Sulfuric Acid Electrolyte Research Articles

Impact of Different Supports on the Performance of Ir Oxide Based Catalysts Synthesized Using Incipient Wetness Method

Development of an active and durable catalyst for oxygen evolution reaction (OER) is a pivotal part of designing an efficient PEM water electrolyser. Iridium is one of the best available catalysts because of its corrosion resistance and activity [1]. Use of Ir is however, limited by its scarcity, limited durability and high cost. Its deposition on a support is a popular way to improve the available surface area, activity and stability [2]. For applications in acidic water electrolysis, supports with the highest chemical resistance and conductivity are preferred. While different methods have been studied to impregnate a support with catalyst nanoparticles, such as Adams’s fusion method and polyol method, their scalability remains questionable due to intensive resource requirements. In this work, Ir oxide based supported catalysts have been synthesized using the incipient wetness method (IWM), one of the most commonly used method of catalyst synthesis in the industry due to its ease of scalability, limited resource requirement and the opportunity to explore the effect of strong metal support interactions. This method however has not been discussed in literature. In this study, Ir oxide (IrOx) (Ir loading on support = 20 wt. percent) was dispersed on commercial supports (ZrO2, Nb2O5, Ta2O5, ATO) using H2IrCl6.xH2O precursor (99.9% trace metal basis, Sigma Aldrich). The catalysts were calcined at 400oC for 2 h in a muffle furnace to produce Ir oxide based catalysts.Electrochemical measurements were carried out on a standard rotating-disk electrode (RDE) system (PINE Research MSR Rotator), and a three-electrode electrochemical cell in 1.0 M sulfuric acid electrolyte (H2SO4 optima grade, Fisher Scientific). The performance of the aforementioned supported Ir oxide catalyst was compared among themselves, and to benchmark commercial catalysts (Umicore Ir Black and IrOx TKK) using metrics such as mass normalized activity (A/g-1 Ir), ECSA normalized activity (mA/cm2 Ir ECSA), Tafel slope (mV/dec) and charge transfer resistance (Rct) measured during the electrochemical test. It was observed that the activity of IrOx/ZrO2 (415 A/gIr, 5.2 mA/cm2 Ir ECSA) was the best among all the 4 impregnated catalysts, and was in fact, more than an order of magnitude greater than that of IrOx/ATO (30 A/gIr, 0.3 mA/cm2 Ir ECSA) at a potential of 1.53 VRHE. A significant drop in the Tafel slope measured in the potential range of 1.45-1.55 VRHE was observed upon changing the support from ATO (80 mV/dec) to ZrO2 (60 mV/dec) hinting towards a change in the reaction mechanism. IrOx/ATO was used as a baseline due to prevalent recognition of ATO as an excellent support for OER catalysts in the literature.Upon comparison with commercial benchmark catalysts it was observed that the Ir ECSA normalized activity of IrOx/Nb2O5, IrOx/Ta2O5, IrOx/ZrO2 surpasses both Umicore Ir black ( 2.23 mA/cm2 Ir ECSA) and IrOx TKK (1.23 mA/cm2 Ir ECSA) with IrOx/ZrO2 providing the highest activity. While Yttria-stabilized zirconia (YSZ) has been a popular choice as an electrolyte and anode for high temperature SOFC due to its non-reducing nature, high thermal stability and mechanical strength, and acceptable oxygen ion conductivity [3], its application in PEM water electrolysis as catalyst support has not been discussed. In this work, we focus on finding the causes for superior performance of ZrO2 as a support for Ir oxide based OER reaction in acidic conditions through the lens of electrocatalysis.

