Electrochemical Impedance Studies Research Articles

Enhanced anti-corrosion characteristics of epoxy-functionalized graphene oxide nanocomposite coatings on mild steel substrates

This experimental investigation focused on coating of functionalized graphene oxide (FGO) on the mild steel to minimize corrosion, using a new method. Prior to the coating, the fundamental chemical and morphological structures of FGO were studied with aid of some characterization techniques: X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Various epoxy/FGO coating formulations with 10, 20, 30, 40 and 50 ppm of FGO were prepared and coated on the mild steel substrate, adopting dip coating method. Immersion test was carried out to observe the corrosion inhibition efficiency of the graphene. The adsorption isothermal behavior was also studied using various models and compared with the data obtained from the experimental results. From the results obtained, the formation of irregular rough patches and separation of platelets like zebra lines indicated the formation of graphene nanoparticles, as observed through morphological analysis. The occurrence of sharp peak at 24.3° in the XRD pattern depicted the existence of graphene in nanoscale. Electrochemical impedance (EI) and potentiodynamic polarization (PP) studies reported the maximum corrosion inhibition efficiency of 87% at 50 ppm concentration of epoxy/FGO. It was evident that an increasing concentration of graphene exhibited significant corrosion resistance in both studies. The bonding energy of randomly oriented graphene platelets reduced the removal of metal, delaying the crack propagation in tortuous path on the coated surface. These results established the significance and applicability of this study in various relevant industries.

Sodium salt of dodecyl benzene sulphonic acid as an effective corrosion inhibition for different heat-treated steel in sulphuric acid medium

Abstract The purpose of this work is to use electrochemical and gravimetric techniques to investigate the inhibition of DBSS on the corrosion of heat-treated dual-phase AISI 1040 steel in a 0.5 M sulphuric acid solution at 35 °C. The corrosion studies are performed by potentiodynamic polarization study (PDP), electrochemical impedance study (EIS), and gravimetric method. To confirm the inhibition surface characterization like x-ray diffraction technique (XRD) analysis, scanning electron microscopy (SEM), and EDS analysis are performed. Depending on the phase change of metals due to heat treatment, the corrosion inhibition of the heat-treated metal increased when it was exposed to 0.5 M H2SO4 at 35 °C in the presence of dodecyl benzene sulphonic acid sodium salt (DBSS) inhibitor. The highest inhibition efficiency of 63 %, 82 %, 87 %, 43 %, and 63 % was obtained for AISI 1040 steel at heat treatment conditions of Normalized, Quenched at 700 °C, Quenched at 750 °C, Quenched at 790 °C and Quenched at 900 °C respectively. In the gravimetric and electrochemical study, the IE increases with the increase with the concentration of DBSS unto 75 % from gravimetric analysis and 87 % from PDP analysis for Quenched at 750 °C and 790 °C respectively. The metal protection is achieved by heat treatment process as well as by using DBSS as inhibitor. Corrosion inhibition on the metal's surface was confirmed by SEM and XRD. In addition, the adsorption of DBSS on the anodic and cathodic sites of the metal surface was well explained.

Treatment of Se-Impacted Wastewater Using a Three-Dimensional Packed Bed Electrochemical Reactor

