercalation in Lithium-Ion Batteries

Researchers around the world are working to increase the energy efficiency and the energy density of lithium-ion batteries. However, the mechanism and the factors influencing the charge transfer (CT) kinetics at the electrode-electrolyte interface remain poorly understood. Recently, Fraggedakis et al. [1] proposed the theory of coupled ion-electron transfer (CIET) to explain the process of charge transfer at the electrode-electrolyte interfaces. In this work, we provide deep atomistic understanding of the interfacial CT mechanism, the underlying microscopic steps, and the factors influencing the CT rates in a Li-ion battery. In addition, we connect our computational results with the experimental measurements and Marcus-like theories of charge transfer (viz. CIET [1]).Using state-of-the-art computational techniques, such as metadynamics and molecular dynamics simulations, we model the electrode-electrolyte interface and compute the free energy profiles of Li-ion adsorption at the interface, subsequent ion-desolvation, and intercalation into the cathode. Specifically, we study the adsorption of Li+ ion on LixCoO2 surface for different (i) electrolytes, (ii) Li+ concentrations in electrolyte, (iii) salt compositions, and (iv) temperatures to uncover the trends governing charge transfer kinetics. Using the obtained free energy profiles of Li+ desolvation and intercalation at the solid-liquid interface, we provide estimation of the adsorption and desolvation energy at the interface and identify the key energy barrier which acts as the roadblock for ion transfer in Li-ion batteries. Based on this identified key kinetic barrier, we then propose strategies to tune the energy barrier for ion transport. In addition, we identify important thermo-physical observations that can explain the existing experimental trends. For instance, we find that increasing the salt concentration in the electrolyte increases the accessible solvation states to Li+ ion, thereby changing the energy barrier for the Li+ ion to intercalate into the electrode, and thus leading to higher currents. Moreover, we find that changing the salt from LiPF6 to LiClO4 further modifies the energy landscape of Li+ ion, leading to increased measured experimental kinetics as well. This work builds an understanding of the influence of various effects, such as salt concentration and electrolyte composition, on the Li+ transport properties at interfacial regions. Our computational framework can also provide descriptors to enhance the performance and stability of lithium-ion batteries.

Photoactive TiO2-V2O5-WO3 film composites immobilized in titanium phosphate matrix by plasma electrolytic oxidation

V-, W-containing oxide-phosphate layers on titanium were obtained by plasma electrolytic oxidation (PEO) for 5 min at anode current density i = 0.08 A/cm2 in electrolytes containing 0.05 mol/L Na6P6O18 and 0.1 mol/L (Na2WO4 + NaVO3). The effect of replacing vanadate with tungstate (NaVO3:Na2WO4 = 0:1, 1:3, 1:1, 3:1, and 1:0) was studied on voltage–time responses, PEO coatings surface morphology, composition, optical and photocatalytic properties. The coatings were investigated by X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray microanalysis, X-ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. Under experimental conditions, amorphous coatings with a thickness of 18–27 μm and a surface porosity of 1.5–3.6% were formed. Results show that vanadium (up to 10.5 at. %) and tungsten (up to 5.2 at. %) are incorporated into surface layers in proportion to their concentrations in electrolyte. The main mechanism for the incorporation of V and W into coatings is assumed to be thermolysis of vanadungstophosphate heteropolyoxoanions, while high concentrations of polyphosphate species contribute to the amorphization of coatings and the formation of a titanium phosphate matrix. The band gap of V-containing composites decreases from 2.22 to 1.97 eV as tungsten replaces vanadium. For W-containing composites (V-free ones), the band gap is 3.19 eV. All formed coatings exhibit photocatalytic activity in the degradation of methyl orange (10 mg/LMO, 10 mmol/L H2O2) in a neutral medium (pH 6.8) under visible and UV irradiation. The gradual substitution of vanadium for tungsten in the coatings leads to a decrease in MO degradation (from 87 to 50% and from 32 to 9% under 3-h UV and visible irradiation) with a simultaneous increase in their durability due to a decrease in vanadium leaching. An electrolyte with Na2WO4:NaVO3 = 1:3 is optimal for the formation of photoactive and stable composites. When using composites obtained in this electrolyte, MO conversions are 83 and 31% under UV and visible irradiation, respectively. The mechanism of the photocatalytic action of WO3-V2O5-TiO2 composites is considered, and the role of hydrogen peroxide is discussed.