Development of MoO3-Based Proton Batteries

Aqueous rocking chair batteries have attracted attention as highly safe and inexpensive secondary batteries. Lithium and sodium ions have mostly been used as the mobile ions, whereas proton systems with potentially the highest mobility have rarely been reported. Recently, research on proton batteries has been conducted using concentrated sulfuric acid solutions as the electrolyte that can assist high-rate performance.[1] Stability under concentrated acidic conditions is required for the electrode materials, as well as the capability of proton accommodation. MoO3 has been reported as a stable negative electrode material for aqueous proton batteries,[2] while few positive electrode materials are known except for bulky organic[3] and Prussian-blue materials[4]. For achieving high energy density and long life, oxide positive electrode materials are desirable. Here we propose the application of MoO3 as the positive electrode material by optimizing the operating composition range. The potential values shown below are all shown versus SHE (actually measured with Ag/AgCl).MoO3 showed a discharge profile at around 0.5 V with the maximum capacity of ca. 100 mAh g-1, as shown in the figure. This potential is sufficiently more positive than the redox potential of protonated MoO3 of around -0.3 V as the negative electrode. With the aid of operando X-ray diffraction analysis, it turned out that the discharge regions at 0.5 V and 0.4 V are respectively associated with a biphasic transition of MoO3/phase I (ca. 0 < x < 0.3 in H x MoO3) and a single-phase reaction of phase I (ca. 0.3 < x < 0.5 in H x MoO3). Deep discharging beyond this range results in the coexistence of phase I and phase III (ca. 0.5 < x < 1.5 in H x MoO3) and the proton extraction from phase III leads to the formation of phase II or phase IIa with its discharging potential of 0.0 V. Structural calculation based on the density function theory is employed to clarify the origin of this irreversible phase transition behavior. Different proton sites between these phases seem to be responsible.An aqueous proton battery with a 7 mol dm–3 sulfuric acid electrolyte was constructed with H-inserted MoO3 and MoO3as the negative and positive electrodes, respectively, and was successfully discharged and charged repeatedly, with the operating voltage of ca. 0.6 V, indicating the launch of aqueous proton battery composed of oxide active materials. Reference s : [1] J. Li, H. Yan, C. Xu, Y. Liu, X. Zhang, M. Xia, L. Zhang, J. Shu, Nano Energy, 89 (2021) 106400.[2] X. Wang, Y. Xie, K. Tang, C. Wang, C. Yan, Angew. Chem. Int. Ed., 57 (2018) 11569.[3] X. Wang, J. Zhou, W. Tang, Energy Storage Mater., 36 (2021) 1.[4] X. Wu, J. J. Hong, W. Shin, L. Ma, T. Liu, X. Bi, Y. Yuan, Y. Qi, T. W. Surta, W. Huang, J. Neuefeind, T. Wu, P. A. Greaney, J. Lu, X. Ji, Nat. Energy, 4 (2019) 123. Figure 1

Obtaining of copper powder by method of a vortex electrolysis from acid sulphate electrolytes

• A vortex electrolysis unit was designed and assembled. • Finely dispersed copper powders were obtained by method of a vortex electrolysis. • Optimum conditions for obtaining finely dispersed copper powder were established. • The particle size of the powder is 5–10 μm, the current efficiency is 95.5%.

Effect of Rotating Magnetic Field on Hydrogen Production from Electrolytic Water

In order to reveal the influence of magnetic field on electrochemical machining, a research method of the influence of rotating magnetic field on hydrogen production from electrolytic water is proposed in this paper. Firstly, taking pure water as electrolyte, this paper selects rigid SPCE water molecular model, constructs the molecular dynamics model under the action of magnetic field, and simulates it. In this paper, the thermodynamics, electric power principle, and electrolytic reaction of hydrogen production from electrolytic water are analyzed, and the working processes of alkaline electrolytic cell, solid oxide electrolytic cell, and solid polymer electrolytic cell are analyzed. Based on solid polymer electrolytic cell, the effects of membrane electrode performance, diffusion layer material, contact electrode plate, electrolytic temperature, and electrolyte types on hydrogen production are analyzed. The experimental results show that the heteroions in the lake electrolyte significantly affect the performance of the membrane electrode, and the number of heteroions in the electrolyte should be controlled during the experiment. The hydrogen production capacity and energy efficiency ratio of the unit are basically not affected by different water flow dispersion. When dilute sulfuric acid electrolyte is selected in the experiment, the concentration should be 0.1%–0.2%; After the proton exchange membrane enters the stable period after the activation period, with the increase of the electrolysis time of tap water, (24 h) the membrane electrode will weaken the catalyst activity and reduce the electrolysis efficiency in the electrolysis process. Furthermore, the correctness of rotating magnetic field on hydrogen production from electrolytic water is verified.

Transitions in porous oxide morphologies on AA2024-T3 anodized under high currents and low temperatures: Impact on corrosion behaviour

The surface morphology, cell geometry, and electrochemical response of porous anodic films of comparable thickness, generated on AA2024‐T3 in sulphuric acid electrolyte under hard and soft anodizing conditions, were studied to disclose the impact of the anodizing parameters on corrosion behaviour. Localised oxide growth associated with a transition from sponge-like morphology to linear cells was observed with increasing current density and/or reducing electrolyte temperature. The anticorrosion performance of films with the higher barrier layer thickness was inferior due to the defective surface induced by localised oxide growth at high currents or low temperatures. Viceversa, the films displaying sponge-like morphology performed better due to the beneficial effect of inter-cell porosity in facilitating the self-sealing process.

