Electrochemical Impedance Parameters Research Articles

Engineering 3D-interconnected graphene nanoplatelets and polyaniline nanocomposite for high energy density energy storage

A high-performance, seaweed-shaped 3D interconnected nanocomposite electrode comprising graphene nanoplatelets (GNP) and polyaniline (PANI) as an electrode material for supercapacitors is synthesized via conventional in-situ chemical oxidative polymerization. This research aims to enhance the electrochemical performance of the GNP/PANI nanocomposite electrode material by manipulating their shape and electroactive characteristics for greater optimization. While seaweed-shaped GNP/PANI nanocomposites have been reported previously, none have demonstrated high electrochemical performance with an optimized 40 wt% of GNP in GNP/PANI nanocomposite. This deficiency is attributed to the lack of 3D well-interconnected nanocomposite formation and the electroactivity of GNP/PANI when compared to individual PANI or GNP in H2SO4 electrolyte.The electrochemical study confirms an upward revision in specific capacitance, from 400 Fg−1 for GNP and 514 Fg−1 for PANI, to 1088 Fg−1 for the GNP/PANI electrode material in an aqueous 1 M H2SO4 electrolyte solution. It is envisioned that formation of such 3D interconnected GNP/PANI nanocomposite contributes in increasing the interplanar and interchain distances in the nanocomposite particularly in GNP layered structure. Additionally, it is observed that the electrochemical impedance parameters, such as charge transfer resistance Rct (0.12 Ω), high response frequency (1.367 Hz), and short relaxation time (τo ∼ 0.73 s) of the GNP/PANI nanocomposite electrode material, demonstrate excellent performance. The seaweed-shaped GNP/PANI nanocomposite exhibits promising potential as an electrode material for next-generation symmetric supercapacitors due to its high specific capacitance, low cost, and ease of fabrication.

Effect of turbulent flow on the oxide properties of carbon steel in alkaline water

The purpose of this study is to investigate the changes in the morphology, chemical state, defect density, and impedance of oxides formed on SA 106 Gr.B carbon steel by turbulent water flow at the micro and atomic levels. A compact magnetite layer composed of multi-faceted particles is formed in stagnant water, while a porous magnetite layer composed of particles without a certain shape is formed in turbulent water. Ferrous ions are preferentially dissolved from the oxide in turbulent water, which increases the vacancies in the oxide lattice. An increase in the concentration of point defects is shown to be comparable to an increase in the corrosion rate of carbon steel. The flow-accelerated corrosion behavior is also well correlated with the electrochemical impedance parameters including the charge transfer resistance and capacitance. Our study provides a further understanding of carbon steel corrosion under turbulent water flow conditions.

A novel phthalocyanine based discotic liquid crystal for efficient corrosion inhibition of mild steel

ABSTRACT Discotic liquid crystals have been extensively investigated for their applications in electro-optical devices. Very recently their potential as corrosion inhibitor has been realised. Effective methods for the prevention of corrosion of mild steel (MS) are still challenging research for industrial chemists. In the present work, MS samples in 1.0 M HCl medium were used to test the corrosion inhibition capacity of a metal-free phthalocyanine (Pc)-based discotic liquid crystal (DLC) using potentiodynamic and electrochemical impedance parameters. The phthalocyanine discotic liquid crystal (PcDLC) exhibited an excellent corrosion inhibition with a maximum inhibition efficiency of 89.61%. This superior ability was attributed to the strong adsorption of PcDLC on to the surface of mild steel as confirmed from the potentiodynamic polarisation data that fit into the cathodic inhibitor category. The protective layer of inhibitors generated on the MS surface was examined using scanning electron microscopy (SEM) and FTIR. The density function theory (DFT) approach was used to investigate the relationship between molecular structures and inhibitory efficacy, which indicated a strong interaction between the inhibitor and the surface iron atoms.

