Sulfuric Acid Electrolyte Research Articles

Утилизация растворов электрорафинирования меди переработки лома цветных металлов

The results of studies on the utilization of copper electrorefining solutions, zinc-containing sublimation dusts of pyrometallurgical processing of non-ferrous metal scrap are presented. Zinc-containing sublimation dusts for the regeneration of commercial electrolyte by the neutralization method were used for the first time. Contained in dust, zinc oxide, when dissolved in a sulfuric acid electrolyte, binds sulfate ions of free sulfuric acid and increases the pH of the solution. When the pH of the precipitation of non-ferrous metals is reached, they are precipitated in the form of hydroxides, which makes it possible to return to processing a significant amount of copper, nickel, zinc, lead and tin contained in them. Studies of the material composition of the commercial electrolyte of copper and zinc sublimates for the processing of non-ferrous metal scrap have been carried out. The conditions for purification of the electrolyte by the method of staged neutralization are determined. The first stage of neutralization was carried out with zinc sublimates, the second and third stages with potash. As a result of the first stage of neutralization to pH 4.7, lead was obtained - a tin-containing product that can be processed together with lead-containing copper electrorefining sludge. As a result of the second stage of neutralization with potash to pH 7.1, a precipitate was obtained, after treatment of which in a KOH solution, a precipitate of copper oxide was obtained. As a result of the third stage of neutralization to pH 9.5, a nickel-zinc-containing precipitate was obtained. After treating the precipitate with a KOH solution, a zinc-containing solution and a nickel-containing precipitate were obtained, after calcining which a nickel oxide precipitate was obtained.

Preparation and Preliminary Evaluation of Silver-Modified Anodic Alumina for Biomedical Applications

The present study reports a specific method for preparation of silver-modified anodic alumina substrates intended for biomaterial applications. Al2O3 coatings were obtained by anodization of technically pure aluminum alloy in sulfuric acid electrolyte. Silver deposition into the pores of the anodic structures was carried out employing in situ thermal reduction for different time periods. The obtained coatings were characterized using scanning electron microscopy (SEM), potentiodynamic scanning after 168 h in 3.5% NaCl solution and bioassays with human fibroblast and NIH/3T3 cell lines. The modified alumina substrates demonstrated better biocompatibility compared to the control anodic Al2O3 pads indicated by increased percent cell survival following in vitro culture with human and mouse fibroblasts. The Ag-deposition time did not affect considerably the biocompatibility of the investigated anodic layers. SEM analyses indicated that mouse NIH/3T3 cells and human fibroblasts adhere to the silver-coated alumina substrates retaining normal morphology and ability to form cell monolayer. Therefore, the present studies demonstrate that silver coating of anodic alumina substrates improves their biocompatibility and their eventual biomedical application.

The potential of tantalum as an efficient electrocatalyst for green hydrogen production

Worldwide, discovering a low-cost, highly active and durable electrocatalyst for green hydrogen production is an attractive research field for future renewable energy. Herein, we study the suitability of utilizing metallic Ta as promising electrocatalytic material for hydrogen creation from acidic solutions. The morphological structure and crystal lattice system, as well as the chemical composition and oxidation states of Ta are examined using scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy, respectively. Hydrogen evolution reaction (HER) on Ta is investigated using cathodic polarization and electrochemical impedance techniques as a function of electrolyte concentration, applied potential, and temperature. Various kinetic parameters distinguishing catalytic activity of the process on Ta including Tafel slope, exchange current density, cathodic transfer coefficient, and HER rates are determined. At −1500 mV cathodic potential in 0.5 M H2SO4 solution, the results confirm well that, to reach a similar HER rate of say 100 mA cm-2, the overpotential on Ta cathode is found equal -520 mV, which is lower than the value of -940 mV attained on the platinum cathode, indicating high electrocatalytic activity of the HER on Ta surface. The obtained results also demonstrated that, for the hydrogen production process the overpotential greatly diminishes and its current density significantly improves with increasing either the electrolyte concentration or its temperature. Additionally, Tafel slope analysis and impedance parameters establish that HER proceeds by the Volmer–Heyrovsky mechanism. The outcome of this study reveals that the valve metal Ta is a sustainable, efficient, and promising cathode for green hydrogen generation fuel from sulphuric acid electrolytes.