Critical Analysis of Published Physical Property Data for Aqueous Potassium Hydroxide. Collation into Detailed Models for Alkaline Electrolysis

Physical properties of aqueous KOH solutions are crucial to the design and operation of alkaline electrolyzers but have been scarcely and sometimes unreliably reported. Obtaining published data for various properties currently requires time-consuming searches and subsequent interpretation, interpolation, and extrapolation. This work collates and critically analyzes published data for a range of physical properties relevant to alkaline electrolysis, including the density, viscosity, conductivity, surface tension, oxygen/hydrogen solubility, oxygen/hydrogen diffusivity, and water vapor pressures of aqueous KOH solutions, as a function of temperature, KOH molarity, and pressure. Correlation functions, in the form of excel spreadsheets, have been developed to allow interpolation of the most reliable data and computation of desired quantities at specific temperatures, pressures, and KOH concentrations. Composite models incorporating these properties have been developed for automated computation of (i) diffusive gas crossover and (ii) gas production volumes, including (iii) water vapor content, and associated (iv) dissolved gas concentrations in the liquid electrolyte, as a function of KOH concentration, temperature, pressure, current density, and separator thickness and porosity. These spreadsheets are provided in the Supporting Information, as tools and reference points for researchers and practitioners in alkaline electrolysis.

Chromium Luminescence in Plasma Electrolytic Oxidation Coatings on Aluminum Surface

With plasma electrolytic oxidation (PEO), one can easily obtain thick (tens of microns), mechanically resilient and chemically stable oxide coating on aluminum and other valve metal alloys. The study of luminescent PEO coatings is a relatively new subfield of the already well-established coating preparation methods. In recent years, many new luminescence-based approaches have been developed, one of which is the detection of ionizing radiation of carbon-doped PEO alumina coating. This study presents an improved approach by doping the alumina coating with chromium using citric acid as an additive in the electrolyte. Trivalent chromium ions replacing aluminum in the crystalline lattice of the coating exhibit characteristic sharp lines in the luminescence spectrum. The effectiveness of different DC voltages, process times and citric acid concentrations in electrolyte were examined. The use of citric acid in the electrolyte also provides the conditions required for the formation of an energy trap in the bandgap of the material, thus opening up the possibility for the coating to be used as an ionizing radiation detector by measuring its thermoluminescence. Chromium atoms are incorporated in the coating from the Al6082 aluminum alloy itself and are not added in the electrolyte, therefore making the process much more reliable, repeatable, and environmentally friendly.

Electrolyte Development for Fast Charging of High Energy Density Li-Ion Cells

Different lithium salt concentrations in carbonate electrolyte were studied on the fast charging performance of LiNi0.6Mn0.2Co0.2O2 (NMC622)/graphite pouch cells. The cells with electrolyte concentration from 0.75 M to 1.50 M showed similar fast charging capabilities. Further increase of the concentration to 1.75 M and 2.00 M decreased the attainable capacity in fast charging. In the long-term cycling test, the capacity retention after 200 fast charging cycles increased with the increase of salt concentration in electrolyte. Cells with 1.5 M electrolyte showed the best overall performance in fast charging capacity and long-term cycling. Li plating were observed in the cells with 0.75 M, 1.00 M and 1.25 M electrolyte. It was improved with greatly reduced Li plating area in 1.50 M, and no Li plating at all in 1.75 M and 2.00 M electrolyte. Post-mortem analysis such as neutron powder diffraction (NPD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the electrode after cycling. It suggests that electrolyte concentration needs to be optimized for a given cell configuration with specific electrode and loading. Figure 1

Understanding the effect of salt concentrations on fast charging performance of Li-ion cells

Different lithium salt (lithium bis(fluorosulfonyl) imide (LiFSI)/LiPF6 9/1 mol ratio) concentrations in carbonate electrolyte were studied on the fast charging performance of LiNi0.6Mn0.2Co0.2O2 (NMC622)/graphite pouch cells. The cells with electrolyte concentration from 0.75 M to 1.50 M showed similar fast charging capabilities. Further increase of the concentration to 1.75 M and 2.00 M decreased the attainable capacity in fast charging. In the long-term cycling test, the capacity retention after 200 fast charging cycles increased with the increase of salt concentration in electrolyte. Cells with 1.5 M electrolyte showed the best overall performance in fast charging capacity and long-term cycling. Li platings were observed in the cells with 0.75 M, 1.00 M and 1.25 M electrolyte. It was improved with greatly reduced Li plating area in 1.50 M, and no Li plating at all in 1.75 M and 2.00 M electrolyte. Post-mortem analysis such as neutron powder diffraction (NPD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the electrode after cycling. It suggests that electrolyte concentration needs to be optimized for a given cell configuration with specific electrode and loading.