Improved electrochemical performance of symmetric polyaniline/activated carbon hybrid for high supercapacitance: Comparison with indirect capacitance

AbstractPolyaniline (PANI) chains doped with very small amount of Activated Carbon (AC) as an electrode material in aqueous H2SO4 electrolyte was successfully employed in this work to enhance the electrochemical capacitive properties of PANI. The aim of this research is to improve overall specific capacitance of PANI by incorporating only minute amount of AC as a PANI dopant. There are many reports available on PANI/AC but the use of such a minute amount of AC in H2SO4 electrolyte which enhances the overall specific capacity of the composite has not been reported elsewhere. An improvement in the specific capacitance from 763.44 to 897.50 F g−1 in aqueous 0.1 M H2SO4 electrolyte solution is observed by adding mere 0.04 g of AC. It is envisaged that AC enhances SO4−2 ion transportation, forwards a stable and fast surface redox reactions, hence collectively improving the overall capacitive performance of supercapacitor electrode. The charge/discharge measurements shows that AC particles stops the PANI chains degradation during charge/discharge cycle. Also, the retention rate (54%) of PANI1.0/AC0.04 indicates approximately 11% more stability than pure PANI (43%) electrode alone. It was further observed that the electrochemical impedance parameters viz., that charge transfer resistance (Rct) (0.79 Ω), response frequency (0.26 Hz), response time (3.84 s) and knee frequency (9.16 Hz) of PANI1.0/AC0.04 electrode material shows excellent performance of the PANI doped AC. Considering its high specific capacitance, low‐cost and ease of synthesis, PANI1.0/AC0.04 seems to be a promising electrode material for next generation symmetric supercapacitors.

Investigation of the wettability, anticorrosion, and accelerated weathering behaviors of siloxane-modified acrylic resin and functionalized graphene nanocomposite coatings on LY12 aluminum alloy

To expand the applications of graphene which has so far been limited by the expensive nature of single-layer graphene, the effects of varying percentages of low-cost functionalized multilayer graphene nanosheets in siloxane-modified organic coatings were studied. The hydrophobic organic siloxane–acrylic resin was prepared by solution polymerization of acrylic monomers, and the graphene nanosheets were functionalized using fluorosilane. The coatings were sprayed on the LY12 aluminum substrate, and the wettability, anticorrosion, conductive, and accelerated weathering behaviors were comprehensively examined. It is shown that the increasing addition of functionalized graphene nanosheets increases the water contact angle and the surface conductivity. At 5% graphene loading, coating–substrate adhesion remains almost unchanged, while the electrochemical impedance parameters revealed good anticorrosion performance up to 10% loading. The surface measurements and Fourier transform infrared spectroscopy (FTIR) results confirmed the photostabilization ability of graphene loading in acrylic coatings during the accelerated weathering test. Also, the mechanical properties of the coatings were not damaged during the exposure, and pitting corrosion sites were observed only on the 20% graphene-filled coatings after 1000 h of exposure. These integrated analyses of mechanical properties and environmental accelerated tests are beneficial to engineering applications of graphene coatings.

Ixora coccinea extract as an efficient eco-friendly corrosion inhibitor in acidic media: Experimental and theoretical approach

The corrosion inhibition power of an eco-friendly green inhibitor Ixora coccinea extract (ICE) for mild steel in 1 M HCl and 0.5 M H2SO4 was analysed using physicochemical and electrochemical techniques. 1–5 v/v% ICE was prepared and added into the corrosive acidic media for different analyses. Weight loss measurements conducted for a period of 24hrs for mild steel immersion revealed 89.38% and 77.96% inhibition capacity of ICE in 1 M HCl and 0.5 M H2SO4 medium respectively. Electrochemical impedance parameters show that as concentration is increased, efficiency increases and double layer capacitance decreases. Potentiodynamic polarization techniques are also in good agreement with impedance studies and exhibit the mixed type inhibition character of ICE. Electrochemical noise spectrum also strongly supports the anti-corrosive property of ICE and the magnitude of noise signal decreases concerning the increase in ICE concentration. Ixorene, which is one of the major constituents of Ixora coccinea leaves was also studied for its corrosion inhibition nature by quantum mechanical calculations and was found to match with all other results. Adsorption studies of ICE are in accordance with Langmuir isotherm. Surface morphological studies confirm the formation of a protective barrier on mild steel surface in both media, i.e., 1 M HCl and 0.5 M H2SO4.

