Electrochemical Impedance Spectroscopy Techniques Research Articles

A novel composite electrode based on graphene oxide/MnO2:h‐MoO3 particles for square wave voltammetric determination of acetaminophen

AbstractA novel composite electrode was developed based on graphene oxide (GO)/MnO2:h‐MoO3 nanocomposite for sensitive and selective voltammetric detection of acetaminophen (ACP). The composite electrode materials were characterized using X‐Ray photoelectron spectroscopy (XPS), X‐Ray Diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetric (CV) techniques. In the optimum conditions, the oxidation peak current (Ipa) of ACP was increased linearly with its concentration over two linear ranges from 0.06 to 10.0 μmol L−1 and 20.0 to 80.0 μmol L−1 with a detection limit of 0.0133 μmol L−1. Due to its higher selectivity and long term stability, the composite electrode was applied to the detection of ACP in pharmaceutical formulations.

Spectroscopic and antibacterial activities of cobalt and nickel nanoparticles: a comparative analysis

This study aimed to compare the spectroscopy, morphological, electrocatalytic properties, and antibacterial activities of cobalt nanoparticles (CoNPs) with nickel nanoparticles (NiNPs). Cobalt nanoparticles and NiNPs were prepared via a chemical reduction approach and characterized utilizing transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD) techniques. The result from XRD and TEM analysis revealed that the synthesized nanoparticles exhibit face-centered cubic with smooth spherical shape, having average particles size of 12 nm (NiNPs) and 18 nm (CoNPs). The electrochemical properties of the nanoparticles were examined via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The CV results showed that GCE-Ni (35.6 μA) has a higher current response compared to GCE-Co (10.5 μA). The EIS analysis revealed that GCE-Ni (1.39 KΩ) has faster electron transport capability compared to GCE-Co (2.99 KΩ) as indicated in their Rct values. The power density of the synthesized nanoparticles was obtained from their "knee" frequency (f°) values, with GCE-Ni (3.16 Hz) having higher f° values compared to GCE-Co (2.00 Hz). The antibacterial activity of the nanoparticles was evaluated against multidrug-resistant Escherichia coli O157, Escherichia coli O177, Salmonella enterica, Staphylococcus aureus, and Vibrio cholerae. The result from the antibacterial study revealed that at low concentrations both CoNPs and NiNPs have significant antibacterial activities against E. coli O157, E. coli O177, S. enterica, S. aureus, and V. cholerae. NiNPs showed better antibacterial activities at low concentrations of 61.5, 61.5, 125, 61.5, and 125 µg/mL compared to CoNPs with minimum inhibitory concentrations of 125, 125, 250, 61.5, and 125 µg/mL against E. coli O157, E. coli O177, S. enterica, S. aureus, and V. cholerae, respectively. These promising antibacterial activities emphasize the potential of CoNPs and NiNPs as effective antibacterial agents, which could aid in the development of novel antibacterial medicines.

Determination of glyphosate using electrochemical aptamer-based label-free voltammetric biosensing platform

Glyphosate is currently the most frequently used herbicide in the agricultural industry. Due to its widespread usage, there are concerns about its potential toxicity when it contaminates water, soil, and agricultural products. In this study, a simple aptamer-based biosensor was developed to detect glyphosate. The electrode surfaces were modified by reducing diazonium salts during electrodeposition and forming carboxylic acid groups. The immobilization of aminoated glyphosate aptamers on the electrode surface was then carried out using a carbodiimide reaction between the amino and carboxylic acid groups. The electrochemical cell circuit was completed using an analyte and redox probe solution on the electrode surface. Cyclic voltammetry, differential pulse, and electrochemical impedance spectroscopy techniques were then explored to investigate their potential as biosensors. Upon exposure to glyphosate, the spatial conformation of the specific aptamer used is altered, which generates an electrochemical response that can be quantified. Glyphosate could be quantified using voltammetry in the 1 to 5000 nM range, with a 0.67 nM detection limit. Furthermore, the constructed aptasensor demonstrated significant selectivity for glyphosate in the presence of interfering substances like glycine, dimethoate, and alanine. This biosensor has considerable potential for evaluating glyphosate in actual samples because of its simple design, high sensitivity, and rapid functionality. Moreover, developing a simple, cost-effective, and portable device for field applications may be possible.

