Simple Electrode Research Articles

Electrochemical degradation and mineralisation of organic dyes in aqueous nitrate solutions

Electrochemical treatment of organic matter for environmental remediation necessitates the development of cheap and robust electrodes that are chemically and structurally stable. To address this challenging requirement, we demonstrate a new electrochemical approach using a simple copper electrode under cathodic conditions to electrochemically generate reactive nitrosonium ions for the degradation of different classes of synthetic organic dyes. This could be achieved in an aqueous HNO3/KNO3 electrolyte at a relatively low cathodic potential of −0.5 V RHE at room temperature. UV–visible absorption spectroscopy, Raman spectroscopy, liquid chromatography – mass spectrometry and total organic carbon measurements revealed the rapid decolorisation and mineralisation of several dye types such as triarylmethane dyes (crystal violet, cresol red), an azo dye (methyl orange) as well as a sulfur containing thiazine dye (toluidine blue). The total organic carbon content of a 50 mg L−1 methyl orange solution was found to decrease by 83% after 1 h of electrolysis. Promisingly, locally sourced river and creek water samples spiked with 50 mg L−1 methyl orange were also successfully treated for up to 6 cycles at a simple Cu electrode, demonstrating potential for the remediation of polluted waterways.

Carbon Inks-Based Screen-Printed Electrodes for Qualitative Analysis of Amino Acids.

Due to the great significance of amino acids, a substantial number of research studies has been directed toward the development of effective and reliable platforms for their evaluation, detection, and identification. In order to support these studies, a new electrochemical platform based on PANI/ZnO nanowires' modified carbon inks screen-printed electrodes was developed for qualitative analysis of electroactive amino acids, with emphasis on tyrosine (Tyr) and tryptophan (Trp). A comparative investigation of the carbon ink before and after modification with the PANI/ZnO was performed by scanning electron microscopy and by Raman spectroscopy, confirming the presence of PANI and ZnO nanowires. Electrochemical investigations by cyclic voltammetry and electrochemical impedance spectroscopy have shown a higher charge-transfer rate constant, which is reflected into lower charge-transfer resistance and higher capacitance values for the PANI/ZnO modified ink when compared to the simple carbon screen-printed electrode. In order to demonstrate the electrochemical performances of the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes for amino acids analysis, differential pulse voltammograms were obtained in individual and mixed solutions of electroactive amino acids. It has been shown that the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes allowed for tyrosine and tryptophan a peak separation of more than 100 mV, enabling their screening and identification in mixed solutions, which is essential for the electrochemical analysis of proteins within the proteomics research field.

Ultrasensitive Electrochemical Sensor Based on SnO2 Anchored 3D Porous Reduced Graphene Oxide Nanostructure Produced via Sustainable Green Protocol for Subnanomolar Determination of Anti-Diabetic Drug, Repaglinide

Herein, we have reported on a simple, environmentally friendly, and ultra-sensitive electrode material, SnO2@p-rGO, used in a clean sustainable manner for rapid electrochemical determination of an anti-diabetic agent, repaglinide (RPG). Three-dimensional porous reduced graphene oxide nanostructure (p-rGO) was prepared via a low-temperature solution combustion method employing glycine. The aqueous extract of agricultural waste “cotton boll peel” served as stabilizing and reducing agents for the synthesis of SnO2 nanoparticles. The structural and morphological characterization was carried out by XRD, Raman, SEM, EDX, FTIR, absorption, and TGA. The oxidation process of RPG was realized under adsorption controlled with the involvement of two protons and electrons. The sensor displayed a wider linearity between the concentration of RPG and oxidation peak current in the ranges of 1.99 × 10−8–1.45 × 10−5 M and 4.99 × 10−8–1.83 × 10−5 M for square-wave voltammetric and differential pulse voltammetric methods, respectively. The lower limit of detection value of 0.85 × 10−9 M was realized with the SWV method. The proposed sensor was applied for the quantification of RPG in fortified urine samples and pharmaceutical formulations. Furthermore, the sensor demonstrated reproducibility, long-term stability, and selectivity in the presence of metformin and other interferents, which made the proposed sensor promising and superior for monitoring RPG.

Sustainable waste-nitrogen upcycling enabled by low-concentration nitrate electrodialysis and high-performance ammonia electrosynthesis

A product-oriented electrolyzer design offers a remarkably high nitrate-to-ammonia performance on a simple nickel electrode in an aqueous NaOH/KOH/H2O electrolyte.