Selenium is an essential element for flora and fauna in trace amounts. It plays a crucial role in bolstering photosynthesis and facilitating thyroid hormone metabolism. However, excessive consumption of selenium can result in health concerns such as reproductive complications and cancer. Selenium usually coexists with minerals such as copper and coal in the natural environment. The associated activities, such as copper mining and coal combustion, have greatly accelerated the mobilization of selenium. The selenium released through coal combustion is mostly captured in the flue gas desulfurization (FGD) wastewater as inorganic selenite and selenate.Our lab previously validated the viability of direct electrochemical reduction (SeDER) to remove dissolved selenite from a simplified FGD water matrix using planar gold and graphite cathodes, where more than 94% of the aqueous selenite can be converted to elemental Se(0) deposited on the cathode surface. Graphite is eventually selected for its low material cost, decent removal performance, and minimum secondary pollution as compared to gold and other non-noble metal cathodes. This direct electrochemical deposition process provides many benefits that existing biological and indirect electrochemical methods lack, such as zero chemical addition and low to zero solid generation. However, this method is only suitable for wastewater with elevated temperatures necessary to generate conductive Se(0) for continuous reduction. The inclusion of a heating process adds complexity to the design, impeding the scalability of the SeDER system. Furthermore, the application of SeDER is constrained to Se-impacted wastewater with an elevated temperature.In this study, we propose a novel reactor design utilizing electrochemical reduction to treat Se-impacted wastewater at ambient temperature. The electrodes we used are made of graphite for the reasoning stated above. The reactor consists of a pair of planar graphite anode and cathode, and the inner chamber is filled with cylindrical graphite particle electrodes (PEs) separated by a nylon spacer to create an anodic chamber and a cathodic chamber. The PEs act as an extension of the planar electrodes, which offers numerous reaction sites and minimizes the travel distance for selenite ions to reach the electrode surface. In our 120-mL batch test with 0.1-mM selenite in 100-mM phosphate buffer, the exact system without filler removed 0% selenite at room temperature, while the filled 3D system removed on average 50% of the selenite in 3 hours. Using the same 3D system, we then investigated performance enhancement with a recirculating operation. The total working volume is fixed at 200 mL, while the flow rate and the applied voltage vary. The flow rate is set at the values with hydraulic retention time (HRT) fixed at 15 min, 30 min, and 60 min. The system-applied voltage is set at -1.9V (just enough for selenite reduction), -2.1V, and -2.3V. We found that the shortest HRT combined with -2.1V system applied voltage yielded the highest selenite removal performance in all tests, with an average of 47% removal in 3 hours. We hypothesized that the shorter HRT provides a faster flow rate that refreshes the PE’s surface from insulative Se(0) deposition, which provides sustainable reaction sites for the incoming selenite. At -2.1V, the potential is negative enough to allow selenite reduction while fewer parasitic reactions (e.g., hydrogen evolution reaction) occur compared to that under -2.3V.With the selected system voltage and flow rate, we eventually explored competing ion behavior and switched from a simplified water matrix to simulated Se-impacted wastewater. We found that of all the commonly found competing ions (i.e., sulfate, nitrate, and chloride), chloride significantly impacts selenite removal, with performance dropping to 10% removal in 3 hours. Nitrate slightly decreased the selenite removal, with an average Se removal performance of 23%. Sulfate, on the other hand, resulted in an increase in selenite removal after addition. We hypothesize that a high sulfate concentration in simulated wastewater could help alleviate the repulsing force from the cathode surface for the selenite ions. The double layer of the PEs could also be compressed by the high ionic strength, which decreases the capacitance and promotes selenite reduction. To confirm this hypothesis, we conducted an electrochemical impedance study to analyze the effect of competing ions on reaction kinetics and capacitance. We also performed surface analysis for the wasted planar electrodes and PEs to investigate the change in morphology and observed possible chemical residue. These characterizations will help us develop a regeneration protocol in long-term operation and help us scale up our prototype to manage actual Se-impacted wastewater.

Excellent corrosion inhibition efficiency of Catharanthus roseus (Nayantara or Sadabahar) leaf aqueous extract on mild steel in chloride-contaminated solutions at different pH

The efficacy of Catharanthus roseus (Nayantara or Sadabahar) leaf extract as a green corrosion inhibitor for mild steel in chloride-contaminated environments has been investigated in the present work. This study has employed a straightforward, practical, and less expensive Maceration process to prepare leaf extract. The adaptability of the extract as a corrosion inhibitor has been evaluated through electrochemical polarization and impedance studies in chloride-contaminated environments with varying pH levels. In addition, long-term corrosion monitoring has been conducted to evaluate the sustainability of the inhibitor against chloride-induced corrosion at a neutral pH level. This novel study has revealed that the extract defends mild steel against chloride assaults better at pH 2 than it does in neutral or alkaline conditions. Moreover, electrochemical studies and subsequent characterizations have confirmed the film-forming nature of the inhibitor.

Exploring Mixed Ionic-Electronic-Conducting PVA/PEDOT:PSS Hydrogels as Channel Materials for Organic Electrochemical Transistors.

