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Longevity is one of key requirements of PEMFC for automotive applications. Hence, understanding degradation phenomena and durability limitations is fundamental to increase PEMFC life time and to make this technology competitive In this contribution a selection of our recent work on these topics is presented. In particular, attention in dedicated to study effect of performance limitations at low Pt loadings and to investigate impact of operation conditions on local degradation phenomena such as drying, contaminations or heterogeneities during dynamic operation. Moreover, specific operando accelerated stress tests are being developed and the relative impact on various stressors on individual MEA components is studied. Eventually, we present results related to on-line fault monitoring using current density distribution measurements linked with impedance spectroscopy.

In this paper we report an approach to improve water management of commercial GDLs by introducing hydrophobicity patterns. Specifically, line and grid patterns have been created in the MPL side by laser radiation. For an in-depth investigation of these modified GDLs the current density distribution was monitored during fuel cell operation. Additionally, the physical properties of these materials were investigated by a number of ex situ methods such as Fourier transform infrared microscopy, electrochemical impedance spectroscopy and water vapor sorption. Furthermore, a comparison of the physical properties of the patterned GDLs with chemically modified GDLs (treated in H2SO4and H2O2) is provided. Our results show a clearly improved homogeneity of current density distribution of the patterned GDLs compared to untreated GDLs. This observation is likely due to a reduced local hydrophobicity which facilitates water diffusion along the flow field of the fuel cell. However, performance of the fuel cell was not affected by the MPL irradiation.

Hydrogen produced by water splitting is a promising solution for a sustained economy from renewable energy sources. Proton exchange membrane (PEM) electrolysis is the utmost suitable technology for this purpose, although the quest for low cost, highly active and durable catalysts is persistent. Here we develop a nanostructured iridium catalyst after electrochemically leaching ruthenium from metallic iridium-ruthenium, Ir0.7Ru0.3Ox(EC), and compare its physical and electrochemical properties to the thermally treated counterpart: Ir0.7Ru0.3O2(TT). Ir0.7Ru0.3Ox(EC) shows an unparalleled 13-fold higher oxygen evolution reaction (OER) activity compared to the Ir0.7Ru0.3O2(TT). PEM electrolyzer tests at 1Acm−2show no increase of cell voltage for almost 400h, proving that Ir0.7Ru0.3Ox(EC) is one of the most efficient anodes so far developed.

The porous transport layer (PTL)/catalyst layer (CL) interface plays a crucial role in the achievement of high performance and efficiency in polymer electrolyte membrane water electrolyzers (PEMWEs). This study investigated the effects of the PTL/CL interface on the degradation of membrane electrode assemblies (MEAs) during a 4000 h test, comparing the MEAs assembled with uncoated and Ir-coated Ti PTLs. Our results show that compared to an uncoated PTL/CL interface, an optimized interface formed when using a platinum group metal (PGM) coating, i.e., an iridium layer at the PTL/CL interface, and reduced the degradation of the MEA. The agglomeration and formation of voids and cracks could be found for both MEAs after the long-term test, but the incorporation of an Ir coating on the PTL did not affect the morphology change or oxidation of IrOxin the catalyst layer. In addition, our studies suggest that the ionomer loss and restructuring of the anodic MEA can also be reduced by Ir coating of the PTL/CL interface. Optimization of the PTL/CL interface improves the performance and durability of a PEMWE.

In proton exchange membrane fuel cells (PEMFCs), platinum (Pt) from the electrodes can be deposited in the electrolyte membrane, altering its properties and causing degradation. To investigate these impacts, in some studies, membranes with artificially deposited Pt were used, however, with contradictory results. In this study, we compared membranes impregnated with 0 to 4.4 wt% Pt. Specifically, the Pt particle distribution and mass transport in the membrane as well as the membrane decomposition is investigated after performing open circuit durability tests for [?]140 h. The properties of the membrane electrode assemblies (MEAs) are studied by electrochemical characterization. The changes upon degradation are investigated by thickness determination, infrared spectroscopy, fluoride emission, hydrogen permeability, and electrical conductivity.Our investigation confirmed that the particle density, not the Pt amount, is the determining factor in the extent of membrane decomposition: fluoride emission decreased exponentially with particle density. We further found a considerable difference in the particle distribution between artificial and in-situ Pt deposits. Moreover, properties of both membrane types changed contrary to each other during the durability test. In conclusion, Pt-impregnated membranes do not reflect the state of degraded membranes with in-situ formed deposits but are suitable to investigate the influence of particle distributions.

