Electron Impedance Spectroscopy Research Articles

Defect chemistry to trigger zirconia densification at low temperatures by Spark Plasma Sintering

In-depth control of reactivity and defects chemistry is shown to be mandatory to reach high density YSZ ceramics at sintering temperatures lower than 900°C. The combination of Cold Sintering Process (CSP) and Spark Plasma Sintering (SPS) has highlighted the role of transient chemistry on the densification of this material. More, optimised conditions were found for achieving densification of YSZ at 850°C in a one-step SPS process. In particular, the vacuum level in the SPS chamber is clearly shown to be a decisive parameter to obtain dense nanostructured YSZ tetragonal ceramics up to 95% below 900°C. The occurrence of oxygen vacancies has thus been addressed associating thermal analyses, X-ray photoelectron spectroscopy, Electron Paramagnetic Resonance, photoluminescence spectroscopy and impedance spectroscopy. Understanding defect chemistry mechanisms and their dependence on the process or combination of processes, is a lever towards high-quality YSZ nanostructured ceramics below 900°C.

Anode and cathode overpotentials under accelerated stress testing of a PEM electrolysis cell

An in-situ reference electrode was used under accelerated stress testing of a proton exchange membrane electrolysis cell. The reference electrode enabled the measurement of anodic and cathodic overpotentials. The accelerated stress test (dynamic load degradation) was conducted for over 1000 h, and it included half-cell measurements of the known anode and cathode potentials, repeated polarization curves, electron impedance spectroscopy and nano-scale imaging.The experiment had an average full-cell degradation rate of 77 μV/h. The anodic overpotential appears to be the main driver of the full-cell efficiency loss. The cathode EIS measurements indicate catalyst layer degradation despite minimal effect on the full-cell performance. The anodic EIS measurements yielded a resistance double that observed at the cathode. By simultaneously analyzing high frequency resistance, corrected half-cell polarization curves and half-cell EIS measurements, half-cell overpotentials can be attributed with greater confidence.

3D-graphene hydrogel and tungsten trioxide-MnO2 composite for ultra-high-capacity asymmetric supercapacitors: A comparative study

Researchers worldwide use graphene extensively in its powder form for various applications such as supercapacitors, solar cells, drug delivery, and polymer composites, owing to its considerably valuable properties. However, relatively few studies have been made on the 3D-hydrogel form of graphene for these applications. Here we report a simple and fresh method to prepare 3D graphene hydrogel (3DGH) and its bimetal composite with tungsten trioxide (WO3) and manganese dioxide (MnO2). The structure of 3DGH and its composite is confirmed by advanced characterization techniques viz. Raman Spectroscopy, X-Ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and tunneling electron microscope (TEM). Further, two symmetric devices using 3DGH, 3DGH-metal composite (3DGHMC), and one asymmetric 3DGHMC-3DGH device are comparatively studied using two electrode systems. The effects of scan rates, current densities, voltage window, and frequency were examined for each device by cyclic voltammetry (CV), galvanic charge-discharge (GCD), and Electron impedance spectroscopy (EIS). The asymmetric device showed a high specific capacitance of 657 F g−1 with an excellent energy density of 48.25 W h kg−1 and a high-power density of 596.06 W kg−1 at the current density of 1 A g−1. Also, the asymmetric device retains 100 % of its initial capacitance after 1000 charging-discharging cycles, also extends its stability after 1000 cycling test. Moreover, the quantitative analysis of the device is also made by Dunn's method to evaluate the percentage contribution from surface and diffusion capacitance.

