Electrochemical Characterization Techniques Research Articles

Asymmetric CapMix Device Exploiting Functionalized Graphene Oxide and SPEEK Coatings for Improved Energy Harvesting From Salinity Gradients

AbstractThis work investigated the possibility of using functionalized graphene oxide and sulfonated poly(ether ether ketone) coatings on activated carbons to obtain an asymmetric device suitable for Capacitive Mixing (CapMix) application. Herein the synthesis and fabrication procedures of both materials and electrodes are reported, together with a comprehensive list of electrochemical characterization techniques. The results from the electrochemical characterization are used to design the optimal operational parameters for CapMix experiments involving the materials being studied. A homemade cell is designed and fabricated for CapMix application by polymer micromachining. Electrochemical tests are conducted to optimize the process parameters and the results of this optimization are reported, proving that both the materials and the process parameters play a key role in CapMix. The final device can generate a net power output of 12 mW m−2 by mixing simulated seawater and freshwater. This result paved the way for further application of graphene oxide in the field of renewable energy.

Ti3C2Tx MXene/reduced graphene oxide/cellulose nanocrystal-coated cotton fabric electrodes for supercapacitor applications

Textile-based electrodes are the most important components of wearable and portable supercapacitors. Ti3C2Tx MXene and reduced graphene oxide (rGO) have a great potential for the fabrication of high-performance textile supercapacitor electrodes. In this work, rGO was synthesized with the presence of cellulose nanocrystal (CNC) and Ti3C2Tx/rGO/CNC dispersions with different rGO/CNC contents were prepared. The plain-woven cotton fabrics were coated by homogenous Ti3C2Tx and Ti3C2Tx/rGO/CNC dispersions (5% wt., 15% wt., 30% wt. and 50% wt. rGO/CNC content) and characterized by X-ray Diffraction, Fourier Transform Infrared spectroscopy and Scanning Electron Microscopy techniques. The electrochemical characterization techniques showed that Ti3C2Tx/rGO/CNC loaded fabric electrodes up to 15 wt.% rGO/CNC content exhibited a high specific capacitance of 501.1 F g−1 at a current density of 0.3 A g−1 with low internal electrode resistance, and a good electrochemical stability. The results also showed that MXene/rGO/CNC based high-performance textile supercapacitor electrodes can be prepared by simple drop-casting method.Graphical

Anticorrosion and adhesion performance of a monolayer and double layer silane-epoxy coating systems applied on carbon steel

Carbon steel is one of the widely used metallic material, although its limited corrosion resistance. To improve its anti-corrosion performance, organic coatings such as epoxy have been an excellent option due to their barrier mechanism. Nevertheless, the elevated brittleness and porosity observed in this type of coating, coupled with the weak bonding interface between epoxy and carbon steel, significantly hampered their protective capabilities. The organofunctional silanes are candidates to be used as pre-treatment between epoxy coating and carbon steel interface because of their good corrosion resistance but as a limitation they can present small pores and microcracks.Therefore, the anticorrosive and mechanical properties of silane films can be adapted and further improved by strengthening the coatings through some modifications, such as the incorporation of green corrosion inhibitors into the film, reducing the access of aggressive species to the metal. In this context, the objective of this research is to evaluate the adhesion and anticorrosive properties of an epoxy-based organic coating pre-treated with a silane film obtained by tetraethoxysilane (TEOS) with γ-glycidoxypropyltrimethoxysilane (GPTMS) modified with the garlic peel powder as a corrosion inhibitor (Allium sativum L.). The investigation of the surface features as morphology and the corrosion resistance of the silane-epoxy coatings were studied by scanning electron microscope (SEM) and electrochemical characterization techniques, such as, electrochemical impedance spectroscopy (EIS), linear and potentiodynamic polarization. Also, the coating adherence was evaluated by pull-off tests. The results of the EIS showed that all samples coated with silane+ epoxy coating have better anticorrosion performance than the sample coated with just epoxy painting. Besides, SEM images showed that the silane film improved the cohesion between substrate and coating system, with the clear appearance of delamination in the system silane free. In general, the results of these different techniques indicate that the film modified with the natural inhibitor has improved anticorrosive properties compared to the film without silane or natural green inhibitors.

