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Ultramicrotomy with automated section collection enables a reliable collection of sequential sections for 3D imaging. Here, we introduce a system for collecting several hundred ultra-thin sections on tape as a flexible polymeric substrate. The tape is stored within a portable cassette, which can be used as a modular platform for different applications. The motorized cassette with its retractable section collection cantilever is installed in front of an ultramicrotome for section collection. Section collection and imaging of the sections can be conducted without requiring any manual handling of the tape, which reduces the risk of specimen contamination and offers various options for automatization and cross-compatibility. For instance, processing steps such as a plasma glow-discharge of the substrate can be performed on the tape while it is enclosed in the cassette. As a proof of concept, more than 300 sequential sections at a thickness of 150 nm were cut from a polymer blend sample and collected on a metal-coated tape. Finally, a subset of 15 × 15 × 15 µm³ of the original sample volume was successfully imaged by confocal Raman microscopy and reconstructed at submicron resolution. The serial section cassette harbors the potential to standardize, simplify, and automate sample library collection, imaging, and storage.

High temperature proton exchange membrane fuel cells (HT-PEMFCs) typically employ either acid-absorbing orhydrophobic electrode binders in their catalyst layers (CLs). A recently introduced alternative is the ionomericbinder PWN, poly(2,3,5,6-tetrafluorostyrene-4-phosphonic acid). In literature, PWN with a phosphonation degreeof 70% was shown to remarkably improve HT-PEMFC performance. Here, we investigate the influence of thephosphonation degree (40–95%) of this ionomeric binder on HT-PEMFC performance. PWN is employed in thecathode CL and compared to the commonly used polytetrafluoroethylene (PTFE) binder. The electrochemicalbehavior is tested at 180 ◦C at ambient pressure under H2/air conditions using a commercial phosphoric acid (PA)-doped PBI-membrane. HT-PEMFCs with PWN generally outperform fuel cells (FCs) with PTFE after a full break-inregarding peak power density (PPD), activation overpotential (as studied by Tafel analysis), and reproducibility inthe mass transport region. Further, PWN-electrodes show higher electrochemically active surface areas (ECSAs)than PTFE-electrodes after completing the break-in. We find that the phosphonation degree has a substantial impacton the PPD, with PWNs with lower phosphonation degrees (40–60%) outperforming highly phosphonated PWNs(70–95%). Taken together, PWN as an ionomeric electrode binder in HT-PEMFCs shows remarkable improvementsin performance, but a precise adjustment of the phosphonation degree is required to obtain optimal results.

Integrating platinum-based recombination catalysts into proton exchange membrane water electrolysis systems effectively reduces the anodic hydrogen content. We studied the effect of the platinum loading of an interlayer close to the anode within the membrane on the anodic hydrogen in oxygen content. For the investigated Pt-loadings between 1 μgPt cm−2 and 140 μgPt cm−2, the results revealed that for a 110 μm membrane, 7 μgPt cm−2 were sufficient to allow a safe operation at cathode pressures up to 10 bar. A further increase of the Pt-loading did not significantly improve the reduction of the anodic hydrogen in oxygen content.

Pt dissolution has already been intensively studied in aqueous model systems and many mechanistic insights have been gained. Nevertheless, transfer of new knowledge to real‐world fuel cell systems is still a significant challenge. To close this gap, we present a novel in situ method combining a gas diffusion electrode (GDE) half‐cell with inductively coupled plasma mass spectrometry (ICP‐MS). With this setup, Pt dissolution in realistic catalyst layers and the transport of dissolved Pt species through Nafion membranes were evaluated directly. We observed that 1) specific Pt dissolution increased significantly with decreasing Pt loading, 2) in comparison to experiments on aqueous model systems with flow cells, the measured dissolution in GDE experiments was considerably lower, and 3) by adding a membrane onto the catalyst layer, Pt dissolution was reduced even further. All these phenomena are attributed to the varying mass transport conditions of dissolved Pt species, influencing re‐deposition and equilibrium potential., An in situ technique is presented that closes the gap between catalyst degradation studies in real devices and fundamental electrochemical analyses. The method involves direct measurement of platinum dissolution in realistic catalyst layers and through Nafion membranes. The impact of catalyst loading and electrode–electrolyte interface on platinum dissolution, as well as transport behavior of dissolved Pt species through Nafion membranes, are investigated.

