Electrochemical Impedance Spectroscopy Experiments Research Articles

Synthesis and performance study of novel antibacterial and anticorrosive polyurethane IPN

Polyaniline has been extensively used for the corrosion protection of polymeric materials. However, there have been few studies on its combined antimicrobial activity when used in combination with silver molybdate. In this study, we synthesized silver molybdate (Ag2MoO4) crystals using a homogeneous precipitation method. Polyaniline-dodecylbenzenesulfonic acid/castor oil(PANI-DBSA/CO) mixtures were prepared in an encapsulated state by in situ polymerisation. Subsequently, PANI/Ag2MoO4-PU interpenetrating polymer network(IPN) composite coatings(P/A-PU) were produced by dispersing Ag2MoO4 and PANI-DBSA/CO in polyurethane using ultrasonic dispersion. The composite coatings were characterized using Fourier transform infrared spectroscopy(FTIR), X-ray diffraction analysis(XRD), and transmission electron microscopy(TEM). The study confirmed that composite coatings with uniformly dispersed nanoparticles of PANI and Ag2MoO4 encapsulated by CO and epoxy resin E-44 grease exhibit improved physico-mechanical characteristics. The research also evaluated the effect of nanoparticles on the corrosion behaviour of the coatings using electrochemical impedance spectroscopy and kinetic potential polarisation experiments. The study investigated the antimicrobial properties of P/A-PU composite coatings on Escherichia coli(E.coli) and Staphylococcus aureus(S.aureus) by conducting bacterial growth curves, protein leakage, and fluorescence staining experiments. The aim was to establish a causal connection between the coated surfaces and the observed antimicrobial properties. The study demonstrated that incorporating IPN of polyaniline polyurethane into the coating composites improved their anticorrosive properties. Furthermore, the addition of silver molybdate at a mass ratio of 0.3 % resulted in a remarkable 99 % antimicrobial activity against E.coli and S.aureus.

Comparison of Approaches for Assessing Linearity of Impedance Measurements

Electrochemical impedance spectroscopy experiments are inherently nonlinear for systems affected by faradaic reactions. The methods used to determine whether an experiment is sufficiently linear include observation of current as a function of potential, known as Lissajous plots, measurement of total harmonic distortion, and post-experiment assessment of consistency with the Kramers–Kronig relations. An experimental approach is employed to compare sensitivity of these methods to determination of nonlinear response in electrochemical impedance measurements. The Lissajous figures showed linear behavior for a total harmonic distortion equivalent to 1 percent of the fundamental; whereas, the measurement model analysis revealed nonlinear behavior only for larger perturbation amplitudes.

Tuning combustion and energy in hydroxylammonium nitrate (HAN)-based electrically controlled solid propellant

Solid propellants have been widely applied due to its high energy, rapid reaction, easy storage and convenient equipment. However, the further development of solid propellants has been hindered by the challenges associated with controlling their combustion process. In this research, we presented an electrically controlled solid propellant (ECSP), and its burning rate could be continuously adjusted with voltage. We investigated thermal decomposition behavior and gaseous products of ECSP using thermogravimetry–differential scanning calorimetry-mass spectrometry (TG-DSC-MS). The solid products were analyzed through energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Based on the thermal decomposition behavior, gaseous products, and solid products, it was found that the thermal decomposition process could be divided into two stages: decomposition of ammonium nitrate (AN) and interactions between hydroxylamine nitrate (HAN) and other substances. The electrochemical impedance spectroscopy (EIS) experiments revealed that the electrical conductivity of ECSP increased with the pressure. Significantly, the peak combustion pressure of propellant increased by the rise of voltage from 3.17 MPa (150 V) to 5 MPa (250 V) in closed bomb. In addition, electricity reinforced the burning rate and powder force of propellant. Additionally, the electricity simultaneously affects electric and thermal decomposition processes. Electricity is used to control the burning rate and the total energy produced by propellant combustion. The characteristics of controllable energy has the potential to achieve controllable range of weapons, providing a new direction for development of smart weapons.