Optimized porous carbon-fibre microelectrode for multiplexed, highly reproducible and repeatable detection of heavy metals in real water samples

This work demonstrates the simultaneous identification of four hazardous heavy metals in water samples, namely copper, lead, cadmium, and mercury. A simple yet selective electrode with the simplest fabrication procedure was used. The modified porous carbon threads coated with gold nanoparticles (AuNPs) was employed as a working electrode. The surface chemistry and morphology of the AuNPs deposited porous carbon thread surface were examined. The electrocatalytic activity of the metals on the Au-modified thread surface was observed using the differential pulse voltammetry (DPV) technique. Furthermore, all four metal ions were detected simultaneously, and no interference was observed. Individual and simultaneous experiments to test the impact of concentration revealed that the limit of detection (LoD) was observed to be 1.126 μM, 1.419 μM, 0.966 μM, 0.736 μM for the Cd2+, Pb2+, Cu2+, and Hg2+ metal ions respectively in a linear concentration range of 10–110 μM of each. Subsequently, the study of pH, interference with coexisting metal ions, repeatability study, and stability analysis was also performed. A real sample analysis utilising three different lake water samples is also carried out to further understand the application of the proposed sensor. A good recovery rate is achieved, and the results are reported. This work paves way for the on-field applicability of the present heavy metal detection platform.

New low-cost, flow-through carbon electrodes characterized in brackish water

We propose a simple and low-cost flow-through electrode for electrochemical cells used for instance in capacitive desalination. We have coated macro-porous carbon fiber papers with various loads of carbon microporous particles to combine both a high surface area and an open structure for good fluid dynamics. In this first study, we restrict our investigation to the charging/discharging behavior, the identification of side reactions, and the effect of geometry on the diffusion of ions. The electrochemical performance was first investigated by cyclic voltammetry and galvanic charge–discharge techniques. The specific capacitance increases by three orders of magnitude upon adding the carbon particles. Then, electrochemical impedance spectroscopy revealed the presence of charge transfer phenomena and modification in the mass transport by the diffusion process for the coated electrode.Graphical abstractSEM image of the surface morphology of the cross section of CP/CFP/CP structure of the flow-through electrode.

Solid Electrolyte Interphase Layer Formation on the Si-Based Electrodes with and without Binder Studied by XPS and ToF-SIMS Analysis

The formation and evolution of the solid electrolyte interphase (SEI) layer as a function of electrolyte and electrolyte additives has been extensively studied on simple and model pure Si thin film or Si nanowire electrodes inversely to complex composite Si-based electrodes with binders and/or conductive carbon. It has been recently demonstrated that a binder-free Si@C-network electrode had superior electrochemical properties to the Si electrode with a xanthan gum binder (Si-XG-AB), which can be principally related to a reductive decomposition of electrolytes and formation of an SEI layer. Thus, here, the Si@C-network and Si-XG-AB electrodes have been used to elucidate the mechanism of SEI formation and evolution on Si-based electrodes with and without binder induced by lithiation and delithiation applying surface analytical techniques. The X-ray photoelectron spectroscopy and time-of-flight ion mass spectrometry results demonstrate that the SEI layer formed on the surface of the Si-XG-AB electrode during the discharge partially decomposes during the subsequent charging process, which results in a less stable SEI layer. Contrarily, on the surface of the Si@C-network electrode, the SEI shows less significant decomposition during the cycle, demonstrating its stability. For the Si@C-network electrode, initially, the inorganic and organic species are formed on the surface of the carbon shell and the silicon surface, respectively. These two parts of species in the SEI layer gradually grow and then fuse when the electrode is fully discharged. The behavior of the SEI layer on both electrodes corroborates with the electrochemical results.

High-Performance Compact Pre-Lens Retarding Field Energy Analyzer for Energy Distribution Measurements of an Electron Gun.