In this study the adsorption and reactions of methanol (CD3OH) on clean and oxygen-precovered PtxRu1–x/Ru(0001) surface alloys with x= 0–0.8 have been investigated using Fourier transform infrared spectroscopy and thermal desorption. Particular interest has been devoted to the influence of coadsorbed (atomic) oxygen. For increasing amounts of Pt the clean surface becomes gradually passivated in agreement with the inertness of the full Pt/Ru(0001) monolayer. On such oxygen-free layers the reaction pathway proceeds similar to clean Ru(0001). Yet, Pt enhances the thermal stability of the methoxy (CD3O) intermediate which represents the only stable reaction product species besides CO. On oxygen-precovered PtxRu1–x/Ru(0001) surface alloys the primary activation of methanol again leads to methoxy species. Depending on the Pt concentration within the Pt/Ru(0001) surface alloy, however, subsequent reactions vary substantially. For x< 0.4 total dehydrogenation to CO prevails, while for x> 0.4 formate (DCOO) is produced, eventually leading to CO2desorption. Formaldehyde formation and desorption are observed for x= 0.1–0.8. Similar to methanol reactions on O/Ru(0001) and O/Ptn/Ru(0001), no experimental evidence for a surface hydroxyl has been found.

Thin pseudomorphic as well as thick “Pt(111)-like” Pt/Ru(0001) bimetallic substrates have been used to study the oxidation of methanol (CD3OH) to CO2. Specifically, molecular (cold deposited) and ordered atomic (annealed) oxygen precovered Ptn/Ru(0001) layers with n= 1–15 ML have been studied. Thereby, the thickness of the Pt films primarily influences the adsorption probability of O2and much less the energy barriers for methanol reactions. In particular, no indication of a strain effect could be detected, and the reactions of methanol on Ptn/Ru(0001) multilayer films closely follow the known reaction scheme on Pt(111) substrates: On O2/Ptn/Ru(0001), methanol is directly oxidized to formate (DCOO) and eventually desorbs as CO2(300 K). The formate producing reaction is thereby promoted by dissociating O2molecules (130 K) and, at higher temperatures (130–200 K), by disordered atomic oxygen. This is in contrast to methanol postadsorbed onto ordered atomic oxygen covered Ptn/Ru(0001) layers, which exhibit formaldehyde formation and decomposition to CO and H. Interestingly, during methanol dissociation at 160–200 K, a remarkable fraction of methanol molecules experiences an H ↔ D exchange of the hydroxyl group hydrogen, leading to the dominant desorption of CD3OD. Our observation that the relative fraction of desorbing CD3OH is exceptionally low implies a bold primary isotope effect, which we attribute to the dissimilar zero point energies associated with OH and OD vibrations of methanol.

A versatile though straightforward process to functionalize materials is to deposit thin metal films or add coadsorbates in a controlled way. Referring to the direct methanol fuel cell, it is desirable to influence chemical reactivity and selectivity of catalysts to convert methanol to CO2instead of CO, which acts as a poison affecting continued and stable operation. In this study Fourier transform infrared spectroscopy, temperature-programmed desorption, and X-ray photoelectron spectroscopy were used to study the reactions of methanol (CD3OH) on Cu monolayers on Ru(0001). In contrast to the inert pure Cu/Ru(0001) monolayer, the oxygen-covered Cu/Ru(0001) layer exhibits enhanced reactivity toward methanol activation and methoxy (CD3O) formation. Interestingly, the ordered (2 × 2)-O phase is unreactive as well, which indicates a reduced affinity of this ordered array of oxygen atoms toward hydrogenation. Activation of methanol therefore occurs primarily in dilute oxygen environments or at defects and domain boundaries of the (2 × 2)-O phase. Under such favorable conditions (upright) methoxy is formed readily, even at low T< 80 K. If oxygen layers are not annealed (T≤ 80 K) prior to methanol admission methanol adsorbs dissociatively even at 20 K. In general, methoxy formation is accompanied by the formation of surface hydroxyl (OH) which desorbs as water at 300–350 K. Methoxy represents the main intermediate up to 350 K. Depending on the oxygen coverage, further annealing transforms methoxy into formaldehyde (D2CO), which desorbs instantaneously, or methoxy is oxidized to formate (DCOO), which represents a stable intermediate and eventually produces (desorbing) CO2at T> 450 K. As a minority species formyl (DCO) is identified.