Solution electrospinning is a facile method for the production of nanofibrous meshes. Here, we present a syringe‐jacket heat exchanger as a simple add‐on for solution electrospinning, which enables spinning from various solvents by a direct and precise solution temperature control between −20 °C and 100 °C. An effective manipulation of the solvent evaporation rate is enabled by adjusting the temperature. Exemplarily, we investigated the spinning of poly(vinylidene fluoride)‐co‐hexafluoropropylene (PVDF‐HFP) in pure dimethylacetamide (DMAc) or acetone as representatives of low and highly volatile solvents. Electrospinning of these solutions is not possible at ambient conditions, either due to a too low or too high evaporation rate. However, we find that PVDF‐HFP nanofibers can be successfully electrospun from DMAc at a solution temperature of 75 °C and from acetone at −19 °C. We show for the first time the use of an active solution cooling for electrospinning from a highly volatile solvent such as acetone. The ability to precisely adjust the solution temperature during electrospinning offers an improved process control and broadens the spectrum of spinnable solution compositions. Especially the prospect of replacing highly toxic solvents with less‐toxic solvents such as acetone opens up a wide field of application for the produced fibers.

The electrochemical activity of modern Fe-N-C electrocatalysts in alkaline media is on par with that of platinum. For successful application in fuel cells (FCs), however, also high durability and longevity must be demonstrated. Currently, a limited understanding of degradation pathways, especially under operando conditions, hinders the design and synthesis of simultaneously active and stable Fe-N-C electrocatalysts. In this work, using a gas diffusion electrode half-cell coupled with inductively coupled plasma mass spectrometry setup, Fe dissolution is studied under conditions close to those in FCs, that is, with a porous catalyst layer (CL) and at current densities up to -125 mA·cm

Confocal Raman microscopy enables 3D imaging of various samples solely based on chemical contrast. However, optical artifacts impair resolution and image quality in subsurface imaging. With serial section Raman tomography, we show that serial ultrathin and semithin sectioning by ultramicrotomy can successfully be combined with subsequent confocal Raman imaging. This new 3D Raman imaging technique reaches a depth resolution of up to 100 nm, which is about 10‐fold better than in confocal Raman microscopy. Structurally complex and optically inhomogeneous samples can not only be imaged, but also be used to quantify structural parameters. Serial section Raman tomography is a promising method for materials science and possibly also for life sciences.

The proton exchange membrane is the heart of many electrochemical energy systems, and their performance and longevity depend on a careful selection and processing of membrane materials. In this work, we use confocal Raman microscopy to investigate application-relevant properties of perfluorinated sulfonic acid (PFSA) membranes. Raman spectra of Nafion, Aquivion, and 3M Ionomer at different equivalent weights show differences in the spectral area and position of various Raman bands but reveal a clear trend of band intensities versus equivalent weight. Characteristics of these ionomers such as swelling and water uptake were determined with through-plane imaging. The technique offers advantages over conventional measurements, such as contact-free and non-destructive data acquisition. Calibration curves for the equivalent weight were derived for the different PFSAs with excellent linear fits that allow a quantification of the ionizable group content. The high spatial resolution of confocal Raman microscopy of less than 2 μm enables the local evaluation of all these ionomer properties. Furthermore, Raman imaging was employed to characterize composite membranes, which shows that it can resolve individual phases and features in multi-layered membranes. This study provides a comprehensive summary of confocal Raman microscopy as a powerful tool for the analysis of ionomer and membrane properties.