Inhibition of copper corrosion by the essential oil of Allium sativum in 0.5M H2SO4 solutions

Materials in general and copper in particular, have a wide variety of industrial applications. However, they can easily corrode in aggressive environments. The anticorrosive action of copper by the essential oil of Allium sativum in a 0.5M H2SO4 solutions has been studied using electrochemical techniques: electrochemical impedance spectroscopy and potentiodynamic polarization. The polarization curves indicate that the studied oil acts as a cathodic inhibitor retarding the cathodic reaction. An appropriate electrical equivalent circuit model was used to calculate the electrochemical impedance parameters. The results obtained showed that the inhibition efficiency depends on the inhibitor concentration and the temperature. This efficiency reached 97% at a concentration of 1.0 g/L. Some thermodynamic parameters for activation process and metal dissolution such as activation energy (Ea) activation entropy (ΔSa) and the activation enthalpy (ΔHa) were also calculated and discussed.

Fast time domain identification of electrochemical systems at low frequencies using fractional modeling

Electrochemical Impedance Spectroscopy (EIS) is widely used in different types of applications to model accurately the internal battery behavior. EIS requires very long time to obtain experimental data, especially for diffusion phenomenon (low frequency). Therefore, fast chronopotentiometry experiment represents an interesting approach to solve this problem. This paper deals with the identification of diffusion electrochemical impedance parameters in time domain using fractional systems where EIS diffusion spectrum is obtained through the identified parameters from chronopotentiometry data. An Equivalent Electric Circuit (EEC) modeling using fractional systems is used to identify diffusion parameters. The method is validated using an experimental electrochemical cell and it shows accurate estimation for the diffusion parameters. Consequently, the fractional system is used as an identification tool to study the impact of external parameters on the diffusion aspects such as polarization point and working electrode rotation speed.

Non-contact electrochemical evaluation of biofilms

Here, we demonstrate a non-contact technique for electrochemical evaluation of biofilms on surfaces in relation to corrosion. Electrochemical impedance spectrometry was employed, incorporating flat patterned electrodes positioned over the surfaces of aluminum and glass with and without biofilms. Signal communication from the working electrode to the counter electrode followed electric field lines passing tangentially through the biofilms. Electrochemical impedance parameters that were evaluated included complex impedance, phase angle, imaginary (out of phase) conductivity and Cole–Cole plots with a corresponding equivalent circuit. Changes in the impedance properties due to the presence of biofilms were monitored and correlated through microbiological, chemical and electrochemical assays. Impedance parameters associated with microbial activity correlated with biofilms on aluminum and glass surfaces. This technical approach provides impedance information about the biofilm without the signal traveling through the underlying conductive media or disrupting the biofilm. In this way, biological contributions to surface fouling can be evaluated with minimal contribution from the inorganic surface under the biofilm. In addition, this technique can be used to monitor biofilms on electrochemically inert surfaces as well as electrically conductive surfaces.Graphic abstract

Enhanced oxygen evolution reaction over glassy carbon electrode modified with NiOx and Fe3O4