The adsorption and reactions of methanol are of considerable technological relevance for the direct methanol fuel cell. Thereby, the stability of intermediates and activation barriers of the various reaction pathways depend critically on specific properties of the substrate materials. Deposition of ultrathin metal layers represents an established means to tune these in a controlled way. In the present study, Fourier transform infrared spectroscopy and temperature-programmed desorption have been employed to study the thermal evolution of adsorbed methanol on Ru(0001) precovered by Cu. While the full Cu monolayer turns out to be inert in the absence of coadsorbates such as oxygen, various reaction intermediates are discernible for ΘCu< 1 ML. In the temperature range 220−300 K, two upright methoxy species (local C3vsymmetry) on uncovered Ru(0001) areas and on Cu/Ru(0001) can be distinguished. The local methoxy coverage on the Cu monolayer amounts to about 0.04 ML which is half the value found on Ru(0001). This value gradually reduces to zero for Cu coverages exceeding 0.75 ML, i.e., approaching the full Cu monolayer. Interestingly, passivation of the Ru(0001) step edges by minute amounts of Cu or Pt effectively delays decomposition of Ru-bound methoxy. Specifically, the thermal stability of methoxy on uncovered Ru(0001) increases from 220 K for clean Ru(0001) to about 300 K for a partially filled Cu/Ru or Pt/Ru layer. The thermal stability of Cu-bound methoxy is even higher, and at least 380 K is required to transform all methoxy molecules into CO and hydrogen. Our study clearly shows that a modification of the reaction kinetics on a catalytically active surface can be achieved even for minute amounts of deposited metal atoms, e.g., by passivation of various types of reaction centers. For extended monolayer films, strain and electronic effects due to the underlying substrate strongly affect stability of intermediate species, as well as their formation and decomposition kinetics.

Fourier transform infrared absorption spectroscopy and temperature programmed desorption have been used to study the reactions of methanol (CH3OH, CD3OH and CH318OH) on the clean Ru(0001) surface in the temperature range 80−600 K. It has been found that the methanol thermal evolution is initiated by a breaking of the OH bond, forming an upright (C3vsymmetry) methoxy species (CH3O). This reaction requires annealing to about 180 K and, for dense layers, proceeds in parallel to molecular desorption. At 220 K, methoxy is found to be the dominant surface species. However, its decomposition into CO + 3H already starts at this temperature, as deduced from the appearance of the ν(CO) mode of CO; that is, methoxy is stable in a narrow temperature range only. Yet, CH3O formed at 220 K can be stabilized up to 320−340 K by means of surface site blocking through CO coadsorption. Hydrogen and carbon monoxide, the resulting reaction products from methoxy decomposition, desorb at 330−350 and 470 K, respectively. No other reaction intermediates have been identified. An entirely new interpretation is presented regarding the production of water detected in thermal desorption at about 190 K. On the basis of experiments with different methanol and oxygen isotopes, we demonstrate that it is the hydrogen of the hydroxyl group of methanol and residual surface oxygen (most likely at steps and a relict of the surface cleaning procedure with oxygen) which contributes to the formation of water. As intermixing of abstracted hydrogen with coadsorbed deuterium is found to be negligible, the hydrogen abstracted from methanol is suggested to react directly with surface oxygen, that is, without adsorbing on the surface in between. CO bond breaking, long believed to act as the primary reaction step toward water formation, can definitely be ruled out.

The most recent data of NA49 on hadron production in nuclear collisions at CERN SPS energies are presented. Anomalies in the energy dependence of pion and kaon production in central Pb+Pb collisions are observed. They suggest that the onset of deconfinement is located at about 30 A GeV. Large multiplicity and transverse momentum fluctuations are measured for collisions of intermediate mass systems at 158 A GeV. The need for a new experimental programme at the CERN SPS is underlined.

The history and the main results of the energy scan programme at the CERN SPS are reviewed. Several anomalies in energy dependence of hadron production predicted as signals of deconfinement phase transition are observed and they indicate that the onset of deconfinement is located at about 30 A GeV. For the first time we seem to have clear evidence for the existence of a deconfined state of matter in nature.

Multiplicity distributions and their second moments fornegatively charged particles produced in32S-S central and minimum bias interactions at 200A GeV are studied in various rapidity intervals. Fritiof and Venus models mostly describe the dependence of second moments on rapidity intervals in minimum bias interactions, but not in central collisions. For central collisions the behaviour of second moments might indicate enhanced multiplicity fluctuations.

Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed.

