Electrochemical Impedance Spectroscopy Investigations Research Articles

Assessment of blended cement containing waste basalt powder: physicomechanical and electrochemical impedance spectroscopy investigations

Basalt powder (BP) is the residue of a plant that crushes basalt stones. This work deals with the effect of waste BP on the properties of cement mortars and the physical properties of hardened mortars. Modified concrete was prepared by partial replacement of BP in amount of 5, 10, 20% by weight of cement. Physico-mechanical properties and corrosion resistance were investigated. Electrochemical impedance spectroscopy (EIS) was used to examine the corrosion behavior of cement pastes with a partial addition of basalt powder in aggressive solutions of 5% NaCl and 5% MgCl2 for up to 270 days. Infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also performed to investigate the hydration process and microstructure formation of the basalt blended paste. Results indicate that the addition of basalt powder as a partial replacement of cement influences the microstructure of the interfacial transition zone (ITZ), which is denser and stronger than in cement paste without basalt powder. The filler effect of the basalt powder improves the compressive strength of cement paste. Also, comparing BP0 and BP20 in 5% NaCl after 270 days, the partial substitution of cement with BP resulted in a higher compressive strength of 671 and 895 kg/cm2, respectively. The EIS results also showed the highest values of Rp 953 ohms cm2 after 270 days. This high corrosion resistance might indicate the binding by high Al2O3 that reduced the free aggressive chloride ions in the solution.

Physical vapour deposition fabrication of MoO3-based photoanode for water splitting to generate hydrogen.

MoO3 thin film was fabricated on an indium tin oxide substrate using the physical vapor deposition technique. X-ray diffraction and scanning electron microscopy study to investigate surface morphology, grain size, and surface structure, which are critical for absorbing solar spectra in water splitting for hydrogen energy generation. Ultraviolet-visible spectroscopy was used to confirm the absorption of solar spectra and the percentage of transmittance. Fourier-transform infrared analysis provided the functional groups present in the deposited thin film. The Tauc plot was used to determine the thin-film band gap, which allowed for the analysis of charge carrier transitions from the conduction band to the valence band. Electrochemical impedance spectroscopy investigations confirmed the charge transfer processes to the counter electrode and electrolyte interfaces. The observed low curve for MoO3 indicated low resistance and allowed efficient charge transfer. Linear sweep voltammetry analysis was used to measure photocurrent and solar light to hydrogen emission when the thin film was exposed to solar spectra. The thin film's observed hydrogen emission rate was 3731.74 mol g-1 h-1, and the STH% of MoO3 was found to be 0.345% at 0.8 V. These findings highlight the promising potential of MoO3 as a material for hydrogen energy generation using solar light.

Carbon aerogel supported Ni–Fe catalysts for superior oxygen evolution reaction activity

Electrochemical water splitting presents an optimal approach for generating hydrogen (H2), a highly promising alternative energy source. Nevertheless, the slow kinetics of the electrochemical oxygen evolution reaction (OER) and the exorbitant cost, limited availability, and susceptibility to oxidation of noble metal-based electrocatalysts have compelled scientists to investigate cost-effective and efficient electrocatalysts. Bimetallic nanostructured materials have been demonstrated to exhibit improved catalytic performances for the oxygen evolution reaction (OER). Herein, we report carbon aerogel (CA) decorated with different molar ratios of Fe and Ni with enhanced OER activity. Microwave irradiation was involved as a novel strategy during the synthesis process. Inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM), Energy dispersive X-ray spectroscopy (EDAX spectra and EDAX mapping), Transmission Electron Microscope (TEM), High-Resolution Transmission Electron Microscope (HR-TEM), and Selected Area Electron Diffraction (SAED) were used for physical characterizations of as-prepared material. Electrochemical potential towards OER was examined through cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS). The FeNi/CA with optimized molar ratios exhibits low overpotential 377 mV at 10 mAcm−2, smaller Tafel slope (94.5 mV dec−1), and high turnover frequency (1.09 s−1 at 300 mV). Other electrocatalytic parameters were also calculated and compared with previously reported OER catalysts. Additionally, chronoamperometric studies confirmed excellent electrochemical stability, as the OER activity shows minimal change even after a stability test lasting 3600 s. Moreover, the bimetallic (Fe and Ni) carbon aerogel exhibits faster catalytic kinetics and higher conductivity than the monometallic (Fe), which was observed through EIS investigation. This research opens up possibilities for utilizing bi- or multi-metallic anchored carbon aerogel with high conductivities and exceptional electrocatalytic performances in electrochemical energy conversion.

