Tafel Plots Research Articles

Green Synthesis of New Heterocyclic Surfactant Compounds by Multicomponent Reactions and Their Antibacterial and Corrosion Inhibitor, Study on Carbon Steel Alloy in Acid Media 2 M HCl

Heterocyclic 1,4-di(1,3,5-dithiazinan-5-yl)benzene (D) and two heterocyclic-cationic Gemini surfactant 5,5'-(1,4-phenylene)bis(5-decyl-1,3,5-dithiazinan-5-ium)bromide (E) and 5,5'-(1,4-phenylene)bis(5-tetradecyl-1,3,5-dithiazinan-5-ium)bromide (F) were prepared and identified by FTIR, 1H-NMR spectroscopies, and GC–MS. Then, they were tested as corrosion inhibitors against carbon steel corrosion in 2.0 M aggressive HCl medium at 25 and 50 °C. They have different carbon chain tails, i.e., E (10 carbons), and F (14 carbons). These new heterocyclic and surfactant categories as corrosion inhibitors. The corrosion process has been studied electrochemically (Tafel Plot). The inhibition efficiency clarified that the decrease in IE(%) is in the order of F > E > D. The biological activity of compounds D and F was investigated using the aforementioned drilling procedure with a cork drill. At a dosage of 3000 mcg/mL, the biological action of compound D demonstrated effective resistance against the two types of negative bacteria. The cation has a diameter of 20 mm against E. coli and 19 mm against S. epidermis bacteria. At the same concentration, the chemical F is solely effective against E. coli with an inhibition diameter of 14 mm.

Catalytic activity of 2D MXenes toward electroreduction processes: Oxygen reduction and hydrogen evolution reactions

In this work, 2D Mo and Ti MXenes (Mo2TiC2 and Ti3C2) were synthesised from the chemical etching of their MAX phases (Mo2TiAlC2 and Ti3AlC2). The physicochemical characterisation demonstrated the removal of Al from precursors obtaining layered structures enriched with metal carbides domains. Focused on potential clean energy applications of these materials, their catalytic activity was assessed in two reactions: the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER). The ORR activity of MXenes is quite low: Mo2TiC2 developed a slightly higher activity towards ORR in acidic media than Ti3C2 MXene, with an onset potential for the reaction at 0.4 VRHE. However, 3-fold higher performances were achieved in alkaline media for all the studied materials, suggesting a strong dependence of their catalytic activity with the pH. On the other hand, Mo2TiC2 and Ti3C2 exhibited high catalytic activity toward the HER in acidic media in comparison to their commercial MAX phases and few commercial carbides. This catalytic activity was evidenced from the low onset potentials for HER, as well as low overpotentials at 10 mA cm−2, especially for Mo2TiC2 (0.17 and 0.379 VRHE, respectively). Differential electrochemical mass spectrometry (DEMS) experiments allowed to establish the onset potentials, avoiding the interference of other faradaic processes in the same potential region, and the rate determining steps (rds) for HER at the studied materials. Tafel plots from ionic currents for m/z = 2 indicate that the Heyrovsky step is the rds for HER at Mo2TiC2, whereas Volmer step is the rds at Ti3C2. Long-term stability tests for the MXenes demonstrated that these materials maintain its activity after 10 h under operation conditions. EIS experiments performed at onset and HER evolution potentials corroborated the relevance of the presence of oxide reduction processes competing with the HER, which explains the higher catalytic activity of Mo2TiC2 with respect to Ti3C2.

Fabrication of a Curcumin@Cu‐BTC MOF Smart Anti‐Corrosion Coating for Copper

AbstractThe curcumin@Cu(II)‐benzene‐1,3,5‐tricarboxylate metal‐organic framework (Cur@Cu‐BTC MOF) coating, as a pH‐sensitive smart anti‐corrosion coating, has been synthesized by encapsulating Cur, as a green inhibitor, in Cu‐BTC MOF. The characteristics of the coating were investigated by scanning electron microscope (SEM) images, energy dispersive X‐ray spectroscopy (EDS), elemental scattering map, FTIR spectroscopy and X‐ray diffraction (XRD) patterns. Corrosion parameters of Cur@Cu‐BTC MOF smart coating in 3.5 % NaCl corrosive solution were investigated using potentiodynamic polarization (Tafel) plots and electrochemical impedance spectroscopy (EIS). Indeed, curcumin loading into Cu‐BTC MOF makes the coating more compact. The inhibition efficiency of Cur@Cu‐BTC MOF coating is 72.57 %. Also, when curcumin is loaded into Cu‐BTC MOF, its consumption is about 6 times lower than using it directly as an inhibitor. Also, the anti‐corrosion performance of the smart coating was measured in different immersion times in 3.5 % NaCl solution. Using UV‐vis spectrometry, it was found that the synthesized Cur@Cu‐BTC MOF nanocapsules have a loading capacity of 16.6 % for curcumin. Cur@Cu‐BTC MOF acts as a smart coating and responds to the decreasing of the local pH caused by the corrosion reaction. Encapsulated curcumin is released in response to the pH stimuli and acts as a corrosion inhibitor.

