Main Degradation Mechanism Research Articles

Inter‐relationships between Oxygen Evolution and Iridium Dissolution Mechanisms

AbstractThe widespread utilization of proton exchange membrane (PEM) electrolyzers currently remains uncertain, as they rely on the use of highly scarce iridium as the only viable catalyst for the oxygen evolution reaction (OER), which is known to present the major energy losses of the process. Understanding the mechanistic origin of the different activities and stabilities of Ir‐based catalysts is, therefore, crucial for a scale‐up of green hydrogen production. It is known that structure influences the dissolution, which is the main degradation mechanism and shares common intermediates with the OER. In this Minireview, the state‐of‐the‐art understanding of dissolution and its relationship with the structure of different iridium catalysts is gathered and correlated to different mechanisms of the OER. A perspective on future directions of investigation is also given.

Degradation of Benzene Using Dielectric Barrier Discharge Plasma Combined with Transition Metal Oxide Catalyst in Air

In this paper, a uniform and stable dielectric barrier discharge plasma is presented for degradation of benzene combined with a transition metal oxide catalyst. The discharge images, waveforms of discharge current, and the optical emission spectra are measured to investigate the plasma characteristics. The effects of catalyst types, applied voltage, driving frequency, and initial VOCs concentration on the degradation efficiency of benzene are studied. It is found that the addition of the packed dielectric materials can effectively improve the uniformity of discharge and enhance the intensity of discharge, thus promoting the benzene degradation efficiency. At 22 kV, the degradation efficiencies of dielectric barrier discharge plasma packed with CuO, ZnO and Fe3O4 are 93.6%, 93.2% and 76.2%, respectively. When packing with ZnO, the degradation efficiency of the dielectric barrier discharge plasma is improved from 86.8% to 94.9%, as the applied voltage increases from 16 kV to 24 kV. The catalysts were characterized by XPS, XRD and SEM. The synergistic mechanism and the property of the catalyst are responsible for benzene degradation in the plasma–catalysis system. In addition, the main physiochemical processes and possible degradation mechanism of benzene are discussed.

Physics and chemistry-based constitutive modeling of photo-oxidative aging in semi-crystalline polymers

This paper proposes a physio-chemically-based constitutive framework to predict the response of severely photo-oxidatively aged semi-crystalline polymers. Photo-oxidation induced by the exposure to Ultra-Violet (UV) light and oxygen is one of the main and dominant degradation mechanisms affecting the lifespan of polymers. In this work, we first characterize the physio-chemical changes of low-density polyethylene (LDPE) to understand and map the photo-oxidation degradation process. Changes in crystallinity and mass loss are characterized by Differential Scanning Calorimetry (DSC) and Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) experiments, respectively. The evolution of crystallinity and mass loss relative to the initial pristine films over exposure time are considered as indicators of material degradation. Based on these tests, we then propose evolution functions for the material properties in the polymer constitutive equations to incorporate the effects of photo-oxidation on the mechanical responses. Connecting the physio-chemical processes affecting polymer network evolution to the mechanical response of LDPE eliminates the need for defining extra fitting parameters that carry no physical meaning. The developed constitutive framework is validated with respect to a series of in-house uniaxial tensile tests performed on LDPE aged for different UV exposure times. Validation of the proposed constitutive framework confirms the accuracy of DSC and QCM-D as rigorous techniques in the characterization of degradation in LDPE films, and confirms the robustness of the developed framework in predicting the mechanical responses of photo-oxidatively aged LDPE.