The membrane is one of the crucial components of fuel cells. Applying composite membranes for fuel cells is a promising option due to better mechanical properties compared to membranes without reinforcement. Composite membranes can be prepared by combining ionomer with a filler which can be selected from many types of materials, such as polymers, ceramics, carbons, and metals. Filler materials exist in different nanostructures which provide flexible designs for composite membranes. However, the main issue in composite membranes is a trade-off among properties when adjusting the ratio between ionomer and filler, especially between ionic conductivity and mechanical modulus. On the one hand, maintaining high protonic conductivity is possible when small concentrations of reinforcing fillers are incorporated. On the other hand, a high amount of reinforcement can improve the mechanical properties significantly but could result in low protonic conductivity as well. Our strategy to overcome this issue is by employing protonic conductive nanofibers as reinforcement. Electrospinning is a versatile method to transform polymer solutions into long and solid nanofibers. Electrospun fibermats possess a high porosity and contain voids which can be filled with an ionomer like Nafion by spraycoating to form a dense composite membrane. We were successful in producing electrospun nanofibers from phosphonated polypentafluorostyrene (PWN70) and unmodified polypentafluorostyrene (PPFSt). PWN70/Nafion and PPFSt/Nafion composite membranes were prepared separately by spraycoating of a Nafion solution into PWN70 and PPFSt fibermats that have comparable thickness and fiber loading. From tensile tests, we found that composite membranes made from PWN70/Nafion and PPFSt/Nafion have much higher Youngs’ modulus (E) than pure Nafion (Figure 1A). Although PWN70/Nafion is a relatively brittle membrane, it has the best Youngs’ modulus and yield stress. Protonic conductivity is also a crucial membrane property which can be determined by electrochemical impedance spectroscopy. In Figure 1B, Nafion reinforced by PPFSt fibers has a reduced conductivity due to non-ion-conductive PPFSt. Surprisingly, the protonic conductivity of a PWN70/Nafion composite membrane is similar to spraycoated Nafion. Without reducing much the protonic conductivity, the PWN70/Nafion composite membrane shows comparable ohmic resistance to the spraycoated D2020 in fuel cell operation which has also been done in this work. Since the PWN70 nanofibers are ion-conductive and electro-spinnable, the nanofibers offer benefits when designing fiber-reinforced composite membrane possessing both good mechanical stability and protonic conductivity. Figure 1

Members of the casein kinase 1 (CK1) family are involved in regulation of crucial cellular pathways including chromosomal segregation, DNA repair, and apoptosis. Therefore, the activity of CK1 isoforms needs to be tightly regulated in order to avoid pathogenesis of proliferative diseases. Regulation of cellular CK1 activity is mainly mediated by (auto-) phosphorylation within its C-terminal regulatory domain. Cellular kinases, among them protein kinase A (PKA), checkpoint kinase 1 (Chk1), protein kinase C α (PKCα), and cyclin-dependent kinases (CDKs) have already been identified to C-terminally phosphorylate CK1δ, thereby modulating its kinase activity. In the present study we analyzed the CK1δ kinase domain for phosphorylation sites targeted by PKCα. Several phosphorylation sites were identified in vitro by initially using GST-CK1δ wild type and phosphorylation-site mutant protein fragments originating from the CK1δ kinase domain. Residues S53, T176, and S181 could finally be confirmed as targets for PKCα. Determination of kinetic parameters of full-length wild type and mutant GST-CK1δ-mediated substrate phosphorylation revealed that integrity of residue T176 is crucial for maintaining CK1δ kinase activity. Functional biochemical and cell culture-based analysis discovered that site-specific phosphorylation of CK1δ by PKCα contributes to fine-tuning of CK1δ kinase activity. In summary, our work for the first time demonstrates the effects of PKCα-mediated site-specific phosphorylation in the CK1δ kinase domain and enhances our knowledge about the regulation of the disease-associated CK1 kinase family.

We present the first results of an anion exchange ionomer membrane, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), in a vanadium redox flow battery. Anion exchange membranes exhibit superior vanadium crossover suppression compared to proton exchange membranes due to the Gibbs–Donnan effect. HMT-PMBI was benchmarked against a similarly thin Nafion XL membrane which allowed us to compare differences based solely on chemical properties of the ionomer materials. We report cycling data of 45 cycles at a current density of 150 mA/cm2 with excellent coulombic efficiency of >99.4%, energy efficiency of 80.6–74.2% and a low ohmic resistance of 0.219–0.255 Ω cm2. In addition, a three times lower self-discharge rate is obtained for the HMT-PMBI membrane compared to Nafion XL. HMT-PMBI is therefore a potential alternative for PFSA based ionomers in VRFB applications. Keywords: Anion exchange membrane, Vanadium redox flow battery, Energy storage, HMT-PMBI, Coulombic efficiency