Nickel-based composites using tungsten carbides as enhancers for electroactivity for the hydrogen evolution reaction

This study explores the impact of incorporating tungsten carbides into a Watts bath on the fabrication of Ni/WC and Ni/W2C composites, comparing them with conventional Ni Watts electrodeposited electrodes. Results indicate that adding tungsten carbides to the conventional nickel bath forms rougher and more porous structures in the deposited composites. Composite electrodes exhibit significantly enhanced current density for hydrogen evolution in alkaline media compared to nickel Watts electrodes. Differential Electrochemistry Mass Spectrometry (DEMS) elucidates the hydrogen evolution mechanism, providing accurate data for Tafel plots. X-ray photoelectron spectroscopy (XPS) shows minimal impact on nickel's surface chemistry. X-ray diffractograms demonstrate that tungsten carbide particles maintain crystalline structure. X-ray dispersive spectroscopy (EDS) reveals an uneven chemical composition, with Ni/WC and Ni/W2C composites containing approximately 17% tungsten carbides. Electrochemical impedance spectroscopy (EIS) indicates higher electrochemical areas and lower charge transfer resistances in Ni/WC and Ni/W2C composites than in Ni Watts. This study contributes insights for the efficient and economical development of electrolysis systems. Notably, Ni/WC and Ni/W2C composites show promising electrochemical performance, emphasizing their potential in advancing electrolysis technology.

Evaluation of physiochemical and electrochemical behaviour of reduced grapheme functionalized copper nanostructure as an effective corrosion inhibitor

This study examines the physicochemical properties and corrosion resistance of hydrothermally produced copper oxide-reduced graphene oxide nanocomposite (CuO/rGO). The CuO/rGO nanocomposite has a well-defined and homogeneous structure, decreased crystal size, and uniformly distributed CuO nanoparticles tethered to the rGO. X-Ray diffraction confirms the fabrication of 15.1 nm crystalline monoclinic CuO nanoparticles. EDX confirms the composite's composition by detecting Cu, O, and C components. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (LSV) tests evaluate the CuO/rGO nanocomposite's corrosion resistance. A mild steel plate under an HCl electrolyte with corrosion in the PPM ratio treats the nanocomposite-coated substrate. The composite's synergistic effect is assessed by comparing its corrosion performance to CuO/rGO concentrations in ppm. The corrosion resistance data demonstrate that the CuO/rGO composite improves with inhibitor concentrations of 0, 25, 50, 75, and 100 ppm. Adding rGO to the composite protects it and speeds up charge transfer, reducing corrosion and improving stability. The composite's synergistic effect of CuO and rGO provides excellent corrosion resistance regardless of concentration, making it a viable material for corrosion-prone applications. The research develops novel and effective anti-corrosion methods to preserve materials in the food, automotive, and large-scale energy industries.
 KEY WORDS: CuO/rGO nanocomposite, Tafel plot, Corrosion protection, Surface analysis
 Bull. Chem. Soc. Ethiop. 2024, 38(1), 269-280. DOI: https://dx.doi.org/10.4314/bcse.v38i1.20

Evaluation of improved corrosion resistance of Zn alloy as electrode material by Co3O4 coatings

