Electrode Impedance Research Articles

Degradation of Pt-Based Cathode Catalysts Upon Voltage Cycling in Single-Cell PEM Fuel Cells Under Air or N2 at Different Relative Humidities

A major degradation mechanism of polymer electrolyte membrane fuel cells (PEMFCs) in transportation applications is the loss of the electrochemically active surface area (ECSA) of platinum cathode catalysts upon dynamic load cycling (resulting in cathode potential cycles). This is commonly investigated by accelerated stress tests (ASTs), cycling the cell voltage under H2/N2 (anode/cathode). Here we examine the degradation of membrane electrode assemblies with Vulcan carbon supported Pt catalysts over extended square-wave voltage cycles between 0.6-1.0 VRHE at 80 °C and 30%-100% RH under either H2/N2 or H2/Air; for the latter case, differential reactant flows were used, and the lower potential limit is controlled to correspond to the high-frequency resistance corrected cell voltage, assuring comparable aging conditions. Over the course of the ASTs, changes of the ECSA, the hydrogen crossover current, the proton conduction resistance and the oxygen transport resistance of the cathode electrode, as well as the differential-flow H2/O2 and H2/Air performance at 80 °C/100% RH were monitored. While the ECSA loss decreases with decreasing RH, it is independent of the gas feeds. Furthermore, the H2/Air performance loss only depends on the ECSA loss. ASTs under H2/N2 versus H2/Air only differ with regards to the chemical/mechanical degradation of the membrane.

Analysis of voltametric data from electrochemical capacitor electrode materials: Method refinement for improved outcomes

A revised model is proposed to improve analysis outcomes from the voltametric analysis of electrochemical capacitor materials and electrodes at different sweep rates (v). Conventional analysis involves breaking down the voltametric current (i) into contributions from capacitive processes (i∝v) and diffusional processes (i∝v1/2). The proposed model introduces a resistance or residual current term, improving the goodness of fit and the quality of data interpretation. This is demonstrated by application of the revised model to artificial voltametric data, electrical double layer capacitor data, as well as pseudo-capacitive electrode data. Analysis with this model also demonstrates the importance of understanding resistive processes in electrode systems, in particular differentiating resistance in the act of charge storage (double layer and redox processes), and ohmic electrode resistance.

Effects of Electrode Curvature in Li-Ion Cells

Bending of electrodes in certain cell designs (cylindrical cells or flat wound jellyrolls) leads to curved electrodes (curvature κ). For double side-coated electrodes, this curvature leads to convex and concave sides of the coating. In this work, we describe the effect of curved electrodes on the microstructure and aging. From a simple elastic model, we find that the porosities of the convex and concave sides of curved electrode coatings can deviate theoretically for first inner winding in a typical cylindrical cell in the order of ±2%, respectively. The elastic model is compared with light microscopy images and Post-Mortem analysis revealing additional plastic deformation for small electrode bending radii. Electrode resistance measurements of the electrode coating as a function of winding radius is added to the overall context. The study concludes with an evaluation and discussion on typical bending radii of electrodes in different cell types (pouch, PHEV1, and 21700) and states (fresh, aged, and abused).

Migration of binder and conductive agent during drying process of Li-ion battery cathodes

Drying of an electrode film during a wet coating process for Li-ion batteries often leads to a heterogeneous distribution of the binder and conductive agent in the film thickness direction. Because this heterogeneous distribution affects battery performance and durability, understanding and controlling the migration behavior are important. Herein, the distribution of the components (active material/conductive agent/binder) of a cathode is investigated by a novel method and their relationship with the electrode properties is determined. The binder distribution is investigated via two methods: pyrolysis gas chromatography mass spectrometry (Py-GC/MS) analysis of cut electrodes, and low-voltage scanning electron microscopy with energy-dispersive X-ray spectroscopy. In the sample dried at 30 °C, more binder and conductive agent exists in the bottom layer. With increasing drying temperature, the binder and conductive agent migrate from the bottom to the surface because they are transported by capillary-driven convective flow through the pores between the active material particles. Drying at high temperatures causes migration, resulting in reduced adhesion between the electrode film and the current collector, and increases the electrode resistance. The Py-GC/MS method of characterizing the cut electrodes is shown to be a complementary method that can analyze a wider area than cross-sectional observation.