The energy distribution of an electron gun is one of the most important characteristics determining the performance of electron beam-based instruments, such as electron microscopes and electron energy loss spectroscopes. For accurate measurements of the energy distribution, this study presents a novel retarding field energy analyzer (RFEA) with the feature of an additional integrated pre-lens, which enables an adjustment of beam trajectory into the analyzer. The advantages of this analyzer are its compact size and simple electrode configuration. According to trajectory simulation theories, the optimum condition arises when the incident electron beam inside the RFEA is focused on the center of a retarding electrode. Comparing I–V curves depending on whether the pre-lens working or not, it is confirmed that the use of the pre-lens dramatically improves the energy resolution and efficiency of the signal acquisition process. The pre-lens RFEA was applied to characterize a Schottky electron gun under various temperatures and extraction voltages as operational conditions. When the tip temperature was increased by 50 K, we were able to measure an energy distribution broadening of 13.8 meV with the proposed pre-lens RFEA. The relative standard deviation of energy distribution was 0.7% for each working condition.

Determining the stoichiometry and binding constant of Lamotrigine with human serum albumin using voltammetry analysis and molecular modeling

In this study, the interaction of an anticonvulsant drug that used in the treatment of epilepsy, Lamotrigine (LTG) with the most important transport protein of the blood, human serum albumin (HSA) has been studied by using the electrochemical methods and molecular modeling techniques. For this purpose, a simple carbon paste electrode (CPE) was applied for electrocatalytic oxidation and investigation of LTG interaction with HSA. The stoichiometry of the complex between LTG and HSA and the binding constant (Kb) of the reaction were calculated from the calibration curves. The results show that binding of LTG to HSA formed two complexes with different stoichiometries with Kb1 (2.46 × 103) and Kb2 (1.75 × 107), respectively. In agreement with the experimental data, molecular modeling approach also confirmed that LTG can bind to the subdomain IIA and IB of HSA. Communicated by Ramaswamy H. Sarma

Nanostructured zig-zag γ-Mo2N thin films produced by glancing angle deposition for flexible symmetrical solid-state supercapacitors

The performance of electrochemical capacitors strongly depends on their accessible surface area, chemical stability, and electrical conductivity. Simple columnar and zig-zag γ-Mo2N thin-film electrodes were prepared by magnetron sputtering. The latter is obtained by glancing angle deposition (GLAD), which is known for open porous structures due to the ballistic shadowing effect. As intended, the zig-zag structured γ-Mo2N electrode presents an outstanding area capacitance of 248 mF/cm2 at a scan speed of 50 mV/s, which is 4 times higher than that of the simple columnar one. Both of them exhibit excellent cycling stability of 95 % over 20,000 cycles (at 200 mV/s). The symmetrical solid-state supercapacitor prepared with the zig-zag structured γ-Mo2N thin film delivers an excellent power density of 107.1 W/cm3 at 33.8 mWh/cm3, and its volumetric capacitance is ∼ 3.5 times higher than the simple columnar structured γ-Mo2N device. Bending tests of such solid-state γ-Mo2N supercapacitors proved their mechanical flexibility to a bending angel of even 107°. Based on these studies we can conclude that the highly porous zig-zag structured γ-Mo2N-based electrodes prepared by GLAD combine outstanding electrochemical energy storage capabilities with excellent mechanical flexibility.

High-performance with a high voltage aqueous supercapacitor cell from a simple hybrid electrode of manganese oxide-phenanthrenequinone-graphite sheet

The present-day energy demand is growing research interest in synthesizing new hybrid electrode materials for supercapacitor applications. The main focus is on the development of new electrode materials which could be easily available, synthesizable, low-cost, environmentally friendly, with worthy electrochemical performance. In this scenario, a simple one-step synthesis of MnO2 is carried out via the solvothermal method. This MnO2 is mixed with a molecule of phenanthrenequinone (PQ). MnO2, PQ, and MnO2-PQ composite are characterized by FT-IR, XRD, TGA, and BET techniques and confirmed the formation of MnO2-PQ composite. The electrode is made by drop-casting the electro-active materials such as MnO2, PQ, and MnO2-PQ on a graphite sheet wherein a graphite sheet acts as an electrode and a current collector. These electrodes are studied in a three-electrode and also in the symmetric cell configuration in 1 M Na2SO4 electrolyte via CV, GCD, and EIS techniques. The device is constructed in Swagelok system exhibits a high energy density of 140 W h kg−1 at a power density of 6000 W kg−1 in the voltage range of 0 to 2 V. A coin cell is built using two MnO2-PQ-GS hybrid electrodes in an aqueous Na2SO4 electrolyte. The cycle life of the coin cell showed a retention capacitance of 74 % after 5000 cycles at a high voltage of 2 V, even at a high current density of 5 A g−1. EIS results carried out before and after 5000 cycles show that the cell works even at 5000 GCD cycles.