This work uses the sonochemical method to represent synthesized cobalt oxide nanoparticles (Co3O4) and analysed using different techniques. The X-ray diffraction analysis (XRD) and Fourier-transform infrared spectroscopy (FTIR) examinations of the synthesized nanoparticles confirmed their cubic structure and average crystallite size of 21.3 nm. The spherical surface shape and presence of components with a particle size of 25.3 nm were revealed. Scanning probe microscopy (SPM) methods analysed the Co3O4 coated plates' surface characteristics, including roughness and topographical ideas. An aqueous electrolyte medium (6 M KOH) was used to investigate the electrochemical corrosion behaviour of Co3O4-coated plates. According to the Tafel plot, coating Zn plates with a high surface area and mesoporous Co3O4 in KOH electrolytes greatly reduced the corrosion of the plates. The coated plates are thermally treated up to 600℃. The temperature-dependent anticorrosive properties of Co3O4 NPs are evaluated.
 KEY WORDS: Co3O4, Zn plate, Tafel plot, Linear sweep voltammetry, Anti-corrosive performance, Nanoindentation
 Bull. Chem. Soc. Ethiop. 2024, 38(1), 241-253. DOI: https://dx.doi.org/10.4314/bcse.v38i1.18

One-step hydrothermal formation of porous N-graphyne decorated TiO2/Ti3C2 composites with enhanced photocatalytic activity

Herein, a series of porous N-graphyne decorated TiO2/Ti3C2 composites (NHGTTC-x) are constructed via hydrothermal treatment of N-graphyne and Ti3C2 in the presence of H2O2. The added H2O2 can serve as both pore-forming reagent of N-graphyne and oxidant of Ti3C2 in the synthesis process. As a result, numerous TiO2 nanoparticles in-situ generate on almost the entire surface of Ti3C2, and the porous wrinkled N-graphyne surrounds or attaches on the surface of TiO2/Ti3C2. The highest NH3 yield is found over the photocatalysis of NHGTTC-1% under UV–visible light for 4 h (0.306 mmol g−1), which is 3.86 times of that for pristine TiO2/Ti3C2 (0.079 mmol g−1). Moreover, the photodegradation efficiencies of tetracycline, rhodamine B, and levofloxacin by NHGTTC-1% are 2.40 folds, 2.58, and 7.90 times greater than that of pristine TiO2/Ti3C2 under visible light illumination. In addition, the primary active species is established to be superoxide radical (·O2−) in the photocatalytic decomposition process. Additionally, the enhanced mechanism of photocatalysis is methodically investigated by photocurrent, Tafel plots, electrochemical impedance, Mott-Schottky curves, etc. This study marks the first construction of porous N-graphyne/TiO2/Ti3C2 composites, which show superior photocatalytic activity for contaminants degradation and nitrogen fixation.

Advanced Anticorrosive Graphene Oxide-Doped Organic-Inorganic Hybrid Nanocomposite Coating Derived from Leucaena leucocephala Oil.

Metal corrosion poses a substantial economic challenge in a technologically advanced world. In this study, novel environmentally friendly anticorrosive graphene oxide (GO)-doped organic-inorganic hybrid polyurethane (LFAOIH@GO-PU) nanocomposite coatings were developed from Leucaena leucocephala oil (LLO). The formulation was produced by the amidation reaction of LLO to form diol fatty amide followed by the reaction of tetraethoxysilane (TEOS) and a dispersion of GOx (X = 0.25, 0.50, and 0.75 wt%) along with the reaction of isophorane diisocyanate (IPDI) (25-40 wt%) to form LFAOIH@GOx-PU35 nanocomposites. The synthesized materials were characterized by Fourier transform infrared spectroscopy (FTIR); 1H, 13C, and 29Si nuclear magnetic resonance; and X-ray photoelectron spectroscopy. A detailed examination of LFAOIH@GO0.5-PU35 morphology was conducted using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. These studies revealed distinctive surface roughness features along with a contact angle of around 88 G.U preserving their structural integrity at temperatures of up to 235 °C with minimal loading of GO. Additionally, improved mechanical properties, including scratch hardness (3 kg), pencil hardness (5H), impact resistance, bending, gloss value (79), crosshatch adhesion, and thickness were evaluated with the dispersion of GO. Electrochemical corrosion studies, involving Nyquist, Bode, and Tafel plots, provided clear evidence of the outstanding anticorrosion performance of the coatings.