Factors Affecting Hydroxide Ion Concentrations in Bipolar Membranes

The useful lifetime of bipolar ion exchange membranes is often limited by nucleophilic attack by hydroxide ions on the ionic groups and polymer backbone in the anion exchange layers (AELs). This is especially problematic in water treatment applications for making acid and base from salt solutions. This research investigated the effect of bulk electrolyte composition, current density, membrane thickness, ion exchange capacity, and bulk solution pH value on hydroxide ion concentrations inside the AELs of a bipolar membrane. Onedimensional Nernst-Plank equations were solved for the species Na+, Cl-, OH- and H+ within 20-100 μm thick anion and cation exchange layers with fixed charged densities ranging from 0.5-2.0 eq/L. In 1 M NaCl solutions at neutral pH values, hydroxide concentrations in the AEL reached as high as 2.2 M at a current density of 100 mA/cm2. In 1 M NaOH solutions, hydroxide ion concentrations reached as high as 3.77 M. Hydroxide concentrations in the AEL were significantly affected by the ratio of Cl- to hydroxide ions in the bulk electrolyte. Where hydroxide concentrations in the bulk electrolyte were an order of magnitude lower than chloride concentrations, membrane hydroxide concentrations were nearly proportional to the current density. Increases in ion exchange capacity and AEL thickness resulted in increased membrane hydroxide ion concentrations. Membrane concentrations of hydroxide ions can be minimized by operation at low current densities, with high background electrolyte concentrations using thin membranes with low ion exchange capacities and producing base concentrations less than 0.1 M.

A two-dimensional transient model for a zinc-cerium redox flow battery validated by extensive experimental data

A two-dimensional transient model accounting for the charge, mass and momentum transport coupled with electrode kinetics is developed for zinc-cerium redox flow batteries (RFBs). The model is validated against an extensive set of experimental data obtained in our laboratory. This includes full-cell voltages, positive and negative electrode potentials monitored against reference electrodes inserted into the battery half-cell compartments and Ce(IV) concentrations in the positive electrolyte over 5 cycles. To the best of our knowledge, this is the most comprehensive set of experimental data used to fit and validate a flow battery model. The validated model is then used to predict the cell voltages and limiting redox reactions during battery operation for different model parameters to provide a guide to further improve the performance of zinc-cerium RFBs.

Operando Measurements of Electrolyte Lithium Ion Concentration during Fast-Charging

The ability to charge a Li-ion battery at high charging rates is critical for widespread electric vehicle adoption, but fast-charging rates can cause battery degradation and performance issues. A primary challenge for fast charging is finding electrolytes with sufficient lithium ion transport to operating under high current densities. However, there are few options for measuring ion transport in operating batteries. A novel diagnostic using Fourier transform infrared spectroscopy (FTIR) with attenuated total reflection (ATR) is reported for operando measurements of lithium ion concentration in a liquid electrolyte during battery operation. This diagnostic uses solvation shifting of solvent molecule vibrational modes to quantify lithium concentration. The diagnostic was calibrated using EC/EMC/LiPF6 electrolytes with known lithium concentrations from 0.03 mol/liter to 1.83 mol/liter. The concentration of PF6 - was also determined with a similar procedure. The resulting diagnostic can measure lithium concentrations from 0.001 to over 2 mol/liter with a minimum detection limit of 0.0011 moles/liter. The diagnostic is demonstrated using a lithium-ion half cell with a graphite anode and EC/EMC/LiPF6 electrolyte assembled in an argon-filled glove box. Measurements on the current collector side of the anode showed that as charging rates increased (i.e. during lithiation), lithium ion concentrations in the adjacent electrolyte decreased. The reverse trend was observed upon delithiation. These results demonstrate the utility of this diagnostic in quantifying ion depletion in electrolytes under fast charge conditions.

Tailoring the Mg-air primary battery performance using strong complexing agents as electrolyte additives

Mg-air primary battery has become an attractive source of energy due to its economic viability, environmental benignity, and high theoretical specific power density. However, low practical delivered power due to high self-corrosion and fast anode fouling are the main reasons that limit their commercial application. Modification of the electrolyte chemistry in Mg-air batteries plays a crucial role in improving the Mg-air battery performance. In this study, the impact of addition of two strong complexing agents at different concentrations in the aqueous electrolyte of Mg-air battery is investigated. Galvanostatic polarization test is conducted in order to evaluate the discharge performance of the half-cell on the anode side in the presence or absence of strong complexing agents. According to the results, strong complexing agents are able to effectively activate magnesium anode and provide a higher delivered potential. A decrease in the additive concentrations in the electrolyte leads to the attainment of higher utilization efficiency at the expense of slight drop in discharge potential.