Nitrogen and boron-doped reduced graphene oxide chemiresistive sensor for real-time monitoring dissolved oxygen in biological processes

We developed a nitrogen and boron-doped reduced graphene oxide (N, B-HRGO) based chemiresistive sensor to measure dissolved oxygen (DO) in a complex biological medium. The N, B-HRGO modified interdigitated micro electrode arrays (IDE) constructed as a chemiresistor by the drop-cast method. A silicon based fluorinated oxygen permeable membrane protects the surface from the interference and provides a specificity to the sensor. The sensor responded to the DO concentration changes due to modulated surface charge carrier concentration by the adsorbed dissolved oxygen molecule (Oad). For DO concentration range 0–5 mg.L−1 there was nearly 80% change in response for the sensor with membrane. The resistance of the N, B-HRGO film was measured at different DO concentrations in KNO3 solution and during the growth of Amycalotopsis methanolica bacterial fermentation. The study showed that the sensor is sensitive to the oxygen present in the solution and can detect DO consumption in a complex fermentation medium. The effect of water and the electrolyte salt ions present in the electrolyte was studied in detail. It was observed that the adsorption of water molecule increases the sensor resistance, whereas the salt ions have negligible effect on the sensor response. Because of the simple electrode structure, this chemiresistive sensor can measure DO in the micro bioreactors with a volume of few microliters. The N, B-HRGO chemiresistive sensor can also be used for DO measurement in other bioprocess applications.

Cycle-Induced Structural Evolution of Sulfur Cathodes in Lithium-Sulfur Batteries

Lithium (Li) ion batteries (LIBs) have been the predominant and fastest growing energy storage technology over the past few decades. A significant amount of LIB research has been carried out and remarkable improvements in the technology have been achieved. As a result, state-of-the-art LIBs offer superior cyclability, high efficiency, and high specific energy relative to competitors [1]. However, the desire for long-range electric vehicles (EVs) and grid-level energy storage and delivery is increasing the demands for batteries with very high gravimetric energy density (e.g. > 500 Wh/kg) [2]. This is simply much higher than what LIB electrode materials can practically offer (~ 260 Wh/kg). Therefore, alternative chemistries are needed at both electrodes.One material that has received significant attention recently as a replacement cathode material in Li-based batteries is sulfur (S). S has 5 times the theoretical specific energy than conventional LIB cathodes and can offer a practical energy density of > 500 Wh/kg when coupled with commercially available lithiated graphite or Li metal anodes [3]. S is also non-toxic, low-cost, and has high natural abundance. These properties make S a promising candidate for next-generation cathodes in Li battery systems. Yet, the path to achieving near theoretical capacity and long cycle life for S cathodes has proven difficult due to numerous unsolved scientific and technical issues including: i) the insulating nature of Sulfur (S8) and its discharged product (Li2S); ii) undesired solubility of the S products in the liquid electrolyte, resulting in the degrading so-called Li polysulfides “shuttling”, and iii) structural change of the S cathode during charge and discharge due to the large volume variation between the fully charged and discharged products [4].Several approaches have been reported to address these challenges and improve the Li-S battery performance and durability. Despite these efforts, the advances have been mostly limited to a small number of cycles, or the need for complex structures and that would lead to expensive synthesis costs at the manufacturing scale. In fact, it is not truly known if such complex structures are even necessary as the literature lacks a truly systematic investigation into i) the influence of the S structure on its behavior; and ii) how the S structure evolves as a result of charging and discharging the cell. It is also likely that complex structures would not be reformed upon deep charging/discharging – making their possible advantages only temporary. Hence, there are a limited number of truly practical S cathodes that can be rationally developed [3, 4]. In this work, new insights are presented regarding the structural evolution of S cathodes throughout cycling. The structural changes experienced by the S cathodes were investigated by scanning electron microscopy (SEM) during charge and discharge (at C/10) over the lifetime of the cell (10’s to 100’s of cycles) for multiple cells. Cycling was done with Li-S coin cells that were made using a Li metal anode and a S cathode. The S cathode was prepared using commercially available S powder, a through low-cost, simple, and scalable electrode recipe and production techniques. Drastic microstructural and compositional transformations were observed in the S cathodes as a consequence of charging and discharging. Results suggest that there was a reversible swelling transfiguration of the support structure (conductive carbon plus binder) during each discharge and charge step. It was also observed that the location and distribution of S was changed, and new structures were formed. These results are expected to cast light on a fairly unknown area in the Li-S battery technology, which can help with future scale-up and manufacturing of these cells.