MICROSTRUCTURAL EVOLUTION AND ANTI-CORROSION CHARACTERISTICS OF AS-CAST AND LPBF PRINTED INCONEL PLATES IN SEAWATER ENVIRONMENT

Inconel 718 (IN 718) belongs to the category of nickel-based superalloys with outstanding mechanical characteristics such as high strength, better corrosion resistance, greater hardness, fatigue and wear resistance. This alloy is mostly implemented in manufacturing the components of aeroengines, nuclear reactors, space shuttles, pressurized boilers and so on. In most cases, the parts made from this alloy work in severe aggressive environments. A prolonged exposure of this alloy in such environments will pave the way for corrosion phenomenon which will minimize the service life of the components. It is reported that the parts made via additive manufacturing will exhibit better mechanical characteristics than the casted and forged parts. This work is aimed to investigate the anti-corrosion characteristics of both as-cast and LPBF printed IN 718 samples at various time intervals in the seawater environment. By means of FESEM micrographs, the microstructural evolution in both as-cast and LPBF printed IN 718 samples was analyzed. The anti-corrosion characteristics of both samples were investigated in the environment containing 3.5 wt.% NaCl (seawater) in terms of EIS and potentiodynamic polarization curves along with the corroded morphology. The results showed that the LPBF printed IN 718 samples exhibit fine cellular and columnar grains decorated with the NbC precipitates along their boundaries, whereas the casted samples have larger and coarser grains with uneven segregation of NbC precipitates. From the Tafel and EIS (Nyquist and Bode) plots, the LPBF IN 718 sample showed greater corrosion resistance in terms of current density and polarization resistance values. In particular, the 15 h LPBF sample has a strong, compact passive film formed on it. This compact passive film paved the way for this sample to exhibit lower current density (3.03 × 10[Formula: see text] A/cm2) and higher polarization resistance (3678 Ω · cm2) when compared with the LPBF and cast samples at other intervals.

Redox-active pigeon excreta mediated metal oxides nanosheets for enhancing co-catalyst for photovoltaic performance in dye-sensitized solar cells

Pigeon excreta (PE) contains a significant amount of organic components, which are harmful to the environment and humans. Hence, the proper disposal of PE deals with practical problems. Furthermore, using PE for other energy sources is an efficient innovation. In this study, an innovative technique was implemented for producing agglomeration free and distinct metal oxides using PE as a surfactant and capping agent. The different characterizations and their analysis explain the mechanism involved in forming distinct metal oxide nanosheets utilizing PE. The obtained samples were confirmed by the characteristic peaks of PE mediated metal oxides such as (NiO, Co3O4 and CuO) observed in X-ray diffraction (43.47°, 36.61° and 35.71°), and the UV-DRS band-gap narrowing (2.4, 2.13 and 2.02 eV). In the FTIR spectrum, it is clearly evident that there is a high amine group in the PE which plays a key role in reducing the agglomeration in the metal oxides. The morphology of PE mediated NiO, Co3O4 and CuO revealed nanoflakes and nanosheets like structures identified from FE-SEM analysis. The photovoltaic performance of the PE mediated metal oxides showed improved photocurrent conversion efficiencies of 1.2–1.6 times more than pure metal oxides. Among all, the CuO-PE had the most significant photovoltaic performance, with a photoconversion efficiency of 3.22 %. The reduction of I3− to 3I− along the counter electrode/electrolyte interaction is facilitated by the PE mediated transition metal oxides, as shown by the photocurrent response, Tafel plot and electrical impedance spectroscopy results, which were discussed in detail.

Anti-Corrosion Properties of Polyaniline/Polyurethane Composite Coatings on Mild Steel Using Coconut-Based/PPG Blend Polyols

Polyurethane coating has been widely used as a protective coating due to its wide range of mechanical strength, excellent abrasion resistance, toughness, low-temperature flexibility, and chemical resistance, simplicity in production and application, and superior protection on corrosion to mild steel. No studies have been reported utilizing coconut-based/PPG blend polyols to produce polyurethane-based protective coatings on mild steel. Therefore, in this work, we fabricated polyurethane-based protective coating using coconut-based/PPG blend polyols for anti-corrosion application. Due to low adhesion strength of Polyurethane-based protective coating, the incorporation of nano-fillers into the polymer matrix improved the adhesion strength of the coating due to its functional benefits and its effects gave rise to increased intermolecular bonding, hydrogen bonding, van der waals, magnetism, and surface energy. Therefore, we fabricated PANI/PU composite coatings with varied amounts of polyaniline nanoparticles on mild steel using coconut-based/PPG blend polyols exposed in 3.5 wt% NaCl aqueous solution for anti-corrosion application. Characterizations like Fourier Transform Infrared Spectroscopy (FTIR), Potentiodynamic Polarization (Tafel plot), contact angle, adhesion test, FESEM, XRD, and UV-VIS were used in this study. Tafel plot revealed that PU-based and PANI/PU composite coatings exhibited a significant reduction in corrosion current density (Icorr), perhaps due to the adsorption of inhibitor in the surface of the mild steel which reduced corrosion rate of the metal by retarding the anodic process and impeding the corrosive species from the surroundings. Among all fabricated coatings, 0.5-PANI/PU composite coating was the best, having a less corrosion rate of 5.66x10-5 mmpy compared to others. In addition, its surface was more compact, smooth, rigid, and no voids present at the interface according to the result of FESEM, suggesting better corrosion protection to mild steel. Hence, PU-based protective coating and PANI/PU composite coatings using coconut-based/PPG blend polyols inhibited the penetration of the corrosive species and served as an adequate barrier protection against corrosion for mild steel.