Recreating Fuel Cell Catalyst Degradation in Aqueous Environments for Identical-Location Scanning Transmission Electron Microscopy Studies

Proton exchange membrane fuel cells (PEMFCs) have long been studied for applications in sustainable transportation. The recent shift in focus from passenger vehicle to heavy duty applications places increased demand on the efficiency and durability of the components used in membrane electrode assemblies (MEAs).[1] Of particular interest are the oxygen reduction reaction electrocatalysts used in the fuel cell cathode. While the relaxed capital cost requirements for heavy duty applications allows for increased precious metal loadings, the four-fold increase in operating lifetime requires improved catalysts which can express their high activity not only at beginning-of-life, but also after 25k-hour equivalent accelerated stress tests (ASTs).This paradigm shift prioritizes efforts aimed at understanding and subsequently controlling catalyst degradation. In situ characterization methods can be instrumental in this effort, but it is critical that the operating conditions in these studies reliably replicate the type and degree of degradation observed in the operating fuel cell.[2,3] In this study, identical-location scanning transmission electron microscopy (IL-STEM) is used to compare catalyst degradation in an aqueous environment to degradation observed ex situ in MEAs following AST cycling.[4] For traditional catalysts, the aqueous environment appears to replicate the dissolution and coalescence mechanisms observed for Pt catalysts with small starting particle sizes (<3nm) supported primarily on the surfaces of graphitized carbon supports. In evaluating more stable alloy catalysts (4-5nm) supported on high surface area carbon supports, the large discrepancy between degradation in the aqueous and MEA environment was observed. In particular, the Ostwald ripening mechanism, which is more dominate in these high surface area carbons, seemed absent in the aqueous environment.[5]To better replicate the type and degree of degradation in the MEA environment, various experimental parameters such as temperature, acid type/concentration, and upper and lower potential limits were explored. By extending the cycling potential window from 0.6-0.95 Vvs . to 0.4-1.0 Vvs . RHE in an sulfuric acid electrolyte containing Pt ions, the Ostwald ripening mechanism was enhanced, resulting in an end-of-test particle size distribution and composition which better match MEA tests. These refined conditions can now be used to perform in situ and identical-location experiments that will play an important role in the development of robust catalysts for heavy-duty vehicle applications.[6]References[1] D. A. Cullen, et al. Nat. Energy 2021, 6 (5), 462–474.[2] J. A. Gilbert, et al. Electrochim. Acta 2015, 173, 223–234.[3] I. Martens, et al. ACS Energy Lett. 2021, 6 (8), 2742–2749.[4] S. Rasouli, et al. Nano Lett. 2019, 19 (1), 46–53.[5] E. Padgett, et al. J. Electrochem. Soc. 2019, 166 (4), F198–F207[6] This material is primarily based on work performed by the Million Mile Fuel Cell Truck (M2FCT) Consortium (https://millionmilefuelcelltruck.org), technology manager Greg Kleen, which is supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office. Electron microscopy was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

Critical Role of Electrochemical Proton Insertion for the Hydrogen Evolution Reaction on Tungsten Oxides

The local electrochemical environment can affect electrochemical reactivity by determining the interactions between the electrode, reactant, reaction intermediates, and products. One method for tuning the local electrochemical environment is through confinement in porous materials. However, experimental evidence of the role of confinement on electrochemical reactivity in porous materials remains elusive due to the challenges of decoupling confinement effects from other variables, such as high surface area. In this work, we compared the structure, morphology and electrochemical reactivity of WO3 ∙H2O and a hybrid organic-inorganic layered material, octylamine-expanded WO3 (OA-WO3). We investigated the electrochemical response in three electrolytes to understand how interlayer modification affects cation adsorption at the outer surface and cation and proton insertion into the bulk of the metal oxide. While the WO3 ∙H2O could reversibly insert protons and lithium ions, OA-WO3 significantly suppressed cation insertion. Interestingly, as OA-WO3 was cycled within a narrow potential window in a sulfuric acid electrolyte, the material transformed to WO3 ∙2H2O, which was evidenced by features in the cyclic voltammograms as well as ex situ Raman spectroscopy and X-ray diffraction. Additionally, we determined that the conversion from OA-WO3 to WO3 ∙2H2O was possible via a chemical reaction by stirring in sulfuric acid – thus resulting in two materials with similar surface areas and particle morphologies. These similar material properties enable the study of how the cation insertion behavior and chemical nature of confined molecules between layers of a transition metal oxide framework influence the electrocatalytic activity toward the hydrogen evolution reaction (HER). Our results showed that the presence of octylamine in the interlayer of WO3 required a ~210 mV higher overpotential compared to WO3 ∙H2O for the HER, and the onset of the HER did not appear until after a reduction reaction associated with proton insertion occurred at a more negative potential compared to proton insertion in WO3 ∙H2O. We discuss three hypotheses for how proton insertion leads to HER activity in WO3 ∙ xH2O: 1) proton insertion changes the electronic band structure of WO3 ∙ xH2O, 2) the presence of bulk protons can influence ∆GH,ads at the surface sites, and 3) inserted protons may participate in the HER mechanism on WO3 ∙ xH2O. Overall, this work demonstrated how tuning the interlayer structure and chemistry of bulk layered materials enables the study of electrochemical reactivity under confinement. Using this materials design approach, our results revealed a correlation between proton insertion capacity and the activity of a transition metal oxide toward the HER, where high proton insertion capacity led to lower HER overpotential.