Quaternized Polybenzimidazole-Cross-Linked Poly(vinylbenzyl chloride) Membranes and Their Performance in HT-PEMFCs Keywords: Proton-exchange membrane, ion pair, high-temperature, phosphoric acid, quaternary ammonium, hydrogen crossover High temperature proton-exchange membrane fuel cells (HT-PEMFCs) are promising electrochemical energy conversion devices for the hydrogen economy. In this fuel cell type, phosphoric acid is immobilized as an electrolyte within a polybenzimidazole (PBI) membrane acting as a matrix. These membrane systems allow operating temperatures up to 200 °C, which is significantly higher than for sulfonated polymers that are used in low temperatures PEMFCs at around 80 °C. Operating PEMFCs above 100 °C harbors advantages such as faster reaction kinetics, higher tolerances against fuel impurities, and easier cooling. Nonetheless, phosphoric acid doped membranes also is the main challenge and drawback of these systems due to leaching of the dopant over time. A high acid-oping level is desired since it ensures high proton conductivity. However, the mechanical properties of PBI-based materials generally deteriorate upon increasing acid doping levels. In this regard, cross-linking PBI with another polymer is a promising route to enhance the mechanical properties of acid-doped membranes. Further, polymers with specific functional groups, such as quaternary ammonium (QA), can be used as cross-linkers to enhance the retention of phosphoric acid by forming strong interactions with biphosphate anions. Here, we present a new ion-pair-coordinated membrane (IPM) system decorated with QA groups. Poly(vinylbenzyl chloride) is used as a macromolecular cross-linker for PBI, and three different amines (Quinuclidine, Quinuclidinol, DABCO) are used as quaternizing agents. The performance of these membranes is evaluated ex-situ as well as electrochemically within HT-PEMFC operation and compared to a commercial m-PBI membrane (Dapazol). The IPMs show reduced swelling and better mechanical properties upon doping. Further, the commercial reference can be outperformed within HT-PEMFC operation at less acid doping than conventional PBI membranes. The best-performing IPM led to a 25% improved fuel cell performance. The peak power density of an HT-PEMFC incorporating a Dapazol membrane was 430 mW cm–2 at 180 °C under H2/air conditions and at ambient pressure, while the HT-PEMFC with the best-performing IPM yielded 530 cm–2 at equal parameters. Further, the hydrogen gas crossover of the IPMs is similar or less than that of the commercial reference even at lower membrane thicknesses, which renders these membranes as promising candidates for application in HT-PEMFC.

Gas crossover through the membrane poses a significant challenge to proton exchange membrane water electrolysers. This work investigates the influence of the position of platinum-based recombination interlayers integrated in the membrane on the anodic hydrogen in oxygen content. The results show that all interlayer positions reduce the anodic hydrogen content without performance losses compared to the reference without interlayer. However, an interlayer positioned closer to the anode is more effective than closer to the cathode. Further, the effect of the interlayer is more pronounced with increasing anode pressure.

Increasing numbers of hepatitis E cases are currently recognized in many European countries. The zoonotic hepatitis E virus (HEV) genotype 3 mainly circulates in domestic pigs and wild boars, and can be transmitted to humans via consumption of insufficiently heated meat or meat products produced from those animals. Here, a detailed protocol for detection of HEV RNA in meat products is provided, which is based on the method originally described by Szabo et al. (Intl J Food Microbiol 215:149-156, 2015). It consists of a TRI Reagent®/chloroform-based food matrix homogenization, a silica bead-based RNA extraction and a real-time RT-PCR-based RNA detection. The method was further validated in a ring trial with nine independent laboratories using pork liver sausage samples artificially contaminated with different amounts of HEV. The results indicate sufficient sensitivity, specificity, and accuracy of the method for its broad future use in survey studies, routine food control or outbreak investigations.