Estimating electrodeposition properties and processes: Cu-Ag alloy at n-Si(001) and Ru substrates from acidic sulfate bath

In alloy electrodeposition, estimations of the initial transient and the potential vs. composition trend of the film system is important for material design, deposition procedure and the deposit characterization. However, solving the diffusion-migration-convection problem based on common simulation methods is often too burdensome and too resource-consuming for ordinary tasks in the context of alloy electrodeposition works. In this work, based on a stagnant diffusion layer model, we have proposed simple estimates on (1) the potential-composition curve, (2) the thickness of the initial deposit, and (3) the time interval to reach the steady state deposition. These estimates were validated by using a Cu-Ag acidic sulfate electrolyte, which upon electrodeposition results in an immiscible Cu-Ag alloy, both at n-Si(001) or at polycrystallline Ru substrates. The limiting current of Cu-Ag electrodeposition is compared with the numerical results given by Selman and Newman in 1970s [17], whereas the film composition deposited at the limiting current from various electrolyte constitutions is compared with the model suggest by Brenner based on stagnant diffusion layer model [21]. The proposed estimation methods show good agreement with the observed values, despite being highly simplified, since they are compared with the actual mass-transfer problem of ions under convection and migration.

Compared EC-AFM Analysis of Laser-Induced Graphene and Graphite Electrodes in Sulfuric Acid Electrolyte.

Flexible and economic sensor devices are the focus of increasing interest for their potential and wide applications in medicine, food analysis, pollution, water quality, etc. In these areas, the possibility of using stable, reproducible, and pocket devices can simplify the acquisition of data. Among recent prototypes, sensors based on laser-induced graphene (LIGE) on Kapton represent a feasible choice. In particular, LIGE devices are also exploited as electrodes for sensing in liquids. Despite a characterization with electrochemical (EC) methods in the literature, a closer comparison with traditional graphite electrodes is still missing. In this study, we combine atomic force microscopy with an EC cell (EC-AFM) to study, in situ, electrode oxidation reactions when LIGE or other graphite samples are used as anodes inside an acid electrolyte. This investigation shows the quality and performance of the LIGE electrode with respect to other samples. Finally, an ex situ Raman spectroscopy analysis allows a detailed chemical analysis of the employed electrodes.

Amorphous silicon carbide thin films doped with P or B for the photoelectrochemical water splitting devices

Photoelectrochemical water splitting devices require semiconductor photoelectrode material fulfilling a number of primary requirements such as band gap, band edge alignment and corrosion resistance to electrolyte. Amorphous silicon carbide films, undoped and doped (P or B), were deposited on Si substrates by PECVD technology. The concentration of elements in the films was determined by RBS and ERD analytical method. Raman spectroscopy study of the SiC films were performed by using a Raman microscope and chemical compositions were analyzed by FTIR, before and after immersion of samples to aqueous pH 2.0 and pH 1.0 sulphuric acid electrolyte. Electrical properties of SiC films before and after immersion of samples to aqueous pH 2.0 and pH 1.0 sulphuric acid electrolyte were studied by measurement of the I–V characteristics on structure Al/SiC/Si/Al. Differences between Raman spectra, FTIR spectra and I–V characteristics before and after immersion to electrolyte are discussed.

Easy preparation of anodic aluminum oxide photonic crystal films with tunable structural colors

Anodic aluminum oxide (AAO) photonic crystal films with Sn nanoparticles electrodeposited at the bottom were prepared using a pseudo-sine-pulse anodization technique followed by an alternating current electrodeposition. Moreover, a pore-widening post-treatment was performed for the Sn electrodeposited films. The phase structure, microstructure and structural color properties of the specimens with different preparation histories were examined. The Sn electrodeposition enabled production of brightly colored AAO photonic crystal films after a short-duration anodization (40 anodization cycles) in a sulfuric acid electrolyte solution at a temperature (around 20 °C) near to room temperature, which is technology-friendly relative to the conventional anodization conditions when using sulfuric acid electrolyte solutions, e.g., after 80–300 anodization cycles at around 0 °C. Moreover, the pore-widening treatment was demonstrated to be convenient and controllable in tuning the porosities and structural color properties of the Sn electrodeposited films. The peak wavelengths of the reflectance spectra were nearly linearly blue-shifted from 681 to 574 nm with increasing pore-widening time from 0 to 8 min, concomitant with a structural color change from bright-red to yellowish-green. Meanwhile, the peak reflectances were linearly enhanced from 59 to 84%, corresponding to an increase of the brightness of the films. The linearly varied peak wavelengths and peak reflectances were related to a linear increase of the porosities of the stem and branched layers in the films with pore-widening time.

