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- Polymer-Elektrolytmembran-Brennstoffzelle (3)
- hydraulic compression (2)
- modular stack design (2)
- Elektrolyseure (1)
- Erneuerbare Energien (1)
- Homogene Kühlung (1)
- Hydraulic cell compression (1)
- Hydraulic compression, Carbon Nano Fibers, PEM Fuel Cells, Catalyst utilization (1)
- Hydrogen evolution reaction (1)
- Kohlenstoff-Nanoröhre (1)
Brennstoffzellen gelten in der Forschung als eine der saubersten Technologien zur Stromerzeu-gung. In den Zellen, die meist z.B. so groß sind wie ein Taschenbuch, werden Wasserstoff und Sauerstoff in einer kontrollierten chemischen Reaktion in Wasserdampf umgewandelt. Dabei entstehen elektrische Energie und Wasser. Im Gegensatz zu den meisten anderen Formen der Stromproduktion wird kein Kohlendioxid freigesetzt. Das macht den Wandlungsprozess der Brennstoffzelle sehr umweltfreundlich.
Der Elektroingenieur Prof. Dr. Michael Brodmann von der Westfälischen Hochschule sieht in dieser Technologie die Zukunft mobiler wie stationärer Energieversorgung. Autos mit Elektro-motoren könnten mit Wasserstofftechnik angetrieben, portable Elektrogeräte oder auch ganze Gebäude umweltfreundlich mit Strom versorgt werden. Jedoch ist die Herstellung und Wartung der Brennstoffzellen derzeit sehr teuer, weshalb am Markt Energiewandler auf Basis fossiler Rohstoffe weiterhin dominieren. An diesem Problem arbeitet Brodmann gemeinsam mit Dr. Ulrich Rost. Im Labor des Westfälischen Energieinstituts haben die beiden Forscher eine neue Zelle entwickelt, die effektiver und günstiger ist – und dabei auf ein bewährtes Patent und neue Materialien gesetzt.
A systematic method for obtaining a novel electrode structure based on PtCoMn ternary alloy catalyst supported on graphitic carbon nanofibers (CNF) for hydrogen evolution reaction (HER) in acidic media is proposed. Ternary alloy nanoparticles (Co0.6Mn0.4 Pt), with a mean crystallite diameter under 10 nm, were electrodeposited onto a graphitic support material using a two-step pulsed deposition technique. Initially, a surface functionalisation of the carbon nanofibers is performed with the aid of oxygen plasma. Subsequently, a short galvanostatic pulse electrodeposition technique is applied. It has been demonstrated that, if pulsing current is employed, compositionally controlled PtCoMn catalysts can be achieved. Variations of metal concentration ratios in the electrolyte and main deposition parameters, such as current density and pulse shape, led to electrodes with relevant catalytic activity towards HER. The samples were further characterised using several physico-chemical methods to reveal their morphology, structure, chemical and electrochemical properties. X-ray diffraction confirms the PtCoMn alloy formation on the graphitic support and energy dispersive X-ray spectroscopy highlights the presence of the three metallic components from the alloy structure. The preliminary tests regarding the electrocatalytic activity of the developed electrodes display promising results compared to commercial Pt/C catalysts. The PtCoMn/CNF electrode exhibits a decrease in hydrogen evolution overpotential of about 250 mV at 40 mA cm−2 in acidic solution (0.5 M H2SO4) when compared to similar platinum based electrodes (Pt/CNF) and a Tafel slope of around 120 mV dec−1, indicating that HER takes place under the Volmer-Heyrovsky mechanism.
This report gives a brief overview to the state of the art of PEM fuel cell technology and a description of a newly developed fuel cell stack concept. One main research activity at the Westphalian Energy Institute of the Westphalian University of Applied Sciences is the development of PEM fuel cells, for which a range of different materials have been investigated for fuel cell pole plate construction. Whereas graphite is a material which has suitable properties concerning conductivity as well as manufacturing e.g. for milling, stainless steel foils are suitable for economical hydroforming processes. However, with steel coating is necessary to increase corrosion resistance as well as electrical conductivity. A new fuel cell stack design is currently under development using separated single fuel cells with hydraulic cell compression. The advantages of this stack concept are modularity, effective heat exchanging and constant, uniform cell compression which are further described in this work.
In this study, a novel design concept for PEMFC (polymer electrolytemembrane fuel cell) stacks is presented with singlecells inserted in pockets surrounded by a hydraulic medium. Thehydraulic pressure introduces necessary compression forces to themembrane electrode assembly of each cell within a stack. Moreover, homogeneous cell cooling is achieved by this medium. First,prototypes presented in this work indicate that, upscaling of cells for the novelstack design is possible without significantperformancelosses. Due to its modularity and scalability, this stackdesign meets the requirements for large PEMFC units.
Performance enhancing study for large scale PEM electrolyzer cells based on hydraulic compression
(2017)
This experimental work deals with the preparation and investigation of PEM fuel cell electrodes, which are obtained using Graphene Related Material (GRM) serving as catalyst support material for platinum nanoparticles. The applied GRM belong to the group of carbon nanofibers and exhibits a helical-ribbon structure with dimensions of 50 nm in diameter and an average length up to a few µm. Furthermore, utilized GRM provide a superior graphitisation degree of about 100 %, which leads to both high corrosion resistance and low ohmic resistance. Material stability plays one of the main roles for long term fuel cell operation, whereby a great electrical catalyst contact combined with high specific surface area yields in high fuel cell performances.
Prior to GRM dispersion and deposition onto a gas diffusion layer, the graphene structures are functionalized by oxygen plasma treatment. Through this step, functional oxygen groups are generated onto the GRM outer surface providing an improved hydrophilic behaviour and facilitating the GRM suspension preparation. In addition, the oxygen groups act as anchors for platinum nanoparticles which are subsequently deposited onto the GRM surface through a pulse electrodeposition process.
Membrane electrode assemblies produced with the prepared electrodes are investigated in-situ in a PEM fuel cell test bench.