Palladium effect on electrochemical hydrogen storage properties of nanoporous silicon

Coating porous silicon with metal catalysts such as palladium is considered a reliable method to improve the hydrogen storage performance of electrodes. Here, in order to evaluate the most effective use of Pd nanoparticle or Pd thin film, Pd nanoparticles with a size of 36 nm obtained by electroless method, and a Pd thin film with a thickness of 30 nm deposited by thermal evaporation were coated onto nanoporous silicon sample” and studied. The Pd deposits were confirmed by Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The obtained electrode materials: PS and Pd/PS were characterized by different electrochemical characterization techniques: cyclic voltammetry (CV) and galvanostatic charge/discharge. The results showed that Pd NPs/PS achieved the highest hydrogen storage capacity with a value of 425.9 mA h g-1. These results confirm that using Pd nanoparticles as catalyst metal is more suitable to improving the hydrogen storage capacity of electrode materials.

Modeling of pulse and relaxation of high-rate Li/CFx-SVO batteries in implantable medical devices

We present a Hybrid Multiphase Porous Electrode Theory (Hybrid-MPET) model that accurately predicts the performance of Medtronic’s implantable medical device battery lithium/carbon monofluoride (CFx) - silver vanadium oxide (SVO) under both low-rate background monitoring and high-rate pulsing currents. The distinct properties of multiple active materials are reflected by parameterizing their thermodynamics, kinetics, and mass transport properties separately. Diffusion limitations of Li+ in SVO are used to explain cell voltage transient behavior during pulse and post-pulse relaxation. We also introduce change in cathode electronic conductivity, Li metal anode surface morphology, and film resistance buildup to capture evolution of cell internal resistance throughout multi-year electrical tests. We share our insights on how the Li+ redistribution process between active materials can restore pulse capability of the hybrid electrode, allow CFx to indirectly contribute to capacity release during pulsing, and affect the operation protocols and design principles of batteries with other hybrid electrodes. We also discuss additional complexities in porous electrode model parameterization and electrochemical characterization techniques due to parallel reactions and solid diffusion pathways across active materials. We hope our models can complement future experimental research and accelerate development of multi-active material electrodes with targeted performance.

Crafting high‐performance polymer‐integrated solid electrolyte for solid state sodium ion batteries

AbstractThe development of modern solid‐state batteries with high energy density has provided the reliable and durable solution needed for over‐the‐air network connectivity devices. In this study, a NASICON‐type Na3Zr2Si2PO12 (NZSP) ceramic filler was prepared using the sol‐gel method and then a polymer‐integrated solid electrolyte consisting of polyethylene oxide (PEO), NZSP, and sodium perborate (SPB) was prepared by Stokes' solution casting process. Through physico‐chemical and electrochemical characterization techniques, the morphology, electrochemical, and thermal properties of the prepared solid electrolyte sample were carefully studied. The PEO/NZSP/SPB electrolyte developed for all‐solid‐state sodium‐ion batteries (ASSSBs) exhibited a strong ionic conductivity, a large window for electrochemical stability, and was effective in controlling the growth of sodium dendrites. Furthermore, the polymer‐integrated solid electrolyte showed impressive rate capability, high discharge capacity (73.2 mAh g−1) at 0.1 mA cm−2, and good faradaic efficiency (98%) even after 100 cycles. These results reveal that the PEO/NZSP/SPB electrolyte is a potential and inevitable candidate for the evolution of high‐performance rechargeable ASSSBs.

Simple construction of gadolinium cobaltite perovskite (GdCoO3): Unveiling the dynamic electrode potential for pseudocapacitors