Abstract: In strength analysis of horizontal geodetic networks it is appropriate to use pairs of functions which involve the relative position of two points and relative position of three points. Using properly chosen pairs of functions, formulae are given which allow the computation of precision criteria for the orientation and scale of the network as well as its shape. To illustrate the presentation of results, new types of errors ellipses are introduced. Analogies and correlations existing among the adopted functions are introduced by using the concept of orthogonal networks which are defined in the paper.

The analysis of the data on the production of ? hyperons and p- in4He-Li,12C-C,12C-Ne and16O-Ne at 4.5 A GeV/c and12C-C collisions at 4.2 A GeV/c are presented. Kinematical features of ?'s are shown to depend on the collision centrality in contrast to the stable behaviour of the pion characteristics. The correlation between the characteristics of ?'s and accompanying pions is observed. The effects seem to be incompatible with the intranuclear cascade approach. The data suggest the formation of a fully stopped and thermalized hot source in central nucleus-nucleus collisions, in which ? hyperons are produced.

The results on spectra of negative particles produced in16O+Au andp-Au collisions at 200 GeV/nucleon and16O+Au at 60 GeV/nucleon are presented. The correlations of average rapidity and average transverse momentum with event multiplicity are studied. Spectral shapes are similar for central16O+Au andp-Au collisions. The transverse momentum and rapidity distributions for central16O+Au andp-Au collisions differ strongly from corresponding distributions forp+p interactions. The FRITIOF model fails to describe the shapes of the transverse momentum distributions. The simple thermodynamical model of a single fireball does not fit the midrapidity transverse momentum distributions, and the rapidity distributions.

Results from a pion interferometric analysis of the system 200 GeV/nucleon16O+Au, central collisions, are reported. Both a Gaussian source model and a model based on the inside-outside cascade are used to fit to the experimental correlation function, giving transverse and longitudinal shape parameters, a freezeout time parameter, and a chaoticity parameter for the pion emitting source. We find a transverse

We report a systematic study of mid-rapidityET production and forward energy flow in the interaction of16O projectiles on Al, Cu, Ag and Au at 60 and 200 GeV/nucleon. First results onET production with32S projectiles are presented.

We present the first preliminary results on ?,Ks0 and production on a gold target with proton and oxygen beams in the NA35 streamer chamber.

The production of ?, andKs0 has been studied in 200 GeV/nucleonp+S and S+S collisions in the streamer chamber of the NA35 experiment at the CERN SPS. Significant enhancement of the multiplicities of all observed strange particles relative to negative hadrons was observed in central S+S collisions, as compared top+p andp+S collisions. The latter collisions show no overall (relative) strangeness enhancement overp+p, but the rapidity distributions and hadron multiplicities indicate some secondary cascading production of ? particles in thep+S andp+Au collisions. The ? polarization in central S+S collisions was found to be compatible with zero up topT=2 GeV/c.

Zusammenfassung: Im Pamir-Gebiet ist ein vollständiges Trias-Profil ausgebildet. Das Perm wird im allgemeinen konkordant von Trias-Schichten überlagert, kurzzeitige Sedimentations-unterbrechungen sind jedoch stellenweise vorhanden. Der in Teilbecken gegliederte triadische Geosynklinaltrog wurde in der Ober-Trias stark differenziert, wobei eine axial liegende Schwellenzone (Axialzone, Tab. 1) und daran symmetrische anschließen- de Trogzonen (Übergangs-, Zwischen-, Randzone) sowie eine peripher liegende Schwellenzone (Peripherzone) entstanden. Die spezielle Faziesentwicklung in diesen Zonen spiegelt unterschiedliche paläobathymetrische Verhältnisse wider (Axial- und Peripheriezonen: flachmarine Ablagerungen; Übergangs- und Zwischenzonen: neritische Sedimente; Randzone: tiefermarine Sedimente). Riff-Bildung fand nur zu bestimmten Zeiten und in bestimmten Berichen (Peripheriezone und Axialzone) statt. Fazies und Fauna können mit der alpinen Trias-Entwicklung verglichen werden. Folgende Rifftypen wurden festgestellt:

We report on a systematic study of midrapidity transverse energy production and forward energy flow in interactions of16O and32S projectiles with S, Cu, Ag and Au targets at 60 and 200 GeV/nucleon. The variation of the shape of theET distributions with target and projectile mass can be understood from collision geometry. AverageET values determined for central collisions show an increasing stopping power for heavier target nuclei. A higher relative stopping is observed at 60 GeV/nucleon than at 200 GeV/nucleon. Bjorken estimates of the energy density reach approximately 3 GeV/fm3 in highET events at 200 GeV/nucleon with16O and32S projectiles. The systematics of the data and the shapes ofET and pseudorapidity distributions are well described by the Lund model Fritiof.