A rational study of transduction mechanisms of different materials for all solid contact-ISEs

The new era of solid contact ion selective electrodes (SC-ISEs) miniaturized design has received an extensive amount of concern. Because it eliminated the requirement for ongoing internal solution composition optimization and created a two-phase system with stronger detection limitations. Herein, the determination of venlafaxine HCl is based on a comparison study between different ion- to electron transduction materials (such as; multiwalled carbon nanotubes (MWCNTs), polyaniline (PANi), and ferrocene) and illustrating their mechanisms in their applied sensors. Their different electrochemical features (such as bulk resistance (Rb**), double-layer capacitance (Cdl), geometric capacitance (Cg), and specific capacitance (Cp)) were evaluated and discussed by using the Electrochemical Impedance Spectroscopy (EIS), Chronopotentiometry (CP), and Cyclic Voltammetry (CV) experiments. The results indicated that each transducer's influence on the proposed sensor's electrochemical characteristics is determined by their unique chemical and physical properties. The electrochemical features vary for different solid contact materials used in transduction mechanisms. The results confirm that the MWCNT sensor revealed the best electrochemical behavior with the potentiometric response of a near-Nernestian slope of 56.1 ± 0.8 mV/decade with detection limits of 3.8 × 10−6 mol/L (r2 = 0.999) and a low potential drift (∆E/∆t) of 34.6 µV/s. Also, the selectivity study was performed in the presence of different interfering species either in single or complex matrices. This demonstrates excellent selectivity, stability, conductivity, and reliability as a VEN-TPB ion pair sensor for accurately measuring VEN in its various formulations. The proposed method was compared to HPLC reported technique and confirmed no significant difference between them. So, the proposed sensors fulfill their solutions' demand features for VEN appraisal.

A comparative study on the corrosion of pure titanium and titanium–12%zirconium alloy after different exposure periods of time in sodium chloride solution

In this work, the powder metallurgy technique was employed to manufacture pure titanium (Ti) and 88% titanium–12% zirconium (TiZr) alloy. The electrochemical corrosion investigations for pure Ti and the TiZr alloy were carried out after exposure for 30 min and 3 days in 3.5% NaCl solutions. The Nyquist and Bode plots obtained from the electrochemical impedance spectroscopy experiments revealed that the presence of Zr remarkably magnifies the corrosion resistance of Ti via increasing the impedance and degree of the phase angle, as well as the polarization and solution resistances. The potentiodynamic cyclic polarization measurements revealed that the presence of 12% Zr highly enhances the corrosion resistance of Ti. These polarization results showed that Zr addition reduces the corrosion of Ti via decreasing its corrosion rate. The intensity of the current when measured with increasing time of the experiment at −0.10 mV (Ag/AgCl) indicated that the addition of 12% Zr greatly decreases the absolute current, which indicates that alloying Zr within Ti reduces the severity of its corrosion in the chloride electrolyte. The morphology of the surfaces and the possible surface layer(s) for the corroded Ti and TiZr samples were analyzed using a scanning electron microscope and energy dispersive x rays. Results collectively depicted that the presence of Zr increases the corrosion resistance when alloyed with Ti.

Inert salt-assisted solvent-free synthesis of high-entropy oxide towards high-performance lithium-ion batteries

High-entropy oxide (HEO) is a promising anode material for lithium-ion battery (LIB) due to the synergistic effect of various metal species. Conventional HEO preparations typically involve a solid-state route or liquid-phase mixing followed by high-temperature calcination, leading to either a small surface area or environmental contamination. Herein, a novel, facile solvent-free preparation of HEOs is introduced, applying inert salt, NaCl, as an easily removable, eco-friendly and recyclable template. This approach realizes high-purity porous HEO (NPHEO) with specific surface area (28.1 m2 g−1) for high-performance lithium-ion batteries. With the enhanced electrochemical kinetics, the NPHEO anodes deliver a high reversible specific capacities of 1143.6 at 0.2 A/g. In addition, the NPHEO-based cells exhibit a desirable rate capability of 315.7 mAh/g at 5 A/g. At 1 A/g the cell delivers a good cyclability of 71.8 % capacity retention over 600 cycles, corresponding to an average coulombic efficiency of above 99.94 % per cycle. Ex-situ X-ray diffraction and in-situ electrochemical impedance spectroscopy experiments further probe the structural evolution and electrochemical behavior during lithiation/delithiation, confirming the structural stability and fast electrochemical kinetics of NPHEO. The proposed advanced synthesis approach offers a new platform for the preparation of HEOs with high quality.