Impedance Analysis on Initiation and Growth of Ant-Nest Corrosion of Copper

The branched pitting corrosion often occurs on copper tubes used in heat-exchanger units in air-conditioners and leads to leakage of heat-exchanger fluid for several months. Figure 1 shows a photograph of this unique localized corrosion formed by galvanostatic polarization in the laboratory. The morphology is characterized by the fractal structure in which pits of several ten micro-m diameter are formed at copper surface and smaller pores are developed on the pit walls randomly. This localized corrosion has been reported with some names: ant-nest corrosion, formicary corrosion, unusual corrosion, branched pits and pinhole corrosion [1]. It’s well known that the occurrence of this localized corrosion is related to trace phosphorus in copper and presence of low molecular weight carboxylic acid such as formic acid. However, the origin to form branched structure has not been clarified. We reported an impedance method to analyze the branched (fractal) pore electrode with transmission line model (TLM) [2, 3]. Impedance spectrum of simple cylinder pore electrode on Nyquist plane normally describes straight-line of 45 degree slope in the high frequency range. In the case of electrode with fractal pores, the slope of straight-line decreases depending on the fractal dimension [3]. In this study, we employed this impedance analysis to investigate the initiation and growth of branched pores in ant-nest corrosion of copper.

Scalable production of electrochemically exfoliated graphene by an extensible electrochemical reactor with encapsulated anode and dual cathodes

Graphene is a carbon material with excellent physical and chemical properties, and the wide-range applications of graphene rely on the realization of its large-scale production. Electrochemical exfoliation is a green and low-cost technology ideal for large-scale graphene production. However, the falling of large particles and disconnection of large chunks of the substrate ascribing to the uncontrolled and uneven exfoliation of graphite during the process leads to low yield. Here, an efficient encapsulate electrode for the electrochemical exfoliation approach is developed, in which graphite particles can be accessed to potential connect during the overall exfoliation. Using flexible encapsulated graphite with filter cloth as both anode and cathode for the electrolyzer can approach deep exfoliation and achieve a high yield of graphene. With this new design, the yield of graphene is increased from 31 % to 57 %, while the graphene’s oxygen content (O% ∼20 %) has no distinct increase compared to the bare one (O% ∼17 %). Moreover, the exfoliation rate of the larger extensible electrochemical reactor can approach 70 g h-1, and the graphene sheets are 3 ∼ 6 layers. This simple and practical electrode with efficient exfoliation will boost the development of large-scale production of graphene and access to its application.

Voltammetry Peak Tracking for Longer-Lasting and Reference-Electrode-Free Electrochemical Biosensors.

Electrochemical aptamer-based sensors offer reagent-free and continuous analyte measurement but often suffer from poor longevity and potential drift even with a robust 3-electrode system. Presented here is a simple, software-enabled approach that tracks the redox-reporter peak in an electrochemical aptamer-based sensor and uses the measurement of redox peak potential to reduce the scanning window to a partial measure of redox-peak-height vs. baseline (~10X reduction in voltage range). This same measurement further creates a virtual reference standard in buffered biofluids such as blood and interstitial fluid, thereby eliminating the effects of potential drift and the need for a reference electrode. The software intelligently tracks voltammogram peak potential via the inflection points of the rising and falling slopes of the measured redox peak. Peak-tracking-derived partial scanning was validated over several days and minimized electrochemically induced signal loss to <5%. Furthermore, the peak-tracking approach was shown to be robust against confounding effects such as fouling. From an applied perspective in creating wearable biosensors, the peak-tracking approach further enables use of a single implanted working electrode, while the counter/reference-electrode may utilize a simple gel-pad electrode on the surface of the skin, compared to implanting working, counter, and reference electrodes conventionally used for stability and reliability but is also costly and invasive. Cumulatively, peak-tracking provides multiple leaps forward required for practical molecular monitoring by extending sensor longevity, eliminating potential drift, simplifying biosensor device construction, and in vivo placement for any redox-mediated sensor that forms parabolic-like data.