Application of pulse current for dissolution of heat-resistant GS32-VI alloy

Objectives. To identify the regularities of electrochemical processing of the heat-resistant GS32-VI alloy in a sulfuric acid electrolyte with a concentration of 100 g/dm3 under the action of a pulsed current in a pulsed mode.Methods. Using the electrochemical technological complex EHK-1012 (developed by IP Tetran) and a non-compensatory method of measuring potential, polarization and depolarization curves with a change in pulse duration and a pause between them were recorded. The current pulses had an amplitude ranging from 0 to 3.5 A (when recording the polarization and depolarization curves), pulse durations ranging from 200 to 1200 ms, and a pause (delay) between pulses ranging from 50 to 500 ms. There were no reverse current pulses.Results. The parameters of the current program that provide the maximum values of the alloy dissolution rate and current output were determined: with a current pulse amplitude of 2 A, a current pulse duration of 500 ms, and a pause duration between pulses of 250 ms, the maximum dissolution rate of the alloy is 0.048 g/h·cm2, while the current output for nickel is 61.6% with an anode area of 10 cm2. The basic technological scheme for processing the heat-resistant GS32-VI alloy, which includes anodic alloy dissolution in a pulsed mode, is proposed.Conclusions. Electrochemical dissolution of GS32-VI alloy under pulsed current action results in an optimal dissolution rate ratio of the alloy components, ensuring the production of a cathode precipitate with a total nickel and cobalt content of 97.5%.

Investigating the Surface and Microstructure of Electrodeposited Cu Films

Both morphology and microstructure play a crucial role in determining the properties of an electrodeposited polycrystalline thin film and its performance in different applications. We have investigated the morphology of Cu films electrodeposited from a chloride-containing acid sulfate electrolyte by applying a combination of conventional ex-situ AFM and in-situ High-Speed AFM (HS-AFM). For the HS-AFM studies, a film was grown on a microelectrode, 30µm in diameter and imaged in-situ in real time. The high-speed flexure stage of HS-AFM enables it to scan the surface of the film up to 1000 times faster than the conventional AFM [1], which provides many details about how the film growth is proceeding and how the structure coarsens with deposition time [2]. Here, we compare data from films prepared by continuous and pulse deposition. We also present microstructural data obtained with the help of focussed ion beam milling.[1] Oliver D Payton, Loren Picco, and Thomas Bligh Scott. High-speed atomic force microscopy for materials science. International Materials Reviews, 61(8):473-494, 2016.[2] Aswathi Koorikkat, Oliver Payton, Loren Picco, and Walther Schwarzacher. Imaging the surface of a polycrystalline electrodeposited cu film in real time using in situ high-speed AFM. Journal of the Electrochemical Society, 167(16):162510, 2020.

(Industrial Electrochemistry and Electrochemical Engineering Division New Electrochemical Technology (NET) Award) Pulse Reverse HF-Free Electropolishing of Niobium Superconducting Radio Frequency (SRF) Cavities for Nuclear Physics and High Energy Physics Applications