Towards novel lignin-based aromatic polyesters: In-depth study of the thermal degradation and crystallization of poly(propylene vanillate)

The growing environmental concerns over the excessive emissions of greenhouse gasses and the accumulation of synthetic plastics in terrestrial and aqueous recipients have driven the public, academic and industrial awareness towards the production of novel bio-based polymeric materials. Within this frame, poly(propylene vanillate) (PPV) is an alipharomatic engineering polyester with promising thermal and mechanical properties, produced via a two-step melt polycondensation of 4-(3-hydroxypropoxy)-3-methoxybenzoic acid, a monomer derived from the potentially lignin-based vanillic acid. Herein, a systematic investigation of the non-isothermal crystallization, the thermal stability and the decomposition mechanism of PPV was performed, with the implementation of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectroscopy (Py-GC/MS), respectively. The Lauritzen-Hoffman parameters (K and U*) of crystallization were calculated using a combination of the Lauritzen-Hoffman theory and isoconversional methods. The determination of the activation energy, using isoconversional methods, along with the model fitting analysis of mass loss data have led to a first assumption about the thermal degradation profile of the synthesized polyester. Furthermore, decomposition products revealed the two different main degradation mechanisms take place: heterolytic β-hydrogen scission and α-homolytic scission.

Effect of Silica on Pyrene-Contaminated Soil Subjected to Mechanochemical Remediation

Soil contaminated by polycyclic aromatic hydrocarbons (PAHs) is a common problem in the world. Mechanochemical treatment is a promising technology for remediation of PAH-contaminated soil. This study investigated the feasibility of pyrene degradation with silica by mechanochemical remediation. The effects of ball milling time and rotation speed on the removal efficiency of pyrene in soil were also studied. When the milling time was 3 h and the rotation speed was 500 rpm, the removal efficiency of pyrene in soil was over 98%. The intermediate products detected by gas chromatography–mass spectrometry proved that the hydrogenation reaction and the destruction of benzene rings occurred in the milling process. Both graphite and amorphous carbon were detected by Raman spectra. The main degradation pathway and mechanism of pyrene by mechanochemical treatment should be the destruction of benzene rings caused by free radicals and further carbonization.

Temperature dependent model of carbon supported platinum fuel cell catalyst degradation

The use of mathematical modelling for describing the degradation of platinum-based carbon-supported catalysts (Pt/C) in PEMFC plays a crucial role in the development of new materials and mitigation strategies as well as in the improved understanding of individual degradation mechanisms and their relation to the operational conditions. In this work we present the first physically based model of Pt/C catalyst degradation that fully covers the effects of temperature on detrimental electrochemical reactions, consequent platinum particles dissolution, detachment and agglomeration, and the resulting loss of electrochemical surface area. The model is verified on the results of six accelerated stress tests performed on an industrial benchmark catalyst at various temperatures and potential cycling windows. The model is capable of reproducing the results of all experiments using the same set of model parameters, compatible with DFT calculations for energy barriers of similar electrochemical reactions as well as with the parameters of existing degradation models, which confirms its plausibility. According to the model results, the dissolution and subsequent redeposition of platinum is strongly affected by the temperature and represents the main mechanism of particle growth at temperatures below 60 °C, with carbon corrosion induced detachment and agglomeration playing only a minor role in particle growth. • Temperature-dependent electrochemical model of Pt fuel cell catalyst is developed. • Catalyst electrochemical surface loss due to dissolution and agglomeration is modelled. • The model is tested on degradation experiments at various potentials and temperatures. • The credibility of the model is confirmed by good agreement with the experimental data. • Platinum dissolution and redeposition is recognised as the main degradation mechanism.

A Review of the Reliability of Integrated IR Laser Diodes for Silicon Photonics

With this review paper we provide an overview of the main degradation mechanisms that limit the long-term reliability of IR semiconductor lasers for silicon photonics applications. The discussion is focused on two types of laser diodes: heterogeneous III–V lasers bonded onto silicon-on-insulator wafers, and InAs quantum-dot lasers epitaxially grown on silicon. A comprehensive analysis of the reliability-oriented literature published to date reveals that state-of-the-art heterogeneous laser sources share with conventional laser diodes their major epitaxy-related degradation processes, such as the generation of non-radiative recombination centers or dopant diffusion, while eliminating cleaved facets and exposed mirrors. The lifetime of InAs quantum dot lasers grown on silicon, whose development represents a fundamental step toward a fully epitaxial integration of future photonic integrated circuits, is strongly limited by the density of extended defects, mainly misfit dislocations, protruding into the active layer of the devices. The concentration of such defects, along with inefficient carrier injection and excessive carrier overflow rates, promote recombination-enhanced degradation mechanisms that reduce the long-term reliability of these sources. The impact of these misfits can be largely eliminated with the inclusion of blocking layers.