A unique redox active ion-electron conductor enabled 5C fast-charging graphite anode for lithium-ion batteries

Enhancing the charging rate of lithium-ion batteries is poised to accelerate the rapid promotion of electric vehicles, decrease greenhouse gas emissions, and reduce the energy crisis worldwide. However, during the fast-charging process, the slow transport of ions and electrons in the graphite anode makes it challenging to achieve a high capacity and good reversible capability. A multifunctional binder that can realize redox reactions with excellent ionic/electronic conduction is reported herein. The electronic/ionic conductance composition is analyzed for the Li-SPODs binder. Thereinto, the total conductivity of Li-SPODs (0.82 mS cm−1) is divided into three parts: lithium sulfonate ionic conductivity (0.54 mS cm−1) in the eigenstate state, electronic conductivity (1.7 × 10−4 mS cm−1) in the doped state, and doping lithium ionic conductivity(0.27 mS cm−1) in the doped state. The conductivity splitting of Li-SPODs binder can reveal the distinct effect of both conductances on graphite electrodes. Benefiting from the high conductive Li-SPODs binder, the contact resistance of the graphite electrode decreased by 54.4 % compared to the carboxymethyl cellulose/butadiene styrene rubber (CMC/SBR) binder. Meanwhile, the full cell based on the lithium iron phosphate cathode and graphite anode (the areal capacity of 2 mAh cm−2) exhibits an extraordinary capacity and outstanding cycling stability (0.04 % capacity decay per cycle during 500 cycles) even at 5C. More importantly, this novel design strategy provides new insight into preparing a multifunctional binder for fast-charging electrodes with high power and energy.

Design of MASnI3 perovskite solar cell with chalcogenide ETLs to achieve high photo conversion efficiency of 31.51% using SETFOS

Perovskite solar cells based on organo-metal halides have gained traction as potentially lucrative devices in the global PV sector. However, the toxicity of Lead (Pb) employed in majority of the perovskite materials limits large scale commercial utility of Pb based PSCs in the market sector. In this paper, a lead-free perovskite solar cell is examined where CH3NH3SnI3 is used as an absorber layer due to its excellent optoelectronic and mechanical characteristics. Various eco-friendly emerging metal chalcogenide (sulphide & selenide) compounds ZnS, SnS2, WS2, MoS2, ZnSe, MoSe2 are explored as Electron Transport Layers (ETL) independently, keeping Cu2O as Hole Transport Layer (HTL) for the said photo active layer using SETFOS 5.3. The influence of thickness of absorber layer, ETL, HTL and their respective doping concentrations, Bulk Trap and recombination at interface, series and parallel resistance, top and bottom electrode work function on PSC performance is also investigated. After analyzing several configurations, it is inferred that the device configuration Glass/FTO/SnS2/MASnI3/Cu2O/Au exhibits exceptional performance with a Power Conversion Efficiency (PCE) of 31.51796%, Fill Factor (FF) of 86.06018%, a short circuit current density (JSC) of 29.19593 mA/cm2 and an open circuit voltage (VOC) of 1.254858 V.

Waterline corrosion behaviors of carbon steel covered by organic coating with artificial defects in seawater

The waterline corrosion behaviors of carbon steel covered by organic coating with artificial defects at and under the waterline simultaneously in simulated artificial seawater were studied by the wire beam electrode (WBE) and electrochemical impedance spectroscopy (EIS) technologies. It was first proposed that the corrosion process of the metal substrate covered by organic coating under the waterline was mainly divided into three stages: no significant corrosion reactions of the metal substrate occurred; the cathodic reaction occurred with relatively slight corrosion on the metal substrate; cathodic delamination of the coating occurred, and the metal substrate was further corroded. Due to the different concentrations of dissolved oxygen, the corrosion reactions of the two exposed electrodes at the waterline and under the waterline were dominated by cathodic and anodic reactions, respectively. For the electrodes under the waterline, on account of the anodic dissolution reaction of the metal substrate, the cathode to anode polarity reversal occurred. In addition, for the yellow corrosion products, the main components were α − Fe2O3, β − FeOOH and γ − FeOOH, while α − Fe2O3 and Fe3O4 were the main components of the black corrosion products. γ − FeOOH participated in the cathodic reaction to form Fe3O4, which resulted in the reduction of the anodic current density at the electrode surface.