BackgroundThe intermittent nature of renewable energy resources has led to an ongoing mismatch between energy demands and supply in modern societies. To address this issue, the design of well-defined nanostructures with unique physicochemical nature, has emerged as a promising solution. In this regard, perovskite (ABO3) nanostructured electrode materials have shown great potential in enhancing electrochemical performance. MethodsA simple co-precipitation technique was utilized to synthesize perovskite phase gadolinium-based binary metal oxide, i.e., GdCoO3. The obtained physiochemical characterization data revealed that the GdCoO3 electrode material possessed a high surface area that facilitates the diffusion of ions and enhances its specific capacitance. Significant findingsExtensive electrochemical characterization techniques were used (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charging and discharging (GCD)) to analyze the electrochemical properties of the electrode material in this study. The charge storage mechanism of GdCoO3 was determined to be diffusion-controlled. When tested in an aqueous electrolyte (3 M KOH), GdCoO3 nano-electrode exhibited an excellent specific capacitance (519 F g–1) by a current density (1 A g–1). Furthermore, it demonstrates a significant capacitance retention rate (CRR) of 84.9 % subsequently 5000 cycles indicating its potential for long-term stability. The fabricated battery-type electrode holds promise in various applications including electric motors, flexible electronics, and energy storage devices.

Sulphate reducing bacteria (SRB) biofilm development and its role in microbial corrosion of carbon steel

The development of biofilm by pure SRB culture on carbon steel, and its role on corrosion were investigated using microscopic, spectroscopic, electrochemical and surface characterization techniques. Tubercle biofilm and irregularly shaped pits were observed on steel surfaces in high-nutrient biotic solution. Owing to development of a protective FeS film in 72 h immersion, corrosion resistance improved. In nutrient-deficient medium, a greater bacterial density attached to the metal surface as the consequence of starved bacteria seeking energy sources from metal. However, electrochemical non-homogeneity developed at the locations of their attachment, that gradually grew over the entire surface.

Synthesis, characterization, and corrosion protection potential of a highly effective and water‐miscible surfactant for mild steel in sulfuric acid solution

AbstractIn the current study, a tetracationic quaternary ammonium salt (TCQAC) was synthesized and characterized and its ability to suppress corrosion on mild steel (MS) in a 0.5 M H2SO4 solution was examined. Various chemical, electrochemical, and surface characterization techniques were utilized to study the inhibition efficiency of TCQAC. The TCQAC manifests 99.83% efficiency at 20 ppm concentration. Out of all the examined isotherm models, the Langmuir isotherm offered the best fit for the TCQAC adsorption on the MS surface. A very high negative value of ΔGads (−45.18 kJ mol−1) suggests that the adsorption of TCQAC followed the chemisorption mechanism. Electrochemical studies indicate that TCQAC increases the linear and charge transfer resistances (LPR and Rct, respectively). TCQAC slows down the anodic and cathodic Tafel reactions; however, it acts as an anodic‐type inhibitor at 5, 10, and 20 ppm. The appearance of extra Cl and N signals in the energy dispersive x‐ray (EDX) spectrum and an improvement in surface smoothness in the scanning electron microscope (SEM) image of the inhibited sample corroborated the adsorption method of corrosion inhibition. X‐ray photoelectron spectroscopy (XPS) study indicates that TCQAC creates corrosion preventive layers by chemical adsorption. In Frontier molecular orbitals (FMOs), highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were delocalized around the central part that comprises two benzyls, four allyls, and one hydrocarbon ((CH2)6) moieties and two quaternary nitrogen atoms. The outcomes of XPS and density functional theory (DFT) analyses indicate that the chemisorption of TCQAC occurs by dπ–pπ bonding with the surface iron atoms. The π‐electrons of aryl and allyl moieties extensively participate in the bonding.

Indolin-2-one derivatives as corrosion inhibitors: Structural insights and evaluation through experimental and computational techniques