In strength analysis of horizontal geodetic networks it is appropriate to use pairs of functions which involve the relative position of two points and relative position of three points. Using properly chosen pairs of functions, formulae are given which allow the computation of precision criteria for the orientation and scale of the network as well as its shape. To illustrate the presentation of results, new types of errors ellipses are introduced. Analogies and correlations existing among the adopted functions are introduced by using the concept of orthogonal networks which are defined in the paper.

The production of neutral strange particlesKso, Λ andhas been studied in 60 and 200 GeV per nucleon OAu and pAu collisions with the streamer chamber vertex spectrometer of the NA35 experiment at the CERN-SPS accelerator. Ratios of neutral strange particle production to negatively charged particle production in selected regions of phase space were measured to be the same in OAu and pAu reactions. The rates of strange particle production in central OAu collisions are about a factor of 16 higher than in pAu collisions when compared in the same regions of phase space. If an enhancement of strange particle production in OAu collisions relative to pAu collisions is considered to be a signature for quark-gluon plasma formation, no evidence supporting it is observed. The experimental results are compared to the Lund FRITIOF model.

This paper is concerned with the computation of asymptotic blocking probabilities for a generalized Erlangian system which results when Mindependent Poisson streams of traffic with rates access a trunk group of Ccircuits with traffic from stream krequiring Akcircuits which are simultaneously held and released after a time which is randomly distributed with unit mean and independent of earlier arrivals and holding times. A call from stream kis lost if on arrival less than Akcircuits are available. Although exact expressions for the blocking probabilities are known, their computation is unwieldy for even moderate-sized switches. It is shown that as the size of the switch increases in that both the traffic rates and trunk capacity are scaled together, simple asymptotic expressions for the blocking probabilities are obtained. In particular the expression is different for light, moderate and heavy loads. The approach is via exponential centering and large deviations and provides a unified framework for the analysis.

Die Siklawa-Einheit der Polonez Cove Formation enthält konglomeratische Sandsteine, grobkörnige Sandsteine mit seltenen feinkörnigen Einschaltungen und Siltsteine. Diese Gesteine werden als vorglaziale Meeresablagerungen interpretiert. Vier Horizonte von Bohrgängen mit Muschelschalen der Gattung Penitella wurden in den Sandstein-Liegendflächen festgestellt. Bohrgänge durchdringen den siltigen Untergrund bis 10 cm tief und sind mit grobkörnigem Sand aus der hangenden Schicht ausgefüllt. Die Muscheln besiedelten siltige Bodenfragmente während ruhiger Phasen; ihre Bohrlöcher wurden dann bei plötzlichen Sediment-Gleitungen gefüllt.

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This study combines local electrochemical diagnostics with ex situ analysis to investigate degradation mechanism associated to start-up/shut-down (SU/SD) of PEMFC and mitigation strategies adopted in automotive stacks. Local degradation resulting from repeated SU/SD was analyzed with and without mitigation strategies by means of a macro-segmented cell setup provided with Reference Hydrogen Electrodes (RHEs) at both anode and cathode to measure local electrodes potential and current. Accelerated Stress Test (AST) for start-up with and without mitigation strategies are proposed and validated. A ten-fold acceleration of performance loss due to un-mitigated SU/SD has been calculated with respect to AST for catalyst support. Under mitigated SU/SD, instead, a strong degradation was observed as localized at cathode inlet region (i.e. ?38% ECSA loss and ?22 mV voltage loss after 200 cycles) due to local potentials transient reaching up to 1.5 V vs RHE. These localized stress conditions were additionally reproduced in a zero-gradient and a new AST protocol (named start-up AST) was proposed to mimic the potential profile observed upon SU/SD cycling. Representativeness of the start-up AST for real world degradation was confirmed up to 200 cycles. Platinum dissolution and diffusion/precipitation within the polymer electrolyte was shown to be the dominant mechanism affecting performance loss.