Here, we report the preparation and evaluation of PVA/PEDOT:PSS-conducting hydrogels working as channel materials for OECT applications, focusing on the understanding of their charge transport and transfer properties. Our conducting hydrogels are based on crosslinked PVA with PEDOT:PSS interacting via hydrogen bonding and exhibit an excellent swelling ratio of ~180-200% w/w. Our electrochemical impedance studies indicate that the charge transport and transfer processes at the channel material based on conducting hydrogels are not trivial compared to conducting polymeric films. The most relevant feature is that the ionic transport through the swollen hydrogel is clearly different from the transport through the solution, and the charge transfer and diffusion processes govern the low-frequency regime. In addition, we have performed in operando Raman spectroscopy analyses in the OECT devices supported by first-principle computational simulations corroborating the doping/de-doping processes under different applied gate voltages. The maximum transconductance (gm~1.05 μS) and maximum volumetric capacitance (C*~2.3 F.cm-3) values indicate that these conducting hydrogels can be promising candidates as channel materials for OECT devices.

Ultra-sensitive electrochemical detection of levofloxacin using a binder-free copper and graphene composite

Given the levels of pollution in the aquatic environment and the development of antimicrobial resistance, it is essential to develop sensors, with sensitivity, selectivity, stability, and cost-effectiveness, for the determination of antibiotics. The present article highlights the fabrication of an ultra-sensitive graphene and copper sensor, Gr/Cu, supported on glassy carbon (GCE/Gr/Cu) for the electroanalysis of levofloxacin through a cost-effective electrodeposition method. The sequential electrodeposition of graphene and Cu was optimised to give GCE/Gr/Cu, with the Cu particles well dispersed on the graphene sheets. The composite exhibited very good conducting properties as evidenced from electrochemical impedance studies. Using cyclic voltammetry, an impressive sensitivity of 19.7 μA μM−1 cm−2 was achieved with a detection limit of 11.86 nM, providing a promising electrocatalytic material for the determination of this antibiotic. Moreover, good selectivity was observed in the presence of various ions typically found in water and other drug molecules, while very good stability exceeding a 21-day period was achieved, and recovery values between 97.7 and 103.8 % were obtained in tap water.

Electrochemically polymerized dopamine activated carbon paste sensor for selective and sensitive detection of rutin in the presence of riboflavin

In this work, a sensor was developed for the quantification of RT in food and medicine samples using electro-polymerization of dopamine (DA) on the surface of a carbon paste electrode in 0.2 M phosphate buffered saline (PBS) of 7.0 pH by cyclic voltammetry (CV). The surface properties of bare carbon paste electrode (BCPE) and poly (DA) modified carbon paste electrode (PDAMCPE) were studied using scanning electron microscopy (SEM), electrochemical impedance study (EIS), and CV techniques. Two electron two proton transfer process was seen during the electrochemical reaction of RT with adsorption-controlled process. Under optimum conditions, the peak current increased linearly with an increase in RT concentration for CV in the range of 0.4 to 2.0 μM and differential pulse voltammetry (DPV) in the range of 0.4 to 2.5 μM and the limit of detection (LOD) was found to be 0.0045 μΜ and for CV and 0.079 μM for DPV techniques respectively. Even in the presence of some interferents like organic compounds and metal ions, the developed electrode exhibits good anti-interference ability for RT, and good selectivity was obtained for RT in the presence of riboflavin (RF). The developed sensor presents good stability, repeatability, and reproducibility. The CV measurement was performed for the analysis of RT in real samples such as green tea and medicine samples which showed a good recovery and this work has been not reported previously.

From trash to treasure: Cattle manure as a potent green corrosion inhibitor

The novelty of this study attributes establishing cattle manure as a potent and sustainable green corrosion inhibitor and identifying organic compounds accountable for the same. A simple and convenient maceration method was used for the extraction of a novel, eco-friendly, low-cost, efficient, and water-soluble green corrosion inhibitor from cattle manure. The inhibitor has been characterized through different spectroscopic, spectrometric, and chemical confirmatory tests. The efficacy of the cattle manure extract (CME) in mitigating chloride-induced corrosion on mild steel was evaluated through electrochemical impedance and polarization studies at ambient conditions. Electrochemical corrosion monitoring revealed the sustainability of CME as a highly efficient inhibitor from a low-cost agricultural biowaste. Post-corrosion characterizations demonstrated the substantial film-forming characteristics of the CME. Mass spectrometry of the corrosion products assisted in identifying the phytochemicals contributing significantly to the film formation. This study defines an ecological route for agricultural solid waste management.