Magnetite iron oxide (Fe3O4)/nickel oxide (NiOx) modified glassy carbon (GC) electrode shows enhancement of oxygen evolution reaction (OER) compared to GC electrode modified with single NiOx or Fe3O4 nanoparticles. Many techniques such as linear and cyclic sweep voltammetry, electrochemical impedance spectroscopy (EIS) have been employed. Field-emission scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) are both used for characterization of the electrocatalysts. Effect of loading amount of both NiOx and Fe3O4 and the order of deposition on the OER was studied. A significant improvement of the electrocatalytic properties of the Fe3O4/NiOx binary catalyst modified GC is obtained when NiOx is electrodeposited on GC/Fe3O4 (i.e. GC/Fe3O4/NiOx) compared to GC/NiOx/Fe3O4 (where NiOx is deposited first on the GC then Fe3O4). The use of GC/Fe3O4/NiOx (where Fe3O4 is deposited first on the GC then NiOx) for OER in alkaline solution support higher currents and consequently negative shifts of the onset potential of OER compared to that of GC/NiOx or GC/Fe3O4. The obtained electrochemical impedance parameters confirmed the above conclusions. Tafel parameters confirm the superior activity of GC/Fe3O4/NiOx and give insight into the mechanism of the OER on the above electrodes.

A two steps method for electrochemical impedance modeling using fractional order system in time and frequency domains

Accurate estimation of electrochemical impedance parameters is related to an appropriate model and the identification method. Electrochemical Impedance Spectroscopy (EIS) allows accurate identification meanwhile it requires a long time to be performed. Chronopotentiometry represents an alternative for EIS especially for low frequencies impedance identification that can be performed faster than EIS. This paper presents a method that combines the EIS and chronopotentiometry in order to identify the impedance parameters of an electrochemical cell. An Equivalent Electric Circuit (EEC) based on Randles circuit is used to describe the impedance aspect of the electrochemical cell. This impedance is represented through fractional systems and is identified using Levenberg–Marquardt algorithm. The validation process is performed using an experimental test bench made of two platinum electrodes immersed into Ferri/Ferrocyanide solution. Results indicate high accuracy for the estimation of the impedance parameters.

Superhydrophobicity, conductivity and anticorrosion of robust siloxane-acrylic coatings modified with graphene nanosheets

The effects of low-cost graphene nanosheets in organic coatings were investigated. The hydrophobic organic siloxane-acrylic resin was synthesized by solution polymerization of acrylic monomers while the graphene nanosheets were modified using fluorosilane, and applied on LY12 aluminum substrate via spraying and a two-step coating system. The superhydrophobic, conductive, anticorrosion, self-cleaning, oleophilic and physical behaviors were comprehensively characterized. The results obtained revealed that addition of modified graphene increases the surface conductivity (≥ 2 μS/cm) and the water contact angle (≥ 152°) with low sliding angle (≤ 7°). The polarization measurement showed a positive shift in the corrosion potential signifying an inhibition of the cathodic reaction. Also, the two-step coated sample gave a good corrosion protection barrier as further confirmed by the electrochemical impedance parameters. The coating revealed good resistance to dirt adhesion, and its superhydrophobic-oleophilic property offered a promising application in oil-water separation. The physical integrity of the coatings was not extensively affected including after 120 days of outdoor exposure to snowing, de-freezing and surface wetting.

Segmented Electrode Analysis of an Anode-Supported Planar Solid Oxide Fuel Cell for the Diagnosis of Marine Power Applications