Novel analytical sensing strategy using a palladium nanomaterial-based electrode for nimesulide electrochemical reduction

• A novel nanopalladium–silsesquioxane composite was designed. • Modifier material was characterized and applied for NIM sensing through reduction. • Long-term stability for the nanomaterial with the guarantee of reproducibility. • NIM voltammetric detection with low LOD and widest linear response range. • Accuracy and selectivity in the electroanalysis of environmental and clinical samples. Nimesulide (NIM) is a non-steroidal anti-inflammatory drug considered an emerging contaminant. Thus, a novel sensing platform composed of an ionic silsesquioxane material and palladium nanoparticles (PdNPs) was designed for NIM sensing. First, PdNPs were synthesized with a mean size of 1.3 nm according to transmission electron microscopy and small-angle X-ray scattering analyses. Then, the bare glassy carbon electrode (GCE) was modified by drop-coating with PdNPs stabilized in a silsesquioxane hybrid material (Si4Pic + NO 3 – ). Electrochemical impedance spectroscopy and cyclic voltammetry performed the electrochemical characterization. Using the electrochemical sensor GCE/Pd-Si4Pic + NO 3 – and optimized conditions of differential pulse voltammetry, in PBS 0.4 mol L –1 , pH 6.5, the peak current intensity varied linearly in the range of 0.13 – 60 μmol L –1 . The limits of detection (LOD) and quantification (LOQ) were estimated as 39 nmol L –1 and 0.132 µmol L –1 respectively (E d = −0.4 V; t d = 80 s). Indeed, the proposed sensor showed an anti-interference response for some metallic cations and inorganic anions as well as humic acid. The proposed analytical method was employed for NIM determination in simulated spiked serum, synthetic urine, and river water samples focusing on the reduction process. Selectivity was investigated; at a significance level of 99 %, the matrix did not interfere with the analysis. Molecular absorption spectrometry evaluated the accuracy; good correspondence was obtained for both methods. The novel method based on a simple and attractive one-step electrode modification is a promising environmental and clinical analysis tool.

A dual bubble layer model for reactant transfer resistance in alkaline water electrolysis

Alkaline water electrolysis (AWE) can only operate efficiently at a relatively low current density of up to 0.6 A cm–2 because bubbles cover the electrode surface at high current densities. Generally, the upper limit of current density in an electrochemical reaction is determined by the mass transfer of the reactant. Here, we propose a dual bubble layer model for the reactant transfer resistance of the oxygen evolution reaction in AWE. Using simple cylindrical nickel electrodes of different diameters, we conducted electrochemical impedance spectroscopy and microscopic observations with a high-speed video camera. The relationship between the polarization curve of the oxygen evolution reaction in AWE and the mass transfer resistance of hydroxide ions was investigated. At current densities above 0.5 A cm‒2, the bubble layer completely covered the electrode surface. This bubble layer consisted of two layers: an inner one formed by numerous primary bubbles generated on the electrode, and an outer one formed by coalesced large bubbles. The outer layer induces an additional solution resistance, Rsb. Changes in Rsb under various conditions were successfully explained by the thickness and void fraction of the bubble layer, conductivity of the solution, and tortuosity through the gap between bubbles. The inner layer resists the diffusion of hydroxide ions, and the resistance to hydroxide ion transfer through it (Rd) was modeled using the Warburg impedance element with a finite-length diffusion boundary. The charge-transfer resistance at the electrode surface (Rct) is roughly inversely proportional to the current density. This result indicates Rct is less sensitive to bubble coverage and almost all electrode surfaces are active in electrochemical reaction. The results showed that Rd increases with current density as much as Rct when the current density exceeds 1.0 A cm‒2. Up to a high current density of 2.5 A cm‒2, the change in polarization curve (ΔE/Δi) could be quantitatively explained by the sum of the bulk solution resistance, Rs0, additional solution resistance Rsb in the gaps between large bubbles, diffusion resistance Rd in the inner bubble layer, and charge-transfer resistance Rct at the electrode surface.

Measurement of magnetostimulation thresholds intheporcine heart.