Prevention of Pacemaker Malfunctions in Patients With Bradyarrhythmia: Results of a Single-Center Follow-up

Objective: To evaluate results of surgical treatment in patients with bradyarrhythmia and risk factors for pacemaker (PM) malfunctions using improved preventive measures.Materials and methods: Our study consisted of two stages. At stage I, we retrospectively analyzed histories and outpatient medical records of 948 patients with various forms of bradiarrhythmias who underwent surgery in the clinic between 2006 and 2021 to identify PM malfunctions that occurred both in the early and late postoperative periods. Based on the data on the most common types of PM malfunctions and possible risk factors for their development, preventive measures were improved in this cohort of patients and were further used at stage II (pilot) to select patients for surgery.During stage II (pilot), 188 patients were operated on between 2019 and 2021: risk factors for malfunctions were identified in 72 (38.3%) cases at the preoperative stage. All the patients underwent surgery with the proposed and improved preventive measures. Follow­up was during the hospital stay and in 6 and 12 months.Results: At stage I (retrospective analysis), 78 (8.23%) patients had signs of PM malfunction. The most common malfunctions were endocardial electrode displacement (30.8%), increased stimulation threshold (25.6%), a change in the endocardial electrode impedance (17.9%), and impaired sensitivity (10.3%). In addition, premature battery depletion and PM syndrome were present in 9% and 6.4% of the patients, respectively.The correlation analysis revealed that the most common findings associated with malfunctions were enlarged right chambers of the heart due to valvular defects and dilated cardiomyopathy, myocardial remodeling caused by chemotherapy and radiation therapy, postinfarction cardiosclerosis in the electrode implantation area, untimely and inadequate PM programming, as well as increased levels of blood uric acid, urea, and creatinine, and prolonged and uncontrolled use of steroid drugs and bronchodilators.At stage II, there were no PM malfunctions requiring changes in the pacing parameters during the hospitalization period. Six months postsurgery, 1 (1.4%) patient had an increase in impedance (to 2843 ohms) caused by the uncontrolled intake of high doses of corticosteroids due to decompensation of chronic obstructive pulmonary disease. After correction of the corticosteroids dose, the ventricular electrode impedance returned to the normal level. Twelve months postsurgery, 2 (2.8%) patients had a decrease in impedance to 215 and 143 ohms, respectively, caused by the ventricular electrode displacement. After correcting the electrode position, normal pacing parameters were restored. No cardiac complications due to malfunctions were observed. Morphofunctional parameters of the heart did not significantly differ when compared with preoperative ones.Conclusions: Surgical treatment of patients with bradyarrhythmia and risk factors for PM malfunctions who underwent surgery with the proposed preventive measures demonstrated high efficiency in reducing the number of malfunctions and cardiac complications associated with inadequate stimulation in the long­term follow­up.

Contribution of macrophages to neural survival and intracochlear tissue remodeling responses following cochlear implantation