Adoption of the liquefied natural gas (LNG) fueled solid oxide fuel cell (SOFC) to the marine power supplies and motive powers is expected to reduce fuel consumption and toxic air pollutant (NOx, SOx, Particulate Matter (PM), CO2) emissions compared with the conventional marine diesel engine. In the near future, SOFC-diesel hybrid motive power would be promising as the marine use where the SOFC power units operate as auxiliary power unit (APU) for the steady power demand, while the diesel engine responds to the load change[1]. SOFC-micro gas turbine combined units for the marine power systems can be developed by scaling-up a combined system under demonstration[2]. We thus focus on the development of real-time abnormal-diagnosis method to improve the reliability and durability required for the long-term safety and stable operation of the marine SOFC. Significant accident due to the breakdown of the cell should also be prevented. We therefore apply electrochemical impedance spectroscopy[1,3] to the diagnosis which enables safety precautions, operating condition modification, and emergency shutdown by prior abnormality detection of the SOFC through an elucidation of the degradation factor accompanying the marine operation. Problems of the SOFCs include current distribution that decays the total cell performance and efficiency, and causes electrode degradation chemically and thermo-mechanically. In the planar SOFCs, the fuel and oxidant distributions cause current and temperature distributions over the electrodes. Although there have been a number of numerical analyses, very few experimental investigations confirming in-situ current distributions have been reported. We have therefore addressed measurements of spatial current variations of an anode-supported microtublar[4] and an electrolyte-supported planar SOFCs[5] having segmented cathodes so far. In the present study, we investigate longitudinal current distribution and electrochemical impedance variation along the anode flow channels. We prepared a planar cell having three longitudinally segmented cathodes assembled with segmented cathode separators for electrical insulation. The cell was composed of NiO-YSZ anode-support, YSZ electrolyte, GDC interlayer, and LSC cathode (ASC-10B, Elcogen, Estonia). Each cathode segment had an area of 2.25 cm2 (1.5 x 1.5 cm) while the anode had 19.5 cm2(6.5 x 3.0 cm). The anode and cathode separators made of stainless steel (Crofer 22 APU, VDM Metals GmbH, Germany) had flow channels with a width of 1 mm and a depth of 1 mm (MAGNEX Co., Ltd., Japan). The anode separator had 8 parallel flow channels having a length of 4.9 cm. Silver mesh was employed as current collector. Current voltage (I-V) measurements were carried out under voltage control using three electric loads to reproduce the electrode potential of a single cell2. The anode and cathode were electrically connected with the four-terminal method. The anode NiO was reduced to Ni by feeding H2/N2 mixture gas for 2 hours prior to measurements. During measurements, anode and cathode were fed with mixtures of H2/N2 and dried air at constant flow rates, respectively, in a cross-flow configuration. The cell was maintained at 650 °C by a tubular electric furnace at open circuit voltage (OCV). As a result, fuel starvation in the downstream segment showed decays in cell performance, giving rise to longitudinal current distribution and impedance variation. These in-situ acquired distribution data are useful as a basis to develop the diagnosis of SOFCs including marine power applications fueled with reformed LNG. References Hironori Nakajima and Tatsumi Kitahara, Real-Time Electrochemical Impedance Spectroscopy Diagnosis of the Marine Solid Oxide Fuel Cell, J. Phys.: Conf. Ser., Vol. 745, 032149 (2016).Mitsubishi to develop, SOFC-turbine triple combined cycle system, Fuel Cells Bulletin, Vol. 2012, 7, 5-6 (2012).Hironori Nakajima, Toshiaki Konomi, Tatsumi Kitahara, and Hideaki Tachibana, Electrochemical Impedance Parameters for the Diagnosis of a Polymer Electrolyte Fuel Cell Poisoned by Carbon Monoxide in Reformed Hydrogen Fuel, J. Fuel Cell Sci. Technol. Vol. 5 041013 (2008).Özgür Aydin, Takahiro Koshiyama, Hironori Nakajima, Tatsumi Kitahara, In-situ Diagnosis and Assessment of Longitudinal Current Variation by Electrode-Segmentation Method in Anode-Supported Microtubular Solid Oxide Fuel Cells, J. Power Sources, Vol. 279, 218–223 (2015).Tatsuhiro Ochiai, Hironori Nakajima, Takahiro Karimata, Tatsumi Kitahara, Kohei Ito, Yusuke Ogura, Jun Shimano, In-situ Analysis of the In-plane Current Distributions in an Electrolyte-Supported Planar Solid Oxide Fuel Cell by Segmented Electrodes, ECS Trans., Vol. 75, 52, 91-98 (2017).