Design and usage of NiO/g-C3N4/CNTs/TiO2 based nanocomposites as improved supercapacitor for energy storage devices

Scientists have been concentrating on storing and converting energy resources in significant scenarios as the entire globe is currently experiencing an extreme energy shortage issue owing to a variety of factors. Supercapacitors and other energy storage technologies based on transition metals are currently in high demand. In this study, multi-component NiO/g-C3N4/CNTs and NiO/g-C3N4/CNTs/TiO2 nanocomposites were effectively constructed, characterised, and the performance of the synthesized materials was reported as super capacitance. The synthesis of NiO/g-C3N4/CNTs and NiO/g-C3N4/CNTs/TiO2 using thermal, heat-treatment, hydrothermal and ultrasonic exfoliation techniques. With impressive findings, the characterisation of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) was conducted. Cyclic Voltammetry (CV), Galvanic Charge Discharge (GCD), and scan rate influence on specific capacitance were used in the electrochemical experiments. Results of Electron Impedance Spectroscopy (EIS) experiments revealed that the NiO/g-C3N4/CNTs/TiO2 electrode had a higher specific capacitance (388.76 Fg−1) than the NiO/g-C3N4/CNTs electrode (362.12 Fg−1). In comparison to NiO/g-C3N4/CNTs (360 Fg−1), the NiO/g-C3N4/CNTs/TiO2 electrode had a gravimetric capacitance of 541 Fg−1. The GCD curve and EIS results also support the conclusion that the NiO/g-C3N4/CNTs/TiO2 electrode material is an excellent candidate with impressive capacitive performance to be used as an energy storing source or supercapacitor because TiO2 contents are available, improving the charge transfer capability linked with CNTs bridged in g-C3N4 interlayered stacked and porous structure, ensuring ion diffusion pathways for better and improved conductivity.

Characterization of sensitized solar cells based on nanocomposites of protoporphyrin IX and microwave reduced graphene oxide quantum dots

In this research we are reporting for the first time the elaboration y characterization of titanium dioxide sensitized solar cells based on nanocomposites of protoporphyrin IX and microwave reduced graphene oxide quantum dots. Reduced graphene oxide quantum dots were synthesized by microwave assisted cutting of reduced graphene oxide and mixed with protoporphyrin IX previous to be drop-casted on titanium dioxide. Characterization was done by dynamic light scattering, ultraviolet visible spectroscopy, Raman spectroscopy, atomic force microscopy, field electron scanning electron microscopy, impedance spectroscopy and current voltage measurements. There were blue and red shifts of Raman and absorption bands of protoporphyrin+reduced graphene oxide quantum dots nanocomposites, evidencing strong interactions because of π−π electrons stacking, this fact was confirmed by microscopy images showing full coverage of protoporphyrin surface by reduced graphene oxide quantum dots. Electrical characterization of titanium dioxide+protoporphyrin+reduced graphene oxide quantum dots showed one of the highest photo-responses and lowest resistivities, in line with impedance measurements in which these composites presented up to ∼200% increase in capacitance, versus TiO2 alone. Efficiency of the optimized cell was 6.13 %, this was a value 9.4 % higher versus titanium dioxide+protoporphyrin cell. The reasons for the behavior of optimized cells are discussed based on a bands diagram showing the possibility of a rectifier effect and because of the strong affinity between protoporphyrin and reduced graphene oxide quantum dots.

Graphene related materials as effective additives for electrical and electromagnetic performance of epoxy nanocomposites

The use of graphene as its ideal form remains an unsolved engineering and industrial challenge, which has led to the exploration of a range of materials called graphene related materials (GRM). Among GRM, graphene nanoplatelets (GNP) are highlighted to improve the general properties of polymers in nanocomposites. Other forms of GRM, such as nanographite and reduced graphene oxide (rGO), are also widely used. This work evaluated the effect caused by the addition of four types of GRM on the electrical, electromagnetic interference shielding efficiency (EMI SE), and Reflectivity (RL) behavior in the epoxy matrix. The nanocomposites with 5, 10, 15, 20, and 30 wt% of GRM were prepared by mechanical mixing of nanoparticles into the epoxy resin. The samples were characterized by Raman spectroscopy, scanning electron microscopy, X-ray diffraction, impedance spectroscopy, EMI SE, and reflectivity. A mathematical tool was also used to estimate the optimum thickness of samples to obtain the maximum reflection loss data. The performance evaluation at elevated GRM contents (20 and 30 wt%) had presented unique outcomes, not previously reported in the literature, which were observed aside from a deep study of the electrical and reflectivity behavior. According to the morphological analyses, each GRM studied presented different average thickness dispersion and lateral sizes. The functionalized graphene nanoplatelets with a higher aspect ratio (G4) achieved electrical percolation in the epoxy matrix for lower content (10 wt%), due to its better dispersibility into the matrix. The composition with 30 wt% of GNP (G2) also with small average thickness and lateral size, but without functionalization achieved the best electrical conductivity (10−4 S/cm) and EMI SE properties (∼20 dB), the G2 nanocomposites presented some GNP were stacked closely and aligned (as a cluster), which had activated an absorptive shielding component and increased the conductivity of the G2 pathways. The composition with 15 wt% of rGO(G3) presented promising reflection loss values RL < -12 dB and 1.3 GHZ wide for a thickness of 7.5 mm (simulated and validated), which was related to the best dissipation due to oxygen defects presence.