Lead-silver anode behavior for zinc electrowinning in sulfuric acid solution

Abstract In recent years, a renewed interest in studying the electrochemical corrosion behavior of lead anodes during zinc electrowinning is probably due to the particularly high sulfuric acid concentrations in zinc electrolyte where lead alloy anodes have high cell voltage and high corrosion rate of lead. The high corrosion rate of lead alloy resulted in Pb contamination on zinc deposit. In zinc electrometallurgy, the electrolyte from a zinc-rich ore contains a significant amount of Mn2+. Mn2+ in the zinc electrolyte results in forming an oxide film on lead anodes during electrolysis. Pb-0.7% Ag anode is generally used in the zinc industry. To improve the technical performance and decrease product cost, other anodes, such as Pb-Ca or Pb-Ag-Ca or Pb-Ag-Ti or Pb-Ag-Se alloys were tested. Till now, none of them has succeeded in the substitution of Pb-Ag anodes in the zinc electrowinning. As an alloying element, silver in small quantities is considered because of the benefits that generates on the anode during electrolysis. During zinc electrolysis, lead dissolution into the zinc electrolyte can be harmful to the quality of zinc deposit. However, the lead silver alloy anode can decrease the lead content in the zinc deposit by pre-treated methods such as blasting and preconditioning.

Mobility Shift Affinity Capillary Electrophoresis at High Ligand Concentrations: Application to Aluminum Chlorohydrate–Protein Interactions

The active ingredients in antiperspirant products are aluminum chlorohydrates (ACHs) that, when interacting with proteins present in sweat and sweat duct walls, lead to the obstruction of the sweat ducts and thus reduce delivery of sweat at the skin surface. This study is aimed at developing a methodology based on affinity capillary electrophoresis (ACE) to obtain a quantitative ranking of the interaction between ACHs and proteins under experimental conditions close to those of industrial applications. Usually, in ACE, the metal ligand is introduced at typically μM to mM concentrations in a background electrolyte (BGE) containing a buffering agent that sets the pH and ionic strength. In this work, ACE was implemented in a range of ACH (ligand) concentrations up to 50 g/L (0.2 M in Al(H2O)6·3Cl) in the absence of other buffering agents, to mimic as much as possible the conditions encountered in the production of antiperspirant products. Under such electrophoretic conditions, the challenge is to extract quantitative information about the interaction from the electrophoretic mobility of the protein, knowing that many effects (including Joule heating, viscosity, pH, ionic strength of the BGE, and distribution of the ligands) vary with the concentration of ACH. With relevant corrections on the effective mobility, it has been possible to observe and quantify a much stronger interaction of ACH components with bovine serum albumin compared to lysozyme.

A BiFEs-based SWASV method for fast screening of multi-heavy metals in Xiaochaihu Tang

Multi-heavy metal residues in traditional Chinese medicines especially their formulas have become a world-wide concern for human's health. A real time analysis of multi-heavy metals with high sensitivity and accuracy is of great necessity. In this study, an anodic square wave stripping voltammetry (SWASV) technique based on the stable Bismuth material was developed for the fast screening of Cd2+, Pb2+ and Cu2+ in Xiaochaihu Tang for its safe medication in practice. Firstly, a flat and compact Bismuth film electrode (BiFE) was prepared by pre-plating Bi crystal on glass carbon electrode (GCE) substrate at special deposition potential and deposition time, which was confirmed through the observation of morphological and electrochemical properties. Then, the heavy metals of interest were isolated from complex Xiaochaihu Tang by using an optimized digestion system and a low-cost sample preparation procedure. Besides, three different deposition potentials were selected to respectively reduce 3 kinds of cations for a better reproducibility and accuracy of the analysis than before. It was demonstrated that the intensity of the remarkable anodic peaks of Cd2+, Pb2+ and Cu2+ at −0.876 V, −0.621 V and − 0.248 V were proportional (R2 = 0.9975, 0.9993, 0.9997) to their concentrations in the decoction electrolyte in the range of 0.008–0.08 μg·mL−1 for Cd2+, 0.01–0.1 μg·mL−1 for Pb2+ and 0.10–1.00 μg·mL−1 for Cu2+, respectively. The developed SWASV method allowed low detection limits of 0.0031 μg·mL−1, 0.0002 μg·mL−1 and 0.0044 μg·mL−1 for Cd2+, Pb2+ and Cu2+, which are much lower than the guideline values in herbs set in the Chinese Pharmacopeia. Real sample analysis showed that Pb2+ was detected in 3 batches of Xiaochaihu Tang samples within 5 min, which were confirmed by the ICP-MS method. Therefore, this developed method can be applied in the fast screening of multi-heavy metals in complex decoction matrices.