On behalf of Faraday Technology, Inc., we are honored to receive the 2021 New Electrochemical Technology (NET) award of the Industrial Electrochemistry & Electrochemical Engineering (IE&EE) division for pulse reverse FARADAYIC® HF-FREE Electropolishing of niobium SRF cavities. The NET award was endowed by the Dow Chemical Company Foundation to recognize significant advances in industrial electrochemistry. We addressed the subject innovation as a multidisciplinary team of electrochemists, engineers and technologists.Niobium superconducting radio frequency (SRF) cavities are used in particle accelerators such as the Large Hadron Collider (LHC) to support nuclear/high energy physics applications. To achieve their required performance, the niobium SRF cavities are electropolished using nine-parts sulfuric acid to one-part hydrofluoric acid.[1] The conventional process follows the well-established “viscous salt-film” model for electropolishing.[2] The conventional electrolyte imparts an extreme hazard to workers requiring costly safety protocols with extensive worker protection (see Fig. 1a).[3] ,[4] To commercialize niobium SRF cavity electropolishing, a simpler, cost-effective industrially compatible process was required.We developed a pulse reverse process to electropolish niobium coupons in low concentration (<5 wt%) aqueous sulfuric acid electrolytes devoid of hydrofluoric acid.[5] The surface roughness was the same as that observed using conventional DC electropolishing.[6] We transitioned the work from coupons to single-cell niobium cavities SRF and the performance was the highest observed at the DOE’s Fermi National Accelerator Facility.[7] ,[8] Due to the avoidance of the safety protocols associated with the conventional process (see Fig. 1b), the capital and operating costs of the pulse reverse electropolishing process were considerably less than the conventional process.[9] Finally, the pulse reverse process was patented and transitioned to DOE’s Thomas Jefferson National Accelerator Facility.[10] ,[11] Finally, the pulse reverse process was adapted to other strongly passive materials.While reviewing the technology developments leading to and associated with the niobium pulse reverse electropolishing process, we will illustrate lessons learned during the development of industrial innovations.[12] [1] H. Tian, S. Corcoran, C. Reece, and M. Kelly, J. Electrochem. Soc., 155, D563 (2008). [2] P. A. Jacquet, Trans. Electrochem. Soc., 69, 629 (1936). [3] T. Dote and K. Kono, Jap. J. Occupational Medicine and Traumatology, 52, 3, 189 (2004). [4] J. Mammoser, “Chemical Safety Awareness for SRF Cavity Work” U.S. Particle Accelerator School, January 19, 2015 (accessed June 9, 2020) https://www.jlab.org/indico/event/98/ other-view?fr=no&detailLevel=contribution&view=standard& showSession=all&showDate=all [5] M. Inman, E. J. Taylor, and T. D. Hall, J. Electrochem. Soc., 160, E94 (2013). [6] M. Inman, T. Hall, E. J. Taylor, C. Reece, and O. Trofimova, Paper TOPO012, Proc. SRF2011, Chicago, IL (2011). [7] E. J. Taylor, T. Hall, M. Inman, S. Snyder, and A. Rowe, Electropolishing of Niobium SRF Cavities in Low Viscosity Aqueous Electrolytes without Hydroflouric Acid, Paper TUP054, Proc. SRF2013, Paris, France, Sept 2013. (ISBN 978- 3-95450-143-4) [8] A. Rowe, A. Grassellino, T. Hall, M. Inman, S. Snyder, and E. Taylor, Paper No. TUIOC02, Proc. SRF2013, Paris, France, Sept 2013. (ISBN 978-3-95450-143-4) [9] E. J. Taylor, M. Inman, T. Hall, S. Snyder, A. Rowe, and D. Holmes, Paper MOPB092, Proc. SRF2015, Whistler, BC, Canada (2015). [10] E. J. Taylor, M. E. Inman, and T. D. Hall, U.S. Pat. No. 9,006,147 issued April 14, 2015. [11] E. J. Taylor, M. E. Inman, and T. D. Hall, U.S. Pat. No. 9,987,699 issued June 5, 2018. [12] E.J. Taylor, M.E. Inman, H.M. Garich, H.A. McCrabb, S.T. Snyder, T.D. Hall in Electrochemical Engineering: The Path from Discovery to Product Alkire, Bartlett, Koper (eds) Wiley-VCH (2019). Figure 1

Study of the effect of electrolyte composition on adhesion and other properties of a coating-base system

Aluminum alloys with electroplated coatings and copper plated in particular gained multiple applications. However, pre-zincate treatment often fails to provide the desired adhesion of the coating. We present the results of studying the effect of the electrolyte composition on the adhesion and other properties of the coating-base system. It is shown that an electrolyte with a reduced content of sulfuric and phosphoric acids can be used for anodizing and the oxide films formed during anodizing are stable in the usual copper-plating sulfuric acid electrolyte which eliminates contact exchange and increases adhesion. The use of a modern scratch-test method provides numerical determination of the values of adhesion of copper coatings. The adhesion value depends on the surface porosity of the oxide film and on the type of anodized alloys. The results can be used to improve the technology of applying copper coatings, both as an independent coating and as an underlayer in multilayer coatings.