Efficient electrochemical nitrogen fixation at iron phosphide (Fe2P) catalyst in alkaline medium

A catalytic system based on iron phosphide (Fe2P) has exhibited electrocatalytic activity toward N2-reduction reaction in alkaline medium (0.5 mol dm−3 NaOH). Based on voltammetric stripping-type electroanalytical measurements, Raman spectroscopic and spectrophotometric data, it can be stated that the Fe2P catalyst facilitates conversion of N2 to NH3, and the process is fairly selective with respect to the competing hydrogen evolution. A series of diagnostic electrocatalytic experiments (utilizing platinum nanoparticles and HKUST-1) have been proposed and performed to control purity of nitrogen gas and to probe presence of potential contaminants such as ammonia, nitrogen oxo-species and oxygen. On the whole, the results are consistent with the view that the interfacial reduced-iron (Fe0) centers, while existing within the network of P sites, induce activation and reduction of nitrogen, parallel to the water splitting (reduction) to hydrogen. It is apparent from Tafel plots and impedance measurements that mechanism and dynamics of nitrogen reduction depends on the applied electroreduction potential. The catalytic system exhibits certain tolerance with respect to the competitive hydrogen evolution and gives (during electrolysis at -0.4 V vs. RHE) the Faradaic efficiency, namely, the selectivity (molar) efficiency, toward production of NH3 on the level of 60%. Under such conditions, the NH3-yield rate has been found to be equal to 7.5 µmol cm−2 h−1 (21 µmol m−2 s−1). By referring to classic concepts of electrochemical kinetic analysis, the rate constant in heterogeneous units has been found to be on the moderate level of 1-2*10−4 cm s−1 (at -0.4 V). The above mentioned iron-phosphorous active sites, which are generated on surfaces of Fe2P particles, have also been demonstrated to exhibit strong catalytic properties during reductions of other electrochemically inert reactants, such as oxygen, nitrites and nitrates.

Distribution function of relaxation times: An alternative to classical methods for evaluating the reaction kinetics of oxygen evolution reaction

Reaction kinetics of RuO2 is precisely evaluated by distribution function of relaxation times (DFRT) model using impedance spectroscopy analysis by genetic programming (ISGP). Effective resistances of the Faradaic processes, measured using Electrochemical impedance spectroscopy (EIS) at various overpotentials, were determined utilizing DFRT, by separating and associating three electrochemical phenomena occurring during the reaction. The effective resistances are used to generate a Tafel plot of potential as a function of log1Reff. The classical method, based on linear sweep voltammetry (LSV), to evaluate the Tafel slope is associated with some considerations for accurate results. For RuO2, a reference catalyst, LSV illustrates an average Tafel slope of 182 ± 8 mV/dec while the effective resistance method, estimated using DFRT, shows an average of 181 ± 3 mV/dec. A relative error of 0.3 % between the two methodologies, and a lower standard deviation for DFRT demonstrate the higher precision and effectiveness of ISGP in determining the reaction kinetics via Tafel slope analysis. Therefore, using DFRT with the ability to separate Faradaic from non-Faradaic processes to evaluate the relevant part of the effective resistance, reaction kinetics can be estimated, avoiding shortcomings of the classical Tafel method.