Longevity is one of key requirements of PEMFC for automotive applications. Hence, understanding degradation phenomena and durability limitations is fundamental to increase PEMFC life time and to make this technology competitive In this contribution a selection of our recent work on these topics is presented. In particular, attention in dedicated to study effect of performance limitations at low Pt loadings and to investigate impact of operation conditions on local degradation phenomena such as drying, contaminations or heterogeneities during dynamic operation. Moreover, specific operando accelerated stress tests are being developed and the relative impact on various stressors on individual MEA components is studied. Eventually, we present results related to on-line fault monitoring using current density distribution measurements linked with impedance spectroscopy.

The function of catalytic layers in fuel cells and electrolyzers depends on the properties of the ionically conductive phase, which are most commonly perfluorinated ionomers based on Nafion and Aquivion. An analysis by atomic force microscopy reveals that the ultrathin ionomer films around Pt/C agglomerates have a thickness distribution ranging from 3.5 nm to 20 nm. Their conductivity and gas permeation properties determine the fuel cell performance to a large extend. For electrodes in Aquivion-based membrane-electrode-assemblies operation-induced structure changes were investigated by means of material- and conductivity-sensitive atomic force microscopy, infrared spectroscopy and electron-dispersive X-ray analysis. The observed thinning of the ultrathin ionomer films was mainly caused by polymer degradation deduced from reduced swelling after long-time operation and a significant loss of ionomer with operation time detected by infrared spectroscopy. From the linear thickness increase of the ultrathin films with rising humidity, a mainly layered structure of the ionomer was deduced. An influence of thickness of such ultrathin ionomer films on fuel cell lifetime was found by analysis of differently prepared membrane-electrode-assemblies, where a linear increase of irreversible degradation rate with ionomer film thickness in the electrodes of unused membrane-electrode-assemblies was found.

We develop a thermally sprayed Ti coating for PEMFC stainless steel (ss) bipolar plates. It is subsequently modified with Au by electro-deposition. SEM reveals that the Au/Ti coating is 30.8 µm thick and rough. The presence of TiO2between Ti and Au is negligible, as confirmed by XRD and XPS. Potendiodynamic characteristics in O2-saturated 0.5 M H2SO4show that the Au/Ti/ss samples have comparable corrosion currents to Au/ss but higher corrosion potentials. The interfacial contact resistance (ICR) of Au/Ti/ss is 8.6 mΩ cm2 under a compaction pressure of 140 N cm-2. The performances of PEMFCs with Au and Au/Ti are similar at cell voltages higher than 0.75 V. However, at 0.6 V the Au/Ti coating diminishes the current and pressure instabilities of the PEMFC operating under strong flooding conditions. The effect also occurs in the oscillation frequency, confirming the unique property of Au/Ti for reducing the effect of flooding.

PEM electrolysis is a promising technology for large scale storage of surplus electricity, though it is still costly mainly due to the manufacture of large area and high purity Ti bipolar plates (BPP). In this work we have developed an Au/Ti coating deposited by electrodeposition/thermal spraying on stainless steel BPP. The coating was physically characterized with SEM and electro-chemically evaluated in simulated anode conditions. Interfacial contact resistance (ICR) vs. compaction pressure measurements showed that the coating is highly conductive. It successfully protected the stainless steel substrate from corrosion. However, the Au modification detached after 6 h of application of a potential of 2 V vs. RHE. Consequently the Au modification has to be replaced by either another precious metal or a corrosion resistant electro-ceramic. The coating reported herein could have a large impact on the cost of PEM electrolyzers for large scale electricity storage from renewables.

In proton exchange membrane fuel cells (PEMFCs), platinum (Pt) from the electrodes can be deposited in the electrolyte membrane, altering its properties and causing degradation. To investigate these impacts, in some studies, membranes with artificially deposited Pt were used, however, with contradictory results. In this study, we compared membranes impregnated with 0 to 4.4 wt% Pt. Specifically, the Pt particle distribution and mass transport in the membrane as well as the membrane decomposition is investigated after performing open circuit durability tests for ∼140 h. The properties of the membrane electrode assemblies (MEAs) are studied by electrochemical characterization. The changes upon degradation are investigated by thickness determination, infrared spectroscopy, fluoride emission, hydrogen permeability, and electrical conductivity.

A comprehensive overview of infrared absorption, Raman, and X-ray photoemission spectroscopy and their application in fuel cell research is given in this paper. Based on these ex-situ spectroscopic techniques a set of methods addressing the specific problems in the development of polymer electrolyte fuel cells are discussed and compared, regarding multi scale chemical characterizations and the analytics of outer surfaces, inner surfaces and buried layers. It is shown, that a combination of complementary methods is necessary to gather a comprehensive view of the occurring processes and mechanisms.