Electrochemical Study and Mechanical Properties of Ti-Zr Alloy for Biomedical Applications

In response to concerns of potential cytotoxicity and adverse tissue reactions caused by vanadium and aluminum in the currently used biomaterial Ti-6Al-4V, the Ti–20Zr alloy was evaluated in this study because it has been suggested as a candidate for human body implant material. The Ti-20Zr alloy was obtained by vacuum-melting, followed by heat treatment at 1000 °C for 1 h, and then air-cooled. Optical and scanning electron microscopy revealed that the sample had an α and β lamellar microstructure. Analysis showed that the mechanical properties, in terms of hardness measurements performed at low loads, were significantly different between the two phases. Thus, it was found out that the α phase is softer by about 30% compared to the β phase. The Electrochemical Impedance Spectroscopy technique (EIS) was employed to study the electrochemical behavior in simulated body fluid (SBF). The electrochemical behavior demonstrated that Ti-20Zr alloy exhibits excellent corrosion resistance due to the stable oxide layer formed on its surface. SEM and EDS investigations showed that the surface topography, after electrochemical studies, is characterized by a porous film with increased oxygen content, which might be suitable for the osteoinductive growth of bone.

Mo6+ bifunctional substitution of P2-type manganese oxide for high performance sodium-ion batteries

Due to its cost-effectiveness and high specific capacity, P2-type manganese (Mn) oxide is considered a highly promising cathode material for sodium ion batteries (SIBs). However, the practical application of this material is hindered by poor cyclic stability caused by the phase transition of P2-P’2 due to the Jahn-Teller effect of Mn3+ at low voltage and significant volume changes at high voltage. In this study, we utilized Mo6+ dual-function P2-Na0.67Mn0.99Mo0.01O1.997(PO4)0.0008 (NMMPO-1) to achieve exceptional magnification performance and cycle stability. Advanced electron microscopy and X-ray diffraction analysis revealed that Mo6+ acts as a pillar in replacing interlayer Na+ sites within the P2 phase, resulting in extended layer spacing and a stable crystal structure. Additionally, Mo6+ substitution for Mn3+ weakens the Jahn-Teller distortion effect of Mn3+. Ex-situ X-ray diffraction experiments demonstrated that NMMPO-1 effectively inhibits the P2-P’2 phase transition at low voltage while minimizing volume changes during charge–discharge cycles. Overall, our modified NMMPO-1 exhibits excellent cycle stability with 144.55 mA h g−1 after 100 cycles at 0.5C, retaining 83 % capacity retention rate, along with impressive rate performance achieving capacity of 100.57 mA h g−1 at 5C. Furthermore, NMMPO-1 demonstrates superior air stability compared to unmodified samples when exposed to air over multiple cycles. Moreover, through detailed analysis using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic intermittent titration technique (GITT) curves; it is observed that NMMPO-1 possesses enhanced Na+ diffusion capacity and kinetic properties compared to other materials. This research provides novel insights into the role of substituting high valence cations in layered Mn oxide materials which can contribute towards designing improved performance for future sodium ion battery applications.

Electrical impedance spectroscopy for potassium content analysis and botanical origin identification of honey

Minerals are reported to dominate the electrical properties of honey and indicate its botanical and geographical origins. In this study, Electrochemical Impedance Spectroscopy (EIS) was used to assess the relation between mineral elements, electrical properties and botanical origin using three honey varieties - Citrus sp., Eucalyptus sp., and Erica sp. These varieties are identified through pollen analysis and market labelling. Flame atomic absorption and emission spectroscopies were used to quantify the concentrations of eight elements (potassium, sodium, calcium, magnesium, manganese, zinc, copper, and iron). Among all the mineral elements, potassium showed a consistent correlation with impedance. The potassium estimation in honey and standard solutions (calibration curve) had similar sensitivities of 153.43 nF/mM and 132.68 nF/mM, respectively. Additionally, the analysis revealed that potassium dominates the mineral composition, with the other species present in minimal quantities. The EIS technique showed high sensitivity to potassium and other ionisable species, making it possible to classify the botanical origin of these three honey types. The EIS technique proved to be both time and cost effective, yielding a classification rate higher than that achieved by analysing mineral composition.