Electrodeposition of Pb and PbO2 on Graphite Felt in Membraneless Flow-Through Reactor: A Method to Prepare Lightweight Electrode Grids for Lead-Acid Batteries.

One of the possible ways of mitigating the primary lead-acid battery downside—mass— is to replace the heavy lead grids that can add up to half of the total electrode’s mass. The grids can be exchanged for a lightweight, chemically inert, and conductive material such as graphite felt. To reduce carbon surface area, Pb/PbO2 can be electrochemically deposited on graphite felt. A flow-through reactor was applied to enhance penetration of adequate coverage of graphite felt fibers. Three types of electrolytes (acetate, nitrate, and methanesulfonate) and two additives (ligninsulfonate and Triton X-100) were tested. The prepared composite electrodes showed greater mechanical strength, up to 5 times lower electrical resistivity, and acted as Pb and PbO2 electrodes in sulfuric acid electrolytes.

Exploring the Additive Effects of Aluminium and Potassium Sulfates in Enhancing the Charge Cycle of Lead Acid Batteries

The adoption of aluminium sulfate and potassium sulfate as electrolyte additives were investigated to determine the possibility of enhancing the charge cycle of 2V/ 20AH lead acid battery with reference to the conventional dilute sulfuric acid electrolyte. The duration and efficiency of lead acid batteries have been a challenge for industries over time due to weak electrolyte and insufficient charge cycle leading to sulfation. This has affected the long-term production output in manufacturing companies that depend on lead acid batteries as alternative power source. Hence there is need to explore the use of specific sulfate additives that can possibly address this gap. The electrolyte solutions were in three separate charge and discharge cycles involving dilute sulfuric acid electrolyte, dilute sulfuric acid-aluminium sulfate mixed electrolyte and dilute sulfuric acid-potassium sulfate mixed electrolyte for one hour each. The total voltage after 30 minutes charge cycle was 2.3V, 2.35V and 5.10V for dilute sulfuric acid, aluminium sulfate additive and potassium sulfate additive respectively. The cell efficiency for dilute sulfuric acid, aluminium sulfate additive and potassium sulfate additive electrolytes are 77%, 77% and 33% respectively. The electrolyte sulfate additives were of no positive impact to the conventional dilute sulfuric acid electrolyte of a typical lead acid battery due to the low difference in potentials between the terminals.

How determinant is the iron precursor ligand in Fe-N-C single-site formation and activity for oxygen reduction reaction?

Metal-Nitrogen-Carbon (M-N-C) materials have emerged as one of the best non-PGM alternatives to Pt/C catalysts for the electrochemical reduction of O2 in fuel cells. In this work, we explore how decisive is the iron precursor ligand in the Fe-Nx site formation when a commercial carbon black (Vulcan XC72) is pyrolyzed in the presence of an iron complex. Iron complexes coordinating different nitrogen ligands such as phthalocyanine, 1,10-Phenanthroline, 2,2’-Bipyridyl, imidazole, EDTA, etc., were tested. Different Fe-N-C catalysts were synthetized by using twelve different complexes to achieve a better understanding on the role of ligands on site formation and activity, i.e. the site density (SD) and the turn-over frequency (TOF), respectively. It was found that Fe-Nx active site can be effectively formed only when ligands containing aromatic nitrogen rings are used and that the ligand decomposition leads to a substantial change in the carbon morphology developing an increased micropore volume, while mesopore surface area is reduced. The activity was checked in both acidic and alkaline electrolyte by RRDE technique showing that the catalytic activity deeply depends on the type of iron complex, even if such difference is much less important when KOH was used as electrolyte. Site density was determined according to nitrite stripping method, and it was found that the activity (E1/2) in sulphuric acid electrolyte well correlate with the SD, which reaches its maximum when Fe(phen)3Cl2 was used as precursor (SD = 4.24 × 1018 sites g−1; TOF = 6.66 e− sites−1 s−1). Indeed, Fe(phen)3Cl2 involves on one hand a higher mesopore occlusion (from 93 to 34 m2 g−1), but on the other hand the etching due to the small molecules developed by the pyrolysis of the ligand leads to higher micropore surface (from 132 to 246 m2 g−1), which is an important aspect for the formation of Fe-Nx active sites. This clearly places a limit on the ability to increase catalytic activity simply by playing on the initial content of complex, since while we try to increase the SD by increasing the complex loading at the same time the textural properties worsen.Stability test and post-stress test site density analysis on the best catalysts show a higher stability in alkaline electrolyte. In acid electrolyte, the kinetic current decreases by 60% after 7000 cycles and this was proven to depends by the decreasing of the SD, attesting the labile nature of Fe-Nx sites when used in demanding conditions.

