EIS Investigations Research Articles

The Effect of Calcium and Iron (III) Oxides on Lead Spent Plates: Spectroscopic, Voltametric, and EIS Investigations.

In this study, xCaO‧5Fe2O3‧(95-x)Pb glasses and vitroceramics containing various concentrations of calcium ions (from 0 to 50 mol% CaO) were prepared using the spent anodic plate of a car battery. X-ray diffraction analysis revealed changes in the network structure as a function of CaO content. The intensities of the IR bands due to the sulfate and sulfite units were lowered, indicating a decrease in the sulfurization degree within the lead network. In the UV-vis spectra, the presence of electronic transitions of the Fe3+, Pb2+, and Fe2+ ions were identified. The EPR spectra were characterized by resonance signals centered at about g ~ 2 and 4.3, corresponding to the trivalent iron ions. For the samples with 5 ≤ x ≤ 12, the signals decreased abruptly, suggesting a Fe3+→Fe2+ interconversion and the formation of the Fe3O4 crystalline phase. A considerable increase in the intensity of the signal centered around g ~ 2 was observed as the CaO concentration increased to 30% in the host matrix. Our results confirm that the higher CaO levels of 3 mol% are responsible for the increase in the radius of curvature of the semicircle arcs in the EIS plots and the decrease in their conductivity.

Synthesis of graphitic carbon nitride (g-C3N4) by high-temperature condensation for electrochemical evaluation of dichlorophen and thymol in environmental trials

The work deals with synthesizing carbon-based nanomaterial, i.e., graphitic carbon nitride, which was carried out using the high-temperature condensation method. Graphitic carbon nitride is characterized by cost efficiency, increased thermal resilience, a two-dimensional molecular layer structure, biocompatibility and stability. These properties can be used in the electrochemical investigations of fungicides such as dichlorophen and thymol. The synthesized nanomaterial was first characterized using XRD, SEM, UV-DRS, BET, FTIR, CV and EIS investigations. The cyclic voltammetry behavior of dichlorophen and thymol shows the proton-coupled irreversible electron transfer process at a modified carbon paste electrode with the participation of same number of protons and electrons. The developed sensor exhibited good detection limits for the dichlorophen and thymol as low as 15.3 nM and 12.0 nM with the sensitivity of 126.8 µA·µM−1·cm−2 and 59.2 µA·µM−1·cm−2, respectively. The applicability of the developed sensor was tested in spiked soil and water samples, and good recoveries were achieved with a% RSD of 1.67 and 1.30, respectively. The anti-interference responses to metal ions demonstrate the selectivity (qualitative) of the developed sensor in the electrochemical detection of dichlorophen and thymol. In the future, the sensor developed would offer the potential to sensitively and selectively detect other pesticide molecules in environmental samples.

Improvement of the anti-corrosion ability of a silane film with β-cyclodextrin-based nanocontainer loaded with L-histidine: Coupled experimental and simulations studies

Recently, due to the chromate and phosphate compounds toxicity and environmental harsh effects, green inhibitors were introduced. Besides, the biocompatible nano-containers were utilized for encapsulating active green inhibitors. In the present research, the β-cyclodextrin, which is a biocompatible/supramolecular type nanocontainer with a high encapsulating capacity of inhibitor, was loaded with the green L-histidine (L-His) amino acid. The inclusion complexes were characterized via different characteristic methods (i.e., XRD, Raman, FT-IR, UV–vis, and TGA), and the particles' morphology was visualized by FE-SEM. The protection performance of the synthesized particles in the solution phase was investigated by EIS/Tafel methods, and the protected substrates were investigated elementally/morphologically via various approaches (i.e., GIXRD, EDS/Mapping, contact angle, and FE-SEM). Evaluation of the β-CD-L-His loaded silane composite coating active inhibition ability was done by the EIS investigations (over the defected composite), and the derived results confirmed the resistance increment from 5540 Ω. cm2 to 12,101 Ω. cm2, approving the desirable active inhibition ability of the designed thin organic-inorganic composite layer. For better evaluation, the defect structure was displayed by FE-SEM and EDS/Mapping microscopies. The excellent durable passive behavior of the inclusion complexes in the intact SiC was depicted by EIS measurements. Besides, the scratched composite coating resistance enhancement (from 13,032 Ω. cm2 to 23,485 Ω. cm2) demonstrated the β-CD-L-His filled SiC coating's excellent active inhibition capacity. Alongside the abovementioned experiments, new fundamental insights concerning the histidine loading capacity, and electronic aspects/adsorption attributes of histidine and histidine/β-CD-based complexes over the target adsorbent were elucidated choosing DFT-D and molecular simulations tools working at electronic/atomic levels.