BackgroundCochlear implants (CIs) restore hearing to deafened patients. The foreign body response (FBR) following cochlear implantation (post-CI) comprises an infiltration of macrophages, other immune and non-immune cells, and fibrosis into the scala tympani, a space that is normally devoid of cells. This FBR is associated with negative effects on CI outcomes including increased electrode impedances and loss of residual acoustic hearing. This study investigates the extent to which macrophage depletion by an orally administered CSF-1R specific kinase (c-FMS) inhibitor, PLX-5622, modulates the tissue response to CI and neural health.Main text10- to 12-week-old CX3CR1 + /GFP Thy1 + /YFP mice on C57BL/6J/B6 background was fed chow containing 1200 mg/kg PLX5622 or control chow for the duration of the study. 7 days after starting the diet, 3-channel cochlear implants were implanted in the ear via the round window. Serial impedance and neural response telemetry (NRT) measurements were acquired throughout the study. Electric stimulation began 7 days post-CI until 28 days post-CI for 5 h/day, 5 days/week, with programming guided by NRT and behavioral responses. Cochleae harvested at 10, 28 or 56 days post-CI were cryosectioned and labeled with an antibody against α-smooth muscle actin (α-SMA) to identify myofibroblasts and quantify the fibrotic response. Using IMARIS image analysis software, the outlines of scala tympani, Rosenthal canal, modiolus, and lateral wall for each turn were traced manually to measure region volume. The density of nuclei, CX3CR1 + macrophages, Thy1 + spiral ganglion neuron (SGN) numbers, and the ratio of the α-SMA + volume/scala tympani volume were calculated. Cochlear implantation in control diet subjects caused infiltration of cells, including macrophages, into the cochlea. Fibrosis was evident in the scala tympani adjacent to the electrode array. Mice fed PLX5622 chow showed reduced macrophage infiltration throughout the implanted cochleae across all time points. However, scala tympani fibrosis was not reduced relative to control diet subjects. Further, mice treated with PLX5622 showed increased electrode impedances compared to controls. Finally, treatment with PLX5622 decreased SGN survival in implanted and contralateral cochleae.ConclusionThe data suggest that macrophages play an important role in modulating the intracochlear tissue response following CI and neural survival.

Tailoring the MAX phase additive for enhanced electrochemical performance of high Ni layered oxide composite electrode

The new strategy of MAX phase application in the LIB's cathode composite with high nickel content was suggested in this work. Two MAX phase candidates – TSC and TAC (Ti3SiC2 and Ti3AlC2, respectively) – with outstanding electronic conductivity were used as LiNi0.85Co0.10Mn0.05O2-cathode composite (NCM) additive in amount of 1 % by weight. Structural and morphology monitoring was conducted on each stage of NCM-modification, performed by wet route with post-heat treatment of active material (AM). We found the optimal post-heat temperature (400 °C) to prepare TSC-composite electrode with the enhanced cycling stability – its capacity retention was 96 % and 89 % after 50 cycles at room and elevated temperature of cycling test, respectively. Based on the morphology of MAX phases milled particles with flaky shape, oxidation stability evaluation and electrode resistance measurements we presented here the mechanism of MAX-phase influence on electrochemical performance of high Ni layered oxide electrode composite.

Impedance of porous electrodes in the presence of electroactive species and solution resistance

In a recent paper, we have presented behavior of the porous electrodes in the presence of electroactive species and the absence of the dc and ac potential gradients. This paper presents a model without dc potential gradient but including ac potential drop due to the solution resistance in pores. In this case, a high-frequency straight line at 45° characteristic of porous electrodes appears at high frequencies on the complex plane plots followed by two semicircles. This high-frequency line increases with the increase of the electrode porosity, i.e. Thiele modulus, and solution resistivity. Fitting these impedances to the classical de Levie’s model does not reproduce well the parameters of the second semicircle although the overall fit is good for moderate porosities.

Antiplatelet effect of acetylsalicylic acid in patients early after cardiac valve surgery: comparative investigation of the impairment of platelet inhibition by dipyrone versus acetaminophen