X-ray Photoelectron Spectroscopy Analysis of Scandia-Ceria-Stabilized Zirconia Composites with Different Transport Properties.

This work aims to study a possible modification in the electronic structure of scandia-ceria-stabilized zirconia (10Sc1CeSZ) ceramics sintered at different temperatures. In addition to using X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy to investigate the structural and electrical properties, we employed X-ray photoelectron spectroscopy (XPS) to determine the chemical state information of the atoms involved, along with compositional analysis. As expected, a significant increase in grain ionic conductivity with the sintering temperature was present. This increase was accompanied by a decrease in the porosity of the samples, an increase in the grain size, and a transformation from the rhombohedral to the cubic phase. The phase transformation was detected not only using XRD, but also using XPS and, for this type of ceramic, XPS detected this transformation for the first time. In addition to the changes in the structural characteristics, the increase in the ionic conductivity was accompanied by a modification in the electronic structure of the ceramic surface. The XPS results showed that the surface of the ceramic sintered at the lower temperature of 1100 °C had a higher amount of Zr-OH bonds than the surface of the ceramic sintered at the higher temperature of 1400 °C. The existence of these Zr-OH bonds was confirmed using Fourier-transform infrared spectroscopy (FTIR). From this result, taken together with the difference between the oxygen/zirconium ratios in these ceramics, also identified using XPS, we conclude that there were fewer oxygen vacancies in the ceramic sintered at the lower temperature. It is argued that these two factors, together with the changes in the structural characteristics, have a direct influence on the conductive properties of the studied ceramics sintered at different temperatures.

Liquid phase sintering of SnO2 varistors for stability improvement

With the new energy reform, higher requirements for the safety of power transmission are put forward, in which SnO2 varistors play an important role. In this paper, samples were prepared by liquid-phase sintering method, and by means of current-voltage, scanning electron microscopy, capacitance-voltage, X-ray diffraction, and impedance spectroscopy tests, it was found that doping Cu could reduce the porosity of SnO2 varistors and improve the densities of SnO2 varistors and exceed the theoretical density. And the effect of doping with different CuO contents on the electrical properties of SnO2 varistors was also investigated. The results show that when the Cu doping amount is 0.04 mol%, the sample has the best electrical properties with voltage gradient of 761.62 V/mm, leakage current of 5.51 μA/cm2, nonlinear coefficient of 32.78, and grain boundary resistance of 71.8 kΩ. It can better suppress the leakage current and improve the stability of the SnO2 varistor in actual operation.

Use of chalky algae in the manufacturing of clayey ceramic membranes: Microstructural and dielectric behavior for electrochemical applications