Polymer electrolyte membrane (PEM) water electrolysis is a key technology for sustainable hydrogen based energy supply. Gas permeation through the PEM leads to hydrogen in oxygen at the anode side posing a safety hazard and therefore restricting the operation window of PEM water electrolysis, especially when operating under pressure. In this work the hydrogen in oxygen content at the anode is significantly reduced when a recombination interlayer is integrated into the membrane electrode assemblies (MEAs) compared to reference MEAs without interlayer. The recombination interlayer with a platinum loading of 0.02 mg cm(-2) is sprayed between two membranes that are coated with anode and cathode catalysts on the outside. The permeating H-2 and O-2 forms water at the recombination interlayer, leading to higher gas purity and resolving safety issues. In case of the MEAs with interlayer also a constant current hold at 1 A cm(-2) for 245 h revealed only a slight increase of the hydrogen in oxygen content (below 140.10(-6) vol.% h(-1)) whereas for the reference MEAs without interlayer a stronger increase was observed (above 1250.10-6 vol.% h(-1)). Furthermore, the long-term experiments showed no increased degradation rates compared to the reference MEAs.

Two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, known as MXenes, are a growing class of 2D materials, which offer great solid lubrication ability for low friction applications due to their weakly bonded multi-layer structure and tribo-layer formation with self-lubricating characteristics. To date, most studies have assessed their tribological response in basic laboratory tests. However, these tests do not adequately reflect the complex geometries, kinematics, and stresses present in machine components. Here, we aim at bridging this gap through assessment of the friction and wear performance of multi-layer Ti3C2Tx MXene solid lubricant coatings used in rolling bearings. MXenes’ tribological response is compared with state-of-the art solid lubricant coatings, which include molybdenum disulfide (MoS2), tungsten-doped hydrogenated amorphous carbon (a-C:H:W), and hydrogen-free, more graphite-like amorphous carbon (a–C). Multi-layer Ti3C2Tx MXene coatings reduce wear on the bearing washers by up to 94%, which can be attributed to the transfer of the lubricious MXene nano-sheets to secondary tribo-contacts of the bearing. While the frictional torque of all solid lubricant coatings is similar during steady-operation, the MXene-coated bearings extend the service life by 30% and 55% compared to MoS2 and DLC, respectively. This contribution demonstrates the ability of MXene solid lubricant coatings to outperform state-of-the-art solid lubricants in dry-running machine components such as rolling bearings.

Members of the casein kinase 1 (CK1) family are key regulators in numerous cellular signal transduction pathways and in order to prevent the development of certain diseases, CK1 kinase activity needs to be tightly regulated. Modulation of kinase activity by site-specific phosphorylation within the C-terminal regulatory domain of CK1δ has already been shown for several cellular kinases. By using biochemical methods, we now identified residues T161, T174, T176, and S181 within the kinase domain of CK1δ as target sites for checkpoint kinase 1 (Chk1). At least residues T176 and S181 show full conservation among CK1δ orthologues from different eukaryotic species. Enzyme kinetic analysis furthermore led to the hypothesis that site-specific phosphorylation within the kinase domain finally contributes to fine-tuning of CK1δ kinase activity. These data provide a basis for the extension of our knowledge about the role of site-specific phosphorylation for regulation of CK1δ and associated signal transduction pathways.

Ionomer membranes are crucial components of many electrochemical devices. In this work, confocal Raman microscopy is employed to characterize Nafion ionomers quantitatively in pristine status and after usage as a proton exchange membrane in a fuel cell. Confocal Raman microscopy allows non-destructive thickness and equivalent weight measurements of Nafion with a 95% confidence interval of ±13 g mol−1 at an equivalent weight of 1000 g mol−1, which is significantly more accurate than previously reported methods. Characterization can be performed at a spatial resolution better than 2 μm, providing insights into local membrane degradation after fuel cell operation. Membrane thinning to less than 40% of the initial thickness of Nafion NR-211 occurs after a 100 h open circuit voltage hold, accompanied by an anisotropic increase of the equivalent weight from 1035 g mol−1 to an average of 1200 g mol−1. Most pronounced increases are found close to the anode. Further, the characterization of a Nafion XL membrane shows that its microporous reinforcement is represented as increased equivalent weight with local heterogeneities within the membrane. These results show that confocal Raman microscopy is a valuable tool to investigate ionomers that are used as ion exchange membranes in electrochemical devices.