Electrochemical investigations of PLA coatings deposited by fused filament fabrication on magnesium alloy in Ringer's solution

In this paper, polylactic acid (PLA) layers were printed on AM60 magnesium alloy through a fused filament fabrication-3D printing manufacturing method, as a low-cost and innovative technology. Then, the effect of coating thickness and anodized layer as a binder on the electrochemical behavior of Mg substrates was investigated in Ringer's solution. Electrochemical impedance spectroscopy, Tafel polarization, and weight loss investigations were performed at various exposure times for 28 days to achieve this purpose. Corroded surfaces were also analyzed through field emission scanning electron microscopy images and Fourier-transform infrared spectroscopy patterns. The obtained results showed that the higher thickness of the layer with a value of 400 µm was not effective in raising the PLA layer impedance without the anodized layer. However, the higher PLA thickness could have a key role in the corrosion rate reduction of PLA layers when printed on the anodized layer. The lowest corrosion rate with a value of 0.3 µA/cm2 was related to the PLA-printed layer with a lower thickness (200 µm) and without an anodized layer. This reduction range in corrosion current density was about 80.2–99.4 % compared to the Mg alloy. The weight loss behavior of PLA layers during a long time of exposure was followed by a logarithmic function. The range of corrosion rate decrease was 9.7–32.2 %. The PLA degradation mechanism was also suggested based on all obtained results.

Fabricating a 3D floating porous PDMS − Ag/AgBr decorated g-C3N4 nanocomposite sponge as a re-usable visible light photocatalyst

In this study, polymeric graphitic carbon nitride (g-C3N4) semiconductors was synthesized via a thermal condensation method. Subsequently, Ag/AgBr nanoparticles with varying ratios were decorated onto the g-C3N4 surface using the water/oil emulsion method. The resulting nanocomposites were characterized using XRD for phase identification and structural analysis, HR-TEM and SEM&EDAX for morphological structure, particle size, and elemental composition analysis, and XPS for investigating the chemical state and electronic structure. The impact of Ag/AgBr content on the optical properties of g-C3N4 were also studied such as (optical bandgap (Eg), refractive index (n), extinction coefficient (k), optical conductivity (σopt) and dielectric function (ε*)), Electrochemical impedance spectroscopy (EIS), PL spectroscopy and Chrono-amperometric investigations were conducted to assess the charge transfer capabilities and long-term durability of the prepared nanocomposites. The results revealed a reduction in Ag/AgBr particle size with an increase in g-C3N4 content, accompanied by a decrease in the optical bandgap from 2.444 eV to 2.393 eV. Furthermore, the nanocomposites exhibited enhanced degradation efficiencies of RhB dye, with the highest tested content of Ag/AgBr achieving 100% degradation after 120 min of irradiation. However, the challenge of catalyst separation after the degradation process remained. To address this issue, we developed a novel approach by impregnating Ag/AgBr@g-C3N4 photocatalyst onto a floating porous sponge using a simple sugar-template technique, offering potential as a reusable photocatalyst material. Furthermore, the 3D PDMS − Ag/AgBr@g-C3N4 photocatalyst was evaluated and found to maintain nearly the same photocatalytic efficiency for up to 5 consecutive cycles.

Investigating the Role of a P(VDF−TrFE) Ferroelectric Separator in Li‐Metal Pouch Cells using Electrochemical Impedance Spectroscopy

AbstractThis study explores the efficacy of employing P(VDF−TrFE), a ferroelectric copolymer, to mitigate the formation of dead lithium in Li‐metal anodes when paired with carbonate electrolytes. Employing non‐solvent induced phase separation (NIPS), self‐standing membranes and coatings on polypropylene (PP) separators were prepared, both demonstrating a homogenous cellular pore structure and excellent ionic conductivity. Rigorous evaluation in pouch cell formats, featuring a thin Li‐metal anode (50 μm), a high‐loading NMC532 cathode (3 mAhcm−2), and a carbonate electrolyte, reveals the superior performance of cells with P(VDF−TrFE)‐coated PP separators. Notably, these cells exhibit slower and more consistent capacity fading, as well as the weakest increase in impedance, as evidenced by Electrochemical Impedance Spectroscopy (EIS) investigations. This work underscores the promising role of P(VDF−TrFE) as a key material for addressing challenges associated with dead lithium, offering valuable insights for advancing Li‐metal battery technologies in practical applications.