Powerful MRI gradient systems can surpass the International Electrotechnical Commission (IEC) 60601-2-33 limit for cardiac stimulation (CS), which was determined by simple electromagnetic simulations and electrode stimulation experiments. Only a few canine studies measured magnetically induced CS thresholds in vivo and extrapolating them to human safety limits can be challenging. We measured cardiac magnetostimulation thresholds in 10 healthy, anesthetized pigs using capacitors discharged into a flat spiral coil to produce damped sinusoidal waveforms with effective stimulus duration ts,eff = 0.45 ms. Electrocardiography (ECG), blood pressure, and peripheral oximetry signals were recorded to determine threshold coil currents yielding cardiac capture. Dixon and CINE MR volumes from each animal were segmented to generate porcine-specific electromagnetic models to calculate dB/dt and E-field values in the porcine heart at threshold. For comparison, we also simulated maximum dB/dt and E-field values created by three MRI gradient systems in the heart of a human body model. The average dB/dt threshold estimated in the porcine heart was 1.66 ± 0.23 kT/s, which is 11-fold greater than the IEC dB/dt limit at ts,eff = 0.45 ms, and 31-fold greater than the maximum value created by the investigated MRI gradients in the human heart. The average E-field threshold estimated in the porcine heart was 92.9± 13.5V/m, which is 6-fold greater than the IEC E-field limit at ts,eff = 0.45 ms and 37-fold greater than the maximum gradient-induced E-field in the human heart. This first measurement of cardiac magnetostimulation thresholds in pigs indicates that the IEC cardiac safety limit is conservative for the investigated stimulus duration (ts,eff = 0.45 ms).

(Digital Presentation) Design of High-Performance Antimony / MXene Hybrid Electrodes for Sodium-Ion Batteries

As a result of the growing electrification and the ever-increasing demand for batteries, scarcity of fossil resources of lithium, and the resulting rise in price, energy storage technologies beyond lithium aroused high interest throughout the past years.1-3 Sodium is a naturally abundant element in the earth and therefore offers the opportunity to develop a promising low-cost, large-scale energy application with favorable energy and power densities. Recently, frequent new and further developments on the anode and cathode materials for sodium-ion batteries have been made. In particular, the development of anode material presents massive challenge while several requirements of high capacity and long lifetime/high durability need to be fulfilled.The unique properties of the novel 2D material MXene, including their excellent electrical conductivity and accessible interlayer space, enable them to be used as attractive electrode materials for battery and supercapacitor. Still, a major drawback is that the capacity of Na+-ion storage by intercalation chemistry is limited due to the limited storage sites.4 As it comes to high-capacity materials, the research field of conversion and alloying materials provides highly attractive candidates. For example, antimony is a promising anode candidate, which undergoes alloying reaction with sodium to form Na3Sb, delivering a high theoretical capacity of 660 mAh g-1. Still, the major drawback of alloying materials is the high volume changes during sodiation and de-sodiation which often leads to electrode cracking, pulverization, continuous reformation of SEI and thus results in poor electrochemical performance. It is, therefore, highly promising to combine both, MXene and antimony for stable, high performance energy storage.Our work explores the best strategy to achieve Sb/MXene hybrid electrodes. There is a tremendous influence in the electrochemical performance dependent on Sb-to-MXene ratio, Sb distribution, and Sb/MXene entanglement. The optimized performance does not align with the highest amount of antimony, the smallest nanoparticles, or the largest interlayer distance of the MXene but by the most homogeneous distribution of antimony and MXene while both components remain electrochemically addressable. With the best optimized hybrid material, we obtained electrodes showing a specific capacity of 450 mAh g-1 at 0.1 A g-1 and 365 mAh g-1 at 4 A g-1, with capacity retention of around 96% after 100 cycles. References Perveen, T.; Siddiq, M.; Shahzad, N.; Ihsan, R.; Ahmad, A.; Shahzad, M. I., Prospects in anode materials for sodium ion batteries-A review. Renewable and Sustainable Energy Reviews 2020, 119, 109549.Skundin, A.; Kulova, T.; Yaroslavtsev, A., Sodium-ion batteries (a review). Russian Journal of Electrochemistry 2018, 54 (2), 113-152.Kundu, D.; Talaie, E.; Duffort, V.; Nazar, L. F., The emerging chemistry of sodium ion batteries for electrochemical energy storage. Angewandte Chemie International Edition 2015, 54 (11), 3431-3448.Kim, Y.; Ha, K. H.; Oh, S. M.; Lee, K. T., High‐capacity anode materials for sodium‐ion batteries. Chemistry–A European Journal 2014, 20 (38), 11980-11992. Figure: De-sodiation capacity and Coulombic efficiency versus cycle number of a simple mechanical mixed antimony MXene electrode (pink) and optimized hybrid material (blue). Figure 1