Morpho-structural and electrical characterization of Bi-doped apatite-type lanthanum silicates prepared by gel-combustion

La10−xBix(SiO4)6O3 ceramics (x = 0; 0.1; 0.15; 0.2; 0.3) were obtained from precursors prepared by gel combustion using l-aspartic acid as fuel. This study presents the effect of Bi3+ doping level and sintering temperature on the morpho-structural and electrical properties of apatites. Processes involved in the apatite formation same as crystallization temperature were examined through TGA. The XRD patterns have showed that all samples adopt the apatite structure and crystallize in the hexagonal space group P-3(147). Samples crystallite size varies between ~ 58 and ~ 118 nm depending on the Bi3+ doping level and the sintering temperature. In order to explain the conduction in apatite, the preferential position of Bi3+ in lattice and the occupancy factors of O5, O6 were calculated by Rietveld refinement. ICP-OES and XPS measurements give the bismuth amount accommodated in apatite lattice and its oxidation states. The morphology, homogeneity and compactness of the ceramics at different Bi doping level were examined through SEM. The relative density of the material is enhanced by the sintering temperature up to 1500 °C, reaching 91.63% for sample doped with 1.5% Bi. Through EIS investigations, the conductivities at 500 °C, for sample doped with 1.5% Bi, are: 9.22 × 10−5 Scm−1 (sintered at 1400 °C) and 1.02 × 10−3 Scm−1 (sintered at 1500 °C), respectively, values which are higher than that of un-doped apatite (6.46 × 10−5 Scm−1).

Vanadium-doped TiO2-B/anatase mesoporous nanotubes with improved rate and cycle performance for rechargeable lithium and sodium batteries

TiO2-B/anatase nanotubes doped by vanadium have been synthesized through a facile one-step hydrothermal reaction. The material shows a mesoporous structure with a specific surface area of 179.1 m2 g−1. XPS data presume the presence of V3+, V4+, V5+, and Ti3+ in doped TiO2-B/anatase. As found by XRD and EIS investigations, the vanadium expands bronze titania crystal structure and enhances the conductivity of material by three orders of magnitude. When tested for lithium storage, the V-modified titania nanotubes show a specific capacity of 133 mA h g–1 after 100 charge/discharge cycles at the current density of 3000 mA g–1 with a Coulombic efficiency of around 98.9%, resulting in its good cycleability. The material still possesses a reversible capacity of 114 mA h g–1 at a very high current load of 6000 mA g–1, demonstrating superior rate characteristics for secondary lithium batteries. Furthermore, V-doped TiO2-B/anatase mesoporous nanotubes show promise performance as anode material for sodium-ion batteries, delivering about 119 mA h g–1 and 101 mA h g–1 at the current loads of 10 and 1500 mA g–1, respectively.

Probing molecular adsorption/interactions and anti-corrosion performance of poppy extract in acidic environments

Abstract In recent years, environmental regulations have forced the researchers to gradually replace the traditional toxic inhibitors with the green/sustainable products based on the plant sources, ion liquids, and biopolymers (such as alginate, chitosan, and Polydopamine). Application of the green inhibitors based on the extracts of the plants in the acidic solution has been found to be the most feasible and cost-effective way for the metals corrosion mitigation. However, most of the plant-based inhibitors are not as efficient as the synthetic inhibitors like bio-polymers due to the presence of so many in-active components in their extracts. Here, we introduce the most powerful plant-based inhibitors extracted from the Papaver somniferum leaves/stems (called poppy) which are rich in some well-known bio-active medicines such as codeine, morphine, noscapine, oripavine, papaverine, thebaine which are full of Nitrogen-based functionalities. This study aims at studying the impact of Papaver somniferum (known as poppy) leaves and stems extract (PSLSE) addition to the 1 M HCl solution in which the mild steel is immersed. Surface characterizations including FE-SEM, EDX, AFM, CA measurements, FT-IR, 1 GIXRD, 2 UV–Vis 3 spectroscopy were carried out. The inhibition potent of the extract was reviewed by EIS 4 and PDS. 5 Moreover, to explore the adsorption action of the poppy extract on the metal surface, the theoretical simulations based on the Monte Carlo (MC), molecular dynamics (MD) and density functional theory (DFT) were done. Surface characterizations proved the inhibitor adsorption on the metallic surface beside the formation of protective complexes such as ternary iron cyanide. EIS investigations indicated the excellent protection provided by PSLSE addition. The magnificent inhibition of around 97.64% was reached in the 600 ppm and 1000 ppm PSLSE samples. A mixed-type action with a dominant performance on the cathodic inhibition was observed. The simulation studies supported the successful interfacial adsorption of inhibitive compounds over the surface.