Enzalutamide-human serum albumin interaction: Electrochemical exploration of complex formation and binding parameters

This research investigation employed electrochemical methods to explore the interaction between the anti-cancer drug Enzalutamide (ENZ) and Human Serum Albumin (HSA). Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV), and Electrochemical Impedance Spectroscopy (EIS) techniques were used via a glassy carbon electrode (GCE) substrate. The interaction between ENZ and HSA was examined based on the changes in the electrochemical behavior of [Fe(CN)6]3−/4− redox species under physiological pH conditions. Electrochemical and kinetic parameters of the redox probe in the presence of HSA, ENZ, and the ENZ-HSA complex were calculated. The results showed significant differences in these parameters due to the formation of an electro-inactive complex between the protein and the drug. Binding parameters of ENZ-HSA, such as the binding constant and complex stoichiometry, were found, revealing the formation of a robust drug-albumin complex with a binding constant value of 2.7 × 108 M−1. A molecular docking study was conducted to examine the possible binding mode of ENZ and its interactions with HSA. This research provides valuable insights and can serve as a reference for future studies to enhance drug delivery systems.

Synthesis and characterization of a new eco-friendly dopamine derivative schiff base as an effective corrosion inhibitor for mild steel in acidic environment

The natural corrosion inhibitor behaviour of a newly synthesized dopamine derivative Schiff base (4-DBAB) has been inspected on mild steel in aggressive 1 M HCl using linear polarization, electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The Schiff base was synthesized by eco-friendly pathway. Characterization of the synthesized new non-toxic inhibitor was performed using FT-IR and 1H-NMR spectroscopy techniques. The anti-corrosive efficiencies at optimum concentration of 4-DBAB inhibitor was 87.4% after 1 h and 98.4% after 120 h by impedance technique in acidic solution. The potential of zero charge of mild steel was also determined to elucidate the inhibition mechanism in the presence of the highest 4-DBAB solution. The atomic force microscopy and field emission scanning electron microscopy researches performed on surface morphology to provide additional support on the interaction between the mild steel surface and 4-DBAB molecules. Adsorption behaviour of the inhibitor was also studied at different durations by experimental inhibition results and showed the Langmuir isotherm involving chemisorption. Highlights A new dopamine-derived Schiff base (4-DBAB) with natural and environmentally friendly corrosion inhibition properties was synthesized. (Synthesis of eco-friendly compound). 4-DBAB demonstrated a high anti-corrosive efficiency after 120 hours in aggressive 1M HCl, as determined by impedance technique. (Exceptional corrosion inhibition). The determination of the potential of zero charge of mild steel provided insights into the inhibition mechanism in the presence of the highest 4-DBAB solution. (Mechanism elucidation). AFM and FE-SEM studies on surface morphology supported the interaction between the mild steel and 4-DBAB molecules, affirming its corrosion inhibition properties. (Surface interaction analysis).

Development of the sustainable green nanosensor using corn silk extract for nitrate detection in leafy vegetables

Nitrate is prevalent in environment and present in foods of plant origin as part of nitrogen cycle. It is now one of the most pervasive and persistent contaminants in animal food chain. Present work is focussed on development of a novel green nanosensor using corn silk extract for nitrate detection in leafy vegetables (Spinacia oleracea, Amaranthus viridis and Amaranthus cruentus). The green reduced graphene oxide (rGO) and a nanocomposite (G-Fe3O4@rGO) was synthesized for the first-time using corn silk extract and used for fabrication of the nanosensor. Various characterization techniques were used to expose the optical, crystallographic and surface morphology details of the nanosubstrates. Electrochemical studies of the fabricated nanosensor were conducted using the electrochemical impedance spectroscopy (EIS) technique. The performance of NiR/G-Fe3O4@rGO/ITO green nanosensor was the best, in terms of the electrochemical performance parameters among different fabricated nanosensors in the study. The developed green nanosensor demonstrated high sensitivity of 122.1 Ohm/log(mg/L)/cm2 and lower limit of detection 0.076 mg/L for detection of nitrate in leafy vegetables. The green nanosensor exhibited higher recovery rates (>86%) and high precision in nitrate detection in leafy vegetables (RSD <5.2%). Validation studies were conducted with HPLC technique also. The results of green nanosensor were found in good agreement with HPLC studies (p < 0.05) highlighting the market acceptability with usefulness and effectiveness of the nanosensor for food quality and safety evaluation.

