Polarization Curve Measurements Research Articles

Synthesis and Performance Evaluation of Multialkylated Aromatic Amide Oligomeric Surfactants as Corrosion Inhibitor/Drag Reducing Agents for Natural Gas Pipeline.

Drag reducing agents (DRAs) including amphiphiles and polymers can enhance energy efficiency and transmission volume in natural gas pipelines. However, the correlation between DRA molecular structure and drag reduction efficiency remains unclear. In this paper, the multialkylated aromatic amides (MAA) oligomeric surfactants with different numbers of amide group/n-dodecane chain (from 1 to 3) were first synthesized and characterized. Then, the potential efficiency of MAA as the corrosion inhibitors (CIs)/DRAs for natural gas pipelines was investigated by interfacial activity analysis, film-forming property test, electrochemical polarization curve measurement, and in-door loop test. The results showed that the molecular structure is the key factor influencing the performance of MAA. By increasing the number of amide group/n-dodecane chains, the interfacial activity of MAA improves greatly, thus outstandingly affecting the film-forming property of the MAA on the carbon steel sheet. For MAA-1, the formed film is too thin to cover the surface roughness, and then the corrosion inhibiting (78.64%)/drag reducing (0-2%) rates are the lowest. For MAA-3, the formed film is the thickest and smooth, thus imparting the largest corrosion inhibiting (93.88%)/drag reducing (10-14%) rates to MAA-3. For MAA-2, the formed film is thicker but not smooth, and the corrosion inhibiting (89.88%)/drag reducing (4-6%) rates are intermediate. We speculate that the structure of the MAA greatly influences the adsorption and self-assembly of MAA on the inner pipe wall and then generates different performances. This work is helpful for guiding the development of natural gas DRAs with high efficiency.

In-Depth Analysis of the Impact of Ionomer Content on PEMFC Degradation By Combining Electrochemical Characterization Techniques and Transmission Line Modeling

This study analyzes the influence of the ionomer-to-carbon ratio (I/C) in cathode catalyst layers (CCL) on carbon corrosion behavior during high-potential cycling accelerated stress tests (ASTs). Membrane electrode assembly (MEA) samples with varying I/C ratios (0.5/0.85/1.2) were evaluated using polarization curve measurements and electrochemical impedance spectroscopy (EIS) under H2/air conditions. Analysis through the distribution of relaxation times (DRT) and equivalent circuit modeling revealed that the MEAs with a high I/C ratio (1.2) and a medium I/C ratio (0.85) exhibited the highest beginning of life (BoL) performance, attributed to their lower ionic resistances. Conversely, the MEA with a low I/C ratio (0.5) showed significant improvement during initial AST cycles and superior carbon degradation resistance, despite poor BoL performance. This study highlights the need for further investigation to fully understand the impact of the I/C ratio on electrode structure and carbon corrosion behavior. Furthermore, the combined results suggest that optimizing the I/C ratio could enhance the durability of PEMFC electrodes.

In-Depth Analysis of the Impact of Ionomer Content on PEMFC Degradation By Combining Electrochemical Characterization Techniques and Transmission Line Modeling

This study analyzes the influence of the ionomer-to-carbon ratio (I/C) in cathode catalyst layers (CCL) on carbon corrosion behavior during high-potential cycling accelerated stress tests (ASTs). Membrane electrode assembly (MEA) samples with varying I/C ratios (0.5/0.85/1.2) were evaluated using polarization curve measurements and electrochemical impedance spectroscopy (EIS) under H2/air conditions. Analysis through the distribution of relaxation times (DRT) and equivalent circuit modeling revealed that the MEAs with a high I/C ratio (1.2) and a medium I/C ratio (0.85) exhibited the highest beginning of life (BoL) performance, attributed to their lower ionic resistances. Conversely, the MEA with a low I/C ratio (0.5) showed significant improvement during initial AST cycles and superior carbon degradation resistance, despite poor BoL performance. This study highlights the need for further investigation to fully understand the impact of the I/C ratio on electrode structure and carbon corrosion behavior. Furthermore, the combined results suggest that optimizing the I/C ratio could enhance the durability of PEMFC electrodes.