State of health estimation of second-life batteries through electrochemical impedance spectroscopy and dimensionality reduction

When lithium-ion batteries (LiBs) reach the end of their useful life in electric vehicles (EVs), they can still be used in less demanding applications, a process known as second-life (SL). Nevertheless, to ensure a safe, efficient and reliable operation of the retired LiBs in a SL application, many tests and procedures should be done to determine their internal conditions, and naturally, one of the most important parameters to be determined in these procedures is the state of health (SoH). However, the tests to obtain this parameter are intrusive, requiring taking the LiBs out of service and performing successive discharge and charge cycles in laboratory benches with special equipment, which is costly, have a high energy demand, and is time-consuming. These limitations hinder the SL market since it is estimated that in the next few years, a significant amount of LiBs will be available for SL purposes. This work suggests an approach that employs experimental electrochemical impedance spectroscopy (EIS) data and neural networks (NN) to assess the SoH of lithium-ion cells subjected to SL conditions. Also, a novel approach to perform the dimensionality reduction of the EIS measurements – reducing the time needed to perform the EIS measurement without the loss of significant data – is proposed, where the measurement time can be reduced to 19.10% of its original value, and the number of assets generated by the measurements can be reduced from 81 to 4. The proposed methodology was validated offline using two datasets of lithium-ion cells under SL conditions, the first one considers the EIS data of 395 Lithium Iron Phosphate (LFP) high-capacity cells, and the second one the EIS data of 36 Lithium Nickel Manganese Cobalt (NMC) medium-capacity cells. Root mean square errors of 1.18% and 0.95% in the SoH estimation were obtained for the LFP and NMC cells, respectively. Therefore, the novel methodology that has been proposed in this work offers significant advantages over the conventional capacity test, including non-invasiveness, fast processing time and low energy consumption.

Synthesis, spectroscopic characterization studies of chelating complexes and their applications as antimicrobial agents, DNA binding, molecular docking, and electrochemical studies

N,N′‐bis(2,4‐dihydroxy benzaldehyde‐1,2‐diaminobenzene) (H4L) formed from the reaction of 2,4‐dihydroxybenzaldehyde and 1,2‐diaminobenzene was complexed with Cu (II), Co (II), Ni (II), Mn (II), and UO2(II) ions. The formed complexes have been characterized by their physical data, spectral studies such as FT‐IR, Uv–Vis., 1H & 13C NMR, Mass, elemental microanalysis (C.H.N.), thermal analysis, X‐ray diffraction, and magnetic susceptibility measurements. The molecular docking between the protein receptors of the H4L ligand and its complexes was studied as theoretical method. The ligand and its metal complexes (1–5) were tested for their ability to inhibit the growth of various pathogenic microbial strains. The biological significance of the Schiff base compound and complexes as antifungal, antibacterial, and anticandidal agents as well as cytotoxicity was studied. The tested microorganisms respond better to the metal complexes than the Schiff base ligand. In comparison to the ligand, complexes, and penicillin, the UO2(II) complex (5) demonstrated the strongest antibacterial activity. In comparison to ligand, complexes, and miconazole, the UO2(II) complex (5) has antifungal activity against Aspergillus niger and Candida albicans. Complexes (1) and (5) have higher activity of antibacterial than other complexes against Pseudomonas sp. and the highest antifungal and anticandidal activity in comparison with miconazole. The ligand and its complexes showed a dose‐dependent antibacterial action according to the minimum inhibition concentration test. Using Tafel polarization and electrochemical impedance spectroscopy experiments, the protective impact of the bis‐Schiff base ligand (H4L) ligand versus Q235 Steel and its adsorption performance were investigated. The interaction between H4L Schiff base and complexes (1)–(5) and calf thymus DNA shows hypochromism effect coupled with obvious bathochromic shift.