Hydrogen production from water electrolysis is considered a promising large-scale solution for energy storage of intermittent, renewable sources. Besides mature alkaline electrolysis employing caustic KOH solutions as a liquid electrolyte, modern technologies focus on the use of ion exchange membranes as a solid electrolyte. While the widespread application of state of the art proton exchange membrane (PEM) water electrolyzers is impaired by the requirement of costly and rare iridium-based catalyst for the oxygen evolution reaction (OER), anion exchange membranes (AEM) are recently reaching higher technological readiness levels. Besides the progress in AEM water electrolysis, also the combination of a PEM for the cathode and an AEM for the anode, referred to as bipolar membrane water electrolysis is gaining more scientific interest. As depicted below, the bipolar interface (preferably decorated with a water dissociation (WD) catalyst [1]) enhances the water dissociation rate into protons and hydroxide, which feed the respective electrode reactions. We have established various modular AEM- and PEM-based building blocks, which allow us to thoroughly investigate zero-gap bipolar membrane electrode assemblies for water electrolysis in various configurations. [2] As the AEM is expected to contribute the most to ohmic losses, we have employed additive manufacturing techniques to decrease the AEM layer thickness stepwise. Moreover, we have evaluated performance determining parameters such as the WD interlayer, operating conditions and water management in the membrane electrode assembly. All these studies allow us a critical assessment of the potential and the drawbacks of this novel MEA system for water electrolysis. Acknowledgements This work was performed in collaboration with the National Research Council of Canada in the Materials for Clean Fuels Challenge Program. References [1] S. Z. Oener, M. Foster, S. W. Boettcher, Science (2020). [2] B. Mayerhöfer, D. McLaughlin, T. Böhm, M. Hegelheimer, D. Seeberger and S. Thiele, ACS Appl. Energy Mater. (2020). Figure 1

Keywords: Acid Doping Level (ADL), Fuel Cells (FCs), High Temperature (HT), Polymer Electrolyte Membrane (PEM), Phosphoric Acid (PA), Polybenzimidazole (PBI), Raman spectroscopy High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are one of the most promising energy conversion devices with zero local CO2 emission. The polymer electrolyte membrane placed between the anode and cathode plays an important role for the overall fuel cell efficiency. The current state-of-the-art membranes used in HT-PEMFCs are PBI-based materials. Compared to Nafion®-based systems used in low temperature PEMFCs, they allow operation at temperatures up to 180-200 °C and do not require water management. Other advantages of the elevated operation temperature are e.g. accelerated reaction kinetics and tolerance improvement against impurities such as carbon monoxide. However, PBI-based membranes are not intrinsically proton conductive and therefore need to be doped with acid in order to ensure proton conductivity. The acid of choice is phosphoric acid due to its non-volatility and thermal stability. Acid doping levels are important since they have a huge influence not only on conductivity, but also onto mechanical and thermal properties of a membrane. Commonly, weighing and titration are used to determine the doping level, but they are bulk sensitive only. In this work, confocal Raman microscopy was used to provide temporal and spatial insights into the acid doping process. It can be performed on the membrane before or after application in a fuel cell due to its non-destructive nature. Our results show that acid doping is a diffusion-limited process. Considerable changes in spatial distribution of dopant were observed within the membrane before reaching saturation. Further monitoring of diffusion of phosphoric acid after removal from the doping solution shows that the diffusion continues even after months. Confocal Raman microscopy offers the option to gather information non-destructively and contact-free from within the membrane. The insights into the phosphoric acid doping process of PBI-based membranes presented here are of great importance for the manufacturing and optimization process of high temperature fuel cells and their overall efficiency.