Enhancing Water Retention, Transport, and Conductivity Performance in Fuel Cell Applications: Nafion-Based Nanocomposite Membranes with Organomodified Graphene Oxide Nanoplatelets

The synergistic combination of Nafion and sulfonated graphene oxide (GOsulf) in nanocomposite membranes emerged as a promising strategy for advancing proton exchange membrane fuel cell (PEMFC) technology. In the pursuit of elucidating the effect of GOsulf introduction on transport properties and electrochemical performance of Nafion, this work provides a systematic study combining swelling tests, water release tests, 1H NMR characterization, and Electrochemical Impedance Spectroscopy (EIS) investigation. The incorporation of organomodified GO nanolayers alters the distribution of water molecules within the hydrophilic domains of Nafion and produces a considerable increase in the “bound-water” fraction. This increases its water retention capability while ensuring very high diffusivity even under high temperatures, i.e., 1.5 × 10−5 cm2 s−1 at 130 °C. These peculiar features enable Naf-GOsulf to successfully operate under a dehydrating environment, yielding a proton conductivity of 44.9 mS cm−1 at 30% RH.

Markedly enhanced hydrogen production in wastewater via ammonia-mediated metal oxyhydroxides active sites on bifunctional electrocatalysts

The ability to substitute oxygen evolution reaction (OER) in water splitting with ammonia oxidation reaction (AOR) represents an important endeavor in producing high-purity hydrogen with the lowered energy consumption. Due to the reduced overpotential of AOR over OER and preventing the hydrogen and oxygen mixing and thus possible explosion. Herein, we report the substitution of slow-kinetics OER with AOR to effectively boost hydrogen evolution reaction (HER) of wastewater electrolysis, thereby rendering energy saving as well as decontamination of ammonia (NH3) in wastewater. Three-dimensional CoS@NiCu electrodeposited on Ni foam is employed as self-supporting bifunctional electrocatalysts for both AOR and HER. The XPS and in-situ Raman studies reveal the generation of electrocatalytically active cobalt oxyhydroxide (CoOOH) on CoS@NiCu during the course of AOR. Interestingly, the density functional theory (DFT) calculation unveils that NH3 preferentially adsorbing on the surface of electrocatalyst prolongs the Co-S bond length, thus promoting the bond cleavage and accelerating the formation of active CoOOH species. Moreover, the rate-determining step of AOR according to the Gerischer-Mauerer (G-M) mechanism only has a 1.79 eV energy barrier to overcome. The electrochemical impedance spectroscopy investigation suggests that the AOR enables an enhanced interfacial charge transfer. As such, the hydrogen evolution rate of the AOR-HER system reaches 41.9 μmol h−1, representing 3.2-fold increase in hydrogen production over the conventional OER-HER water splitting. This study highlights a promising perspective of integrating AOR with HER to synergize efficient hydrogen production.

Study of Atomic Layer Deposition Nano-Oxide Films on Corrosion Protection of Al-SiC Composites.

In recent years, aluminum matrix composites (AMCs) have attracted attention due to their promising properties. However, the presence of ceramic particles in the aluminum matrix renders AMCs a high corrosion rate and makes it challenging to use traditional corrosion protection methods. In this study, atomic layer deposition (ALD) techniques were used to deposit HfO2, ZrO2, TiO2, and Al2O3 thin films on AMC reinforced with 20 vol.% SiC particles. Our results indicate that the presence of micro-cracks between the Al matrix and SiC particles leads to severe micro-crack-induced corrosion in Al-SiC composites. The ALD-deposited films effectively enhance the corrosion resistance of these composites by mitigating this micro-crack-induced corrosion. Among these four atomic-layer deposited films, the HfO2 film exhibits the most effective reduction in the corrosion current density of Al-SiC composites in a 1.5 wt% NaCl solution from 1.27 × 10-6 A/cm2 to 5.89 × 10-11 A/cm2. The electrochemical impedance spectroscopy (EIS) investigation shows that HfO2 deposited on Al-SiC composites has the largest Rp value of 2.0 × 1016. The HfO2 film on Al-SiC composites also exhibits effective inhibition of pitting corrosion, remaining at grade 10 even after 96 h of a salt spray test.