Investigation of the behavior of benzimidazole and its derivatives as corrosion inhibitors for cobalt in alkaline medium

Cobalt, as a barrier layer between copper and dielectric during the integrated circuit (IC) copper interconnect process, is commonly applied to stop diffusion each other below the 14 nm technology node. And the corrosion problem is a significant focus of research in the cobalt barrier chemical mechanical polishing process. Corrosion inhibitors are essential additives in polishing slurries to reduce corrosion and improve polishing performance. In this paper, the inhibition behavior of benzimidazole and its two derivates (2-hydroxybenzimidazole and 2-aminobenzimidazole) for cobalt in alkaline medium was investigated. The static corrosion rates of cobalt decreased with rising inhibitors concentration and the corrosion inhibition efficiencies (IE) exceeded 90 % when the concentration of the three inhibitors was above 5 mM. Under conditions of sufficient inhibitor concentration, the removal rates of the dynamic polishing process decreased, and 10 mM was determined as the optimal concentration due to achieving the required removal rate (100–300 Å/min). The contact angles and polishing results for cobalt immersed in solutions with corrosion inhibitors showed that the three inhibitors led to the more hydrophobic cobalt surface, indicating the passivation film formation. The results of potentiodynamic polarization and electrochemical impedance spectroscopy experiments exhibited the similar inhibition characteristics for cobalt according to the decreased corrosion current density (icorr), the increased polarization resistance (Rp) and the reduced capacitance of the interface (Cdl). The inhibition efficiency for cobalt is in the order of 2-aminobenzimidazole > 2-hydroxybenzimidazole > benzimidazole. The adsorption of the three inhibitors obeyed the Langmuir’s adsorption isotherm. The corrosion inhibition is attributed to the adsorption of inhibitors molecules through the combination of physical and chemical adsorption on the cobalt surface.

Determination of the distribution of relaxation times through Loewner framework: A direct and versatile approach

In this work, a direct data-driven approach is employed to extract the distribution of relaxation times (DRT) from impedance data. The proposed procedure is based on the Loewner framework, that is a data driven methodology with theoretical basis in the linear system theory. One of the main advantages is that the DRT can be computed without need of regularization procedures or iterative optimization algorithms. We test the Loewner framework based algorithm on synthetic impedance data generated through equivalent circuit models widely used for modeling electrochemical systems. Impedance data set including noise are also processed. In addition, experimental electrochemical impedance spectroscopy (EIS) data are analyzed. The study shows a significant improvement in the accuracy and a high versatility of the methodology. However, the presence of significant amount of noise compromises the reliability of the obtained DRT due to the occurrence of artifact peaks. Some recommendations how to deal with noisy data are discussed.

The biochemical and electrochemical characteristics of a microbial fuel cell used to produce electricity from olive mill wastewater

Olive Mill Wastewater (OMW) is a hard to treat by-product with low biodegradability and high toxicity due to its high phenolic content. Ιn the present study, OMW after centrifugation, was used for combined electricity and methane production. A three-air cathode single-chamber MFC operating continuously was set up for the exploitation of the liquid fraction of OMW obtained via centrifugation, while batch anaerobic digestion (AD) was employed for valorization of the solid residue. The MFC was also operated with a glucose-based medium, supplemented with phenolics, in order to assess the effect of phenolic compounds on its performance. In order to highlight the mechanisms and determine the limitations and electrochemical losses, electrochemical impedance spectroscopy experiments were conducted, using both the synthetic and the real wastewater. The experimental results showed that power densities of 0.7–2.0 W/m3 OMW were achieved in the MFC, corresponding to an energy of 6.2 MJ/m3 OMW while 664 MJ/m3 OMW could be obtained through AD of the solid residue. However, as the energy which could be recovered directly from AD of OMW was calculated as 1439 MJ/m3 OMW, indicates that it is a competitive technology for OMW treatment and valorization.