Alternative energy studies are crucial since the energy demand in the world increases rapidly. Nowadays, due to limited reserves of fossil fuel and CO2 emission, environmentally green energy is the most promising and desirable energy source for the future. In this context, fuel cells becoming one of the most promising alternative energy conversion devices. Especially polymer electrolyte membrane fuel cells (PEMFCs) are of great research interest. Theoverall efficiency of PEMFCs is strongly influenced by the polymer membrane placed between the anode and cathode. The current state-of-the-art perfluorosulfonic acid (PFSA)-based membranes used in PEMFCs, such as Nafion, rely on the presence of water as the charge carrier for an efficient proton conductivity, and operate usually only up to 80 °C. Therefore, Nafion-based systems require water management, which can be avoided by using polybenzimidazole (PBI)-based membranes instead; operating at higher temperatures (up to 180 °C). Nevertheless, pristine PBI-based membranes need to be doped with acid in order to produce a highly proton conductive system. In this context, phosphoric acid (PA) is the most promising acid as the proton conduction medium. PA doping levels are essential as they govern conductivity, while an excess acid doping can deteriorate mechanical and thermal properties of the membrane. Therefore, the optimization and determination of the doping levels are important for high temperature polymer electrolyte membrane fuel cells. Commonly, titration or weighing of the membranes are used for the determination of the acid doping level, but they suffer from low accuracy and precision. In this work, the acid doping level (ADL) of PBI-based membranes was studied by Raman, impedance, and energy-dispersive X-ray (EDX) spectroscopy, gravimetric and thermogravimetric analysis, and titration. The use of Raman spectroscopy is of great interest due to its non-destructive nature. It can be performed on the sample prior or post application in a HT-PEMFC. This study presents a new measurement protocol for ADLs by using Raman spectroscopy, which is a helpful tool for choosing the optimal ADL for a PBI-based membrane. Thus, the manufacturing process of high temperature fuel cells and their overall efficiency can be optimized. Keywords: Acid Doping Level (ADL), Fuel Cells (FCs), High Temperature (HT), Polymer Electrolyte Membrane (PEM), Phosphoric Acid (PA), Polybenzimidazole (PBI)

Anion exchange membrane fuel cells (AEMFCs) show great promise in overcoming high cost of currently state of the art proton exchange membrane fuel cells, that rely on expensive Pt catalysts for both the hydrogen oxidation reaction (HOR) as well as the oxygen reduction reaction (ORR). With recent advancements in demonstrating high ORR activity and stability of Fe-N-C catalysts in alkaline environments,1 the HOR suddenly became the bottleneck reaction towards high power density platinum group metal (PGM) -low or -free AEMFCs. While application of PGM-free ORR catalysts is an eventual goal, current state of the art NiM nanoparticles show relatively poor performance in terms of both activity and irreversible oxidation and dissolution.2 Hence, at least for some time, one will need to rely on PGM catalysts for alkaline HOR, where the biggest challenge will be lowering the loading and meanwhile increasing the stability in an alkaline environment. To this end, fundamental understanding of surface processes is required. In this work we investigate model CeOx covered Pt and Pd electrocatalysts as benchmark materials for the HOR reaction3 , 4. To prepare such model electrodes, we use physical vapor deposition for the formation of PGM and atomic layer deposition subsequently, to yield CeOx surface layers of variable thickness. Activity and stability of the CeOx@Pt and CeOx@Pd electrodes are studied in common rotating disk electrode and on-line inductively coupled plasma mass spectrometry setups, respectively. External analytics, e.g. X-ray photoelectron spectroscopy, are used to further characterize the electrodes before and after degradation studies. We show that stability of the electrodes at the higher anodic potentials can be greatly improved by tuning the thickness of the CeOx layer. Interestingly, this can be achieved without sacrificing and even with a significant enhancement in the HOR activity. This unique performance is explained by assuming that the deposited CeOx films form an ion selective semipermeable passivation layer on the surface of Pd and Pt. We anticipate that, as a next logical step, such layers can be used to stabilize PGM-free Ni alloys and reach the goal of having completely PGM-free AEMFCs. References 1. P. G. Santori, F. D. Speck, J. Li, A. Zitolo, Q. Y. Jia, S. Mukerjee, S. Cherevko and F. Jaouen, J. Electrochem. Soc., 166, F3311 (2019). 2. E. S. Davydova, F. D. Speck, M. T. Y. Paul, D. R. Dekel and S. Cherevko, ACS Catalysis, 6837 (2019). 3. N. M. Markovića, S. T. Sarraf, H. A. Gasteiger and P. N. Ross, J. Chem. Soc., Faraday Trans., 92, 3719 (1996). 4. H. A. Miller, F. Vizza, M. Marelli, A. Zadick, L. Dubau, M. Chatenet, S. Geiger, S. Cherevko, H. Doan, R. K. Pavlicek, S. Mukerjee and D. R. Dekel, Nano Energy, 33, 293 (2017).