Improved cycle stability and high-rate capability of LiNbO3-coated Li3VO4 as anode material for lithium-ion battery

Lithium vanadate (Li3VO4) has garnered considerable attention as an alternative negative electrode material for non-aqueous lithium-ion batteries due to its high capacity, energy efficiency, and stable discharge voltage. Nonetheless, the Li3VO4 material displays a low rate capability, attributed mainly to its poor intrinsic electronic conductivity. Here, we report the synthesis of lithium niobate LiNbO3-coated Li3VO4 (LVO@LNO) using a one-pot sol-gel method. The resulting LVO@LNO demonstrates a high reversible capacity of approximately 530 mAh/g, which is more than double that of free Li3VO4. To explore the effect of the LNO coating process on the morphological and structural properties, Raman, XRD, operando XRD, XPS, SEM and HTEM analyses were conducted. To explain the enhancement of electronic conductivity in our modified material after a LiNbO3 coating, we conducted an Ex-Situ electrochemical impedance (EIS) and Density Functional Theory (DFT) computational study. Additionally, we designed a full cell utilizing a 1 wt% LNO-coated LVO anode and NMC-811 cathode. The cell yielded an output voltage of approximately 2.8 V with a high initial specific capacity of 350 mAh/g versus to the anode, at 1C with a capacity retention of 85 % after 100 cycles.

Functionalized borosilicate-silica-epoxy nanocomposite superhydrophobic coating for corrosion inhibition under harsh environment

Current work proposes a facile scheme for fabrication of robust superhydrophobic borosilicate-silica-epoxy nanocomposite coatings on steel substrate with hierarchical structures, capable of inhibiting corrosion under harsh environment. The scheme amalgamates the advantageous properties of three ingredients: acid resistant property of borosilicate glass, superhydrophobic features of functionalized silica nanoparticles and durability of epoxy resin. The various steps of synthesis include 1. ball milling of borosilicate glass to micron and submicron size (~500 nm to 1.5 μm) 2. grafting of silica nanoparticles (~20 nm, through stober method) on the borosilicate particles to form rough hierarchical structure and 3. preparation of stable dispersion of the nanoparticles in epoxy-based resin followed by coating through immersion technique. Efficacy of the scheme was established through morphological, durability and electrochemical impedance studies. The surface morphology revealed hierarchical structures of functionalized silica nanoparticles (size range 20–100 nm) grafted on micro-sized borosilicate particles, which sustained water droplets with contact angle as high as 164.5° ± 2°. Sandpaper abrasion test proved excellent durability retaining hydrophobicity up to 250 abrasion cycles. The prepared surface maintained notable interface stability under aggressive environment: 3 and 10 days under pH 1 and 13 respectively. The electrochemical study in 3.5 wt% NaCl aqueous solution showed significant decrease in corrosion current density of coated surface (0.3585 μA/cm2) compared to uncoated surface (43.918 μA/cm2) suggesting excellent corrosion resistance. The results highlight scope of using this robust coating for abrasive and harsh environment.

Synthesis and characterization of Mo-doped PbS thin films for enhancing the photocatalytic hydrogen production