Design of highly effective organic catalyst for hydrazine electrooxidation: Iodobenzo[b]furan derivatives

In this study, we investigate the electrochemical characteristics of 2-aryl/alkyl-3-iodobenzo[b]furans as anode catalysts for hydrazine (N2H4) fuel cells. Cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) techniques are employed to investigate the performance of these heteroaromatic compounds. The results demonstrate the promising potential of the 2-aryl/alkyl-3-iodobenzo[b]furans in fuel cell technology. Among the tested organic catalysts (2a, 2b, 2c, 2d, and 2e), 2a exhibited the highest electrocatalytic activity, giving a total current density of 26.62 mA/cm2 within the potential range of −0.4 to −0.8 V. 2-aryl/alkyl-3-iodobenzo[b]furans were synthesized by using palladium/copper-catalyzed Sonogashira cross-coupling reactions, followed by electrophilic cyclization with iodine (I2). All products were characterized using 1H and 13C NMR spectroscopy, confirming their structures and providing insights into their chemical properties.

A nanoDiamond/gold nanoparticle-based electrochemical immunosensor for the detection of HER 2 cancer biomarker

We report a highly sensitive electrochemical immunosensor based on a nanohybrid platform for the detection of the breast cancer biomarker human epidermal growth factor receptor 2 (HER 2). NanoDiamond (nanoD) and gold nanoparticles (AuNPs) immobilised by drop coating and electrodeposition methods, respectively, were employed to fabricate an immunosensor for HER 2 detections on a glassy carbon electrode (GCE). Voltammetry and electrochemical impedance spectroscopy (EIS) techniques were used to characterise each step of the modification process of the immunosensor. In addition, transmission electron microscopy (TEM), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques were used to characterise the materials used to fabricate the modified electrode. Under optimal conditions of temperature, time, and pH (35 °C, 50 min, and pH 7.2), different concentrations were investigated within a wide range of 1 pg mL−1 to 50 ng mL−1 using differential pulse voltammetry (DPV). With a low detection limit of 0.29 pg mL−1 from the DPV analysis, the immunosensor showed very good sensitivity and had a high specificity for HER 2. Additionally, the immunosensor demonstrated good applicability in the analysis of HER 2 in human serum samples, demonstrating a potential for use in the early identification of breast cancer.

Electrochemical Properties and Determination of Serotonin with Graphene/Coal Tar Pitch/Pencil Graphite Sensor Electrode using Square Wave Adsorptive Stripping Voltammetry Technique

In the present work, electrochemical and spectroelectrochemical behaviors of Serotonin (5-HT) were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Cyclic voltammetric experiments of 5-HT on graphene/coal tar pitch/pencil graphite electrode (GR/CTP/PGE) were carried out between 0.0 V and 1.8 V potential range at a scan rate of 100 mV s-1 with 20 cycles in non-aqueous media. Surface characterizations were performed using CV, EIS and scanning electron microscope (SEM). Effect of different pH values was investigated by square wave voltammetry (SWV) for determination of 5-HT. Optimization of accumulation time was determined using square wave adsorptive stripping voltammetry (SWAdSV) within potential range of -0.2 to +0.6 V. 5-HT standard solutions changing from 75 µM to 1.0 µM were prepared and the corresponding peak currents were measured. From the obtained data calibration equation was derived Ip = 0.0329C5-HT + 0.1511 with correlation coefficient (R2) 0.9958. LOD was 3.51x10-7 M and LOQ was 1.05x10-6 M.