GaN-based power devices: Physics, reliability, and perspectives

Over the last decade, gallium nitride (GaN) has emerged as an excellent material for the fabrication of power devices. Among the semiconductors for which power devices are already available in the market, GaN has the widest energy gap, the largest critical field, and the highest saturation velocity, thus representing an excellent material for the fabrication of high-speed/high-voltage components. The presence of spontaneous and piezoelectric polarization allows us to create a two-dimensional electron gas, with high mobility and large channel density, in the absence of any doping, thanks to the use of AlGaN/GaN heterostructures. This contributes to minimize resistive losses; at the same time, for GaN transistors, switching losses are very low, thanks to the small parasitic capacitances and switching charges. Device scaling and monolithic integration enable a high-frequency operation, with consequent advantages in terms of miniaturization. For high power/high-voltage operation, vertical device architectures are being proposed and investigated, and three-dimensional structures—fin-shaped, trench-structured, nanowire-based—are demonstrating great potential. Contrary to Si, GaN is a relatively young material: trapping and degradation processes must be understood and described in detail, with the aim of optimizing device stability and reliability. This Tutorial describes the physics, technology, and reliability of GaN-based power devices: in the first part of the article, starting from a discussion of the main properties of the material, the characteristics of lateral and vertical GaN transistors are discussed in detail to provide guidance in this complex and interesting field. The second part of the paper focuses on trapping and reliability aspects: the physical origin of traps in GaN and the main degradation mechanisms are discussed in detail. The wide set of referenced papers and the insight into the most relevant aspects gives the reader a comprehensive overview on the present and next-generation GaN electronics.

Group velocity dispersion in terahertz frequency combs within a generalized Maxwell-Bloch framework

As many molecules have their rotovibrational resonance frequencies in the mid-infrared or terahertz regime, efficient generation of corresponding frequency combs may lead to large progress in gas spectroscopy and sensing. Quantum cascade lasers (QCLs) are among the most promising candidates for a compact and cheap radiation source in this frequency range. This contribution presents a full-wave numerical solution of the Maxwell-Liouville-von Neumann equations, thus avoiding the limited applicability of the rotating wave approximation to moderate field strengths and spectral bandwidths. We include losses and chromatic dispersion of the optically active material in the QCL. The semiclassical approach uses the finite-difference time-domain (FDTD) method to derive update equations for the electric field, starting from the one-dimensional Maxwell equations. There, the optical full-wave propagation is coupled to the electronic quantum system via a polarization term that arises from the evolution of the density matrix. Furthermore, dispersion effects are considered through a classical polarization term and losses are introduced by a finite material conductivity. This work mainly focuses on the integration of group velocity dispersion (GVD) due to the bulk material and, if applicable, the waveguide geometry into the update equations. It is known to be one of the main degradation mechanisms of terahertz frequency combs, but has not yet been added to the existing full-wave solver. The implementation is carried out as Lorentz model and is applied to an experimentally investigated QCL frequency comb setup from the literature. The reported results are in good agreement with the experimental data. Especially, they confirm the need for dispersion compensation for the generation of terahertz frequency combs in QCLs.

Capacity of concrete structures with corroded reinforcement and prestressing tendons

The main degradation mechanism for concrete structures is corrosion of the reinforcement and prestressing tendons. Management of structures with such degradation requires detailed understanding of their remaining strength and safety and if necessary, make a decision regarding repairs or replacement of the structure or components. Some simplified methods for estimating the residual capacity of concrete structures do exist, primarily based on a reduction of the flexural capacity equal to the percentage of the corroded area. In this paper, a more physical understanding and description of the influence of corrosion on the strength is investigated, based on a reduction of the area of the reinforcement and prestressing tendons both due to uniform corrosion and pitting corrosion. The results of these models are successfully compared to experimental results of concrete beams with corrosion. Particularly corrosion of post-tensioned tendons is a concern for concrete structures. Some disturbing examples of collapse of concrete bridges have been seen as a result of such corrosion. The paper highlights the importance of the significant strength loss of the reinforcement as a result of corrosion itself, but also the loss of ductility due to possible hydrogen embrittlement and hydrogen induced stress corrosion cracking. The paper also suggests sulphate reducing bacteria as a possible explanation to corrosion issues related to corrosion of post-tensioned tendon structures where no chloride is found. The aim of the paper is to propose a method to calculate a lower bound estimate of the remaining capacity of concrete beams with corrosion damage to reinforcement and to the prestressing tendons.

