Electrolysis seals play an important role in the chemical industry and are used to seal liquids and gases in electrolysis cells. A good seal is critical to the performance and reliability of the electrolysis process, ensuring that no unwanted substances enter the system and that the correct amount of liquid and gas flows through the cell.This article explains the most important aspects of seal geometries, materials for electrolytic seals and required equipment.

Titanium polymer composites are evaluated concerning their suitability as bipolar plates in acid water electrolysis as a replacement of milled Titanium bipolar plates. It turns out that our highly filled polymer composites with 80 wt.-% Titanium powder meet all criteria given by US Department of Energy concerning electric conductivity and mechanical stability. Concerning the electrochemical corrosion test, an improved behavior is obtained by coating the composites by a 0.5 mum thin Titanium layer. The coated Titanium composite bipolar plate has been successfully integrated in a PEM fuel cell. The polarization curves show good electrolysis performances for short time, but further improvements on the coating and the surface roughness need to be made for long-time stability.

For the energy transition to succeed, the growing amount of solar and wind power need to be stored for night-time or low-wind periods. Redox flow storage offers a good way of balancing out the fluctuations in renewable energies and is considered a promising energy storage system because it is potentially inexpensive and relatively easy to scale. However, the costs are still too high for this technology to be a resounding success. New manufacturing and joining technologies can help here. This will be demonstrated using the central element of the redox flow battery, the stack, as an example. Here, novel bonding ideas will be investigated and explained. The aim was to improve the contact between the gas diffusion fleece on the active side of the bipolar half plates and the current collector on the bipolar edge plates. A media and temperature-resistant adhesive was tested and tried out in different geometries.

Three bipolar plates (BPP) comprised of a composite of polypropylene or polyvinylidene fluoride polymer and varying average graphite particle size were studied for application in a vanadium redox flow battery (VRFB). The BPPs were electrochemically aged via 3000 cyclic voltammetry curves in 1.8 M VOSO4 + 2.0 M H2SO4 electrolyte. After every 500th cycle the aging progression was determined by performing cyclic voltammetry on the bipolar plates in 0.1 M H2SO4 solution where the double layer capacitance, the quinone/hydroquinone and the vanadium species redox activity were quantitatively evaluated. Prior to the aging, the composite plates were extensively characterized using various physical methods. The performed studies reveal that the wettability, surface roughness and accessible porosity of the bipolar plates significantly influence their electrochemical stability. Cycling tests in vanadium redox flow single cells at a constant current density of 60 mA cm−2 revealed a close correlation of the cell efficiencies to the electrochemical stability of the bipolar plates. Thus, the proposed electrochemical characterization method can be an effective foresight to predict the applicability of a bipolar plate in a vanadium redox flow battery.

An almost abrupt change in attitude towards applications in the field of renewable energies has emerged in recent months, both among decision-makers in politics and in companies. [1]
 In particular, the topic of hydrogen production by electrolysis plays an eminently important role. In water electrolysis, water is split into its constituent ¬parts hydrogen and oxygen using electrical energy. The resulting hydrogen is of interest to future energy systems for a number of reasons, including the fact that hydrogen can serve as a storage medium for electrical energy from renewable energy conversion systems such as photovoltaic or wind turbines.

Efficient bipolar plates are needed to store electricity from renewable energies. Here the focus is concentrating on graphite-compound-Bipolar plates, which are one of the most used components in a Fuel Cell Stack system. Among other things, polypropylene is a suitable matrix material, but other polymer materials such as PPS and PVDF and phenolic resins can also be considered. However, for a correspondingly high conductivity in the fuel cell system, the plastic must be filled with up to more than 80 % graphite. To ensure that the compound is not brittle afterwards and is as easy to process as possible, an impact modify cation was further developed that makes it possible to produce thin films.

The systematics and biogeographical history of the Eastern Mediterranean and Macaronesian land snail tribe Allognathini (Helicidae: Helicinae) is investigated based on mitochondrial and nuclear DNA sequence data. Our molecular phylogenetic analyses indicate that the genus-group systematics of the tribe needs to be revised. We show for the first time that the narrow-range endemics Lampadia and Idiomela from the Madeira Archipelago belong to Allognathini and represent together the sister group of the diverse Canary Island Hemicycla radiation. We therefore suggest synonymising Lampadiini with Allognathini. Sister to these Macaronesian genera was the Balearic Island Allognathus radiation. Pseudotachea was not recovered as a monophyletic group and the two currently recognised species clustered in Iberus. Similarly, Adiverticula was not recovered as a monophyletic group and clustered in Hemicycla. We therefore suggest synonymising Pseudotachea with Iberus and Adiverticula with Hemicycla. The six genera in Allognathini, which we distinguish here (Cepaea, Iberus, Allognathus, Hemicycla, Idiomela and Lampadia), originated in Western to South-western Europe according to our ancestral area estimation and the fossil record. The disjunct distribution of the Balearic Islands and Macaronesian sister clades and the mainly Iberian Iberus clade that separated earlier can be explained by the separation of the Betic–Rif System from the Iberian Peninsula during the late Oligocene to early Miocene, along with independent Miocene dispersals to the Balearic Islands and Macaronesia from the Iberian Peninsula, where the ancestral lineage became extinct.

