Filtern
Erscheinungsjahr
Dokumenttyp
- Wissenschaftlicher Artikel (237)
- Konferenzveröffentlichung (216)
- Teil eines Buches (Kapitel) (32)
- Sonstiges (31)
- Video (14)
- Buch (Monographie) (13)
- Preprint (12)
- Dissertation (4)
- Bericht (4)
- Arbeitspapier (4)
- Beitrag zu einer (nichtwissenschaftlichen) Zeitung oder Zeitschrift (2)
- Lehrmaterial (2)
- Masterarbeit (1)
Sprache
- Englisch (572) (entfernen)
Schlagworte
- Robotik (8)
- Flugkörper (7)
- UAV (7)
- Rettungsrobotik (5)
- Dissipative Particle Dynamics (4)
- Polymer-Elektrolytmembran-Brennstoffzelle (4)
- adhesion (4)
- Bionik (3)
- Deep Learning (3)
- Erweiterte Realität <Informatik> (3)
- Gespenstschrecken (3)
- Haftorgan (3)
- OCSR (3)
- stick insects (3)
- Augmented Reality (2)
- CDK (2)
- Competency-Oriented Exams (2)
- DECIMER (2)
- Deep learning (2)
- Electrodeposition (2)
- Field measurement (2)
- Human-Robot Interaction (2)
- OCSR, Optical Chemical Structure Recognition (2)
- Solar modules (2)
- Transformer (2)
- Twitter <Softwareplattform> (2)
- biomimicry (2)
- hydraulic compression (2)
- modular stack design (2)
- open quantum systems (2)
- social innovation (2)
- water electrolysis (2)
- carbon nanofibers, platinum electrodeposition, ele ctrochemical surface area (1)
- 360 degree Feedback (1)
- 360° Panorama (1)
- AEM-Electrolysis (1)
- AI (1)
- API 1130 (1)
- Additive manufacturing Directed energy deposition-arc 316L stainless steel Corrosion behavior Electrochemical corrosion (1)
- Aerosol (1)
- Aggregation-prone (1)
- Air handling unit (1)
- AlphaFold, ColabFold, PyMOL (1)
- Alternative Geschäftsmodelle (1)
- Amylase, Enzymcharakterisierung (1)
- Anorganische Analyse (1)
- Artificial Intelligence (1)
- Assessment Center (1)
- Assisted living technologies (1)
- Assistive robotics (1)
- Augmented (1)
- Augmented Electromagnetic Accelerators (1)
- Augmented Multiphase (1)
- Augmented Multiphase Rail Launcher (1)
- Augmented Three-Phase AC-Railgun (1)
- Autonomous Agents (1)
- Bildverarbeitung (1)
- Biomechanics (1)
- Biomedical monitoring, Hospitals, Electrocardiography, Wireless communication, Patient monitoring, Wireless sensor networks (1)
- Biomimetics (1)
- Bone Morphogenetic Protein, BMP, BMP2 (1)
- Bone morphogenetic protein 2 (1)
- Brand theory (1)
- CFD Simulation (1)
- COIL (1)
- CPM (1)
- Carboxylate (1)
- Case-Study (1)
- Catalysis (1)
- Cell-free implant (1)
- Chemical image depiction (1)
- Chemical space (1)
- Chemical structure depictions (1)
- Cheminformatics (1)
- Chemistry Development Kit (1)
- Chemistry Development Kit, CDK, Molecule fragmentation, In silico fragmentation, Scaffolds, Functional groups, Glycosidic moieties, Rich client, Graphical user interface, GUI (1)
- Chief Executive Officer (1)
- Climate change (1)
- Clustering (1)
- Codegenerierung (1)
- Communication management (1)
- Constructive Alignment (1)
- Continuous Assessment (1)
- Continuous Queries (1)
- Cookie <Internet> (1)
- Cr(VI) and Zn(II) cations (1)
- Crowdfunding (1)
- Current Pulses (1)
- DPD, Dissipative Particle Dynamics (1)
- Data Collection (1)
- Data Journalism (1)
- Datalog (1)
- Datenjournalismus (1)
- Datensatz (1)
- Datenschutz (1)
- Deductive Databases (1)
- Depiction generator image augmentation (1)
- Deutschland / Technische Regeln für brennbare Flüssigkeiten (1)
- Dissipative particle dynamics, DPD, Surfactant, Bilayer, Lamellar, Simulation, Mesoscopic (1)
- Distributed Software Development (1)
- E. coli SHuffle® T7 (1)
- Elastizitätsmodul (1)
- Electrolysis (1)
- Electromagnetic Launcher (1)
- Elektrodenvorbereitung (1)
- Energy Storage Mode (1)
- Enterprise JavaBeans (1)
- Erneuerbare Energien (1)
- Europe (1)
- Evidence-based Management (1)
- Exams with Third-Party Applications (1)
- Fehlererkennung (1)
- Fehlerortung (1)
- Flat-Channel (1)
- Flipped Classroom (1)
- Flory-Huggins parameter (1)
- Flügelform (1)
- Formative Assessment (1)
- Fragmentation (1)
- Future capacity needs (1)
- Gas Diffusion Electrode (1)
- Greek dept crisis (1)
- Hand-drawn chemical structures (1)