Degradation evaluation of acrylamide in advanced oxidation processes based on theoretical method: Mechanisms, kinetics, toxicity evaluation and the role of soil particles

Acrylamide (AA) is now recognized as an imminent hazardous chemical in the aqueous environment, causing a potential threat to human health. As a neo-formed contaminant (NFC), the degradation measure of AA is largely lacking. In this work, we used quantum chemistry and experimental methods to identify the main degradation mechanism of AA in the UV/H2O2 advanced oxidation process (AOP) for the first time. Radical addition reactions dominate the •OH-initiated AA reaction, resulting in few toxic nitrosamines formation. The interaction between AA and the surface model of soil particles (SixOy(OH)z) is weak, and AA can rapidly migrate down to groundwater via seepage. However, the total rate constants of AA and COMADS2-AA with •OH are 2.75 × 109 and 2.09 × 109 M−1 s−1, and the removal of AA from aqueous and heterogeneous systems reaches 62.30% and 62.05% within 2 h. Whether in the aqueous-phase or on the surface of soil particles, •OH initiated AA reaction is an efficient way to remove AA. Furthermore, the toxicity of the main by-products of AA show less harmful to three aquatic organisms and rats than AA. UV/H2O2 AOP is evaluated as an efficient method to degrade AA while decreasing harm.

Perovskite Photovoltaic Devices with Carbon‐Based Electrodes Withstanding Reverse‐Bias Voltages up to –9 V and Surpassing IEC 61215:2016 International Standard

One of the key challenges of perovskite photovoltaics (PV) is the long‐term stability. Although efforts are made to improve the lifetime of perovskite PV devices, their degradation under reverse‐bias conditions is barely addressed. Herein, perovskite solar cells with carbon‐based electrodes are presented which demonstrate superior resilience against reverse‐bias‐induced degradation. Although their breakdown voltage is identified to be at approximately −3.6 V, cells do not degrade until the applied reverse‐bias exceeds −9 V. Two main degradation mechanisms are identified: 1) iodine loss due to hole tunneling into perovskite, which takes place even at low reverse‐bias but decomposes the perovskite only after long time durations; and 2) rapid heating at large reverse‐bias leading to formation of PbI2, which starts at shunts and then follows the path of the least resistance for the cell current, which is primarily influenced by the electrode sheet resistances. Finally, perovskite solar modules with carbon‐based electrodes are demonstrated, which are subjected to a “hotspot” test described in the IEC 61215:2016 international standard at an accredited module testing laboratory. Passing this accelerated test for the first time confirms the superior stability of perovskite PV devices with carbon‐based electrodes and highlights their large industrialization potential.

Degradation Mechanisms of Solid Oxide Fuel Cells under Various Thermal Cycling Conditions.