To meet the world’s energy requirements, advanced technologies for energy storage and provision have to be developed. Hydrogen offers a promising way to solve fluctuating electricity demands as well as the possibility of energy storage. When fed to a fuel cell, the chemical energy of the hydrogen molecule can be converted to electrical energy, which can be consumed in stationary and mobile applications.A Hydrogen-based fuel cell consists of various components, such as the membrane electrode assembly, where oxygen and hydrogen gas are reacting. To ensure a controlled conduction of electrons via an external pathway, so called bipolar plates (BPPs) are necessary. The bipolar plates have several functions inside the fuel cell as they provide the gases to the electrodes and separate the individual cells in a fuel cell stack from each other. The material itself has to be gas-impermeable and must ensure heat conductivity for heating and cooling of the cells. Moreover, it has to withstand acidic conditions under potentials ranging from 0-1.5 V and elevated temperatures up to 160 °C present in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs).In this work, we present a detailed analysis of composite-based bipolar plate materials with application in HT-PEM fuel cells. Such bipolar plates mostly contain graphite and varying low amounts of a polymeric binder. While graphite has a low mechanical stability, it provides the required electrical conductivity. It is mixed with a binder polymer to enable mechanic flexibility and stability as well as gas tightness. From previous studies it was shown that fundamental knowledge about BPPs electrical and thermo-mechanical properties and their stability is crucial for the development of fuel cells with high power outputs1-3.Our study includes the investigation of the BPP materials properties in correlation to the nature of the different components and to their fabrication processes. Therefore, a series of different characterisation methods are applied to the composite material provided by the manufacturer. The surface morphology is analysed by scanning electron microscopy (SEM), confocal microscopy and atomic force microscopy (AFM), while X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS) in combination with SEM will give insight in the surface composition. In addition, µ-computed tomography (µ-CT) is used to reveal inhomogeneities in the compounds volume. Those methods will enable us to analyse surface properties such as roughness and elemental composition as well as bulk composition.The electrical conductivity of the different BPPs is addressed by conductive-AFM and correlated to the materials composition. In this regard, Figure 1 shows the current distribution of two different BPP (PPS 1 and PPS 2) materials. The comparison shows significant differences in the current responses when applying a potential to the sample. While at one type of BPP already at 0.5 V high currents are observed locally, the overall current distribution for the other type of BPP is much lower (even at 1.0 V) but shows a very homogeneous distribution (Figure 1b). We will correlate such differences in current distribution to the surface morphology analysed by REM and confocal microscopy.Furthermore, the corrosion behaviour is analysed by extended chemical treatment in concentrated phosphoric acid at 160 °C and physicochemical changes of the composite material are tracked. This comprehensive study will enable us to gain new insights into the behaviour of carbon-based BPPs for HT-PEM fuel cells. Lee, D.; Lee, D. G., Journal of Power Sources 2016, 327, 119-126.Pilinski, N.; Nagappan, N. K.; Satola, B.; Rastedt, M.; Dyck, A.; Wagner, P., ECS Transactions 2018, 86, (13).Hartnig, C.; Schmidt, T. J., Electrochimica Acta 2011, 56, (11), 4237-4242. Figure 1

An electrochemical reactor based on a moving graphite–polymer composite (GPC) cathode and boron-doped diamond anode is developed and used for the electrochemical water softening and treatment of artificial vacuum toilet wastewater. The magnetically actuated cathode is designed for the in situ removal of insoluble compounds, which usually precipitate on the cathode during electrochemical water treatment processes. To obtain a suitable GPC cathode, the chemical stability and conductivity of various composites and their flexion and magnetic actuator characteristics are investigated. The most suitable GPC cathode is a 0.5 mm thick polypropylene-based composite, which presents chemical stability, the lowest resistivity of all analyzed samples (5.06 ± 1.80 mΩ cm), and enables flexions up to 2.4 mm. The water softening performance of the reactor featuring this electrode was evaluated using two configurations. Water hardness was decreased up to 72% and more than 90% in mixed and separated electrolyte modes, respectively. Further investigations demonstrate that this reactor can also be used for wastewater treatment. Artificial toilet wastewater was successfully discolored for reuse as toilet flushing water. Lastly, a treatment test over 120 h demonstrates that the magnetically actuated flexible GPC cathode removes in situ deposits on its surface and requires low maintenance. The performance of the new electrode configuration is similar to that of the state-of-the-art polarity reversal system and does not shorten the electrode service life.

In this work, different methods and electrochemical set-ups were investigated in order to study the corrosion behaviour of bipolar plates (BPP) for high temperature (HT) polymer electrolyte membrane fuel cell application. Using confocal and scanning electron microscopy, it was shown that chemical and electrochemical aging significantly increases surface roughness as well as morphology changes, confirming material degradation. Identical electrochemical corrosion behaviour was observed for both set-ups with typical quinone/hydroquinone peaks in the potential range ~0.6–0.7 V versus reversible hydrogen electrode (RHE). The appearance of the peaks and an increase of double layer capacitance can be related to the oxidation of carbon surface and, consequently, material corrosion. Simultaneously, an optimised corrosion set-up was introduced and verified regarding suitability. Both investigated set-ups and methods are useful to analyse the oxidation behaviour and corrosion resistance.