Photocatalytic hydrogen production has gained considerable attention as a sustainable method for renewable energy production. Lead sulfide (PbS) compound has significant reserves and a suitable bandgap for the production of hydrogen gas via the water photo-splitting process. However, the charge recombination effect of the charge carriers severely limits their potential use in solar water splitting. Herein, the photoelectrodes of PbS were fabricated through the chemical bath deposition method and then doped with different Mo concentrations to optimize the hydrogen photo-production activity. Both structural and performance characterizations of the photoelectrodes have been carried out using various characterization techniques. The photoelectrochemical (PEC) performance of molybdenum (Mo)-doped PbS photoelectrodes exhibits a significant increase in the photocurrent density with the optimum photocurrent density of 1.2 mA/cm2 obtained at 0.8 % Mo doping atomic ratio which was twelve times higher than that of a pure PbS photoelectrode. The doping of Mo induces the electron-hole separation yield which results in improved electron transport characteristics. The Mo doping was as act as a donor site that increased the PbS film conductivity. The newly optimized Mo–PbS was used as a promising photoelectrode supported on commercial glass using the optimum Mo-doped PbS photoelectrode, the photoelectrochemical (PEC) hydrogen production rate was reached 122 μmol/h cm2 during the solar water splitting process and the conversion efficiency of the incident photon-to-current (IPCE) value was 7.0 % at 390 nm monochromatic exposure. Moreover, the stability of the optimum electrode was evaluated as a function of the number of runs and exposure time in addition to the electrochemical impedance study.

Electrochemical impedance study of corrosion of pure Ni, Fe, Cr, and Fe‐5Cr alloy in molten nitrides

AbstractMolten nitrates or nitrate–nitrite mixtures have been used as heat transfer fluid as well as thermal energy storage medium in concentrated solar power plants and other industrial applications. However, containment materials in contact with these molten salts are subjected to molten salt corrosion, which has been a concern over the years. In this investigation, the corrosion behavior of pure Ni, Fe, Cr, and Fe‐5Cr alloy (in weight percent) has been examined at 400°C in molten nitrates using electrochemical impedance spectroscopy and gravimetric tests. It is shown that Ni, Fe, and Fe‐5Cr exhibit mass gain, with the best corrosion resistance for Ni followed by Fe‐5Cr and Fe, while pure Cr goes through fast dissolution, forming hexavalent chromium product K3Na(CrO4)2. The increase of salt basicity from Solar Salt to Hitec could accelerate the dissolution of Cr. Nevertheless, the formation of an inner Cr‐containing scale could still offer the alloy good protection because the external insoluble Ni or Fe oxides can protect it from dissolution.

An electrochemical impedance study to analyse the phase transformation pattern and stability during electro-crystallization of CIGS photo-voltaic thin films

In this study, an effort has been made to gain a thorough knowledge of the phase transformation mechanism of quaternary thin films Cu (In, Ga) Se2 on FTO-glass substrates through electrochemical impedance spectroscopy (EIS). Here, a methodical strategy that starts with the investigation of unitary (Cu, Se, In and Ga), binary (Cu-In, Cu-Se, Cu-Ga, In-Se, In-Ga, and Se-Ga), tertiary (Cu-In-Se, Cu-In-Ga, In-Se-Ga, and Cu-Se-Ga), and finally quaternary (Cu-In-Ga-Se) deposition has been put forward. CuCl2, H2SeO4, InCl3, and GaCl3 were the salts utilized, and their combinations for each stage of deposition. The information obtained from EIS i.e., solution resistance (Rs), double layer capacitance (Cdl), charge transfer resistance (Rct), film resistances (Rfilm), and film capacitances (Cfilm) were used to find the mechanism. For unitary baths, Cu has the highest Rct and high Cdl under the optimized concentration. Binary baths further explained that Se-Ga and In-Ga can be used to perform one stage of deposition considering the low Rct and moderate Cdl. The tertiary bath combinations favored CIS as one stage of deposition in a similar manner (i.e., low Rct and Cdl). While using the quaternary bath, Rct and Cdl were found to have values of 483.6 Ω.cm2 and 285.78 µF/cm2. From the impedance pattern, it was deduced that the deposition takes place in two layers i.e., CIS and CGS tertiary films which eventually give the quaternary composition. Further, the stability of the films was also evaluated in the Na2SO4 solution, the CIGS film is found to be sufficiently stable.