Trisodium phosphate-loaded magnesium‑aluminum layered double hydroxides/oxidized-multiwalled carbon nanotubes self-assembled 2D-nanohybrid for designing a multifunctional smart epoxy nanocomposite

In this study, a hybrid nanomaterial based on layered double hydroxides (LDH) and multi-walled carbon nanotubes (MWCN) was fabricated using a co-precipitation method. Trisodium phosphate (TP) was loaded into the designed nanocarrier to enhance the corrosion resistance of mild steel in 3.5 wt% NaCl media. Fourier transform infrared (FT-IR) spectroscopy, Raman, and X-ray diffraction (XRD) analyses were carried out to investigate the magnesium‑aluminum layered double hydroxides/oxidized-multiwalled carbon nanotubes (Mg-AL-LDH/O-MWCN) structure and morphology before and after loading of trisodium phosphate. Furthermore, the nanocarrier inhibition capability was evaluated through electrochemical impedance spectroscopy (EIS), polarization, and field emission-scanning electron microscopy (FE-SEM) techniques. Electrochemical impedance spectroscopy (EIS) was also employed to estimate the anticorrosion properties of the epoxy coating loaded with TP-LDH/O-MWCN. The EIS evaluation of the intact coating revealed the impedance at the lowest frequency (|Z|0.01 Hz) of about 109 Ω.cm2 after 42 days of immersion for the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes@epoxy (TP-LDH/O-MWCN@EP) sample and the lowest value of breakpoint frequency was obtained for this sample (fb = 0.063 Hz). These findings prove the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes (TP-LDH/O-MWCN) particles' effectiveness in the epoxy coating water/ion barrier function enhancement. EIS results indicated the enhancement of the charge transfer resistance (Rct) of the scratched coatings, from 65.97 kΩ.cm2 for the pure epoxy (EP) sample to 94.87 kΩ.cm2 for the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes@epoxy (TP-LDH/O-MWCN@EP) sample, revealing the self-repairing behavior of the designed coating. In addition, the adhesion properties of the samples coated with LDH/O-MWCN@EP and TP-LDH/O-MWCN@EP were studied by pull-off and cathodic disbonding tests, leading to a 33% reduction in adhesion loss and a 52.23% reduction in the diameter of cathodic delamination. The tensile test conducted on the samples indicated an increase in the ultimate tensile strength (σUTS), elongation break (Ɛb), and toughness values by 188%, 223%, and 800%, respectively, in comparison with the pure epoxy (EP) sample.

Ethylenediamine-functionalized metal-organic frameworks for applications of electrochemical supercapacitors as an additive

In this study, the impact of incorporating ethylenediamine (ED)-functionalized metal-organic frameworks (MOFs) on enhancing the electrochemical performance of polypyrrole(PPy)-based conducting polymers as supercapacitor electrode materials was investigated. The stability of terephthalic acid-containing MOFs in different environments, including exposure to acids, relies on the specific metal ions and ligands utilized in their construction. In this research, ED treatment was chosen for its resistance to acid attack. Unlike the post-synthetic modifications observed in previous literature regarding ED-modified MOF5, this study introduces a unique approach where ED is directly integrated into the framework in a single step. The resulting materials, referred to as ED-MOF, were employed in creating a novel composite material concurrently with polypyrrole, designed for use as electrode materials in supercapacitor applications. The optimal loading in the electrochemical preparation of polypyrrole-based conducting polymers was determined using cyclic voltammetry and electrochemical impedance spectroscopy techniques. Areal capacitance for the resulting electrodes was evaluated through cyclic charge-discharge experiments. The areal capacitance of the ED-ZnMOF/1@/PPy/PGE electrode was found to be 575.2 mF.cm−2 at a charge/discharge current density of 1 mA.cm−2. This research underscores the potential advantages of combining conducting polymers and metal-organic frameworks in supercapacitors, as well as other electrochemical systems.