Ultralow-concentration electrolyte boosting K0.486V2O5 for high-performance proton storage

High-concentration electrolytes are considered a promising tool for widening stable electrochemical windows and enhancing the electrochemical performance of aqueous batteries. However, their high cost, high viscosity, and low conductivity remain thorny issues. Because of the special Grotthuss mechanism of protons in water, proton batteries can use a low-concentration electrolyte to obtain sufficient kinetic performance. Herein, we present an unusual, ultralow-concentration sulfuric acid (0.01 mol L−1) electrolyte to boost the electrochemical stability of K-ion pre-intercalated V2O5 (K0.486V2O5, KVO). The KVO electrode exhibits a high reversible capacity of approximately 129 mA h g−1 at a low current density of 50 mA g−1 and impressive capacity retention of 78% over 20,000 cycles at 1 A g−1. Ultralow-concentration electrolyte chemistry will open a novel route to exploit durable and low-cost aqueous energy storage systems.

Adhesion properties of tartaric sulfuric acid anodic films assessed by a fast and quantitative peel tape adhesion test

The adhesion capabilities of sulfuric acid and tartaric-sulfuric-acid anodic oxide films on cladded AA2024-T3 aluminium substrates have been investigated in a quantitative manner. A relatively simple, versatile and industrially applicable test methodology based on DIN EN ISO 29862 has been used. In addition, the effect of anodising process parameters on the oxide film morphology has been studied and correlated with the adhesion results. The process parameters considered are the chemistry of the acidic pickling pre-treatment step, the addition of tartaric acid to the sulfuric acid electrolyte, the formation voltage, and the electrolyte temperature. The suggested tape peel adhesion test is able to differentiate among pre-treatments and anodising conditions showing a good correlation with the morphological features at the ultimate surface. High peel adhesion strengths are measured when topographies such as pore mouth widening and dissolution-driven roughness take place. These morphologies are typically found in anodic layers formed at elevated electrolyte temperatures. The proposed method can be beneficial for a fast assessment of anodising parameters for good adhesion, which is of special interest for the industrial optimisation of anodising processes.

The Role of Anodising Parameters in the Performance of Bare and Coated Aerospace Anodic Oxide Films

The anodising process parameters (voltage, temperature, and electrolyte) control the morphology and the chemical composition of the resulting anodic oxide film by altering the balance between oxide growth and oxide dissolution reactions. The porosity of the oxide film is reduced by the addition of tartaric acid to a sulfuric acid electrolyte, while anodising at elevated temperatures enhances oxide dissolution, leading to wider pores and rougher surfaces. No significant changes in the oxide chemical composition as a function of anodising parameters was found; in particular, no tartrate incorporation took place. The resistance of uncoated anodic oxide films against aggressive media and galvanic stress as a function of anodising parameters has been studied by electrochemical methods. Anodising in a mixed tartaric and sulfuric acid electrolyte improves the resistance of the anodic oxide against galvanic stress and aggressive media in comparison to sulfuric acid anodising processes. However, the corrosion protection performance of the anodic oxide films in combination with a corrosion-inhibitor loaded organic coating is not governed by the blank oxide properties but by the adhesion-enhancing morphological features formed during anodising at elevated temperatures at the oxide/coating interface.