Fatty Imidazolines as a Green Corrosion Inhibitor of Bronze Exposed to Acid Rain

Acid rain is one of the primary corrosive agents on bronze exposed to the atmosphere. Bronze naturally forms a layer of oxides on its surface called patina, protecting it from corrosion. However, when exposed to acid rain, this layer dissolves, making it necessary to use a corrosion inhibitor or stabilize the patina. This study investigated fatty imidazolines derived from agro-industrial waste bran as a corrosion inhibitor of SAE-62 bronze in simulated acid rain (pH of 4.16 ± 0.1). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve (PC) measurements were used to evaluate corrosion inhibition efficiency, which was 90% for an inhibitor concentration of 50 ppm. The EIS measurements showed that the fatty imidazolines formed a protective film that stabilized the patina on the bronze surface to a certain extent by hindering the charge transfer process. SEM–EDS analyzed the morphology and composition of the protective oxide layer. The results were complemented by Raman spectroscopy and XRD analysis, indicating cuprite, tenorite, cassiterite, and covellite in the patina layer formed on the bronze surface. The SEM analysis showed that the protective coating on the bronze surface was homogeneous using a 50-ppm inhibitor concentration. The XRD analysis suggested the presence of an organic complex that stabilizes the corrosion products formed on the bronze surface.

Chitosan grafted with gallic acid and cerium dioxide hybrid nanocomposites as environmentally friendly corrosion inhibitors for mild steel: An experimental and computational study

Chitosan grafted with gallic acid (CS-GA), along with CS-GA doped with CeO2 nanoparticles (CS-GA-CeO2) were synthesized as novel environmentally friendly mild steel corrosion inhibitors. The formation of these derivatives was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), hydrogen nuclear magnetic resonance spectroscopy (1H NMR), and thermal analysis (TGA). Based on potentiodynamic polarization curves (PDP) measurements, the inhibitors acted primarily as hybrid inhibitors, while following the Langmuir adsorption theory model. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy(XPS) and 3D surface profiles, confirmed that CS-GA-CeO2 adsorbed on the mild steel forming a protective layer thus preventing the invasion of corrosive media. The corrosion protection mechanism of chitosan derivatives was investigated by molecular dynamics simulations. Electrochemical measurements were used to investigate the corrosion inhibition by CS-GA and CS-GA-CeO2 on mild steel in a 3.5 % NaCl solution. At room temperature, the highest inhibition efficiency (93.58 %) was achieved at 200 ppm CS-GA-CeO2. Modified chitosan nanocomposites were confirmed as promising corrosion inhibitors.

Self-powered wearable biosensor based on stencil-printed carbon nanotube electrodes for ethanol detection in sweat

Herein we introduce a novel water-based graphite ink modified with multiwalled carbon nanotubes, designed for the development of the first wearable self-powered biosensor enabling alcohol abuse detection through sweat analysis. The stencil-printed graphite (SPG) electrodes, printed onto a flexible substrate, were modified by casting multiwalled carbon nanotubes (MWCNTs), electrodepositing polymethylene blue (pMB) at the anode to serve as a catalyst for nicotinamide adenine dinucleotide (NADH) oxidation, and hemin at the cathode as a selective catalyst for H2O2 reduction. Notably, alcohol dehydrogenase (ADH) was additionally physisorbed onto the anodic electrode, and alcohol oxidase (AOx) onto the cathodic electrode. The self-powered biosensor was assembled using the ADH/pMB-MWCNTs/SPG||AOx/Hemin-MWCNTs/SPG configuration, enabling the detection of ethanol as an analytical target, both at the anodic and cathodic electrodes. Its performance was assessed by measuring polarization curves with gradually increasing ethanol concentrations ranging from 0 to 50 mM. The biosensor demonstrated a linear detection range from 0.01 to 0.3 mM, with a detection limit (LOD) of 3 ± 1 µM and a sensitivity of 64 ± 2 μW mM−1, with a correlation coefficient of 0.98 (RSD 8.1%, n = 10 electrode pairs). It exhibited robust operational stability (over 2800 s with continuous ethanol turnover) and excellent storage stability (approximately 93% of initial signal retained after 90 days). Finally, the biosensor array was integrated into a wristband and successfully evaluated for continuous alcohol abuse monitoring. This proposed system displays promising attributes for use as a flexible and wearable biosensor employing biocompatible water-based inks, offering potential applications in forensic contexts.Graphical A novel water-based graphite ink modified with multiwalled carbon nanotubes designed for the development of a wearable self-powered biosensor enabling alcohol abuse detection through sweat analysis.