Barrier and passivation effects of 2D PANI@JNSs Janus nanosheets in epoxy anticorrosion coating

AbstractThe filled sheet‐like inorganic materials can usually improve the anticorrosion performance of the coating. Herein, the Janus nanosheets (JNSs) with two‐dimensional structure were prepared by phase separation method, modified by polyaniline (PANI) on the amino side of JNSs and composited with epoxy resin (EP). Scanning electron microscope (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FT‐IR), thermogravimetry (TG) were used to characterize the morphology and chemical structure of JNSs and PANI@JNSs. The anti‐corrosion performance of coatings was measured by electrochemical impedance spectroscopy (EIS) and salt spray experiment. Compared with pure EP, the |Z|0.01Hz of 0.5%‐JNSs/EP coating and that of 0.5%‐PANI@JNSs/EP coating reached 5.6 × 108 and 5.4× 1010 Ω·cm2 after immersed for 35 days, nearly 2 and 4 orders of magnitude higher than pure EP respectively. The excellent anti‐corrosion performance of 0.5%‐PANI@JNSs/EP coating is due to the synergistic effect of physical barrier effect of PANI@JNSs, interfacial interaction between PANI@JNSs and epoxy resin and passivation effect of PANI. Moreover, PANI@JNSs possess both strengthening and toughening effects on composite coating. Janus nanosheets provide a new idea and method for preparing high‐performance anticorrosive materials.

Lamellar Ionenes with Highly Dissociative, Anionic Channels Provide Lower Barriers for Cation Transport.

Solid polymer electrolytes have the potential to enable safer and more energy-dense batteries; however, a deeper understanding of their ion conduction mechanisms, and how they can be optimized by molecular design, is needed to realize this goal. Here, we investigate the impact of anion dissociation energy on ion conduction in solid polymer electrolytes via a novel class of ionenes prepared using acyclic diene metathesis (ADMET) polymerization of highly dissociative, liquid crystalline fluorinated aryl sulfonimide-tagged ("FAST") anion monomers. These ionenes with various cations (Li+, Na+, K+, and Cs+) form well-ordered lamellae that are thermally stable up to 180 °C and feature domain spacings that correlate with cation size, providing channels lined with dissociative FAST anions. Electrochemical impedance spectroscopy (EIS) and differential scanning calorimetry (DSC) experiments, along with nudged elastic band (NEB) calculations, suggest that cation motion in these materials operates via an ion-hopping mechanism. The activation energy for Li+ conduction is 59 kJ/mol, which is among the lowest for systems that are proposed to operate via an ion conduction mechanism that is decoupled from polymer segmental motion. Moreover, the addition of a cation-coordinating solvent to these materials led to a >1000-fold increase in ionic conductivity without detectable disruption of the lamellar structure, suggesting selective solvation of the lamellar ion channels. This work demonstrates that molecular design can facilitate controlled formation of dissociative anionic channels that translate to significant enhancements in ion conduction in solid polymer electrolytes.

Fabrication of “wooden ear”-like filler and anti-corrosion of composite coating under high temperature environment

A composite coating composed of high temperature resistant fillers, resin and curing agent was fabricated to protect carbon steel from corrosion in 3.5 wt% NaCl solution and high temperature environment. In this work, the modification filler K-ZrP was prepared through the intercalation of α‑zirconium phosphate (α-ZrP) and the modification of KH550, which avoids the accumulation of filler during the preparation of coating, that is, the filler is evenly distributed in the coating. At different temperature (room temperature, 90 °C and 140 °C), the EP/K4 coating referring to the epoxy coating containing 4 wt% K-ZrP filler shows good corrosion resistance performance, which is reflected in electrochemical impedance spectroscopy and salt spray experiment. In particular, after soaking in 3.5 wt% NaCl solution at 140 °C for 7 days, the EP/K4 coating remained intact, while the other two comparison samples (EP, EP/α4 coatings which refers to the epoxy coating containing 4 wt% α-ZrP) are completely destroyed, the reason is that the microstructure of modified α-ZrP has better compatibility with epoxy resin. The “wooden ear”-like structure and functional groups guaranteed that K-ZrP could distribute uniformly in the system, fill the defects, block the corrosion medium, and most importantly, keep the nonliquidity property of coating under high temperature by forming skeleton structure of nanoparticle stack. Under this condition, the anti-corrosion performance of composite coatings could be improved. The microstructure of the skeleton structure formed by composite coatings in high-temperature corrosive media is more difficult to damage than that of pure epoxy coating.