Core-shell type Tourmaline@ZnO composites equipped with carbon dots for high efficiency photocatalyst

Here we report that a novel type of Tourmaline@ZnO core-shell composite equipped with carbon dots (CDs) as multi-band light active sensitizer has been successfully designed and efficiently ultilized as the superior photocatalyst towards the degradation of methyl orange (MO) under Xenon lamp at room temperature. The bare ZnO, CDs/ZnO, Tourmaline@ZnO and CDs/Tourmaline@ZnO were systemically synthesized following the facile homogeneous precipitation process and characterized in detail by XRD, FTIR, FESEM, HRTEM, UV-Vis, PL, PC and EIS investigations in succession. Bare ZnO displays as 3-dimensional hierarchical nano-flowers with large specific surface area reaching up to 62.049 m2/g by BET measurement, while the other composite products confirm the core-shell structures with CDs inlaying on ZnO layer surfaces. The photocatalytic activities of the polynary hybridations obtain effective enhancements compared to pure ZnO, the ternary system (CDs/Tourmaline@ZnO) deserves more attention for achieving the maximum (91.25%). It should been the synergistic effect on the highly efficient catalysis performances exerting by the presence of CDs modifier and the Tourmaline core, which make ZnO matrix receive more photo-generated electrons and broaden the visible light response originated from CDs, and synchronously hinder the recombination of electrons-hole pairs by the spontaneous polarization and surface electric field of Tourmaline.

Application of Electrochemical Impedance Spectroscopy to evaluate cathodically protected coated steel in seawater

Two types of organic coated carbon steel (S235JR2 grade) electrodes were exposed to artificial seawater environment. One prepared type was defect free while the other one had an intentionally introduced ϕ0.5 cm coating defect. Both kinds of samples were polarized during the exposure to four potentials corresponding to four different cathodic protection levels. Evolution of their EIS spectra is presented in this paper. Results obtained in the experiment indicate that protective organic coating condition could be estimated and monitored in time based on EIS investigations. If a sample is defected EIS allows recognition of overprotected and unprotected sample. Distinguishing a fully protected sample from partially protected sample based on EIS was troublesome.

Effect of Ni dopant in TiO2 matrix on its interfacial charge transportation and efficiency of DSSCs

Employing the prepared pure TiO2 and Ni doped TiO2 as photoanode material, dye sensitized solar cells (DSSCs) are fabricated with ruthenium complex as dye-sensitizer [Cis-bis(isothiocyanato) bis(2, 2′-bipyridyl-4, 4′-dicarboxylato)ruthenium(II) also called as N3 dye] and LiI as redox electrolyte. In this concern, pure TiO2 and Ni–TiO2 are prepared through sol–gel technique. The structural, optical and electrical properties of the prepared materials are investigated using XRD, UV–Vis and impedance analyses respectively. The XRD pattern reveals pure crystalline anatase phase of pure TiO2 and Ni–TiO2 and the crystallite size was found to be in the range of 7–11 nm. UV–Vis spectroscopy shows the enhancement of absorption spectrum in UV region with red shift was observed by Ni doping. The electron transport properties of the prepared TiO2 and Ni doped TiO2 shows higher conductivity in 3% Ni doped TiO2 confirmed from impedance studies. The interfacial charge transport resistances and chemical capacitances of the fabricated DSSCs are evaluated from the EIS investigations and the photovoltaic performance of Ni doped TiO2 based DSSC shows enhanced efficiency up to 4%.