Effects of concentrated CO2 on the performance of a PBI/H3PO4 high temperature proton exchange membrane fuel cell

In this study, the impact of mimic reformate of formic acid decomposition on the anode polarization of HT-PEMFC is investigated under various operating conditions of the anode, including different concentrations of CO2, N2, CO, and humidification. Polarization curve and EIS measurements indicate that there is no significant difference (less than 5 mV when i < 0.4A/cm2) between the same concentrations of CO2 and N2 up to 75 vol%. No significant poisoning of the anode by CO2 (up to 75 vol%) has been observed, suggesting that the addition of concentrated CO2 acts more as a diluent than a poison. Upon separating the polarization effects, it is found that the oxygen reduction reaction (ORR) is a crucial step limiting the fuel cell performance, with cathodic activation losses reaching as high as 70 % at 0.8A/cm2. However, with 1 vol% CO in a H2/CO2 1/1 mixture, a significant poisoning effect on the fuel cell is observed. DRT (distribution of relaxation times) analyses reveal two peaks related to CO in high-frequency regions above 100 Hz associated with the anode polarization, with the peak integration being five times larger than in pure hydrogen. Humidification doesn't improve the voltage or mitigate CO poisoning. A one-dimensional flux model that includes the anode polarization is developed to analyze the polarizations for both cathode and anode under different concentrations of diluents, well describing the experimental results. When i < 0.8 A/cm2, the predicted values from the model closely match the measured values (within 5–10 mV). Calculations suggest that the anode polarization cannot be ignored, especially when the anode is fed with diluted gases.

From 2e- to 4e- pathway in the alkaline oxygen reduction reaction on Au(100): Kinetic circumvention of the volcano curve.

We report the free energy barriers for the elementary reactions in the 2e- and 4e- oxygen reduction reaction (ORR) steps on Au(100) in an alkaline solution. Due to the weak adsorption energy of O2 on Au(100), the barrier for the association channel is very low, and the 2e- pathway is clearly favored, while the barrier for the O-O dissociation channel is significantly higher at 0.5eV. Above 0.7V reversible hydrogen electrode (RHE), the association channel becomes thermodynamically unfavorable, which opens up the O-O dissociation channel, leading to the 4e- pathway. The low adsorption energy of oxygenated species on Au is now an advantage, and residue ORR current can be observed up to the 1.0-1.2V region (RHE). In contrast, the O-O dissociation barrier on Au(111) is significantly higher, at close to 0.9eV, due to coupling with surface reorganization, which explains the lower ORR activity on Au(111) than that on Au(100). In combination with the previously suggested outer sphere electron transfer to O2 for its initial adsorption, these results provide a consistent explanation for the features in the experimentally measured polarization curve for the alkaline ORR on Au(100) and demonstrate an ORR mechanism distinct from that on Pt(111). It also highlights the importance to consider the spin state of O2 in ORR and to understand the activation barriers, in addition to the adsorption energies, to account for the features observed in electrochemical measurements.

Corrosion inhibition ability of L-tryptophan and 5-hydroxy-L-tryptophan for mild steel: a combination of experimental and theoretical methods.

An investigation into the corrosion inhibition properties of L-tryptophan (TP) and 5-hydroxy-L-tryptophan (5-OH-TP) for mild steel in a 1.0 M HCl acidic medium was conducted using experimental and theoretical methods. Results obtained from polarization curve measurements reveal that TP and 5-OH-TP are effective mixed-type inhibitors, exhibiting the highest inhibition efficiencies of 91.22% and 94.05%, respectively, at a temperature of 293 K and a concentration of 10-2 M. However, their inhibition efficiencies gradually decline with increasing temperature, reaching the lowest values of 70.65% for TP and 73.55% for 5-OH-TP at a concentration of 10-4 M and a temperature of 323 K. The adsorption of TP and 5-OH-TP on the steel surface follows the Langmuir isotherm, suggesting monolayer adsorption. Electrochemical impedance spectroscopy analysis indicates that the adsorbed inhibitors form a protective film, effectively shielding the steel from corrosive agents in the solution. Notably, 5-OH-TP consistently exhibits superior inhibition efficiency compared to TP, attributed to the presence of polar OH groups that facilitate stronger bonding of the inhibitor molecule with the metal surface. Quantum chemical parameters and molecular dynamics simulations further confirm the superior corrosion inhibition ability of 5-OH-TP over TP in acidic environments. In particular, the binding energies of protonated TP at the N3 position and 5-OH-TP at the N4 position are 556.40 and 579.27 kJ mol-1, respectively.