An artificial neural network model for capacitance prediction of porous carbon-based supercapacitor electrodes

Among energy storage devices, the last decades have witnessed the rapid spread of usage of carbon-based electrodes for electric double-layer capacitors (EDLCs) due to their large surface area, low cost, and high porosity. It is crucial to develop an accurate and efficient forecasting model for electrochemical performance to reduce the time needed for making suitable designs and choosing testing electrode materials. As a result, the use of machine learning (ML) approaches in creating a predicting model for the capacitance of carbon-based supercapacitors looks critical and provides the electrode characteristics' relative relevance. Data extracted from nearly a hundred published experimental research papers to select supercapacitors with certain electrode morphologies such as mesoporous, nanoporous, microporous, and hierarchical porous carbon electrode. The data was examined using machine learning techniques to predict the supercapacitor's specific capacitance (F/g). Electrode material structural qualities and various physicochemical test features such as electrolyte material, pore volume, and specific surface area. Electrochemical test features acquired via electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD) test investigations for the same purpose include: cell configuration, current density, applied potential window, charge-transfer resistance (RCT), and equivalent series resistance (ESR) were used as input features to predict the corresponding capacitance performance. In the present study, Lasso, Support Vector Machine Regression (SVMR), and Artificial Neural Networks (ANN) with different structures were examined to predict the capacitance of the supercapacitor. The exhibition of the ML models measured concerning the root mean square error (RMSE), the correlation between expected yield and yield provided by the system. The developed ANN model with RMSE, MAE, and R values of 30.82, 46.5624 and 0.89537, respectively, provides outcomes for the prediction that are highly accurate compared to other models created for this purpose. According to the analysis of the input features done using the SHAP (SHapley Additive exPlanations) framework, the specific surface area had the biggest impact on the ANN model.

NMR Investigation of Water Molecular Dynamics in Sulfonated Polysulfone/Layered Double Hydroxide Composite Membranes for Proton Exchange Membrane Fuel Cells.

The development of nanocomposite membranes based on hydrocarbon polymers is emerging as one of the most promising strategies for overcoming the performance, cost, and safety limitations of Nafion, which is the current benchmark in proton exchange membranes for fuel cell applications. Among the various nanocomposite membranes, those based on sulfonated polysulfone (sPSU) and Layered Double Hydroxides (LDHs) hold promise regarding their successful utilization in practical applications due to their interesting electrochemical performance. This study aims to elucidate the effect of LDH introduction on the internal arrangement of water molecules in the hydrophilic clusters of sPSU and on its proton transport properties. Swelling tests, NMR characterization, and Electrochemical Impedance Spectroscopy (EIS) investigation allowed us to demonstrate that LDH platelets act as physical crosslinkers between -SO3H groups of adjacent polymer chains. This increases dimensional stability while simultaneously creating continuous paths for proton conduction. This feature, combined with its impressive water retention capability, allows sPSU to yield a proton conductivity of ca. 4 mS cm-1 at 90 °C and 20% RH.

Decoration of Bi2O3NPs-AgNPs-ErGO as a first electrochemical nanosensor for sensitive determination of nelarabine in pharmaceutical dosage form and human serum samples