Effective corrosion management is a pivotal challenge facing various industries and holds crucial importance in aligning industrial processes with sustainability goals. This study focused on the synthesis and evaluation of two indolin-2-one derivatives: (E)-1-allyl-3-(2-(5-oxo-4,4-diphenyl-4,5-dihydro-1H-imidazol-2-yl)hydrazono)indolin-2-one (AIHI) and (E)-3-(2-(5-oxo-4,4-diphenyl-4,5-dihydro-1H-imidazol-2-yl)hydrazono)-1-(prop‑2-yn-1-yl)indolin-2-one (PIHI), as sustainable corrosion inhibitors for N80 carbon steel (N80CS) in a 15 wt. % HCl medium. Chemical, electrochemical, and surface characterization techniques were utilized to evaluate the corrosion inhibition mechanism and the performance of the compounds under investigation. The weight loss method highlighted that tested compounds exhibited promising inhibition efficiencies: 91.54 % for AIHI and 81.97 % for PIHI, respectively, at 303 K, with an outstanding performance of 87.17 % at 363 K for AIHI. The simultaneous addition of AIHI and PIHI in HCl led to a substantial increase in the polarization resistance (RP) and a remarkable decrease in the corrosion current density (icorr). The potentiodynamic polarization (PDP) technique validated that both indolin-2-one compounds function as anodic/cathodic corrosion inhibitors with remarkable anodic effect. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that inhibitors altered steel surface morphology, forming a protective layer, and significantly reduced surface roughness. Atomistic simulations (DFT and SCC-DFTB methods) pointed out that the inhibitors AIHI and PIHI acted by physico-chemical adsorption through donor-acceptor interactions between AIHI or PIHI molecules (s and p orbitals) and the 3d orbitals of Fe(110). The insights obtained serve as a foundation for future advancements in greener corrosion management strategies for sustainable industrial applications, thus reinforcing our commitment to bio-circular economies and sustainable chemistry.

Electrochemical Hydrogen Charging on Corrosion Behavior of Ti-6Al-4V Alloy in Artificial Seawater

This study employs advanced electrochemical and surface characterization techniques to investigate the impact of electrochemical hydrogen charging on the corrosion behavior and surface film of the Ti-6Al-4V alloy. The findings revealed the formation of γ-TiH and δ-TiH2 hydrides in the alloy after hydrogen charging. Prolonging hydrogen charging resulted in more significant degradation of the alloy microstructure, leading to deteriorated protectiveness of the surface film. This trend was further confirmed by the electrochemical measurements, which showed that the corrosion resistance of the alloy progressively worsened as the hydrogen charging time was increased. Consequently, this work provides valuable insights into the mechanisms underlying the corrosion of Ti-6Al-4V alloy under hydrogen charging conditions.

Electrochemical Performance of Dry Processed Graphite Electrode with PTFE Binder for Lithium-Ion Batteries

Both cathode and anode in Lithium-ion batteries (LIBs) are being manufactured by slurry coating process; however, currently used wet coating process has some drawbacks, including the difficulty in further increasing the electrode thickness as well as high fabrication cost mainly due to the use of facility for drying process. To address these issues, dry electrode fabrication process has been proposed and actively investigated as an alternative electrode manufacturing process. Dry electrode fabrication process with PTFE binder offers several advantages over conventionally used slurry coating process such as high manufacturing efficiency due to the non-solvent process and the ease of increasing the electrode thickness resulting from fibrillization of the PTFE binder. However, the instability of PTFE binder in dry processed graphite anodes remains a challenge, as the irreversible reaction of PTFE binder leads to the deterioration of the electrode. Furthermore, the properties of graphite materials including specific surface area, the particle size and shape can also affect the microstructure of the electrode and the electrochemical performance of graphite anode. In this work, the relationship between the properties of graphite and the electrochemical performance of dry processed graphite anode was investigated using various analytical techniques and the electrochemical characterization techniques. More detailed analyses results will be discussed in the presentation.

(Keynote) Evidence of the Interplay of Temperature on Local and Global Battery Phenomena

Temperature is an important parameter in electrochemical processes and battery operation; for instance, open circuit voltage and resistance values of cells are temperature sensitive. Several recent studies have shown temperature within battery packs are not uniform. This non-uniformity of temperature produces localized thermal gradients within cells that can dictate cell construction, thermal management scheme, cell bussing, etc. Our research group has been working to understand how thermal gradients within battery cells effect material properties, electrochemical performance and stability. We have demonstrated through a range of electrochemical and materials characterization techniques, how dynamic external conditions, specifically thermal gradients and transients, can induce differing degradation modes of the positive and negative electrodes. The directionality and magnitude of thermal gradient dictate the degradation mode, whether loss of lithium inventory, loss of active material, etc.We have also observed strong electrochemical-mechanical coupling the result of low temperature cycling, where lithium plating on the negative electrode causes a physical deformation and collapse of the cylindrical cell jellyroll. In this talk, we will present in-operando optical microscopy and X-ray computed tomography data to show how dynamic electrical and external thermal conditions can irreversibly effect the chemistry, structure and subsequent safety of lithium-ion battery materials, components and cells. Lastly, the importance of testing materials and cells outside of isothermal laboratory conditions in favor of operating under dynamic thermal conditions, to include austere and stressful operating conditions will be discussed.