Highly Exposed MoS2 Nanosheets Grown Under pH Modulated Non-Equilibrium Hydrothermal Route and Its Electrocatalytic Hydrogen Evolution Performance

: Molybdenum disulfide (MoS2) has emerged as a highly potential noble metal-free electrocatalyst for the Hydrogen Evolution Reaction (HER). However, edge sites of MoS2 created by sulphur non-stoichiometry play a prominent role in influencing the HER activity. In this work we adopt a simple hydrothermal route under a non-equilibrium condition with in-situ pH modulation, to synthesize its highly exposed edge sites MoS2 which have not been reported so far, and study the variation of its physio-chemical properties that enable an efficient electrocatalytic activity. Electrochemical measurements and impedance studies are conducted to understand harmonic morphology, and structural and composition variation, which were responsible for the activity. Additionally, the Density Functional Theory is adopted to support the enhanced hydrogen absorption and desorption processes in synchronous with various non-stoichiometric structures.

Nitrogen doped biomass derived carbon and BiVO4 composite for simultaneous detection of furazolidone and chloramphenicol

An efficient electrochemical sensor based on nitrogen functionalized biochar (N-BC) and BiVO4 hybrid nanocomposites was prepared, and used for simultaneous detection of furazolidone (FZD) and chloramphenicol (CAP) with highly sensitive and selective in food sample. The N-BC was obtained by acid activation method which using biomass waste (rice halls) as the raw and processed material and urea as the nitrogen source, which was further mixed with BiVO4 to synthesized N-BC/BiVO4 composite. The surface morphology and structured properties were characterized by Scanning electron microscopic (SEM), Nitrogen (N2) adsorption/desorption isotherms, X-ray powder diffraction (XRD) patterns, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry (CV) and electrochemical impedance studies of N-BC/BiVO4 film on GCE showed that electron transfer rate in [Fe (CN)6]3−/4− solution was rapider than bare GCE, N-BC/GCE and BiVO4/GCE. The sensor was successfully used for the detection of FZD and CAP with wide linear ranges of 0.1–1600 μM for FZD and 0.1–3200 μM for CAP, low limit of detection of 0.053 μM for FZD and 0.087 μM for CAP (S/N = 3), respectively. In addition, the proposed sensor has shown good anti-interference ability, reproducibility and stability, and obtained satisfactory results for respective or simultaneous detection of FZD and CAP in milk sample.

Experimental and theoretical investigation of spiro heterocyclic compound as potential inhibitor for mild steel in acid media

The corrosion inhibition performance of spiropyrazoline was explored for mild steel corrosion in 1M HCl and 0.5M H2SO4 using weight loss, potentiodynamic polarization and electrochemical impedance studies. Inhibition efficiency of the inhibitor increased with increase in concentration within the range of 1–9 ppm. Spiropyrazoline inhibitor showed better inhibition performance of 92.6 %, 97.7 % in 1 M HCl and 0.5 M H2SO4, respectively at 9 ppm concentration by forming protective film on the metallic surface. Electrochemical impedance spectroscopy analysis (EIS) revealed an increase in polarization resistance due to the adsorbed inhibitor molecules. Potentiodynamic polarization analysis reveals that spiropyrazoline behaved as a mixed type inhibitor. The adsorption of the inhibitor on the metal surface found to obeying Langmuir and Temkin adsorption isotherm at room temperature. Surface morphology of the protective layer was examined by FTIR, scanning electron microscopy and atomic force microscopy. The inhibition mechanism of the inhibitor molecule was proposed in the light of the quantum chemical calculations using DFT.

Titanium-embedded nanocomposite material stimulates ion-exchange characteristics to deal with toxic heavy metal pollutants in aquatic environment

ABSTRACT Nano-sized composite ion-exchanger can be applied as an electrochemically switchable ion-exchanger for waste water treatment, especially in the separation of heavy metal ions from the polluted aquatic system. Advanced polyaniline/Ti(IV) iodomolybdate nanocomposite ion-exchanger have been synthesized by in-situ chemical oxidation polymerization shows better ion-exchange capacity than individual inorganic counterpart. The physico-chemical characterization was done by FT-IR, XRD, simultaneous TGA-DTA, SEM, HR-TEM and electrochemical impedance studies. According to impedance/dielectrical study, it has high resistivity in the low-frequency region. The distribution studies and binary separation revealed that the ion-exchange material is highly selective for Pb2+, which is a most important environmental pollutant. Thus, PANI/TIM nanocomposite ion-exchanger can be used for Pb(II) ion-selective membrane for the treatment of aquatic pollutants in future.