A critical issue to tackle before successful commercialization of solid oxide fuel cells (SOFCs) can be achieved is the long-term thermal stability required for SOFCs to operate reliably without significant performance degradation despite enduring thermal cycling. In this work, the impact of thermal cycling on the durability of NiO-yttria-stabilized zirconia-based anode-supported cells is studied using three different heating/cooling rates (1, 2, and 5 °C min-1) as the temperature fluctuated between 400 and 700 °C. Our experiments simulate time periods when power from SOFCs is not required (e.g., as might occur at night or during an emergency shutdown). The decay ratios of the cell voltages are 8.8% (82 μV h-1) and 19.1% (187 μV h-1) after thermal cycling testing at heating/cooling rates of 1 and 5 °C min-1, respectively, over a period of 1000 h. The results indicate SOFCs that undergo rapid thermal cycling experience much greater performance degradation than cells that experience slow heating/cooling rates. The changes in total resistance for thermally cycled cells are determined by measuring the Rpol of the electrodes (whereas the ohmic resistances of the cells remain unchanged from their initial value), signifying that electrode deterioration is the main degradation mechanism for SOFCs under thermal cycling. In particular, fast thermal cycling leads to severe degradation in the anode part of SOFCs with substantial agglomeration and depletion of Ni particles seen in our characterizations with field emission-scanning electron microscopy and electron probe microanalysis. In addition, the mean particle size in the cathode after thermal cycling testing increases from 0.104 to 0.201 μm for the 5 °C min-1 cell. Further, the presence of Sr-enriched regions is more significant in the La0.6Sr0.4Co0.2Fe0.8O3-δ cathode after fast thermally cycled SOFCs.

Electrochemical and Post-Mortem Degradation Analysis of Parallel-Connected Lithium-Ion Cells with Non-Uniform Temperature Distribution

Prior work on Li-ion cells which were parallel-connected in a stack and subjected to long term cycling showed that non-uniform temperature distribution caused non-uniform and accelerated degradation. To elucidate the degradation mechanisms, electrochemical and post-mortem degradation analysis were performed. Electrochemical impedance spectroscopy analysis suggested that the main degradation mechanism for the middle cell was a solid electrolyte interface (SEI) layer growth. Nevertheless, post-mortem analysis using X-ray diffraction, optical microscope, and scanning electron microscopy paired with energy dispersive X-ray spectroscopy shows the presence of Li2CO3 in both baseline and middle cell anodes. This points towards a combined degradation mechanism of SEI layer growth and lithium plating. A combination of microstructural particle cracking and lithium plating is considered the main mechanism for blocking the anode’s porosity network, which hindered further lithium diffusion, resulting in the abrupt failure for the middle cell. The observation and quantitative analysis provides insight into the performance and reliability impacts of non-uniform conditions within lithium-ion batteries.

Tracking and Erosion of Silicone Rubber and EPDM Insulation in the DC Inclined Plane Test

This paper investigates the tracking and erosion of silicone rubber and EPDM insulation in the DC inclined plane tracking and erosion test. Silicone rubber filled with alumina tri-hydrate fails due to combustion in the gas phase or erosion paths, but with no evidence of tracking. EPDM fails due to tracking and surface capturing fire, from dry-band arcing leaving a black residue while impinging the surface. Carbonaceous residue on EPDM gives rise to leakage current magnitude, whereas fused silica-based residue on silicone rubber is shown to promote combustion. A high amount of alumina tri-hydrate replacing the polymeric fuel in the composite is shown as a primary factor preventing failure and changing the nature of the residue in the DC inclined plane tracking and erosion test. Depolymerization is the main degradation mechanism reported for silicone rubber and EPDM, with notable degrees of crosslinking reported only for silicone rubber. Crosslinking reduces the amount of silicone rubber undergoing depolymerization, thus, the amount of fuel prone to combustion is reported to promote a coherent residue shield against the eroding dry-band arcing.

Balancing Degradability and Physical Properties of Amorphous Poly(d,l‐lactide) by Making Blends

AbstractThe problem in using the existing biodegradable polymers for day‐to‐day commodity and specialty applications (non‐physiological) is the trade‐off between the degradability and physical properties of polymers. Therefore, the authors study the properties of polyester films made by solution blending of amorphous poly(d,l‐lactide) and semi‐crystalline poly(l,l‐lactide) (PLLA) with an aim to achieve a good balance of mechanical properties and degradability under environmental conditions. The degradation test using proteinase K enzyme shows faster degradation of blends in comparison to homopolymers by weight loss. Faster fragmentation of blends and fragments of lower masses in comparison to PLLA is also seen in immature compost with bulk degradation as the main mechanism of degradation. A detailed investigation shows increased crystallinity and the formation of crystalline stereo‐complex in fragmented samples that may limit degradation after a stage causing microplastics persisting for a longer period. Therefore, further degradation studies in compost for at least 8–10 weeks are recommended. Other environmental sinks, such as activated sludge water, fresh, and seawater, provide either extremely slow or no degradation excluding the use of such blends for applications intended for these sinks. In future, smart solutions are required to enhance the degradation of polylactide in different environmental sinks.