Batteries Worth Their Salt: Targeting Next Generation Stationary Storage with Molten Salt Electrolytes

There is an imminent need for batteries capable of meeting the evolving demands of a growing stationary storage landscape, one rich in renewable energy sources and challenged with unprecedented global electrification. Key to our future electrical grid, desirable large-scale, long-duration batteries must not only meet demands for high power and energy density, but they must be safe, cost-effective, and should be sustainably sourced from earth-abundant materials. Here, we will highlight our research and development of low temperature molten salt batteries that employ active materials such as sodium, aluminum, iron, chloride, and iodide. We will demonstrate the promise of our approach through a low-temperature (100°C) molten sodium battery that comprises a molten sodium anode, a solid-state NaSICON ceramic separator, and a low-cost molten metal-halide salt catholyte. These batteries, with remarkable voltages greater than 3.1V, are capable of months of cycling as well as high current charge and discharge behavior, greater than 50mA/cm2. Here, we will not only highlight these performance metrics, but we will describe how we used specialized electrochemical and chemical characterization technique to understand the impacts of molten salt electrolyte composition, electrochemistry, and interfacial interactions on battery performance. By understanding the connections between specific electrochemical phenomena and battery chemistry, we have learned to improve battery performance through tuning of properties, such as molten salt Lewis acidity and current collector composition. This scientifically-motivated battery design approach continues to enable agile innovation and advances to realize the potential of molten salt batteries as a new, impactful stationary storage technology.Sandia National Laboratories is a multimission 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.

Electrochemical behavior of zinc in alkali-activated fly ash solution

To study the passivation process and chloride-induced corrosion mechanism of galvanized steel in alkali-activated fly ash (AAFA) solution, pure zinc was chosen as the working electrode. Moreover, two other simulated concrete pore solutions, e.g., saturated Ca(OH)2 solution and ordinary Portland cement (OPC) solution were also tested for comparative purposes. Based on various electrochemical measurements and surface characterization techniques, the passivation capability and the chloride-induced corrosion behavior of zinc and its critical chloride concentration were investigated. Although no calcium hydroxyzincate (CHZ) was formed for zinc in AAFA solution due to the lack of sufficient calcium ion, a zeolite-like adsorption layer as well as a silicate gel adsorption layer could be formed on the zinc surface. Accordingly, compared with the other alkaline solutions, enhanced corrosion resistance was evident for zinc in AAFA solution even in the presence of high chloride concentration. These findings of this study serve as the first step towards enhancing our understanding of the possible application of galvanized steel in alkali-activated materials exposed to harsh marine environments.

Corrosion behaviors and passive film properties of a newly developed cost-effective AlCrFeNi eutectic high entropy alloy in different corrosive solutions

Eutectic high entropy alloys (EHEAs) are of great interest among the scientific community because of their excellent combination of strength and ductility. The mechanical properties of various EHEAs were extensively studied in previous studies; however, investigations on corrosion behaviors and passive film properties of EHEAs in different corrosive solutions were relatively few. In this work, the corrosion behaviors and film properties of a newly developed cost-effective AlCrFe1.5Ni2.6 EHEA in solutions of 3.5 wt% NaCl, 0.5 M H2SO4 and 0.5 M HCl were investigated by combining electrochemical measurements and surface characterization techniques; furthermore, the results were compared with those obtained in AlCoCrFeNi2.1 EHEA. The results showed that AlCrFe1.5Ni2.6 EHEA exhibited better corrosion resistance abilities in three different corrosive solutions compared to AlCoCrFeNi2.1 EHEA, which was due to the higher fraction of the corrosion resistant FCC phase in the alloy and a more compact and protective passive film with a higher oxides/hydroxides ratio formed on the surface. The present work will provide guidance for designing EHEAs with a combination of excellent mechanical properties and good corrosion resistance abilities.