MoS2 modified NiFe LDH hierarchical structure as efficient photoanode towards photoelectrochemical water splitting

Designing effective photo electrode for photo-electrochemical (PEC) water splitting is highly demanded yet challengeable because of the limited sunlight utilization and retarded redox reaction kinetics. This work introduces a feasible one-pot hydrothermal strategy of fabricating MoS2/NiFe LDH p-n heterojunctions on conductive porous nickel foam as an efficient photoanode for PEC water splitting. A great enhancement for PEC water oxidation is achieved because of the improved sunlight absorption and the increased photo-excited charge separation. The optimal 10% MoS2/Ni0.9Fe0.1 LDH/nickel foam photoanode demonstrates 3.8 times enhanced PEC activity than the Ni0.9Fe0.1 LDH/NF counterpart and a low Tafel plot of 54 mV dec−1. The bandgap modulation and the Z-scheme charge transfer dynamics due to the formation of MoS2/NiFe LDH p-n heterostructure, along with the high conductivity of porous nickel foam account for the increased photo-current conversion efficiency and the boosted charge transfer.

Microstructural evolution and improved corrosion resistance of NiCrSiFeB coatings prepared by laser cladding

Abstract Inconel 625 (IN 625) is widespread in the manufacturing of critical components such as nuclear reactors, control rods, steam turbines, supercritical boilers, rotary shafts, aerospace engines, etc., that operate in severe harsh environments. However, if the service environments consist of sulphur (fuel tanks), chlorine (supercritical boilers and heavy water plants), H2S, HCl, etc., this alloy will suffer from localized corrosion attacks that minimize its resistance towards corrosion, followed by sudden failure. This study is aimed to facilitate the anti-corrosion characteristics of IN 625 by cladding it with Colmonoy 5 (NiCrSiFeB) alloy particles. The clad microstructure was revealed by micrographs captured by means of optical and field emission scanning electron microscopy followed by the nanoindentation study to analyze the hardness offered. Corrosion testing was carried out on both IN 625 and Colmonoy 5 clad samples at various intervals (0, 13, 27 and 56 h) for interrogating the corrosion behavior in terms of Tafel and impedance plots along with the surface roughness examination using scanning probe microscopy. The results showed that the clad region consists of dendritic microstructure along with the segregation of interdendritic Cr-rich precipitates after solidification. These interdendritic precipitates aid in improving the hardness at the clad region. Moreover, the clad samples have better anti-corrosion characteristics because of the existence of dendritic and interdendritic phases compared to the IN 625 samples in terms of current density, polarization resistance and average surface roughness values.

Nickel and/or platinum modified crystalline silicon–carbon composites and their electrochemical behaviour towards the hydrogen evolution reaction

Generation of hydrogen is very important, as it is one of the most desired alternatives to fossil fuels. Moreover, designing of cheap and stable electrocatalysts is the task for the efficient generation of hydrogen with reasonable activity. Materials hybridization can be considered a tool for engineering different material properties. Composites of modified silicon such as C–Si, Ni/(C–Si), Pt/(C–Si), and Pt–Ni/(C–Si) were prepared (in weight percent) and studied as electrocatalysts for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 solution. The surface morphologies and chemical compositions of the composites were confirmed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), elemental mapping, and BET surface analysis. The electrochemical measurements of linear sweep voltammetry (LSV), Tafel plots, chronoamperometry, and electrochemical impedance spectroscopy (EIS) were used to study the behaviour of the prepared electrodes toward the hydrogen evolution process. Among the various prepared composites, [7%Pt–3%Ni]/[C–Si (1:1)] composite shows the best catalytic activity with the highest HER rate (940.95 µA cm−2 s−1), the lowest overpotential [0.358 V vs. (Ag/AgCl) ≈ 0.161 V vs. (RHE)] at 10 mA cm−2, and the lowest charge transfer resistance (2.657 Ω) compared to other prepared electrodes. In addition, it gives the highest values of 4.219 × 10−3 s−1 turn over frequency (TOF) and 642 mA g−1 mass activity. It shows good stability towards the hydrogen evolution reaction as the current density reaches about 34.28 mA cm−2 after 5 h.Graphical abstract

How to Consider the Interfacial Phenomenon in All‐Solid‐State Batteries? – Quantitative Analysis using µ‐Cavity Electrode

AbstractUnderstanding the intrinsic properties of cathode active particles is required to understand how they depend on the charge transfer resistance at solid–liquid or solid‐solid interfaces. Depth‐of‐discharge (DOD)‐dependent charge transport occurs when lithium ions move from the bulk electrolyte to the cathode active particles. However, composite electrodes consist of unevenly distributed active material, conductive additives, and polymeric binder, which complicates the electron/ion conduction path; hence, estimating the DOD‐dependent charge transfer resistance is difficult. However, micro‐sized spherical cathode active particles can be arranged into a cylindrical cavity trap on a microelectrode to evaluate the interfacial behavior of LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode active particles in liquid and solid electrolyte systems. The electrochemical parameters calculated from the resultant Tafel plot can encourage meaningful discussions and demonstrate the reliability of the measurement technique.