In view of the unquestionable necessity for rapid and accurate analysis of drug molecules to monitor patient overdose, numerous nanosensor-based technologies have been developed in addition to quality control of pharmaceutical manufacture and drug administration. In this regard, sensitive detection of a potent anticancer agent, nelarabine (NEL) was examined at the bare and modified glassy carbon electrode (GCE) with the help of differential pulse (DP) and cyclic voltammetry (CV) techniques. A unique and highly effective nanosensor was developed using a combination of bismuth (III) oxide nanoparticles (Bi2O3NPs), silver nanoparticles (AgNPs), and electrochemically reduced graphene oxide (ErGO) onto the GCE surface. The modified Bi2O3NPs-AgNPs-ErGO/GCE was characterized by scanning electron microscopy (SEM), CV, and electrochemical impedance spectroscopy (EIS) investigations. Influences of various parameters viz., loading of Bi2O3NPs, AgNPs, and GO on the modified GCE, electrolyte pH (PBS 7.0), accumulation potential (–0.2 V), and time (60 s), and scan rate (50 mV s−1) were optimized for NEL response. An enhancement in the current responses toward the oxidation of NEL was observed with the Bi2O3NPs-AgNPs-ErGO/GCE compared to that noticed with bare GCE. The modified GCE affirmed high sensitivity, low limit of detection (LOD), excellent reproducibility, repeatability, and storage stability that clearly indicated the effective accuracy of the developed nanosensor. The linear behavior in the concentration range was found to be 0.02–1.0 µM, with LOD values of 0.003 nM in PBS 7.0 and 0.065 nM in serum samples. The electrochemical mechanism of NEL at the bare and modified GCEs were revealed as diffusion-controlled and adsorption-controlled mechanism processes, respectively. The linear calibration curves at both the bare and modified GCEs were noticed for increasing NEL concentrations, as constructed from the DPV measurements. Applications of the Bi2O3NPs-AgNPs-ErGO/GCE for NEL detection in pharmaceutical dosage form and human serum sample showed well-accepted recovery results of 98–99 %. The effect of interfering agents was checked on the selectivity of the developed method, and the modified electrode was found to be selective toward NEL in the presence of these interfering agents.

Composite anion exchange membranes based on polysulfone and silica nanoscale ionic materials for water electrolyzers

Anion exchange membrane water electrolysis (AEMWE) offers the ambition of combining the advantages of alkaline electrolysers, i.e. the use of cheap and plentiful catalytic materials, with those of proton exchange membrane electrolysis of water, i.e. high performance and fast response to changing operating conditions. However, the development of performing and durable anion exchange membranes is still the major challenge for the ultimate industrial adoption of AEMWE. Here, we introduce an innovative nanocomposite AEM based on trimethylammonium functionalized silica nanoscale ionic materials (NIM-N+) incorporated in quaternized polysulfone (qPSU). The presence of NIM-N+ in the hydrophilic clusters of qPSU produces a remarkable enhancement in the dimensional and thermo-mechanical stability of the composite AEM. Furthermore, Nuclear Magnetic Resonance (NMR) and Electrochemical Impedance Spectroscopy (EIS) investigations highlighted that the nanoparticles are directly involved in the transport process of hydroxide ions. This enabled qPSU/NIM-N+ composite membrane to achieve impressive anionic conductivity values, e.g. about 110 mS cm−1 at 80 °C and 95% relative humidity (RH). The AEMWE single cell, equipped with this membrane, operated properly both with 1 or 0.5 M KOH solution, displaying a current density larger than 3.5 A cm−2 at 2.2 V and 80 °C.

UV and solar-based photocatalytic degradation of organic pollutants from ceramics industrial wastewater by Fe-doped ZnS nanoparticles

UV and solar-based photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) as an organic contaminant in ceramics industry wastewater by ZnS and Fe-doped ZnS NPs was the focus of this research. Nanoparticles were prepared using a chemical precipitation process. The cubic, closed-packed structure of undoped ZnS and Fe-doped ZnS NPs was formed in spherical clusters, according to XRD and SEM investigations. According to optical studies, the optical band gaps of pure ZnS and Fe-doped ZnS nanoparticles are 3.35 and 2.51 eV, respectively, and Fe doping increased the number of carriers with high mobility, improved carrier separation and injection efficiency, and increased photocatalytic activity under UV or visible light. Doping of Fe increased the separation of photogenerated electrons and holes and facilitated charge transfer, according to electrochemical impedance spectroscopy investigations. Photocatalytic degradation studies revealed that in the present pure ZnS and Fe-doped ZnS nanoparticles, 100% treatment of 120 mL of 15 mg/L phenolic compound was obtained after 55- and 45-min UV-irradiation, respectively, and complete treatment was attained after 45 and 35-min solar light irradiation, respectively. Because of the synergistic effects of effective surface area, more effective photo-generated electron and hole separation efficiency, and enhanced electron transfer, Fe-doped ZnS demonstrated high photocatalytic degradation performance. The study of Fe-doped ZnS's practical photocatalytic treatment capability for removing 120 mL of 10 mg/L 2,4-DCP solution made from genuine ceramic industrial wastewater revealed Fe-doped ZnS's excellent photocatalytic destruction of 2,4-DCP from real industrial wastewater.