Temperature dependent performance analysis of all-oxynitride asymmetric solid-state supercapacitor

A facile and scalable urea-based method synthesises chromium oxynitride (CrOxNy) and cerium oxynitride (CeOxNy) nanoparticles instead of the conventional ammonothermal method. These nanoparticles are used to fabricate asymmetric coin cell devices, where CeOxNy is used as a positive electrode, and CrOxNy is used as negative electrode material. The fabricated asymmetric device is subjected to electrochemical characterisation techniques such as cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), leakage current analysis, and electrochemical impedance spectroscopy (EIS). CV measurement reveals that the device exhibits an areal capacitance of 31.82 mF cm−2 at 10 mV s−1, cycled up to 105 cycles at room temperature (25 °C). Further, the asymmetric device is tested at a range of temperatures (−30 °C to 70 °C) using an environmental climate chamber to explore the temperature tolerance of the device. Measurements reveal that the areal capacitance increases when the testing temperature increases from 10 °C to 70 °C (51.46 % increment observed) and decreases with temperature below the freezing range (0 to −30 °C). Furthermore, temperature-dependent leakage current and cyclic stability are investigated. The temperature-based study highlights the promising nature of an all-oxynitride solid-state asymmetric supercapacitor.

A new perspective on the corrosion of carbon steels in H2SO4 acid environments: Statistical analysis of corrosion mechanisms by response surface modeling

This study investigated synergistic effect of temperature, solution velocity, and sulphuric acid concentration on corrosion behaviour of carbon steel using response surface methodology. Electrochemical and surface characterisation techniques were employed. A statistically significant mathematical model was obtained, correlating corrosion rate to the environmental parameters. Temperature affected anodic reactions, while solution velocity influenced cathodic reactions. Acid concentration profoundly influenced corrosion mechanisms by altering deposition, dissolution, and properties of FeSO4 surface layer. The lowest corrosion rate was 0.546 mm/year at 35 °C, 98.5 wt%, 0 rpm, and the highest was 368.223 mm/year under 70 °C, 49 wt% and 500 rpm.

Commercially Accessible High-Performance Aluminum-Air Battery Cathodes through Electrodeposition of Mn and Ni Species on Fuel Cell Cathodes.

This study presents a cost-effective method for producing high-performance cathodes for aluminum-air batteries. Commercial fuel cell cathodes are modified through electrodeposition of nickel and manganese species. The optimal conditions for electrodeposition are determined using a combination of structural (Raman, SEM, TEM) and electrochemical (LSV, EI, discharge curves) characterization techniques. The structural analysis confirms successful incorporation of nickel and manganese species onto the cathode surface. Electrochemical tests demonstrate enhanced electrochemical activity compared to unmodified cathodes. By combining the favorable properties of electrodeposited manganese species with nickel species, a high-performance cathode is obtained. The developed cathode exhibits capacities of 50 mA h cm-2 in aluminum-air batteries across a wide range of current densities. The electrodeposition method proves effective in improving electrochemical performance. A key advantage of this method is its simplicity and cost-effectiveness. The use of commercially available materials and well-established electrodeposition techniques allows for easy scalability and commercialization. This makes it a viable option for large-scale production of high-performance cathodes for the next-generation energy storage devices.

Application of the Electrochemical Impedance Technique for the Study and Evaluation of Corrosion in HSLA X65 Steels in a Simulated Environment of Sour Gas H2S

The main sources for primary energy generation are oil and natural gas, high demand requires the use of pipelines that guarantee transportation in large quantities. Increased use of pipelines, for which it was necessary to develop high-strength steel tubes for long-distance transportation. High-strength, low-alloy steels (HSLA) are a great alternative for transportation, they mechanically resist high pressures and the reduction in manufacturing and maintenance costs is important for large industries. However, in sour gas (H2S) media it may be susceptible to corrosion, therefore studies to assess corrosion resistance are important. The present investigation evaluated the HSLA X65 steel in sour gas media through electrochemical and microstructural characterization techniques, showing its resistance to corrosion in aggressive media and showing that it can be used reliably for the transportation of oil and natural gas.