Abstract Background Low-dose acetylsalicylic acid (ASA) is recommended in current guidelines for a period of 3 months after surgical implantation of a bioprosthesis in aortic position or after surgical repair of the mitral valve. Dipyrone (D; metamizole) and acetaminophen (A; paracetamol) are frequently used non-opioid analgesics after surgery. The active metabolite of dipyrone (4-methylaminoantipyrine) is a reversible inhibitor of cyclooxygenase-1 and an interaction with the antiplatelet effect of ASA in more than 50 % of patients has been reported. Material and methods We enrolled 162 patients scheduled for cardiac surgery in this prospective investigator-initiated clinical study. Patients were randomized at day 1 after surgery to either 4 x 1g dipyrone iv/day or 4 x 1g acetaminophen iv/day. All patients were on ASA 100 mg daily (200 mg at day 1). The primary endpoint was the proportion of patients with adequate antiplatelet response to ASA assessed via determination of thromboxane B2 in platelet rich plasma after stimulation with arachidonic acid (AA) at day 4/5 after surgery (cutpoint ≤209.8 ng/ml thromboxane B2). Key secondary endpoints comprised platelet reactivity assessed by light transmission aggregometry [LTA] and by multiple electrode impedance aggregometry [MEIA]. Results 15 patients dropped out of the study. Thus, data from 71 patients randomized to dipyrone and 76 patients randomized to acetaminophen were available for data analysis. Patients had a mean age of 66.5±7.6 years and 97 were male and 50 female. Aortic valve was replaced in 92 patients, 54 underwent mitral valve reconstruction and combined surgery was performed in a single patient. The primary endpoint analyzed at day 4/5 after surgery is shown in the Figure. The proportion of non-responders was 12.5% (D) and 3.0% (A), respectively. Platelet reactivity at day 4/5 after surgery was assessed after stimulation with arachidonic acid by LTA or MEIA. No statistically significant difference between the treatment strata was determined in both assays: Maximum aggregation in LTA was 5.0% (median; 95% confidence interval [95% CI]: 4.0 - 8.0%) in D+ASA and 6.0% (95% CI: 5.0 - 11.0%) in A+ASA (p=0.528) and MEIA AUC was 345.5 AU*min (95% CI: 268.0 - 419.0) in D+ASA and 276.5 AU*min (95% CI: 241.0 - 330.0) in A+ASA (p=0.098). Plasma concentrations of MAA in patients treated with dipyrone were higher in patients identified as responders to ASA (86.6 µM; 95% CI: 67.9 - 102.4 µM) compared to non-responders (31.0 µM; 95% CI: 2.9 – 146.7 µM; p=0.0147). Summary and conclusion The proportion of non-responders to ASA is higher in patients treated with dipyrone compared to acetaminophen. The proportion of non-responders in the dipyrone-treated group in our study is substantially lower than reported in previous studies. High plasma concentrations of MAA in responders may contribute to enhanced inhibition of COX-1 in patients treated with dipyrone.

Architecture design of TiO2 with Co-doped CdS quantum dots photoelectrode for water splitting.

Photoelectrochemical hydrogen production is a critical key to solving the carbon-zero goal of countries due to renewable sources of solar light and combustion products of hydrogen-only water. Here, an architecture design for an n-type nano rosettes-rod TiO2 (RT) surface using CdS and Co-doped CdS quantum dots (QDs) is carried out utilizing the SILAR (simple ionic layer adsorption and reaction) method. Furthermore, the photocatalytic behaviour of Co-doped CdS QDs SILAR cycles deposition is investigated in various cycles, including 5, 8, 10, and 12. The FESEM, Raman XRD, Uv-Vis spectrometer, and vibration modes are used to evaluate the photoelectrode surface structure, crystal structure, and solar light absorption, respectively. FESEM images and XRD pattern revealed successive CdS QDS and Co-doped CdS QDs deposition on the RT boundary and rising SILAR cycles of Co-doped CdS QDs lead to further coverage of RT surface. UV-vis spectrometer indicated shifting solar light absorption to the visible region by applying more SILAR cycles of Co-doped CdS QDs deposition. The electrochemical parameters obtained from EIS showed total polarization resistance (Rp) of the RT electrode dramatically decreased with 10 SILAR cycle Co-doped CdS QDs deposition (5093 Ω cm2 and 617 Ω cm2). Linear sweep voltammetry (LSV) and chronoamperometric photocatalytic performance measurements indicated Co-doped CdS QDs on RT extremely enhanced photoresponse under solar irradiation and 10 SILAR cycle Co-doped CdS QDs improved photocurrent density about fourfold according to blank RT electrode.

Facile Synthesis of Needle-like Copper Sulfide Structures as an Effective Electrochemical Sensor Material for Neurotransmitter Detection in Biological Samples.