Electrochemical sensor based on the synergy between Cucurbit[8]uril and 2D-MoS2 for enhanced melatonin quantification

We present the development of an electrochemical sensor towards melatonin determination based on the synergistic effect between MoS2 nanosheets and cucurbit[8]uril. For the sensor construction cucurbit[8]uril suspensions were prepared in water, and MoS2 nanosheets were obtained by liquid exfoliation in ethanol:water. The sensing platform was topographically characterized by Atomic Force Microscopy. Electrochemical Impedance Spectroscopy experiments allowed us to study the charge transfer process during melatonin oxidation. Moreover, stoichiometry of the resulting complex has also been determined. After the optimization of the sensor construction and the experimental variables involved in the Differential Pulse Voltammetric response of melatonin, detection limit of 3.80 × 10−7 M, relative errors minor than 3.8% and relative standard deviation lower than 4.4% were obtained. The proposed sensor has been successfully applied to melatonin determination in pharmaceutical and biological samples as human urine and serum, with very good recoveries ranging from 90 to 102%.

Morphology-dependent catalysis on nanostructures Fe2O3@MWCNT as Pt-free counter electrode for dye-sensitized solar cells

The doped transition metal oxides (TMOs) substitute for the traditional Pt as the counter electrode (CE) catalyst is a unique way to reduce the cost and improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Herein, four different morphologies and size of Fe2O3 (nanodiscus (ND), nanocubes (NC), nanorings (NR), nanoball (NB)) assisted by multi-walled carbon nanotube (MWCNT) to prepare Fe2O3@MWCNT composites, and then were further utilized in the encapsulated DSSCs. The obtained different morphologies Fe2O3@MWCNT composites had been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption-desorption. The significant effects of different morphologies of Fe2O3 on the electrochemical activity of Fe2O3@MWCNT composites as CEs were confirmed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization experiments. The DSSCs using Fe2O3@MWCNT composites CEs achieved high PCEs of 6.34 (ND), 6.53(NC), 6.65(NR), and 7.09% (NB) to regenerate traditional I3−/I− shuttles by the photocurrent-photovoltage (J-V) test, respectively, which is due to the synergistic effect between Fe2O3 and MWCNT to improve electrical conductivity and promote a high number of active catalytic sites, implying a remarkable alternative of Pt-free catalyst that can be applied to the encapsulated DSSCs as CEs.

Polyoxovanadate derived VN@C composite catalysts by different synthesis routes as Pt-free counter electrode for dye-sensitized solar cells

Vanadium-based nitrides have been applied as Pt-free counter electrodes (CEs) electro-catalysts for dye-sensitized solar cells (DSSCs) due to inexpensive cost and easy doping and modification. Herein, polyoxovanadate (NH4)2V6O16 assisted by melamine to prepare VN@C composites by five different synthesis routes, including solvothermal, sol–gel, hydrothermal, ball milling, and chemical mixing method. And then, five VN@C composites were assembled as CEs in the encapsulated DSSCs, and yielded power conversion efficiencies of 4.47, 5.04, 5.35, 5.49 and 6.11% for regenerate traditional I3−/I− shuttles by the photocurrent-photovoltage (J-V) test, respectively. The catalytic performances of VN@C composites CEs were assessed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization experiments, and the significant effects of different synthetic routes were confirmed. The results revealed that VN@C composite CEs prepared by chemical mixing method had higher catalytic performance in DSSCs, which is due to the improvement of conductivity and the high concentration of active sites.