Novel ceramic membrane filters were manufactured from kaolino-illitic clays and calcareous algae (up to 20 wt.%) as porogenic agent. The produced membranes were investigated using X-ray diffraction, thermogravimetric analysis, scanning electron microscope, impedance spectroscopy, and Fourier-transform infrared spectroscopy. All of the filtration suitability, electrical properties, and dielectric behavior were assessed and interrelated to the microstructure. It was found that the original clay minerals were involved in the mineralization development while the inclusion of large pores (8–12 μm) was observed at high magnification alongside porosity increase (up to 70%) due to the addition of the bio-based pore-former. Both electric and dielectric measurements revealed that the sintering process was governed by the densification phenomenon and was accompanied with lower activation energy. The order of magnitude of the values taken by electrical impedance was close to average Mega-Ohms suggesting the suitability of the produced ceramic membranes as an electrical insulator for typical electrochemical devices. The tests of filtration have shown that the ceramic membranes produced operate normally in the microfiltration range for a period of 50 min without clogging and at pressures up to 0.12 bar. Conclusively, the developed ceramic membranes could be considered for applications in industrial wastewater treatment and electrochemical media.In addition to this, a perspective has been proposed on the improvement paths or designs for ceramic membrane filters with good performance in wastewater treatment present in some electrochemical environments as well as methods to cope with the challenges regarding the performance of such materials.

Novel Bismuth Sulfide-Indium (Hydroxy) Sulfide [Bi2S3–In(OH)xSy] nanoarchitecture for efficient photoelectrochemical water splitting

In photoelectrochemical (PEC) water splitting, visible light active semiconductors exhibit high conversion efficiency as they are more responsive. Herein, we have realized novel Bi2S3–In(OH)xSy nanoarchitectures for efficient PEC water splitting. We have electrodeposited bismuth vanadate (BiVO4) thin films, and In and S were incorporated via hydrothermal treatment, leading to the formation of novel Bi2S3–In(OH)xSy nanoarchitectures. Bi2S3–In(OH)xSy plane view field emission scanning electron microscope shows a novel patty-packed structure covered with some urchin-like structures, implying a strong surface effect. Electron Impedance spectroscopy (EIS) was employed for impedance measurements. Flat band potential and carrier concentration were determined from Mott-Schottky (MS) plots. The realized novel Bi2S3–In(OH)xSy nanoarchitecture-based photoanodes exhibited a remarkable photocurrent density of 7.77 mA/cm2 at a bias voltage of 1.2 V/RHE under 1.5 AM illumination (1000 W/m2). The heterojunction nanoarchitectures have a reduction in the surface states of the nanocrystal, low lattice misfit, and quick charge transfer, which leads to effective PEC activity. The ABPE for the novel Bi2S3–In(OH)xSy nanoarchitecture-based photoanodes is 4.5% at 0.6 V vs. RHE in an electrolyte solution containing 0.1 M Na2SO4. The results are encouraging and suggest that the Bi2S3–In(OH)xSy nanoarchitectures-based photoanodes can be a prospective material for efficient solar-to-hydrogen generation devices.

The preparation of reduced graphene oxide - Cu2S by hydrothermal method for quantum dot sensitized solar cells

In our last paper, we found that the efficiency of quantum dot-sensitized solar cells with a Cu2S counter electrode was better, but the current density was not very high. In this research, we operated the solar cells from a reduced graphene oxide-Cu2S counter electrode in order to improve the efficiency of the charges moving over the FTO/rGO-Cu2S/polysulfide interface by taking advantage of the special properties of graphene oxide due to its large electricity, low resistance, high electron mobility, and large surface resistance. Here, we studied the influence of electrochemistry and the conversion efficiency of devices when changing the mass of graphene oxide. The results for the rGO/Cu2S electrode with 18 mg of GO exhibiting the best electrochemistry in the polysulfide electrolyte are presented through the results of C–V measurement and electronic impedance spectroscopy. The resistance of FTO/rGO-Cu2S/electrolyte is the smallest (2.54 Ω) to match the current density of 10.2 mA/cm2. This result is also presented through the J-V curves, with quantum dot sensitized solar cells having the best performance (ȵ is 5.24%, Voc is 0.503 V, FF is 0.421, and Jsc is 24.9 mA/cm2) at 18 mg GO.