Numerical analysis of PEMFC stack performance degradation using an empirical approach

This paper proposes a performance degradation model based on empirical approaches, which can break down the power loss and quantify the influence of each aging phenomena from the overall performance degradation. With the presence of primary degradation mechanisms, the approach can be used to analyze the performance degradation of fuel cells under different degradation conditions. The aging parameters that represent hydrogen crossover, membrane resistance increase, and electrochemical active surface area (ECSA) loss are introduced to characterize the performance degradation. Based on the polarization behavior of proton exchange membrane fuel cells (PEMFCs), the variations of degradation stressors are determinated by fitting the aging parameters to the measuring polarization curves. The empirical approach is validated by a 150 h durability experiment and agrees well with all polarization curves. The results show that ECSA loss always maintains an apparent influence and hydrogen crossover accounts for 56% of the performance degradation in OCV.

Method for Systematic Validation of a Physically Based PEMFC Model By Spatially Resolved Impedance Measurements

Loss mechanisms in PEM Fuel Cells related to charge transfer reactions or diffusive gas transport result in a strongly nonlinear performance, which is furthermore affected by operating conditions as temperature, relative humidity of the gases and stoichiometries. These dependencies have to be considered and validated in fuel cell models to ensure accuracy. Thus, the interpretation of the simulated results becomes more reliable.Direct comparison of simulated and measured current/voltage-relation only allows to evaluate deviations in resulting cell voltages but exclude internal state variables of the model such as overvoltages due to different loss mechanisms. In consequence, simulated and measured values of voltage or current can concur by unnoticed compensation of different errors in magnitude and sign. Additionally, limited numbers of measurements and comparisons increase the probability and impact of this effect.Aggravating, every single process within the cell depends on the comprehensive combination of all operating conditions and runs simultaneously with all other ones. A direct comparison of individual simulated and measured polarization curves therefore is not a suitable and sufficient validation.We address this challenge by applying measurements of electrochemical impedance spectroscopy (EIS) during systematically varied operating conditions spatially resolved along the gas flow direction [1]. The loss processes within the cell can be separated by distribution of relaxation times (DRT) and quantified by a physico-chemical meaningful transmission line model. The resulting amount and distribution of resistances caused by loss processes is compared with the corresponding simulated values of a multiphysical model for observation and monitoring during operation [2]. These insights support the investigation of deviations between simulated and measured polarization curves and therefore the validation the model.In this contribution, the resulting physical interpretation is discussed. Consequences and conclusions for the further development of the cell model are demonstrated.[1]: P. Oppek et al., „ Spatially Resolved Deconvolution of Loss Processes in PEM Fuel Cells”, 241st ECS Meeting, Vancouver[2] T. Goosmann et al. „Impedance-Based, Multi-physical DC-Performance-Model for a PEMFC Stack”, 241st ECS Meeting, Vancouver

Technical and economic feasibility of applying fuel cells as the power source of unmanned aerial vehicles

This study aims to quantitatively compare the weight, cost, and flight endurance of small unmanned aerial vehicles (UAVs) powered by batteries and fuel cells. We compare the use of lithium-polymer (LiPo) batteries, proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs) in powering two representative small UAVs: KHawk-Thermal (fixed-wing, 1.4 m wingspan) and KHawk-CarbonQuad (quadcopter, 0.7 m diagonal length). This study uses experimentally measured polarization curves of fuel cells and power consumption data of LiPo-powered UAVs during flight tests as input to obtain the minimum mass, power consumption, and life cycle costs (LCC) of these power systems. The analyses consider the voltage, efficiency, and power at each current density to find the optimal operating current density to obtain the minimum weight and cost of fuel cell systems to obtain the desired flight endurance. The LiPo battery is the most cost-effective option to power UAVs with an endurance of 0.7 hrs (42 min) or less. At medium flight endurance (e.g., 0.8 – 2.1 hrs), the PEMFC system has the lowest mass and LCC. While hydrogen is the most energy-dense fuel, hydrogen storage significantly increases the mass and cost of the system. For UAVs undergoing long endurance missions (>2.2 hrs for fixed-wing UAVs, > 4.3 hrs for quadcopter UAVs), a DMFC system has the lowest mass and power consumption due to the high energy density of methanol and its simple storage requirements. This study also analyzes the impact of key parameters, such as the specific energy and power of battery and fuel cells, the mass ratio of hydrogen storage, and the lift-to-drag ratio, on UAVs' mass and power consumption.