TiO2 flowers and spheres for ionic liquid electrolytes based dye-sensitized solar cells

Micro-sized 3D branched flower like and sphere TiO2 have been synthesized through a controlled hydrolysis followed by hydrothermal process. The resultant flower and sphere TiO2 were characterized by SEM, XRD, BET and light scattering measurements. Overwhelming anatase and strong light scattering were exhibited for the flower sample. Pure sphere and flower and sphere-mixed (flower/sphere) films were formed and applied as photoelectrodes for dye-sensitized solar cells (DSCs) with both ionic liquid and gelled ionic liquid electrolytes. The devices exhibited considerably enhanced overall energy conversion efficiency in comparison with that of those derived from TiO2 nanoparticles. The superior performances were attributed to their fast electrolyte diffusion and good interfacial contact of TiO2/electrolyte as validated by EIS investigations as well as light scattering. The participation of flowers with the sphere films further improved the electrolyte penetration and light scattering, making the flower/sphere device the most efficient with a low dye loading.

Electronic effects at self-assembled 4,4′-thio-bis-benzenethiolate protected Au nanoparticles on p-GaAs (1 0 0) electrodes

The effects of the self-assembled 4,4′-thio-bis-benzenethiolate protected gold nanoclusters onto a p-GaAs (100) electrode were examined by AFM, XPS, SHG and EIS investigations. The AFM and XPS results revealed a well-ordered overlayer exhibiting a bi-modal highly correlated fractal behavior which, however, cannot fully protect the semiconducting surface against the oxidation in air. The EIS data pointed out the influence exerted by the gold-monolayer protected clusters (Au-MPCs) over the charging/discharging processes observed at p-GaAs (100) electrode. Although the applied potential is varied linearly, the potential drop within the semiconductor space charge region as well as that across the Au-MPCs layer undergoes stepped changes supposed to result in the discrete charging of the Au-MPCs. These effects point to an electronic equilibrium between the Au-MPCs and the semiconducting substrate. Fermi level pinning and enhancement of the SHG response in the potential range where the surface/interface states in the semiconductor band gap become electrically active bring further proof in this respect.

Magnetohydrodynamic transfer function applied to ultramicroelectrode systems

The magnetohydrodynamic (MHD) transfer function (∂ I/∂ B), which has been successfully used in the investigation of various electrochemical systems, has also proved useful for the elucidation of reaction mechanisms involved in electrodeposition of metals. Yet, its use had been so far restricted to macroscopic electrodes. We propose here its application for ultramicroelectrodes (UMEs). In a recent work carried out in our laboratory with classical EIS techniques, we have demonstrated the reliability of the UMEs for the characterisation of the magneto-induced convective effect. We confirm this behaviour through the measurement of (∂ I/∂ B): at the limiting current, (∂ I/∂ B) shows an evolution in agreement with the previous stationary studies and the EIS investigations. In particular, the variation of the low frequency modulus confirms the relationship between the limiting current and the product B 1/3× C 4/3 insofar as the non-MHD convection has been taken into account.

Electrochemical behaviour of vanadium in aqueous solutions of different pH

he electrochemical behaviour of vanadium in aqueous solutions of pH covering the range 1–13 in oxygen saturated, oxygen free and naturally aerated solutions was investigated. The behaviour of the vanadium electrode in alkaline solutions ( pH > 8) is different from that in acid or neutral solutions (pH 1–8). The equilibrium electrode potential is a linear function of the solution pH. The slope of the linear relation changes from −0.039 V/decade for solution of pH ≤ 8 to −0.058 V/decade for solutions of pH > 8. EIS investigations have shown that the metal undergoes active dissolution in aqueous solutions. In solutions of pH > 8 the corrosion behaviour of vanadium can be simulated to a Randles equivalent circuit model. In oxygen saturated solutions the electrode surface is covered with an oxide film. The interaction of this film with the H + and OH − in solutions with different pH was discussed. Polarization measurements have shown that the rate of corrosion in acid solutions is not affected by the prevailing gas. In alkaline solutions, removal of oxygen or air from the solution leads to a decrease in the corrosion rate of the metal.