Modification of Pt-Porous Composite Material (Pt-PCM) and Its Application for Electroanalysis of Uric Acid and Electrosynthesis of Acetic Acid from Ethanol

Research on the synthesis of Pt-Porous Composite Material (Pt-PCM) has been done. This material is used for the electrochemical activity of uric acid and electrochemical synthesis of acetic acid from ethanol. Pt-PCM is made by mixing 99.995% platinum powder and PVC or Poly (vinyl chloride) homogeneously with a homogenizer for 3.0 h, plus tetrahydrofuran solvent, and pressed with a strength of 10 tons/cm2. The material produced was analysis using Scanning Electron Microscopy (SEM), voltammetry potential V and Tafel plot. The material is used as an electrode for the determination of uric acid and the synthesis of acetic acid from ethanol. The results showed that Pt-PCM has evenly distributed pores and has a perfect Tafel slope compared to metal platinum or solid platinum. Pt-PCM also has the excellent ability as a working electrode for the analysis of uric acid in human urine and electro synthetic acetic acid from alcohol. In conclusion, Pt-Porous Composite Material (Pt-PCM) is a porous material, so it is excellent as a candidate for electrodes.

The potency of spores and biosurfactant of Bacillus clausii as a new biobased sol-gel coatings for corrosion protection of carbon steel ST 37 in water cooling systems

The structures of water cooling systems are prone to microbially-influenced corrosion (MIC) due to the favorable conditions for microbial growth. Biofilm formation accelerates corrosion, leading to reduced system efficiency, structural damage, and significant financial losses. Encapsulating viable bacterial spores and biosurfactant within a silica-based sol-gel coating offers an eco-friendly approach to prevent this type of corrosion. Bacillus clausii, known for its antimicrobial biosurfactant production capability, was utilized in this study to investigate the impact of spores and biosurfactant addition to silica-based sol-gel coatings in inhibiting biofilm formation and preventing corrosion in water cooling systems. Microbiological analysis of the biofilm was conducted using the total plate count method, while the corrosion process was analyzed through electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The viability of B. clausii spores within the sol-gel matrix was determined to be 20.8 %. The presence of bacterial spores and biosurfactant significantly increased the hydrophobicity of the sol-gel coating. Incorporating spores within the sol-gel matrix delayed biofilm formation for up to 12 days, while biosurfactant addition showed the smallest biofilm abundance (2.23×105 CFU/mL) at its maturation phase compare to others. After 180 days of incubation, analysis of Bode and Tafel plots demonstrated that the sol-gel coating containing biosurfactant maintained excellent anti-corrosion performance, exhibiting an impedance of 104 Ω cm2, Ecorr of -0.398 V vs SCE, and icorr of 0.51 µA/cm2. SEM-EDS analysis of the surface sample revealed a comparably smooth and uniform surface with a minimal abundance of exposed Fe atoms at 0.12 %. In conclusion, this study demonstrated the high potency of the sol-gel coating supplemented with biosurfactant in inhibiting biofilm formation and corrosion on metals in water cooling systems.

Impact of active material ion diffusion coefficient on overpotential in lithium-ion batteries

Simulating battery performance is crucial for effectively developing lithium-ion batteries (LIBs). However, ensuring the accuracy of the input parameters remains a significant challenge. Key parameters of active materials, including the exchange current density and ion diffusion coefficient, mutually affect each other, posing challenges for independent measurement. This study utilized single-particle measurements and battery performance simulations to evaluate the impact of the diffusion coefficient on the exchange current density in LiCoO2, the active material of LIBs. The findings revealed that diffusion coefficients below 10-8 cm2 s−1 influence the Tafel plot, representing the exchange current density. Fitting analysis of the LiCoO2 single-particle measurement by Simcenter Battery Design Studio (BDS) yielded an exchange current density of 6.6 × 10-4 A cm−2, a diffusion coefficient of 5.9 × 10-11 cm2 s−1, and a charge transfer coefficient of 0.55.