Exploring the Effectiveness of Carbon Cloth Electrodes for All-Vanadium Redox Flow Batteries

Vanadium redox flow batteries (VRFBs) have shown to be a promising technology for integrating intermittent renewable energy sources into the existing electrical grid. Incorporation of carbon cloth electrodes into VRFB is an area of interest for their enhanced electrochemical performance, however, issues with performance degradation throughout the duration of the experiment persist. This study investigates the performance evolution of carbon cloth electrodes during VRFB cycling to build a hypothesis on possible reasons for the declining performance. Electrochemical impedance spectroscopy and polarization curve measurements are used in conjunction to monitor the electrode degradation and shed light on the effectiveness of carbon cloth electrodes during extended cycling experiments. A detailed investigation into the structure of the carbon cloth electrodes before and after cycling, via several material characterization tests, provides insight needed to determine an explanation for the increasing resistance. The structural integrity and surface morphology of the carbon cloth electrodes are evaluated to compare the electrode before and after cycling, displaying any changes to the electrode due to cycling. Durability of hydrophilicity during RFB cycling is found to be a key feature for future carbon cloth electrode design efforts.

The corrosion resistance of dental Ti6Al4V with differing microstructures in oral environments

The impact of the microstructural properties of a Ti6Al4V alloy on its electrochemical properties, as well as the effect of the α- and β-phases present within it, is still unclear. With the introduction of new, emerging technologies, such as selective laser melting and post heat treatments, the effect of the microstructure on an alloy's corrosion properties has become increasingly interesting from a scientific perspective. When these alloys are produced through different methods, despite an identical chemical composition they have diverse microstructures, and consequently display varying resistance to corrosion. In the present research study, Ti–6Al–4V alloy specimens produced by three different processes, leading to the formation of three different microstructures were investigated: heat treated specimen fabricated by selective laser melting, wrought and cast specimens. The impact of the microstructure of these alloys when immersed in artificial saliva was studied through the use of various electrochemical techniques, by microscopical examinations, and time-of-flight secondary ion mass spectrometry. Corrosion properties were investigated by the measurement of open circuit potential, linear polarization, and potentiodynamic curve measurements followed by microscopical examinations, and time-of-flight secondary ion mass spectrometry examination was conducted to reveal spatial distribution of alloying species on oxide film. It was found that the difference between specimens containing an α+β microstructure was small and not dependent on the aspect ratio of the β-phase, alloy grain size, and vanadium partitioning coefficient, but rather on the size, shape, and content of this phase.

Effect of square wave potential polarity and amplitude on property of trivalent chromium conversion coating applied on Zn−Al hot-dip coating

The formation of Cr(III) chemical conversion coating (TCC) on Zn−Al hot-dip coating was unraveled and cathode or anode square wave potential (φp) was applied during the TCC construction progress in terms of comparatively investigating the effectiveness of φp. Corrosion resistance of TCC in chloride-containing solution was obtained by EIS and polarization curve measurements, combined with the discussion of macro/micro-morphology using 3D microscope and chemical composition distribution analysis using XPS, AES, FTIR and Raman spectra. The results showed that the cathode φp enhanced the corrosion resistance and reduced the content of Cr(VI) on the surface of freshly-prepared TCC better than anode φp. Besides, the hydrophobicity of TCC and adhesion to epoxy primer were also improved due to the reconstruction of the micro−nano structure.

Exploring the influence of composition and morphology on the oxygen evolution reaction performance of Co-based catalysts

Efficient catalysts for the oxygen evolution reaction (OER) are essential for advancing renewable energy technologies. This study focuses on the synthesis and characterization of CoxPy, CoO, CoP, NiCoP, and NiCo/C nanoparticles as catalysts for the oxygen evolution reaction (OER). The CoxPy nanoparticles exhibited a sea-urchin-like morphology, providing a high surface area for electrocatalytic activity. Other catalysts exhibited distinct morphologies, including spherical particles and porous structures. Characterization techniques, such as transmission electron microscopy and X-ray diffraction, confirmed the morphology and composition of the synthesized nanoparticles. The electrocatalytic performance of the catalysts was evaluated through polarization curve measurements, and a microkinetic steady-state model based on the Electrochemical Oxide Path was developed to understand the OER mechanism. The impact of adventitious Fe on catalyst activity was also investigated, revealing the high sensitivity of CoxPy to Fe. The findings suggest the dominance of the Electrochemical Oxide Path in the OER mechanism for all catalysts, with NiCoP showing the lowest onset potential.

Study on Commercially Available Membranes for Alkaline Direct Ethanol Fuel Cells.