Ionomer membranes are crucial components of electrochemical energy systems such as fuel cells, electrolyzers, or redox-flow batteries. They need to meet demanding requirements for high-performance and long-term stable devices, and a targeted optimization of the membranes requires exact knowledge of parameters such as membrane thickness, ion exchange capacity, or water uptake. We employ confocal Raman microscopy as a tool for in-depth characterization of membranes that are used in proton exchange membrane fuel cells and water electrolyzers. Raman spectroscopy as a vibrational spectroscopy technique is well suited to characterize ionomer membranes, and the combination of Raman spectroscopy with a confocal microscope additionally adds spatial resolution to this chemical analysis. Confocal Raman microscopy is a valuable tool to complement classical characterization of ionomer membranes that provides a plethora of chemical information about the investigated specimen on a single-digit micron scale. We present our latest results on application-relevant ionomer degradation and water management in membranes determined by confocal Raman microscopy. We found that a Nafion NR-211 membrane that was aged in an accelerated stress test in a fuel cell suffered from severe thinning and an anisotropic increase in its equivalent weight between the electrodes.1 Both are signs of chemical-mechanical degradation and were quantified with high spatial resolution using confocal Raman microscopy (Fig. 1A). Further, we used confocal Raman microscopy to characterize ionomer composite membranes. Composite membranes are a promising approach to optimize membrane properties by e.g. integrating mechanically stabilizing porous networks. We quantified the equivalent weight along the depth profile of a Nafion XL membrane, and also analyzed the influence of the reinforcement layer on water distribution within the hydrated membrane (Fig. 1B).2 Figure 1: Results of ionomer membrane characterization by Raman microscopy. A) Quantification of degradation of Nafion NR-211 in a fuel cell (open circuit voltage (OCV) hold as stress test). B) Through-plane Raman image of water distribution in a Nafion XL membrane. 1. T. Böhm, R. Moroni, M. Breitwieser, S. Thiele and S. Vierrath, J. Electrochem. Soc., 166(7), F3044-F3051 (2019). 2. M. S. Mu’min, T. Böhm, R. Moroni, R. Zengerle, S. Thiele, S. Vierrath and M. Breitwieser, J. Memb. Sci., 585, 126–135 (2019). Figure 1

This article deals with the measurement of lightning current on high structures and, in particular, wind turbines. It offers a synopsis of the special lightning current characteristics for high building structures. The special requirements for lightning current measurements on high objects and, especially, wind turbines, are derived from this. It presents a measurement system for determining lightning currents in wind turbines based on Rogowski coils. In order to verify this lightning current recording unit, comparison measurements were carried out at the lightning measurement stations Gaisberg (Austria) and Peissenberg (Germany). First measurements have also been carried out on wind turbines.

The paper gives an overview on the forthcoming requirements that surge protective devices (SPD) will face in modern DC-grids. Therefore, the current and future structure of DC-grids which is under discussion will be analysed. Based on the characteristics of modern DC-grids the required protection levels, the behaviour of possible follow currents and the maximum surge current discharge capacity needed in DC-grids will be investigated. Furthermore, this work shows the requirements on SPDs protecting the DC grid from transient overvoltages with regard to their withstand capability to temporary overvoltage in DC-grids caused by power crossing events and fault situations.

The railway and mass transportation system is composed of industrial goods with substantial capital investments and long life cycles. This applies to rolling stock like trains, locomotives,wagons, and even more to the infrastructure like signaling, catenary, tracks, bridges, and tunnels. The lifespan of rolling stock is 30 to 40 years while the infrastructure is used 30 to 60 years even more than 100 years in case of tunnels and bridges. As in other industrial goods, the cost drivers are determined in the early design phases but realized mainly during a long time of operation. Maintenance is one of the main cost drivers but essential to a reliable, capable, and – above all – safe operation.