Durable self-healing coating system based on pH-responsive core-shell nanostructures

A critical access to high-efficiency anti-corrosion coatings is adding pH-responsive nanocontainers encapsulated with corrosion inhibitors into epoxy resin as it endows the composite coating with significant active long-term corrosion protection. Here, two self-healing coating systems (I-PBZ-EP and II-PBZ-EP) were constructed based on epoxy coating (EP) and benzotriazole-loaded zeolitic imidazolate framework (ZIF-8) encapsulated with polydopamine (PDA) by one-pot and two-pot methods, respectively. Electrochemical impedance spectroscopy (EIS) investigation shows that the low-frequency impedance modulus value (|Z|0.01Hz) of I-PBZ-EP still reaches 2.16 × 1010 Ω·cm2 which is the highest among all the coatings after 35 d of immersion. |Z|0.01Hz of the scratched I-PBZ-EP is 1.10 × 105 Ω·cm2 after 13 h of immersion in 3.5 wt% NaCl solution, which far surpasses |Z|0.01Hz of the scratched II-PBZ-EP, exhibiting its excellent self-healing properties. This is because I-PBZ can release more benzotriazole (BTA) (22.5 mg/L and 13.4 mg/L) than II-PBZ (15.8 mg/L and 9.4 mg/L) under acidic and basic conditions to repair the micro-defects. In short, by changing the loading mode of corrosion inhibitors, I-PBZ-EP with a simpler synthesis method manages to provide the long-term anticorrosion protection for the carbon steel substrate.

WO3 layer sensitized with BiVO4 and MIL-101(Fe) as photoanode for photoelectrochemical water oxidation

Thick tungsten oxide layers were prepared electrophoretically in order to be used as photoanodes in photoelectrochemical water oxidation applications. The highest photocurrent density was obtained for a WO3 layer with thickness of ∼900 nm. Additionally, WO3/BiVO4 and WO3/BiVO4/MIL-101(Fe) heterojunctions have been fabricated using WO3 layer as substrate. WO3/BiVO4 shows an increased value of the electrochemical active surface area indicating that more sites of this photoanode are activated through the formation of the heterojunction. The small V5+ signals observed in the V 2p XPS spectra of these heterojunctions were attributed to the substitution of V5+ atoms with W6+ atoms on the surface of BiVO4. Excessive W doping of the BiVO4 film determined the decrease of the photoelectrochemical performance of WO3/BiVO4 photoanode. The significant improvement of the photoconversion efficiency of the sample decorated with MIL-101(Fe) indicated that this co-catalyst provides sites more efficiently in the photoelectrochemical process. This performance was correlated with the reduced value of the charge transfer resistance at electrode/electrolyte interface obtained from electrochemical impedance spectroscopy investigation.

Design and Synthesis of Novel NIR‐Sensitive Unsymmetrical Squaraine Dyes for Molecular Photovoltaics

Two novel near‐infrared (NIR)‐sensitive unsymmetrical squaraine dyes, SQ‐258 and SQ‐259, for their suitability as a sensitizer in dye‐sensitized solar cells (DSSCs) are designed and synthesized, followed by photophysical and photovoltaic characterizations. It is demonstrated that introducing a 1,3‐indandione acceptor unit in the central squaric acid core of SQ‐259 leads to the suppression of dye aggregation owing to its nonplanar molecular geometry and the broadening of the optical absorption and photon‐harvesting window up to 800 nm. Owing to the extended wavelength photon harvesting, SQ‐259 improves the photoconversion efficiency (PCE) compared to its SQ‐258 dye counterpart. However, despite its wide wavelength photon harvesting, the improvement in the PCE of SQ‐259 is less pronounced, and this is attributed to the small driving force for injection of electrons (0.29 eV), hampered electronic coupling, and decreased electron lifetime for resistance to recombination (7.9 ms), which is confirmed by the cyclic voltammetry, quantum chemical calculation, and electrochemical impedance spectroscopic investigations, respectively.

N,N-Bis(9-methyl-3-carbazolyl)-4-anisidine as an Electroactive Material for Use in Perovskite Solar Cells.