This study provides a comparison of different commercially available low-cost anion exchange membranes (AEMs), a microporous separator, a cation exchange membrane (CEM), and an anionic-treated CEM for their application in the liquid-feed alkaline direct ethanol fuel cell (ADEFC). Moreover, the effect on performance was evaluated taking two different modes of operation for the ADEFC, with AEM or CEM, into consideration. The membranes were compared with respect to their physical and chemical properties, such as thermal and chemical stability, ion-exchange capacity, ionic conductivity, and ethanol permeability. The influence of these factors on performance and resistance was determined by means of polarization curve and electrochemical impedance spectra (EIS) measurements in the ADEFC. In addition, the influence of two different commercial ionomers on the structure and transport properties of the catalyst layer and on the performance were analyzed with scanning electron microscopy, single cell tests, and EIS. The applicability barriers of the membranes were pointed out, and the ideal combinations of membrane and ionomer for the liquid-feed ADEFC achieved power densities of approximately 80 mW cm-2 at 80 °C.

Full-scale multiphase simulation of automobile PEM fuel cells with different flow field configurations

ABSTRACT In this study, a 3D + 1D (three-plus-one dimensional) multiphase PEM (proton exchange membrane) fuel cell model is developed, in which the detailed channel two-phase flow is also considered based on the two-phase Darcy’s law. Compared with conventional 3D fuel cell models, the 3D + 1D model improves calculation efficiency and stability. Utilizing this model, the simulation work is conducted on an automobile PEM fuel cell (309.12 cm2) with the full flow field morphology considered. Its accuracy is comprehensively validated at this scale against the experimentally measured polarization curves and HFR (high frequency resistance) under different anode and cathode stoichiometric ratios and pressures and operating temperatures, indicating the model reliability. Subsequently, we numerically investigate the influence of four flow field configurations on cell performance characteristics, including the wave-like, dotted, baffled, and straight flow fields. It is found that the dotted and baffled configuration effectively improved cell performance, but the wave-like flow field has little influence on cell performance compared with straight flow field. Moreover, it is found that decreasing the channel/rib width decreases the concentration loss, but it also increases the ionic ohmic loss, resulting in an optimal channel/rib width for cell performance improvement.

Spatial Mapping of Conductance and Electric Defects in Polymer Electrolyte Membrane Electrode Assemblies Using Lock‐In Thermography with AC Excitation

The characterization of performance and losses of proton exchange membrane (PEM) and anion exchange membrane (AEM) electrolysis cells is typically carried out by electrochemical impedance spectroscopy and polarization curve measurements. With these common methods, lateral inhomogeneities, local degradation, or defects cannot be mapped. Lock‐in thermography (LIT) offers the possibility of mapping current flows and electrical losses. It has already been used successfully for many years in microelectronics and photovoltaics, among others. Conventional LIT with pulsed DC excitation does not work below the reversible voltage of water electrolysis. Therefore, high frequencies are used to generate the conductivity of the ion exchange membrane. Herein, for the first time, the method variable‐frequency AC excitation (VACE)‐LIT is presented. It combines aspects of electrochemical impedance spectroscopy with LIT and is applied to a PEM electrolysis membrane electrode assembly. It is shown that PEMs can exhibit strongly nonhomogeneous current densities, presumably resulting from contact resistances in the layer stack. In addition, local currents flowing at low frequencies indicate electronically conductive defects in the membrane.

The electrochemical corrosion behaviour of compacted (Bi, Pb)-2223 superconductors in aqueous solutions

The corrosion behaviour of (Bi, Pb)-2223 samples compacted at 0.3–1.9 GPa in 0.5 M of HCl, NaCl, and NaOH solutions at 30 °C was investigated using potentiodynamic polarization curves measurements and electrochemical impedance spectroscopy (EIS) technique as well as scanning electron microscopy (SEM) and energy dispersive X-ray emission spectroscopy (EDX). Polarization results showed that the increase in compaction decreases both cathodic hydrogen evolution or oxygen reduction and anodic (BiPb)-2223 superconductor dissolution in 0.5 M HCl, and 0.5 M NaOH. On the other hand, compaction mainly affects the anodic part of the polarization curves of (Bi, Pb)-2223 in 0.5 M NaCl solution. EIS measurements revealed that the highest protection of the superconductors was achieved in 0.5 M NaCl, while the lowest degree of protection was observed in 0.5 M HCl. SEM images show a random plate-like morphology fitted with the marker of (Bi, Pb)-2223 material. The compacted sample at 1.9 GPa indicates deformation of the grains and the formation of a micro-crack. The corrosion mechanism of the superconductor at different pH values was also discussed.