Sonoelectrochemical exfoliation of graphene in various electrolytic environments and their structural and electrochemical properties

Graphene synthesized via electrochemical exfoliation of graphite is considered to be a simple, fast, and scalable technique. This exfoliation technique leads to the formation of multi-layer graphene sheets with some defects, which is feasible for developing supercapacitor electrodes due to the presence of various pseudocapacitive functionalities. We report the exfoliation of multi-layer graphene via pulse sonication assisted electrochemical exfoliation technique (sonoelectrochemical) and studied the effect of three different aqueous electrolytes having acidic, neutral, and basic properties. The pulse (2/4) of 2 s sonication and 4 s rest time significantly improve the exfoliation process without hindering the electrochemical reaction that takes place on the graphite. The structural quality and functional groups attached to the surface of the exfoliated graphene sheets were evaluated using spectroscopic techniques. The investigation reveals that the nature of electrolyte and intercalation ions highly influences the exfoliation duration, yield, size, and quality of the graphene. The graphene layers exfoliated in sulfuric acid and ammonium sulfate electrolytes possessed many defect sites than those exfoliated in KOH. However, this graphene demonstrated better electrochemical performance than the graphene exfoliated in KOH electrolyte due to the presence of various electroactive defect sites on the surface and edges of the graphene.

A Multi-Scale Structural Engineering Strategy for High-Performance MXene Hydrogel Supercapacitor Electrode.

MXenes as an emerging two‐dimensional (2D) material have attracted tremendous interest in electrochemical energy‐storage systems such as supercapacitors. Nevertheless, 2D MXene flakes intrinsically tend to lie flat on the substrate when self‐assembling as electrodes, leading to the highly tortuous ion pathways orthogonal to the current collector and hindering ion accessibility. Herein, a facile strategy toward multi‐scale structural engineering is proposed to fabricate high‐performance MXene hydrogel supercapacitor electrodes. By unidirectional freezing of the MXene slurry followed by a designed thawing process in the sulfuric acid electrolyte, the hydrogel electrode is endowed with a three‐dimensional (3D) open macrostructure impregnated with sufficient electrolyte and H+‐intercalated microstructure, which provide abundant active sites for ion storage. Meanwhile, the ordered channels bring through‐electrode ion and electron transportation pathways that facilitate electrolyte infiltration and mass exchange between electrolyte and electrode. Furthermore, this strategy can also be extended to the fabrication of a 3D‐printed all‐MXene micro‐supercapacitor (MSC), delivering an ultrahigh areal capacitance of 2.0 F cm–2 at 1.2 mA cm–2 and retaining 1.2 F cm–2 at 60 mA cm–2 together with record‐high energy density (0.1 mWh cm–2 at 0.38 mW cm–2).

Synthesis and characterization of aluminium oxide nanoparticles from waste aluminium foil and potential application in aluminium-ion cell