Flower-like Layered NiCu-LDH/MXene Nanocomposites as an Anodic Material for Electrocatalytic Oxidation of Methanol

Direct methanol fuel cell (DMFC) technology has grabbed much attention from researchers worldwide in the realm of green and renewable energy-generating technologies. Practical applications of DMFCs are marked by the development of highly active, efficient, economical, and long-lasting anode catalysts. Layered double hydroxide (LDH) nanohybrids are found to be efficient electrode materials for methanol oxidation. In this study, we synthesized NiCu-LDH/MXene nanocomposites (NCMs) and investigated their electrochemical performance for methanol oxidation. The formation of NCM was verified through field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), and X-ray photoemission spectroscopy (XPS) analyses. The cyclic voltammetry, chronoamperometry, and electron impedance spectroscopy techniques were carried out to assess the electrocatalytic ability of the methanol oxidation reaction. The incorporation of MXene enhanced the methanol oxidation 2-fold times higher than NiCu-LDH. NCM-45 exhibited high peak current density (86.9 mA cm-2), enhanced electrochemical active surface area (7.625 cm2), and long-term stability (77.8% retention after 500 cycles). The superior performance of NCM can be attributed to the synergistic effect between Ni and Cu and, further, the electronic coupling between LDH and MXene. Based on the results, NCM nanocomposite is an efficient anodic material for the electrocatalytic oxidation of methanol. This study will open the door for the development of various LDH/MXene nanocomposite electrode materials for the application of direct methanol fuel cells.

Effect of Sn doping on sinterability and electrical conductivity of strontium hafnate

The effect of isovalent substitution of hafnium by tin in strontium hafnate on sinterability and electrical conductivity was studied for the first time. The ceramic samples SrHfxSn1–xO3–δ (x = 0–0.16) were synthesized by solid-state reaction and sintered at 1600 °C for 5 h. The samples were examined using the methods of X-ray diffraction, scanning electron microscopy, impedance spectroscopy, and four-probe direct current technique. It was shown that all samples were phase pure and had the orthorhombic structure of SrHfO3 with the Pnma space group. Sn doping resulted in an increase in grain size, relative density and conductivity; the sample with x = 0.08 demonstrated the highest conductivity, which was ~830 times greater than that of undoped strontium hafnate at 600 °C. The conductivity of SrHf0.92Sn0.08O3–δ was 4.1∙10–6 S cm–1 at 800 °C in dry air. The possible reasons for the effect of Sn on the electrical properties of strontium hafnate were discussed.

Synthesis of GdFeO3/α-Fe2O3 heterostructure with enhanced photo-Fenton-like performance for organic pollutant degradation

The synergistic effects of photo-Fenton-like oxidation and heterostructure photocatalysis are highly beneficial for wastewater treatment. In this work, photo-Fenton-like GdFeO3 (GFO)/α-Fe2O3 catalysts with Z-scheme heterostructures were successfully fabricated via a facile ultrasonic method and then characterized using X-ray diffraction, transmission electron microscopy (TEM), field emission scanning electron microscopy, high-resolution TEM, ultraviolet–visible diffuse reflectance spectroscopy, X-ray photoelectron microscopy, photocurrent analysis, and electron impedance spectroscopy. The heterostructure with a GFO/Fe ratio of 3:7 showed the highest photocatalytic activity during degradation of organic pollutants, and adding small amounts of H2O2 increased its visible-light-driven catalytic activity by 9.5, 2.3, and 16.4 times that of rhodamine B, methylene blue, and tetracycline, respectively. The catalytic results were significantly improved due to the synergy of the Z-scheme heterostructure and photo-Fenton-like oxidation. The results indicate that an appropriate composition ratio can accelerate the conversion rate of surface ≡Fe3+ to ≡Fe2+ and promote the separation of electron–holes that can form more reaction active sites. Furthermore, a possible photocatalytic mechanism associated with the GFO/Fe composite was proposed using an electron spin resonance test and active-species trapping experiments. Overall, this work presents an important synthesis route for photo-Fenton-like catalysts that can degrade organic pollutants in wastewater.