Photovoltaic performance of MOF-derived transition metal doped titania-based photoanodes for DSSCs

The enduring effort toward stabilizing and improving the efficiency of dye-sensitized solar cells (DSSCs) has stirred the solar research community to follow innovative approaches. Current research centered on electrode materials design, which improves photoanodes' light-harvesting efficiency (LHE). Metal–Organic Frameworks (MOFs) are a new family of materials that can be used as competent materials due to their desirable qualities, including high porosity, flexible synthesis methodology, high thermal and chemical stability, and good light-harvesting capabilities. MOF-derived porous photoanodes can effectively adsorb dye molecules and improve LHE, resulting in high power conversion efficiency (PCE). Doping is a prospective methodology to tune the bandgap and broaden spectral absorption. Hence, a novel and cost-effective synthesis of high surface area transition metal (TM) doped TiO2 nanocrystals (NCs) via the metal–organic framework route for DSSCs is reported here. Among the TM dopants (i.e., Mn, Fe, Ni), a remarkable PCE of 7.03% was obtained for nickel-doped samples with increased Jsc (14.66 mA/cm2) due to the bandgap narrowing and porous morphology of TiO2. The findings were further confirmed using electrochemical impedance spectroscopy (EIS) and dye-desorption experiments. The present study expedites a promising way to enhance the LHE for many innovative optoelectronic devices.

Helianthus-annuus assisted synthesis of ZrO2 nanoparticles: Enhanced electrochemical, photoluminescent, and optical properties

Cubic-phase ZrO2 nanoparticle (NPs) were synthesized using a cost-effective single-pot green combustion method and Helianthus annuus extract, and their properties were evaluated. Powder X-ray diffraction was used to investigate the purity, crystal structure, and size of the NPs, and the average size of the NPs was determined to be ∼ 25 nm. The internal surface morphology of the NPs with distinct voids and pores were observed using scanning electron microscopy (SEM) Ultraviolet–visible (UV-vis) absorption spectroscopy was used to analyze the optical properties of the as-synthesized ZrO2 NPs, and their energy bandgap was determined to be 4.5 eV. The photoluminescence (PL) spectrum of the cubic-phase ZrO2 NPs presented a broad band in the UV-vis region. The PL emission properties of the ZrO2 NPs were studied by analyzing their emission wavelength at ∼490 nm, and the results revealed that the NPs can be efficiently used for display applications. The electrochemical properties of a graphite–ZrO2 NP electrode was qualitatively analyzed by performing cyclic voltammetry (CV) and electrochemical impedance spectroscopy experiments in a three–electrode system with a 0.1 M KCl solution as the electrolyte. Our results suggested that the NPs can be used to evaluate the thermodynamics of the redox reaction, and their capacitance was determined using the CV curves of a graphite–ZrO2 working electrode at different scan rates in the range of 0.01 ∼ 0.05 V/s at room temperature. Furthermore, the photodegradation rate of Reactive Blue 4 textile dye over the as-prepared ZrO2 NPs reached 97% under UV-vis light irradiation.

Effect of cryogenic cycling and above-Tg annealing on the corrosion behavior of Zr-Cu-Ti-Be metallic glass

This work investigates the electrochemical properties of Zr-based Zr35Ti30Cu8.25Be26.75 metallic glass after cryogenic treatment and isothermal annealing above glass transition temperature. Potentiodynamic polarization and electrochemical impedance spectroscopy experiments are used to understand the effect of structural state on the corrosion behavior of Zr-based metallic glass. The metallic glass samples are cycled between liquid nitrogen to room temperature and isothermally held at liquid nitrogen to unravel the effect of cryogenic treatments on the electrochemical properties. The corrosion of cryogenically treated and high temperature annealed samples is compared with the as-cast samples. The results show that holding at liquid nitrogen temperature improves the corrosion resistance of metallic glass compared to cryogenic cycling and the high temperature annealing. These findings are explained based on the changes in structural state of metallic glass.