Electrochemical sensors, due to their excellent and unique features, are of high interest nowadays for the detection and monitoring of several biological compounds. In such a case, serotonin (SRN), an important neurotransmitter, was herein studied for its detection in biological fluids since its presence is more crucial to be monitored and detected in clinical and medical applications. Several study strategies have been used to determine the chemical and physical properties. The crystalline size of the constructed copper sulfide (Cu2S) material was measured to be 25.92 nm. The Cu2S was fabricated over the working surface and further analyzed for several sensor parameters to be optimized. The charge transfer resistance of the copper sulfide-modified glassy carbon electrode (Cu2S/GCE) was determined to be about 277.0 Ω. With the linear range from about 0.029 μM to 607.6 μM for SRN, the limit of detection (LOD) was calculated as 3.2 nM, with a good sensitivity of 13.23 μA μM-1 cm2. The sensor experienced excellent repeatability, reproducibility, and long-term stability. The fabricated electrode was selective with the presence of different interfering compounds. The real sample analysis, as determined with the regular addition method with human serum and urine samples, revealed a good recovery percentage. Thus, the employed fabricated electrode material will be highly effective in sensing other analytes of choice.

Pathway to high performance, low temperature thin-film solid oxide cells grown on porous anodised aluminium oxide

Reversible solid oxide cells (rSOCs) present a promising solution to future energy challenges through the efficient conversion between electrical and chemical energy. To date, the benefits of rSOC technology have been off-limits to portable power and electrolysis applications due to the excessive polarisation resistance of the oxygen electrode at low temperatures, characterised by high area specific resistance (ASR) values below 500 °C. In this work we demonstrate growth of symmetric and complete rSOC structures based on state-of-the-art vertically aligned nanocomposite (VAN) films grown by pulsed laser deposition (PLD) on porous Pt-coated anodised aluminium oxide (AAO) substrates. The symmetric rSOC structures give the first demonstration of an rSOC oxygen electrode with ASR below 0.1 Ωcm2 at temperatures less than 450 °C. This is achieved through oxygen vacancy tuning by annealing, as confirmed by Time-of-Flight Elastic Recoil Detection Analysis (ToF-ERDA) and Rutherford Backscattering Spectrometry (RBS) measurements. Thus, the present work describes a promising route towards future high-performance rSOC devices for portable power applications.

Highly Flexible and Acid-Alkali Resistant TiN Nanomesh Transparent Electrodes for Next-Generation Optoelectronic Devices.

Transparent electrodes are vital for optoelectronic devices, but their development has been constrained by the limitations of existing materials such as indium tin oxide (ITO) and newer alternatives. All face issues of robustness, flexibility, conductivity, and stability in harsh environments. Addressing this challenge, we developed a flexible, low-cost titanium nitride (TiN) nanomesh transparent electrode showcasing exceptional acid-alkali resistance. The TiN nanomesh electrode, created by depositing a TiN coating on a naturally cracked gel film substrate via a sputtering method, maintains a stable electrical performance through thousands of bending cycles. It exhibits outstanding chemical stability, resisting strong acid and alkali corrosion, which is a key hurdle for current electrodes when in contact with acidic/alkaline materials and solvents during device fabrication. This, coupled with superior light transmission and conductivity (88% at 550 nm with a sheet resistance of ∼200 Ω/sq), challenges the reliance on conventional materials. Our TiN nanomesh electrode, successfully applied in electric heaters and electrically controlled thermochromic devices, offers broad potential beyond harsh environment applications. It enables alternative possibilities for the design and fabrication of future optoelectronics for advancements in this pivotal field.

A novel distributing–collecting on-line insulation monitoring system and line selection technology for the DC supply system

At present, the power supply system of 5G base stations is a micro smart grid, it generally uses 240 V DC power supply with multiple branches, and leakage accidents will threaten personal and property safety, so it is vital to identify the fault line accurately and remove the faults rapidly. In this paper, the leakage phenomenon of transmission lines in the HVDC power supply system of a 5G communication base station is studied. To address the issue of multi-branch line leakage diagnosis and line selection in the 240 V DC system, a new distributed DC insulation monitoring and fault line selection technology and system are proposed. The distributed DC insulation monitoring line selection technology is used to collect the leakage current of each branch by setting a unique single-core DC leakage transformer and process the signal primarily. In addition, a high-resistance bridge switchgear is added to the bus bar. According to different leakage currents caused by the imbalance of the bridge before and after the switch, the insulation resistance of electrodes to the ground is calculated accurately, which solves the problem that the current technology cannot judge the fault of the positive and negative electrodes to the ground at the same time. Through both simulation and prototype experiments, the feasibility of this technology and system device in line insulation monitoring and line selection of the HVDC communication base station power supply system is verified.