Abstract Aluminium waste accumulated in landfills is a solid waste in abundance. Various methods have been employed to alleviate the waste only to yield secondary pollution effects. This study seeks to provide an alternative greener recycling procedure that is beneficial to society in terms of health and economics through energy storage materials. The study aimed to synthesize and characterize aluminium oxide nanoparticles from waste aluminium foil and its potential applications in fabricating aluminium-ion cell, FAIC. 1 Aluminium oxide nanoparticles were obtained by co-precipitation of waste aluminium foils at constant annealing room temperature followed by mechanical milling to nanoparticulate range. The particles were then characterized for particle size and phases (X-ray diffraction), functional groups and optical activity (infra-red and ultra-violet-visible spectroscopy respectively). Cell assembling of FAIC was done using a graphite anode while the cathode had a standard and the synthesized aluminium oxide nanoparticles. Sulfuric acid and magnesium sulfate electrolytes were used with two binders; polyacrylate and silicone adhesives. The average synthesis yield was 40.64 ± 19.69%. Most of the particles had a α-Al2O3 and γ-Al2O3 phase with an average size of 63.763 nm and 66.5144 nm for the two polymorphs respectively. There were several OH-groups coupled to Al–O bonds. The optimal absorption peak was λmax = 237 nm corresponding to a band gap of 5.25eV. The synthesized nanoparticles exhibited great electrochemical potential, nearing the standard one in most of the parameters. The FAIC potential, current, power densities and polarization curves from sulfuric acid electrolyte and polyacrylate binder were significantly higher to those of magnesium sulfate and silicone binder (P > 0.05).

Characterization of the Electrochemical Behavior of MnSO4 with and without TiOSO4 in H2SO4 Solution

An electrochemical characteristic evaluation of the Ti-Mn electrolyte system in sulfuric acid aqueous solution was conducted in different acid concentrations with and without the mixing of TiOSO4 and MnSO4 electrolyte system for a redox flow battery application. The reaction mechanism of Mn in sulfuric acid electrolyte was studied using the cyclic voltammetry and anodic voltage hold techniques. The overall anodic behavior of the Mn system can be described by the oxidation reaction of Mn2+ to MnO2 where Mn3+ is an intermediate species. As the acid concentration increases, less MnO2 is formed on the working electrode and more Mn3+ is formed in the solution; however, due to the instability of Mn3+ in an aqueous solution, Mn3+ undergoes a hydrolysis reaction to precipitate as MnOOH in the electrolyte solution. The addition of 1 M TiOSO4 to the Mn electrolyte is suggested to lower the H+ concentration which increases the amount of MnOOH in the solution and lowers the concentration of the aqueous Mn3+ species. The MnOOH formed by the Mn3+ hydrolysis reaction is found to be electrochemically active if it is deposited on the working electrode.

Lead-Air Electrochemical System with Acid Electrolyte

The possibility of utilization of the lead-air electrochemical system as a power source is shown. The system consists of a standard lead electrode and H2SO4 electrolyte, used in the lead acid battery and a gas diffusion electrode developed in the Institute of Electrochemistry and Energy Systems. Three catalysts have been checked for applicability with the new system-active carbon Norit NK, cobalt tetramethoxyphenylporphyrin and cobalt phthalocyanine. Cyclic voltammetry has been applied to all three catalysts and the results have been presented as galvanostatic charge-discharge curves. Polarization and Tafel dependences have been studied in a three-electrode cell. An original method for formation of the lead electrode has been elaborated. It has been established that the gas diffusion electrode is sufficiently stable in the sulphuric acid electrolyte. The energy values obtained at laboratory conditions provide a good perspective for a practical application of the lead-air system for energy storage and in the automobile industry.

Gas Evolution from Mixed-Acid Vanadium Redox Flow Batteries

Mixed-Acid (MA) Vanadium Redox Flow Batteries (VRFB) improve on standard VRFBs’ energy density by adding hydrochloric acid (HCl) to the standard sulfuric acid (H2SO4) electrolyte. This improves the stability of the vanadium (V) in the solution, which allows for electrolytes with higher concentrations of V ions and increased operating temperatures. The addition of HCl to the system introduces a new safety risk, the evolution of chlorine gas (Cl2) from the catholyte. In this study, we cycled an MA VRFB under a range of conditions to understand the fundamental causes of gas evolution. We constructed a single cell MA VRFB using a standard electrolyte composition of 2M H2SO4, 5M HCl and 2M V, with a gas analyzer sampling the head space of the catholyte chamber. Cl2 gas quantity was measured under systematically varied SOCs, cycling rates, electrolyte flow rates, electrode materials and electrolyte temperatures. Mechanisms of gas evolution at each condition were determined from analysis of the cycling data and the fundamental chemistry of the system. Conditions that lead to high rates of gas evolution were identified. This new understanding of gas evolution will aid development of safer MA VRFB systems that mitigate Cl2 formation during operation.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.