Recent Advances in ROS-Sensitive Nano-Formulations for Atherosclerosis Applications.

Over the past decade, ROS-sensitive formulations have been widely used in atherosclerosis applications such as ROS scavenging, drug delivery, gene delivery, and imaging. The intensified interest in ROS-sensitive formulations is attributed to their unique self-adaptive properties, involving the main molecular mechanisms of solubility switch and degradation under the pathological ROS differences in atherosclerosis. This review outlines the advances in the use of ROS-sensitive formulations in atherosclerosis applications during the past decade, especially highlighting the general design requirements in relation to biomedical functional performance.

Reactivity and Potential Profile across the Electrochemical LiCoO2-Li3PS4 Interface Probed by Operando X-ray Photoelectron Spectroscopy.

All-solid-state lithium batteries are a promising alternative for next-generation safe energy storage devices, provided that parasitic side reactions and the resulting hindrances in ionic transport at the electrolyte-electrode interface can be overcome. Motivated by the need for a fundamental understanding of such an interface, we present here real-time measurements of the (electro-)chemical reactivity and local surface potential at the electrified interface (Li2S)3-P2S5 (LPS) and LiCoO2 (LCO) using operando X-ray photoelectron spectroscopy (XPS) supplemented by X-ray photoemission electron microscopy (XPEEM). We identify three main degradation mechanisms: (i) reactivity at open circuit potential leading to the formation of reduced Co in the +2 oxidation state at the LCO surface, detected in the Co L-edge, which is further increased upon cycling, (ii) onset of electrochemical oxidation of the LPS at 2.3 V vs InLix detected in the S 2p and P 2p core levels, and (iii) Co-ion diffusion into the LPS forming CoSx species at 3.3 V observed in both S 2p and Co 2p core levels. Concurrently, a local surface overpotential of 0.9 V caused by a negative localized charge layer is detected at the LPS-LCO interface. Furthermore, in agreement with previous theoretical results, the presence of a sharp potential drop at the interface between active materials and solid electrolyte is demonstrated in all-solid-state batteries.

Identification of photodegradation product of organophosphorus pesticides and elucidation of transformation mechanism under simulated sunlight irradiation

Organophosphorus pesticides (OPs) are posing great threat to the environment and human health, due to their overuse and persistence in the environment. Photolysis has been established as an effective method to degrade OPs. The influence of pH value, the initial concentration of pesticides and the light source on the photolysis of two OPs, including chlorpyrifos and dimethoate, was investigated. The optimal reaction condition for OPs degradation was under pH 9, with xenon lamp as the light source, in which the photodegradation efficiencies of chlorpyrifos and dimethoate (500 mg/L) were 75.12% and 94.31%, respectively. The photodegradation products of chlorpyrifos and dimethoate were identified by GC-MS. Also, density functional theory (DFT) calculations were used to characterize the molecular properties of chlorpyrifos and dimethoate, as well as predicting potential photolysis reactions. Photodegradation mechanisms of chlorpyrifos and dimethoate were proposed, in which 3,5,6-trichloropyridinol (TCP), O,O-diethyl thiophosphate (DETP), 2,3,5-Trichloro-6-methoxypyridine (TMP) and O,O,S-trimethyl phosphorothioate were identified as the main products of chlorpyrifos degradation. Omethoate, O,O,S-trimethyl thiophosphorothioate, N-methyl-2-sulfanylacetamide, O,O,O-trimethyl thiophosphate, O,O,S-trimethylphosphorothiate, and O,O,O-trimethyl phosphoric ester as the main photodegradation products for dimethoate. The main degradation mechanisms included ring opening, cleavage, oxidation and demethylation. This work demonstrated the feasibility of combining chemical analysis with quantum chemical calculation in unraveling degradation mechanisms of OPs. Also, it is of great significance for evaluating the environmental fate of OPs in aquatic system and further environmental risk assessment.