Nitrogen-rich palladium tetra amino-hippuric acid phthalocyanine complex and its hybrid composite with multi-walled carbon nanotubes for supercapacitor application

Supercapacitors are the most attractive alternative energy storage and conversion systems for the future generation to successfully overcome the global energy dilemma. An extensive number of studies have been conducted to enhance the performance of an electrode and to find an appropriate electrolyte for high power density and energy density. However, it is still challenging to develop a suitable electrode/electrolyte system to boost the performance of supercapacitors. Here, a novel nitrogen-rich palladium amide bridge hippuric acid phthalocyanine complex (PdTAHAPc) is synthesized in pure state. The purity and structural characteristics of the synthesized dark green-colored PdTAHAPc are analyzed by various analytical and spectroscopic techniques. To further enhance its performance, PdTAHAPc is combined with multi-walled carbon nanotubes to prepare the PdTAHAPc-MWCNTs hybrid composite. The supercapacitance behavior of the PdTAHAPc-MWCNTs is investigated with respect to that of PdTAHAPc. The hybrid composite electrode exhibits a superior specific capacitance of 245 F·g−1 and 221 F·g−1 at a current density of 0.2 and 1 A·g−1, respectively, in 1.0 M sulfuric acid electrolyte. Furthermore, the developed hybrid composite electrode exhibits an excellent stability towards 5000 electrochemical cycles and a higher capacitance value at 80 °C compared to room temperature. The combination of PdTAHAPc with MWCNTs provides an exceptionally high surface area, leading to a lesser charge transfer resistance and a superior charge storage capacity of the developed PdTAHAPc-MWCNTs hybrid composite.

Using High Voltage Electrochemical Oxidation (HVEO) to obtain protective coatings, surface finishing on electronic materials

Electronics and microelectronic components such as printed circuit board, capacitors, CPU heat sinks, hard drive, etc. commonly encounter harsh environmental conditions during their operational lifetime. To protect the electronics materials from conditions like corrosion, wear, humidity and contaminants, aluminium protective coating materials can be used. However, the behavior of materials in harsh environments and their effect on the reliability of electronics in industrial products has been studied only very little. Moreover, the changes in the parameters (current density, temperature and time) of commonly used aluminium under various conditions remain largely unknown. In this paper, High Voltage Electrochemical Oxidation (HVEO) was used to produce a high microhardness of 440HV and high surface thickness of up to 44µm oxide coatings on aluminum alloy AMg2 (analogues of 5052-H32 alloy) for electronic components protection. The process was carried out in electrolyte of tartaric acid and sulfuric acid as an electrolyte under constant duration for each sample and various anodizing temperatures and current densities. The samples used in the study were aluminum used for commercial electronics devices designed for use in harsh conditions.

High-performance supercapacitors using carbon dots/titanium dioxide composite electrodes and carbon dot-added sulfuric acid electrolyte

The H 2 SO 4 system used carbon dots as electrode/electrolyte additives. The charge storage of pristine titanium oxide is dominantly controlled by the surface mechanism. Carbon dots act as pseudocapacitive boosters via improving surface wettability, interaction at the electrode/electrolyte interface, and the diffusion-controlled process. The supercapacitors achieved the highest areal specific capacitance of 643 mF cm -2 , representing a total enhancement of 1,261%. • The carbon dots were used as additives in TiO 2 /H 2 SO 4 -based supercapacitors. • The capacitance was enhanced of 237% by adding carbon dots in TiO 2 electrode. • The capacitance was further improved by 292% by adding carbon dots in H 2 SO 4 . • An areal specific capacitance of 643 mF cm −2 was obtained with 98.4% retention. • The overall enhancement is 1,261% better than pristine TiO 2 and H 2 SO 4 system. Herein, the electrochemical performance of nanocomposite comprised of TiO 2 nanoparticles and sodium polyacrylate-derived carbon dots (CDs) was investigated in H 2 SO 4 electrolyte. The specific capacitance of 5% w/w CDs-containing TiO 2 electrode in 1 M H 2 SO 4 demonstrated a significant enhancement of 237%, compared to pristine TiO 2 . Interestingly, when added to the electrolyte, the specific capacitance was further increased by 292% or as high as 643 mF cm −2 . As a result, the addition of CDs in both electrode and electrolyte produced overall improvement of 1,261% through favorably synergistic effects of lessening the series resistance, enhancing surface wettability, diffusion-controlled contribution, and pathways for ion diffusion. These findings are confirmed by thorough electrochemical analysis and data fitting. To the best of our knowledge, this supercapacitor gave the highest areal capacitance value among prior reports of TiO 2 -based supercapacitors containing H 2 SO 4 electrolytes. Furthermore, it also delivered a high areal energy density of 24.3 μWh cm −2 at a power density of 187.5 μW cm −2 and extraordinary cycling stability of 98.4% capacitance retention after 5,000 cycles. Our work proved that the utilization of CDs as pseudocapacitance promoters and ion facilitators can significantly improve the supercapacitor performance. This strategy will be an innovative way to develop energy storage devices with high performance, excellent stability, simple manufacturing process, and low production cost for practical applications.