Sulfonated poly(ether ether ketone)-Protic ionic Liquid-Based anhydrous Proton-Conducting composite polymer electrolyte membranes for High-Temperature fuel cell applications

A high-temperature polymer electrolyte membrane fuel cell (PEMFC) has enormous potential to produce clean energy with minimal environmental pollution along with high energy density and conversion efficiency. In the present work, anhydrous proton-conducting polymer electrolyte membranes for prospective high-temperature fuel cell application were successfully prepared using different protic ionic liquids (PILs) and sulfonated poly(ether ether ketone) (SPEEK). The protic ionic liquids (PILs), 2-hydroxyethylammonium formate, diethylmethyl ammonium triflate, 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide, 1,2-dimethyl imidazolium bis(trifluoro methylsulfonyl)imide, and diethylmethylammonium methanesulfonate were selected based on their favorable physicochemical properties. The effect of the incorporation of the PIL on the structural, thermal, and electrical transport properties of the composite SPEEK polymer electrolyte membranes was studied. The prepared polymer electrolyte membranes (PEMs) were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and electrochemical impedance spectroscopy (EIS) techniques. FTIR results indicated an interaction between the PIL and the SPEEK, which resulted in homogeneous and flexible membranes. The DSC results confirmed good miscibility and elucidated plasticizing effect of the incorporated PIL on the SPEEK polymer matrix. All the PEMs showed good thermal stability and high-temperature anhydrous proton conductivity, achieving best proton conductivity, ≈8 × 10–3 S cm−1 at 120 °C and low activation energy ≈0.26 eV, making it suitable for prospective high-temperature PEMFC applications.

Enhancing Corrosion Resistance of Mild Steel in 1M HCl: Investigation of New Benzoxazepine Derivatives Through Synthesis, Electrochemical Analysis, Surface Analysis, XPS, DFT, and Molecular Dynamics Simulation

AbstractThis research delineates the corrosion inhibitory efficiency of two newly synthesized benzoxazepine derivatives – [3,3‐dimethyl‐11‐phenyl‐3,4,5,11‐tetrahydrodibenzo[b,e] [1,4]oxazepine‐1(2 H)‐one (S1)] and [11‐(4‐chlorophenyl)‐3,3‐dimethyl‐3,4,5,11‐tetrahydrodibenzo[b,e][1,4]oxazepine‐1(2 H)‐one (S2)] – on mild steel in 1M HCl milieu. These derivatives were characterized by proton (1H NMR) and carbon (13C NMR) nuclear magnetic resonance spectroscopy. The experimental approach encompassed potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The corrosion inhibition efficacy of S1 and S2 was concentration‐dependent, with their efficiencies peaking at 92.0 % and 92.1 %, respectively, at a 10−3 M concentration. Surface characterization, conducted using scanning electron microscopy (SEM), energy‐dispersive X‐ray analysis (EDS), X‐ray diffraction (XRD), contact angle measurements, and X‐ray photoelectron spectroscopy (XPS), corroborated the formation of a protective barrier layer on the mild steel surface. Additionally, using an inductive approach, UV‐visible spectrometry was employed to elucidate the adsorption behaviors of these inhibitors on the steel surface. Density functional theory (DFT) and molecular dynamics (MD) simulations were utilized to decipher the interaction mechanisms and adsorption modalities, unveiling critical insights into the interactions of S1 and S2 with the mild steel surface. This comprehensive analysis highlights the robust corrosion inhibition potential of the newly synthesized benzoxazepine derivatives and illuminates their prospective utility as effective inhibitors for mild steel in corrosive environments.

Tracking activity behavior of oxygen evolution reaction on perovskite oxides in alkaline solution via 3-dimensional electrochemical impedance spectroscopy

Developing electrocatalysts for the oxygen evolution reaction (OER) is essential for enhancing the efficiency of electrochemical water electrolysis. Among potential candidates, certain metal oxides, such as Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF), undergo structural transformations at their surface during OER operation, and the in situ-formed active layer enhances their OER activities. However, it is challenging to quantitatively evaluate the time-variant electrochemically active surface area (ECSA) and inherent catalytic activity per surface area (area-specific activity) of the oxides. In this study, we utilize the 3-dimentional electrochemical impedance spectroscopy (3D EIS) technique to reveal the variations in the ECSA and area-specific activity of the perovskite oxides during OER operation in an alkaline solution. In BSCF, the diameter of instantaneous Nyquist plots decreases as the number of potential cycling in the OER potential range increases, contrasting with other perovskite oxides, such as La0.5Sr0.5Co0.8Fe0.2O3−δ and LaCoO3. The fitting results of the Nyquist plots demonstrate that in BSCF, the ECSA significantly increases while the area-specific activity drops to less than half of its initial value during OER operation. Consequently, enhanced OER activity of BSCF mainly attributed to the increased ECSA rather than area-specific activity. This study demonstrates the utility of 3D EIS for tracking the ECSA and the area-specific activity of electrocatalysts.