Fabrication of TiO2 Nanostructures on Ti3SiC2 Substrate by Anodic Oxidation

A TiO2 nanostructure was prepared on a Ti3SiC2 substrate with different water and NH4F concentrations in a fluoride-containing ethylene glycol electrolyte via an anodization process using the same constant-anodization potentials, anodization duration and temperature. The as-prepared samples were characterized by a field-emission scanning electron microscope equipped with an energy dispersive X-ray spectroscope, as well as by X-ray diffraction and X-ray photoelectron spectroscopy. The influence of the anodizing parameters and annealing temperature on the morphology of the nanostructure and the phase structure was studied. The results showed that the scattered TiO2 nanotubes and TiO2 nanoporous films were successfully fabricated in the glycol electrolyte containing (3.0 wt%) NH4F +(5.0 vol%) H2O. The as-prepared samples before calcination were amorphous and could transform to the anatase phase at temperatures higher than 500 °C. As the annealing temperature increased, the crystallization of the anatase phase was enhanced, and the rutile phase appeared at 600 °C. The as-prepared samples mainly consisted of oxides. Ti2O3 and SiO2 oxides were present in addition to TiO2.

Influence of Concentrations of KOH and Na2SiO3 Electrolytes on the Electrochemical Behavior of Ceramic Coatings on 6061 Al Alloy Processed by Plasma Electrolytic Oxidation

In this study, ceramic coatings were deposited on 6061 Al alloy using a plasma electrolytic oxidation (PEO) technique, and the effect of concentrations of KOH and Na2SiO3 as electrolytes for PEO process was studied on microstructure, chemical composition, and electrochemical behavior of PEO coatings formed on the 6061 Al alloy. The results indicated that the increase in concentration of KOH led to rise in electrical conductivity of electrolyte. Consequently, the breakdown voltage reduced, which in turn improved the surface quality and the corrosion behavior. Moreover, the increase in concentration of Na2SiO3 resulted in the increase in incorporation of Si in the coating, which led to a higher corrosion potential in the concentration of 4 g L−1. According to this investigation, the best protection behavior of coatings can be obtained when the KOH and Na2SiO3 concentrations in PEO electrolyte are equal to 4 g L−1.

The Effect of TAUNIT Carbon Nanotubes on the Properties of Electroplating and Anodic Oxide Coatings

The properties of the coatings produced by electrodeposition from electrolytes containing TAUNIT carbon nanotubes have been studied. The technology of zinc depositing from electrolytes with nanocarbon additives to increase the resistance to corrosion has been developed. Due to the fact that carbon nanotubes appear to be additional crystallization centers, the crystal size of the coating is reduced. The potentiodynamic method for determining the corrosion rate shows that the corrosion rate decreases fourfold, provided the concentration of TAUNIT carbon nanotubes in the electrolyte is 100 mg/l. It is suggested that the improved corrosion resistance is due to a change in the structure of zinc coating. It is found that anodic oxidation in electrolytes containing TAUNIT CNTs leads to a change in the morphology of coatings and improves heat-release properties in air. The effect of different concentrations of CNTs in silver plating electrolyte on the characteristics of coatings has been described. The study of nanomodified palladation electroplating has revealed the effect of different CNT concentrations in palladation electrolyte on the microstructure and mechanical properties of coatings.

A highly sensitive BTX sensor based on electrochemically derived wall connected TiO2 nanotubes

This paper concerns development of electrochemically synthesized titanium dioxide (TiO2) nanotube array for sensing the carcinogenic aromatic hydrocarbons like benzene, toluene, and xylene (BTX) with enhanced sensitivity achievable at relatively low temperature. Structural characterizations (XRD, FESEM), revealed that variation of the H2O concentrations (1%, 2%, 5%, 8%, 10%, and 100% by volume) in mixed electrolyte, comprising of ethylene glycol (EG) and ammonium fluoride (NH4F), resulted in the formation of six distinctly different TiO2 nanoforms. Photo luminescence spectra (PL spectra) analysis authenticated different stoichiometry of these six samples. Besides, the X-ray photoelectron spectroscopy (XPS) was carried out to investigate the defect states. The XPS study enables to correlate the oxygen vacancy concentration with the anodization parameters. Among the various nanoforms, the wall connected TiO2 nanotube array was found to be the most efficient one for BTX sensing in the concentration range 1–400ppm at relatively lower operating temperatures (50–200°C). Among the three target species, benzene was found to offer the highest response magnitude followed by that of toluene and xylene at all the concentrations. The concerned sensing mechanism was also discussed correlating the experimental findings.