Redox-Cycling – A Tool for Artificial Electrochemical Aging of Solid Oxide Cells

Solid Oxide Cells (SOC) have an important role and hold great promise with their diverse and versatile portfolio in the energy application sector, ensuring opportunities for integration of renewable energy sources into the overall energy system. However, the spectrum of applications still meets some general barriers, summarized as durability and costs. The initial performance degrades over their lifetime due to the effect of use (electrochemical ageing), of time (calendar ageing), of different permanent and/or accidental stress conditions - thermal, current load, mechanical, poisoning etc. Considering the expected useful commercial maintenance-free lifetime of up to 80 000 hours for stationary applications, the performance of durability tests looks quite unrealistic, which opens the niche for introduction of accelerated stress tests.In respect to the fuel electrode, the main degradation mechanism during operation in both fuel cell and electrolysis mode is the reduction of the triple phase boundary points and of the Ni/gas specific surface area caused by microstructural changes in the Ni network due to Ni migration and coarsening. The migration over long distances can bring to Ni depletion near the electrolyte interface. Similar processes of Ni coarsening and migration can occur faster during oxidation of Ni caused by incidental change in the operation conditions (leakage, fuel starvation). Thus, artificial redox cycling can be applied for accelerated degradation testing. However, the oxidation/reduction cycles should mimic the normal aging.The most common experimental approach for evaluation of the redox cycling effect on the degradation is the oxidation in a furnace at high temperature for at least one hour, followed by post mortem analysis. However, this approach introduces severe oxidation conditions, even full oxidation of the Ni network, which does not represent the most common electrochemical and calendar aging.The aim of this work is to develop a procedure for accelerated stress tests by artificial aging of the anode via redox cycling. It is performed before the operation of the cell thus eliminating the influence of the degradation mechanisms coming from other components. The proposed procedure ensures reproducible and fine-tuned level of oxidation based on in situ impedance monitoring of the Ni network reduction/oxidation. A two-step algorithm is developed and approbated. Step 1. Performance of redox cycling on anode sample with in situ impedance monitoring of the Ni network reduction/oxidation. The anode sample (pellet with thickness 250 µm and diameter 20 mm) is placed between two Pt meshes. In the initial state (YSZ/NiO) the impedance of the anode has capacitive behavior with resistance about 20 kΩ which after reduction transforms into inductive one with resistance about 40 mΩ corresponding to the electronic conductivity of the produced Ni network (Fig. 1). In the same way the oxidation can be registered. Its level may vary from small oxidation depth (for instance two times increase of the resistance, i.e. from 40 mΩ to about 70-80 mΩ as it is presented in Fig. 1) to big oxidation (above 10 kΩ).For the performance of Step 2 small level of oxidation was chosen, as shown in Fig. 1, which prevents from potential irreversible damages. Thus, the redox cycling of single anode serves for definition of the experimental redox cycling conditions. The deepness of degradation is regulated by the number of cycles. Step 2. Performance of redox cycling on full cell. In this configuration the oxidation of the anode Ni network cannot be monitored, but the conditions are already defined in Step 1 which guarantees reproducible identical redox cycles. The impedance measurements ensure monitoring of the total cell behavior during redox cycling. The procedure is applied for fuel cell mode, but it is also valid for electrolyzer mode. The results are shown in Fig. 2 where the impedance diagrams after the initial reduction and after the 8th redox cycle are compared. Although there is a decrease of the ohmic resistance which is usually observed during the first 1000 hours of standard operation mainly due to improved contacts, the polarization resistance after the 8th cycle is about 14% higher. This behavior is similar to that observed for standard testing for at least 600 hours. The 8 cycles are performed for 16 working hours which confirms the accelerated aging produced by the developed algorithm. Acknowledgements: The research leading to these results received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 825027. The experiments were performed with equipment supported by the Bulgarian Ministry of Education and Science under the National Roadmap for Research Infrastructure 2017-2023 “Energy storage and hydrogen energetics (ESHER)”, approved by DCM No 354/29.08.2017. Figure 1