Cyperus pangorei porous carbon electrodes for the sustainable symmetric supercapacitor application

AbstractEfficiently addressing natural biowaste has the potential to effectively mitigate pressing environmental concerns. Given the growing demand for energy, it is imperative to identify a safe and environmentally friendly method for producing biowaste‐based porous carbon (PC). Biowaste serves valuable carbon sources for the cost‐effective production of efficient PC materials. In this study, we focus on ongoing research aimed at converting a small‐scale industrial waste of Cyperus pangorei, into PC. To achieve this, we employed a simple and eco‐friendly approach, optimizing the process at four different temperatures to enhance its suitability for supercapacitor applications. By subjecting the Cyperus pangorei waste to a two‐step chemical activation process using potassium hydroxide (KOH) at 800°C (referred to as CPC8), we obtained a PCs with a well‐defined pore matrix, exhibiting a surface area of 711.2 m2g−1. The resulting PC exhibited 194.6 Fg−1 (0.5 Ag−1) of specific capacitance when tested in a 1 M Na2SO4 aqueous electrolyte. The galvanostatic study demonstrated remarkable 88.5 Whkg−1 of energy density at 1.7 kWkg−1 power density, along with a capacitance retention rate of 97.9% at 5000th cycle (8 Ag−1). Furthermore, electrochemical impedance study revealed 0.053 Ω of internal resistance, indicating enhanced ionic diffusion. Based on the excellent performance characteristics exhibited by CPC8, its practical application in supercapacitors holds great promise.

Recycled eggshell waste in zinc-rich epoxy coating for corrosion protection of mild steel in a controlled elevated temperature saline environment

Eggshell wastes have attracted interest in the fabrication of anticorrosion coatings due to chemical compositions (high calcite content) and widespread availability. This study presents the use of chemically and thermally treated eggshell nanoparticles as fillers in a zinc-rich epoxy matrix in corrosion protection of mild steel in sodium chloride solution at an elevated temperature. Three samples of zinc-rich coatings containing “as ball-milled” eggshell, chemically and thermally treated eggshell nanoparticles were fabricated to form zinc-rich eggshell nanoparticles epoxy (ZENE) coatings. The structural characterizations indicated that chemical and thermal treatment removed the protein materials from eggshell nanoparticles, leading to a 10-fold increase in electrical conductivities and prolonged the cathodic sacrificial behaviour of the ZENE coatings throughout the immersion period. The electrochemical impedance study of these coatings after immersion in an elevated-temperature corrosive environment showed that chemically-treated eggshells in comparison with thermally-treated ones could effectively remove protein materials from the eggshell nanoparticles. These nanoparticles as fillers in the zinc-epoxy matrix significantly enhanced the anticorrosion performance by improving the cathodic as well as barrier protection properties of the coating. A proposed corrosion protection mechanism of the ZENE coatings in 3.5 wt% NaCl solution revealed that the improved electrical conductivity of the treated eggshell nanoparticles enhanced the galvanic contact at the interstitial spaces between the zinc particles while prolonging the zinc cathodic sacrificial behaviour. Thus, this study demonstrated the sustainable use of eggshell wastes in enhancing the anticorrosion properties of zinc-rich epoxy coatings.

Copper coordination polymer with lattice water molecules and strong electrocatalytic OER activity

The versatility of organic ligand and metal coordination geometry produced coordination polymer with intriguing network structure and exciting functional properties. Herein, we have synthesized a copper coordination polymer (Cu-HS) using an amino acid based multidentate ligand and explored its electrocatalytic OER activity in alkaline condition. Single crystal structural studies showed the formation of 1D coordination network structure and inclusion of lattice water. Copper ions in Cu-HS displayed octahedral and square pyramidal coordination geometry. Electrocatalytic OER studies in alkaline medium showed strongly enhanced activity for Cu-HS polymer that required an overpotential of 273 mV to achieve the benchmark current density of 10 mA/cm2. Tafel slope analysis and electrochemical impedance studies suggested faster reaction kinetics at the electrode surface modified using Cu-HS. After catalysis, XPS and FTIR spectra of Cu-HS suggested the conversion to metal oxide during the electrocatalysis.