Influence of electrochemical hydrogenation parameters on microstructures prone to hydrogen-induced cracking

When pipeline steels are exposed to hydrogen-rich environments during service, this can lead to a degradation in mechanical properties and premature failure. These steels are often susceptible to hydrogen embrittlement and hydrogen-induced cracking (HIC) and contain very sensitive microstructures for HIC formation. This work aims to find a suitable hydrogenation methodology that allows to charge pipeline steel specimens without inducing any hydrogen related damage during the charging process. Therefore, different electrochemical hydrogen charging methodologies are evaluated. The susceptibility to HIC and blisters of two pipeline steels (API 5L grades X70 and X56), is first investigated in a sulfuric acid electrolyte. Both grades are prone to HIC in the mid-thickness section of the pipeline wall. For X56, significant blistering occurs as well, and hydrogen-induced damage could be linked to elongated MnS inclusions. For the X70 steel, hard bands are found to be vulnerable to HIC. The electrochemical charging conditions are modified for the X56 steel, where the extent of the damage is greatest due to its prone microstructure, as revealed by scanning electron microscopy. Lowering the sulfuric acid concentration and applied charging current density does lead to some reduction of blistering. However, changing to a different, sodium hydroxide-based electrolyte is more effective in mitigating the extent of the hydrogen-induced damage and the time at which it appears.

Green and Effective Anodizing of AA 2024-T3 in Methionine-Sulfuric Acid Electrolyte

Sulfuric acid anodizing (SAA) is a common corrosion protection method for aluminum alloys. Selected additives, usually organic compounds, can be added to the sulfuric acid (SA) electrolyte to improve the corrosion resistance of the anodized layer. It is a widespread opinion that certain organic compounds minimize the dissolution rate of an alloy in the SA electrolyte, thereby improving the structure, morphology, and consequently, the corrosion resistance of the resulting porous film. This work introduces Methionine-Sulfuric Acid (MSA) anodizing as a green and energy-efficient method for developing corrosion-resistant anodic oxide films on AA 2024-T3. Electrochemical investigations at free-corrosion potential revealed that methionine retards the alloy dissolution rate in SA with an inhibition efficiency of above 90%. During anodizing, MSA electrolytes decreased the current density, leading to a decrease in energy consumption of up to 52% compared to the SA counterpart. The Field Emission—Scanning Electron Microscopy (FE-SEM) showed that MSA films have lower thickness and improved pore morphology than SA film generated at the same experimental conditions. The corrosion analyses via salt spray and immersion tests complemented by electrochemical and surface studies indicate superior corrosion performances for MSA films before and after hydrothermal sealing.

Reunderstanding the Reaction Mechanism of Aqueous Zn-Mn Batteries with Sulfate Electrolytes: Role of the Zinc Sulfate Hydroxide.

Rechargeable aqueous Zn-Mn batteries have garnered extensive attention for next-generation high-safety energy storage. However, the charge-storage chemistry of Zn-Mn batteries remains controversial. Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO2 /Mn2+ dissolution-deposition reaction in strong acidic electrolytes. Herein, a Zn4 SO4 ·(OH)6 ·xH2 O (ZSH)-assisted deposition-dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn-Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and Znx MnO(OH)2 nanosheets in which the MnO2 initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn-Mn batteries and guide the design of high-capacity aqueous Zn batteries.

РАЗРАБОТКА ГАЛЬВАНИЧЕСКОГО ПОКРЫТИЯ С ИСПОЛЬЗОВАНИЕМ ДОБАВКИ ПРОИЗВОДНОГО РУБЕАНОВОДОРОДНОЙ КИСЛОТЫ ДЛЯ КОРПУСА ЦЕНТРОБЕЖНОГО НАСОСА

The article presents the results of a study of the process of obtaining a shiny nickel coating on steel from sulfuric acid electrolyte in the presence of an organic brightening additive - a de-rivative of rubeanhydric acid - under different modes of electrolysis. The expediency of using a nickel coating for corrosion protection of the housing of a high-pressure centrifugal pump has been substantiated

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.