Di(9-methyl-3-carbazolyl)-(4-anisyl)amine is presented as an effective hole-transporting material suitable for application in perovskite solar cells. It is obtained by a three-step synthesis from inexpensive starting compounds. It has a relatively high glass transition temperature of 93 °C and thermal stability with 5% weight loss at 374 °C. The compound exhibits reversible double-wave electrochemical oxidation below +1.5 V and polymerization at higher potential. A mechanism for its oxidation is proposed based on electrochemical impedance and electron spin resonance spectroscopy investigations, ultraviolet-visible-near-infrared absorption spectroelectrochemistry results, and density functional theory-based calculations. Vacuum-deposited films of the compound are characterized by a low ionization potential of 5.02 ± 0.06 eV and hole mobility of 10-3 cm2/(Vs) at an electric field of 4 × 105 V/cm. The newly synthesized compound has been used to fabricate dopant-free hole-transporting layers in perovskite solar cells. A power conversion efficiency of 15.5% was achieved in a preliminary study.

The Role of Superadsorbent Polymers on Covalent Organic Frameworks‐Based Solid Electrolytes: Investigation of the Ionic Conductivity and Relaxation

AbstractThe scarcity of fossil fuels calls for immediate action toward the development of clean and renewable energy resources. In this context, proton exchange membrane fuel cells (PEMFCs) are gaining ever‐increasing attention as clean technology. Although covalent organic frameworks (COFs) do not usually exhibit high intrinsic proton conductivity (σ), they have been recently proposed as solid polymer electrolytes in PEMFCs, thanks to their high crystallinity and stability to acids and bases. Here, a simple strategy is presented to improve the performance of poor COF‐based proton conductors through addition of sodium polyacrylate (PANa) superadsorbent polymer. Electrochemical impedance spectroscopy investigations after activation at high temperature and relative humidity (RH) provide insights into the role of PANa, whose presence is key to preserve high σ at low RH. The humidity‐dependent X‐ray diffraction study reveals a strengthening of the stacking interaction along the COF (100) plane direction with increasing humidity, through the formation of H‐bonding, thus promoting proton hopping. The study of the dielectric properties as a function of PANa content enables to determine a Debye relaxation regime for the COF/PANa blend with a maximum relaxation frequency of 1513 and 6606 Hz for the pristine COF and the COF/PANa blend, respectively, at their maximum operating temperatures.

Insight into mitigation of corrosion behavior of novel chalcone derivative for AZ91 Mg alloy in saline solution: synthesis, characterization, electrochemical and adsorption studies

Magnesium is the lightest structural metallic element, and exhibited an important developmental potential due to the growing need for lightweight electronics and transportation (aerospace, automobile, etc.). A novel chalcone derivative 4-(3-(4-(4-((4-(4-(3-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acryloyl)-5-methyl-1H-1,2,3-triazol-1-yl)phenyl)sulfonyl)phenyl)-5-methyl-1H 1,2,3-triazol-1-yl)-3-oxoprop-1-en-1-yl)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (DMPO) was synthesized. The chemical structure of the newly synthesized DMPO was inferred from its spectral data (H1-NMR, C13-NMR, and FT-IR). Its structure was also affirmed by field emission scanning electron microscopy-energy dispersive X-ray (SEM-EDX), and thermal stability was studied by thermal gravimetric analysis (TGA-DTA). Then, its potency as a remarkable corrosion inhibition for AZ91 magnesium alloys in NaCl (3.5 wt%) solution was studied. Hydrogen evolution, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) investigations were utilized to assess the impact of the newly synthesized chalcone derivative DMPO on the electrochemical performance of AZ91 Mg alloy in NaCl solution (3.5 wt%). SEM-EDX was used to evaluate the surface and elemental analysis of an AZ91 Mg alloy immersed in NaCl solution (3.5 wt%) with and without DMPO inhibitor. The obtained electrochemical evaluation revealed that DMPO functions as a high-performance, environmentally friendly AZ91 Mg alloy inhibitor in NaCl (3.5%) recording inhibition efficiency 93.7% at 100 ppm. Potentiodynamic polarization experiments revealed that the corrosion was inhibited due to the adsorption of inhibited molecules which follows the Langmuir adsorptive process. The findings also affirmed the development of protective film on Mg alloy surface. In electrochemical tests, it was discovered that DMPO molecules were mixed-type corrosion inhibitors.