Highly Efficient Platinum Free Multi‐Walled Carbon Nanotubes/Silver Nanocomposites as Counter Electrode for Dye Sensitized Solar Cell

AbstractIn this report we have synthesized multi‐walled carbon nanotubes (MWCNT)/silver (Ag) nanocomposites using reduction method. Integrating properties of MWCNT and Ag as nanocomposites have shown potential application as counter electrode (CE) in dye sensitized solar cells (DSSCs). Different analyses were performed using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and Raman, analysis to examine the successful incorporation of Ag nanoparticles with MWCNT. A systematic morphological study was carried out using scanning and transmission electron microscopy. The cyclic voltammetry (CV) reveals the enhancement in catalytic activity towards redox couple (I3−/I−) in DSSCs. Thus, current density vs voltage (J‐V) curve assists in evaluating the influence of Ag nanoparticles on MWCNT during photovoltaic conversion. The optimum photo‐conversion efficiency (η) of 5.44 % was achieved using MWCNT/(0.75 %)Ag nanocomposites as CE which is analogous to conventional Pt CE. Finally, electrochemical impedance parameters endorse well in the improvement of photo conversion efficiency through reduction in charge transfer resistance (Rct).

Core/shell (ZnO/polyacrylamide) nanocomposite: In-situ emulsion polymerization, corrosion inhibition, anti-microbial and anti-biofilm characteristics

Polyacrylamide nanoparticles of 20nm were prepared using emulsion polymerization technique. Core/shell nanocomposites of functional core of zinc oxide nanoparticles surrounded by a shell of polyacrylamide were also prepared using in-situ emulsion polymerization technique. Potentiodynamic polarization and Electrochemical impedance parameters for corrosion of carbon steel in absence and presence of ZnO/PAM.NCs indicated that, as the ZnO nanoparticles ratio increased, the corrosion inhibition efficiency increased; 50%, 80% and 94% for 1, 5 and 10% ZnO; respectively. Scanning electron micrographs of carbon steel specimen surface immersed in HCl in absence and presence of ZnO/PAM.NC10 indicated that carbon steel surface is less damaged in presence of ZnO/PAM.NC10 which confirms the observed high inhibition efficiency. ZnO/PAM.NC10 was found to display a broad spectrum antimicrobial activity with the inhibition zones in the range of 15–22mm. ZnO/PAM.NC10 demonstrated a higher antibacterial activity for the Gram-positive than for the Gram-negative bacteria and exhibited lower minimum inhibitory concentrations and minimum bactericidal concentrations for the Gram negative bacteria than the Gram positive bacteria. Moreover, it showed MICs/MFCs against yeast and fungal strains at concentrations (250/250ppm). Additionally, ZnO/PAM.NC10 exhibited antibiofilms activity against the standard bacterial strains; Bacillus subtilis and Escherichia coli as confirmed by SEM imaging.

Combined voltammetric and spectroscopic investigation of binding interaction between nifedipine and human serum albumin on polyelectrolyte modified ITO electrode

The binding interaction between the drug molecule, nifedipine (Nf), and the human serum albumin (HSA) on polyelectrolyte modified indium tin oxide (ITO) electrode has been investigated by the combination of electrochemical and fluorescence spectroscopy techniques. Surface modification has also been characterized by scanning electron microscopy (SEM) and Contact Angle (CA) measurements in each step. The cyclic voltammetry, electrochemical impedance parameters (peak potential difference (ΔEp)), peak current difference (ΔIp) and charge-transfer resistance (Rct) indicate that nifedipine strongly interacted with human serum albumin molecule on the polyelectrolyte modified ITO electrode surface. Stern–Volmer quenching constant Ka is inversely correlated with the temperature, which indicates that the probable quenching mechanism of the nifedipine-human serum albumin binding reaction is initiated by complex formation. The results obtained from these techniques showed that Nf could bind to HSA. The binding constant (Kb) and the number of binding sites (n) of the drug with HSA at different temperatures were determined. At 298K, Kb was found as 4.04×10−3 and n was 1.08 for Nf-HSA. According to the van’t Hoff equation, the thermodynamic parameters, ΔG, ΔH and ΔS, were obtained, showing the involvement of hydrophobic and electrostatic force in this interaction.