Corrosion Inhibition of Carbon Steel by Some Schiff Base Compounds in HCl and H2SO4 Solutions

AbstractThe inhibition power of two Schiff bases on carbon steel corrosion in 1 M HCl and 0.5 M H2SO4 solutions has been investigated using weight loss, Tafel polarization, and electrochemical impedance spectroscopy techniques. The results revealed that increasing the concentration of inhibitors in acidic solutions led to a higher inhibition efficiency. The polarization curves indicated that the Schiff bases acted as mixed inhibitors, affecting both the cathodic and anodic reactions. The adsorption of the inhibitors on the carbon steel surface followed the Langmuir adsorption isotherm, and various adsorption isotherm parameters such as Kads, ΔGads, ΔHads, and ΔSads were determined at room temperature. Furthermore, the effect of temperature on the inhibitors′ performance was examined within the range of 25–45 °C. The corrosion‐related activation energy, pre‐exponential factor (k), activation enthalpy, and entropy were calculated to assess the inhibitors′ behavior. Scanning electron microscopy (SEM) was employed to examine some carbon steel samples, revealing differences in inhibition efficiency attributed to the inhibitors′ chemical structure. The results highlighted the highest inhibition efficiency in H2SO4 medium at 93.4 %, with a corresponding free energy of 39.51 KJ/mol indicating physical‐chemical adsorption of inhibitor molecules. Furthermore, an enthalpy value of −40.6 KJ/mol suggested an exothermic inhibitor absorption process. The findings are presented and discussed in detail.

Supercapacitive performance of 3D-cobalt oxide (Co3O4) nanowires grown onto anodized stainless-steel substrate: Effect of anodization time

3D-Co3O4 nanowires were grown on anodized stainless steel (SSA) using a simple hydrothermal technique, with SSA as a cost-effective porous substrate. The originality of this work is to enhance surface activity and material adhesion by anodizing stainless steel (SS). After growth, the nanowires were thermally treated at 400 °C for 2 h. By varying the SS anodization time from 0 to 900s, changes in the structural, morphological, and electrochemical properties of Co3O4 were observed. XRD analysis confirmed the polycrystalline nature of Co3O4 with a face-centered cubic phase. SEM imaging showed noticeable changes in density and surface roughness. Supercapacitive properties were evaluated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) techniques, with SSANWs-300 exhibiting the highest specific capacitance of 529 Fg-1. Dunn's method was used to analyze the contribution of capacitive and diffusive mechanisms to charge storage. EIS results indicated excellent electronic conductivity. The study suggests that SSANWs-300 holds promise for energy storage applications.

Tribological and corrosion behavior of hydrided zirconium alloy

Zirconium alloys (Zr-alloys) are used for the core components of nuclear reactors due to their exceptional properties, which make them suitable for the given applications such as low neutron absorption cross-section, good corrosion resistance, good wear resistance, good mechanical stability at high temperatures etc. The coolant water that flows inside the pressure tube contains LiOH to control the pH value of the coolant water, which can cause corrosion. The flow of coolant water produces low amplitude vibration, which can cause fretting wear of the components. Further, the coolant water at high temperature causes the hydride formation in the material, degrading the properties of zirconium alloys. The safe working of nuclear reactors is the prime objective, and the corrosion and wear behavior of the core components must be explored to prevent possible failure. Fretting wear or tribo-corrosion experiments were conducted on Zr‐2.5Nb alloy against SS-410 for varied fretting duration to understand the tribological response. Electrochemical corrosion experiments were performed under the aqueous solution of LiOH (10.4 pH) using Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization technique. The comparison was made between the tribological and corrosion response of unhydrided‐Zr‐2.5Nb alloy (Zr‐2.5Nb) and hydrided- Zr‐2.5Nb alloy (Zr‐2.5Nb‐H). The hydride formation causes the reduction in corrosion resistance of Zr‐2.5Nb alloy. The oxide layer is formed during the wear and corrosion process which protects the material from further wear and corrosion respectively.