Long-Term Electrode-Skin Impedance Variation for Electromyographic Measurements.

This study aims to observe the evolution of the electrode-skin interface impedance of surface EMG electrodes over the time taken to determine the time of stabilization. Eight healthy subjects participated in the study. Electrode-skin impedance was evaluated in the rectus abdominal muscle every five minutes, over a total period of 50 min. A reduction of 13.23% in the impedance values was observed in minute 10 (p = 0.007), and a reduction of 9.02% was observed in minute 15 (p = 0.029). No statistically significant differences were observed in the other instants evaluated. The findings obtained in the present study demonstrate a decrease in electrode-skin impedance from minute 5 to minute 15, followed by a stabilization period with a low percentage of variation till minute 50.

Microstructural and electrochemical properties of Ni-impregnated GDC10 and 8YSZ freeze tape cast scaffolds as fuel electrodes for solid oxide cells

Ni-impregnated Gd0.1Ce0.9O2 and Y0.08Zr0.92O2 fuel electrodes for solid oxide cells are manufactured by the combination of the freeze tape casting and infiltration techniques. Their morphological properties are investigated by scanning electron microscope and X-Ray microtomography while their electrochemical performance is evaluated in symmetrical Y0.08Zr0.92O2-supported button cells by electrochemical impedance spectroscopy. The microstructural analysis of the manufactured scaffolds highlights the characteristic anisotropy of porosity provided by the freeze tape casting method. The average tortuosity factor across the out of plane direction has been calculated equal to 1.38, being considerably lower than the average values of the other components, (τx = 10.2) and (τy = 6.87). The contribution provided by gas diffusion to the overall polarization resistance of the freeze tape cast electrodes has been estimated around 6·10−4 Ω cm2 in the 600–750 °C temperature range, thus lower than the best reported values for the state-of-the-art electrodes featuring sponge-like porosity. The measured impedance data highlighted the higher electrochemical performance of the Ni-impregnated Gd0.1Ce0.9O2 architecture, holding a polarization resistance of 0.823 Ω cm2 at 750 °C, which is regarded as a very promising result for a ∼600 μm thick electrode. The interpretation of the impedance data was supported by the distribution of relaxation times analysis and the complex non-linear least square fit. In particular, the electrochemical investigation highlighted the presence of two major resistive contributions which have been ascribed to the occurrence of a chemical capacitance within the GDC10 lattice (low frequency contribution) and to the multi-layered architecture of the tested symmetrical cells which increases the contact losses (high frequency contribution).

Biocompatible Gel-Free Coconut Oil and Carbon Black Electrodes for ECG and Respiration Measurements

The current state of the art in telemedicine has increased the interest in long term monitoring of physiological and bioelectric signals. This motivated the development of materials and techniques for the fabrication of biocompatible, user and environmentally friendly alternatives to conventional resistive wet electrodes. Here we report a method for the fabrication of dry flexible and stretchable electrodes based on Coconut-Oil and Carbon Black for the monitoring of electrophysiological signals without conductive gels. The highly stretchable material shows a specific resistance ρ down to 33.2±12.3Ωm, high conformability, and a stretchability up to 1500%. The epidermal electrodes were used to record Electrocardiographic (ECG) signals and measure respiration in a 3-lead configuration and compared to commercial wet electrodes. Even after being elongated by 100% for 100 stretch/release cycles, a reliable recording of the QRS-complex is demonstrated without the need for any contact enhancer or substances that cause skin reaction, demonstrating the potential use of this material for long term ECG monitoring applications.