Heterostructure of Metal Oxides Integrated on a GCE for Estimation of H2O2 Capacity in Milk and Fruit Juice Samples

High levels of H2O2 in food can lead to oxidative stress. Which has been linked to a number of neurological diseases. Hence, its detection in beverages is essential. However, a complicated structure of the reaction medium of H2O2 makes the detection procedure very difficult. For this reason, sensitive strategic methods are required. In this study, quantification of H2O2 in milk and apple juice has been obtained via the electrochemical sensing platform based on GCE/SiO-CeONPs. Scanning Electron Microscopy (SEM), Cyclic voltammetry(CV), and electron impedance spectroscopy(EIS) were employed to characterize the composite. The kinetics investigation of the sensor with H2O2 revealed an a quasi-reversible one -electron adsorption process. Under optimized conditions, the Differential Pulse Voltammetry (DPV) in 0.1 M Phosphate buffer (PB) pH 5.5 of the H2O2 displayed a peak at 0.13 V vs. Ag/AgCl with the detection limits of 0.0004 µM, linearity range of 0.01–0.08 µM. The observed LOD values of this method for real samples were calculated to be 0.006 µM and 0.007 µM with LOQ of 0.02 µM for milk and apple juice, respectively. The recovery of the analyte was from 92 to 99%. Furthermore, due to good selectivity and stability, the benefit of this sensor is its applicability in multiple fields.

The starting stoichiometry, keys parameter to enhance the intrinsic microstructural and functional properties of synthesized hybrid nanocomposites chitosan/Na-montmorillonite/ZnO nanoparticlest type

To improve the intrinsic qualities of hybrid nanocomposite (NC), polymer, clay, and metallic oxide are combined. This study investigates the effects of starting stoichiometry variation on the microstructural and functional properties of synthesized hybrid NC composed of chitosan (CTS), Na-montmorillonite (MMT), and ZnO nanoparticles (NPs). To carry out the synthesized process, a solution blending approach is used. A correlation of the outcomes from the several analyses methods such as X-ray diffraction (XRD), Fourier Transform InfraRed spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Impedance spectroscopy (IS), and UV–VIS spectrophotometry ensures the accuracy of the analysis. Regardless of the initial stoichiometry rate, the microstructural analysis shows that NC can be successfully synthesized. The growth and changes in the intensity and sharpness of the characteristic reflections shown by the semiquantitative XRD analysis suggest that the synthesis process was certainly successful. The apparent structure aberration, caused by the stoichiometry fluctuation, is manifested as an XRD reflection position shift and varied intensity strength.The intercalation process and the exfoliation of "clay-particles" enclosing the organic fraction, according to TEM/EDX experiments, occurred as the clayey fraction's abundance surged. Despite the variable ratio approved at the start of the synthesis process, FTIR spectroscopy displays the polymer fraction's characteristic absorption bands. Synthesized NC has significant UV blocking properties while retaining good transparency in the visible range. This behavior may have its roots throughout the fact that the CS surface modification has induced the bandgap energy fluctuation of ZnO NPs. The photocatalytic activity of the produced NC is evaluated using MB degradation measurements. The outcomes are extremely positive for the sample with a starting stoichiometry almost equally distributed between CTS and ZnO (NPs). Results from the IS, for the selected sample, shows that synthesized NC exhibits semiconductor behavior,and as a dielectric material, the sample is dispersive with a power loss over a specific frequency range.

Enriched photocatalytic and photoelectrochemical activities of a 2D/0D g-C3N4/CeO2 nanostructure.

Sunlight-powered photocatalysts made from CeO2 nanosized particles and g-C3N4 nanostructures were produced through a thermal decomposition process with urea and cerium nitrate hexahydrate. The preparation of g-C3N4, CeO2, and a binary nanostructured g-C3N4/CeO2 photocatalyst was done through a facile thermal decomposition method. The structural properties were analyzed using powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS). Photocatalyst properties were characterized by using crystal violet (CV), a UV-Vis spectrophotometer, photocurrent and electron impedance spectroscopy (EIS). The structural and morphological analyses revealed that the g-C3N4/CeO2 nanostructures significantly enhanced the photoactivity for CV dye degradation under simulated sunlight, with a degradation rate of 94.5% after 105 min, compared to 82.5% for pure g-C3N4 and 45% for pure CeO2. This improvement was attributed to the noticeable visible light absorption and remarkable charge separation abilities of the nanostructures. Additionally, the g-C3N4/CeO2 nanostructures showed notable PEC performance under simulated sunlight. This study presents an easy and efficient method for producing g-C3N4 photocatalysts decorated with semiconductor materials and provides insights for designing nanostructures for photocatalytic and energy applications.