Influence of concentration of supporting electrolyte on electrochemistry of redox systems on multi-walled carbon nanotubes

In the present work, the effect of the concentration of supporting electrolyte on the electrochemical behaviour of the redox couple ferrocyanide/ferricyanide, [Fe(CN)6]3−/4− on film consisted of multi-walled carbon nanotubes (MWCNTs) was investigated. The MWCNTs were selectively grown on oxidised silicon substrate by means of catalytic chemical vapour deposition (CCVD) technique with decay of acetonitrile (ACN) in the presence of ferrocene (FeCp2) that served as catalysts. For the electrochemistry studies, the techniques of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in three-electrode system were employed. The correlation between the solution's ionic strength and the electrochemical impedance parameters are discussed.

Electrochemical impedance spectroscopy investigation on indium tin oxide films under cathodic polarization in NaOH solution

The electrochemical corrosion behaviors of indium tin oxide (ITO) films under the cathodic polarization in 0.1M NaOH solution were investigated by electrochemical impedance spectroscopy. The as-received and the cathodically polarized ITO films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction for morphological, compositional and structural studies. The results showed that ITO films underwent a corrosion process during the cathodic polarization and the main component of the corrosion products was body-centered cubic indium. The electrochemical impedance parameters were related to the effect of the cathodic polarization on the ITO specimens. The capacitance of ITO specimens increased, while the charge transfer resistance and the inductance decreased with the increase of the polarization time. The proposed mechanism indicated that the corrosion products (metallic indium) were firstly formed during the cathodic polarization and then absorbed on the surface of the ITO film. As the surface was gradually covered by indium particles, the corrosion process was suppressed.

Electrochemical impedance parameters elucidate performance of carbazole–triphenylamine–ethylenedioxythiophene-based molecules in dye-sensitized solar cells

Abstract Organic dyes are synthesized containing bridging ethylenedioxythiophenes (EDOT) between the electron donors and electron acceptors (2-cyanoacetic acid) on carbazole–triphenylamines. These compounds are then characterized by photophysical, electrochemical, and theoretical computational methods. Nanocrystalline TiO 2 -based dye-sensitized solar cells (DSSCs) are fabricated using these dye molecules as light-harvesting sensitizers. The overall efficiency of the sensitized cells is high (5.20%) compared to the efficiency of a cis-di(thiocyanato)-bis(2,2′-bipyridyl)-4,4′-dicarboxylate ruthenium (II) (N3 dye)-sensitized device (7.57%) fabricated and measured under the same conditions. The dye (ETPA3) containing one carbazole, two EDOT bridges, and two 2-cyanoacetic acid groups appears to assist in the charge transfer from the excited dye molecules to the conduction band of TiO 2 , leading to the higher efficiency of the devices using assembled with this dye. A supplementary study of the electrochemical impedance supports the enhancement of the charge transfer of TiO 2 (e − ) with the ETPA3 dye. A computational examination of the ETPA3 compound also indicates higher charge transfer efficiency in the electronically excited state.

Electrochemical corrosion behaviour of a Ti‐IF steel and a SAE 1020 steel in a 0.5 M NaCl solution

AbstractInvestigations concerning the electrochemical corrosion behaviour of low carbon (LC) and ultra‐low carbon (ULC) steels are relatively scarce and limited. The present study aims to compare electrochemical impedance parameters and potentiodynamic polarization curves of an LC steel and an ULC Ti‐interstitial free (IF) steel evidencing the effects of carbon content and pearlite fraction on the electrochemical corrosion behaviour. Corrosion tests were carried out in a 0.5 M NaCl solution at 25 °C with a pH range between 6.5 and 6.8. It was found that the IF steel sample presents an electrochemical corrosion resistance, which is slightly higher than that of the LC steel sample.