Understanding the Redox Mechanism of Sulfurized Poly(acrylonitrile) as Highly Rate and Cycle Stable Cathode Material for Sodium-Sulfur Batteries

Room temperature sodium-sulfur (RT Na-S) batteries are considered potential candidates for stationary power storage applications due to their low cost, broad active material availability and low toxicity. Challenges, such as high volume expansion of the S-cathode upon discharge, low electronic conductivity of S as active material and herewith limited rate capability as well as the shuttling of polysulfides (PSs) as intermediates often impede the cycle stability and practical application of Na-S batteries. Sulfurized poly(acrylonitrile) (SPAN) inherently inhibits the shuttling of PSs and shows compatibility with carbonate-based electrolytes, however, its exact redox mechanism remained unclear to date. Herein, we implement a commercially available and simple electrolyte into the Na-SPAN cell chemistry and demonstrate its high rate and cycle stability. Through the application of in situ techniques utilizing electronic impedance spectroscopy (EIS) and X-ray absorption spectroscopy (XAS) at different depths of charge and discharge, an insight into SPAN’s redox chemistry is obtained.

Preparation and Characterization of PLA/Polypyrrole Blends with Antibacterial Properties

We discuss the preparation of Polypyrrole and Polylactic Polyacid (PPy/PLA) based blends and the subsequent investigation of their antibacterial properties. After being molded through injection processing, the blends were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Impedance Spectroscopy (IS), contact angle, thermogravimetry (TGA), and dynamic mechanical analysis (DMA). FTIR analysis confirmed the presence of PPy chains and the IS results indicated that the blends prepared with a 50% mass fraction of PPy have a conductive character. While the SEM images reveal the presence of small cracks on the surface of the samples, DMA analyses show that a decrease in their mechanical strength occurs in the 50°C-60°C range, with the blend with a 50% PPy load exhibiting the greater resistance and being able to withstand temperatures of the order of 120°C. The TGA degradation profile varies according to the amount of polypyrrole present in the blends, with those containing 50% PPy being able to retain about 32% of the polypyrrole mass at 600°C. The antibacterial activity tests done with the injected blends reveal that while no inhibition halo was formed for the Escherichia coli bacterium, the growth of Staphylococcus aureus is inhibited in the 50% PPy blend.

Sensitive and selective determination of vanillin in the presence of dopamine and uric acid using low-cost and trouble-free pencil graphite electrode modified with methyl orange

A simple, low-cost, and trouble-free electrochemical sensor has been developed by electropolymerization of methyl orange (MO) on a pencil graphite electrode (PGE) for the selective and sensitive voltammetric investigation of vanillin (VNL). Surface morphology of poly (methyl orange) modified pencil graphite electrode (poly (MO)/PGE) and bare pencil graphite electrode (BPGE) were examined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) and electron impedance spectroscopy (EIS). The poly (MO)/PGE shows good electrocatalytic activity over BPGE which was assessed by linear sweep voltammetry (LSV), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer solution (PBS). Under optimized conditions, the anodic peak current of the analyte was directly proportional to the concentration of the analyte (1.0–26.0 μM) with the limit of detection (LOD) 0.10 μM. Various parameters like heterogeneous rate constant (k0 = 1.13 × 10−9 cm s−1), number of electrons transferred, and surface concentration (Γ = 4.85 × 10-11 mol cm−2) were calculated. The analytical applicability and selectivity of the modified sensor were deliberated by real sample analysis of VNL in presence of dopamine (DA) and uric acid (UA). Thus, a developed electrochemical sensor could be successfully employed for the analysis of VNL present in real samples.