- Hand-drawn images (1)
- Hands-free Interaction (1)
- High Reynold Numer (1)
- Homogene Kühlung (1)
- Human-centered computing (1)
- Hydraulic cell compression (1)
- Hydraulic compression, Carbon Nano Fibers, PEM Fuel Cells, Catalyst utilization (1)
- Hydrogen evolution reaction (1)
- Hydrophilicity enhanced hBMP2 variant (1)
- ICP-Massenspektrometrie (1)
- Implantat (1)
- In-silico-design (1)
- Incremental Evaluation (1)
- Indigo (1)
- Interactive Voting Systems (1)
- Intercultural Collaboration (1)
- Journalismus (1)
- Juristenausbildung (1)
- Kalman filter (1)
- Kernspintomografie (1)
- Kohlenstoff (1)
- Kohlenstoff-Nanoröhre (1)
- Laser Synthesis Electrocatalytic Water Splitting (1)
- Launcher (1)
- Leadership Competencies (1)
- Leak detection (1)
- Leckerkennung (1)
- Leckortung (1)
- Lecksuchgerät (1)
- Lecküberwachung (1)
- Linear Electromagnetic Accelerator (1)
- Lüftungsanlage (1)
- MITRE (1)
- Machine Learning (1)
- Magnetic Pressure (1)
- Mapping (1)
- Maus (1)
- Media Brands (1)
- Media brand characteristics (1)
- Media positioning (1)
- Membrane (1)
- Methodology (1)
- Middle-range Theory (1)
- Mikrofotografie (1)
- Mixed Reality (1)
- Modular Augmented Launcher (1)
- Modular Design (1)
- Molecule images (1)
- Multi-Agent System (1)
- Multiphase Rail Launcher (1)
- Mund-Nasen-Schutz (1)
- Muzzle Velocity (1)
- N,N,O Ligands (1)
- N,N′ Ligands (1)
- Nanofaser (1)
- Natural products (1)
- Naturstoff (1)
- NeRF (1)
- New Public Governance (1)
- New Public Management (1)
- New Work, Information and Communication Industry, Innovation, Organizational Goals, Survey (1)
- Ni-Mo alloy Catalyst (1)
- NiCrBSi coatings; flame spraying; induction remelting; wear resistance (1)
- Normalisierung (1)
- ORR OER (1)
- OSINT (1)
- Object Recognition (1)
- Object-relational Mapping (1)
- Objektverfolgung (1)
- Ohrwurm (1)
- Online Programming Exams (1)
- Online Supervision (1)
- Online-Werbung (1)
- Optical Chemical Structure Recognition (1)
- Ortsbestimmung (1)
- PEM Electrolysis, Hydrogen, Hydraulic Compression, High Pressure (1)
- PEM electrolysis (1)
- PEM fuel cell (1)
- PEM fuel cell electrocatalysts, Carbon nanofibers, Oxygen plasma activation, Pulsed electroplating. (1)
- PEM fuel cells (1)
- PEM water electrolysis (1)
- PEM-Brennstoffzelle (1)
- PEMWE (1)
- Peer Assessment (1)
- Peer Instruction (1)
- People with disabilities (1)
- Performance prediction (1)
- Persistenz <Informatik> (1)
- Physics-Informed Deep Learning (1)
- Physics-informed deep learning; unsupervised learning; Reynolds-averaged Navier-Stokesequations; high Reynolds number flow; turbulence modeling (1)
- Politische Berichterstattung (1)
- Polymere (1)
- Porous Transport Layers (1)
- Powder feed rate HVOF Cermet Wear Corrosion (1)
- Privatsphäre (1)
- Project-based Learning (1)
- PtCoMn (1)
- RDKit (1)
- RIS (1)
- Rail Launcher (1)
- Railgun (1)
- Regeln der Technik (1)
- Rescue Robotics (1)
- Robot assistive drinking (1)
- Robot assistive eating (1)
- Rwanda (1)
- SARS-CoV-2 (1)
- Sauerstoffplasmaaktivierung (1)
- Scaffold (1)
- Scaffold network (1)
- Scaffold tree (1)
- Segmentation; Correlation; Diseases; Convolutional Neural Networks (1)
- Semi-Infinite Plate (1)
- Sinusoidal (1)
- Small UAVs (1)
- Smart Grid (1)
- Social Innovation (1)
- Social Learning (1)
- Social Media (1)
- Spondylodese (1)
- Stack <Brennstoffzelle> (1)
- Stellite 6; HVOF-spraying; Laser remelting; Cavitation erosion; Coatings (1)
- Student Activation (1)
- TRFL (1)
- Temperature coefficients (1)
- Ternary alloy catalyst preparation (1)
- Tetraplegie (1)
- Thermal Performance (1)
- Thermal Stress (1)
- Titanium; Al2O3–TiO2 coatings; Nanoindentation (1)
- Tracking (1)
- Transformative Teaching (1)
- Twitter (1)
- Update Propagation (1)
- Upscaling laboratory models (1)
- Urban heat island (1)
- Visual Monocular SLAM (1)
- Young´s modulus (1)
- Zinc (1)
- Zustandsmaschine (1)
- academic and job-related self-control demands (1)
- activated sludge (1)
- additive manufacturing; polylactic acid (PLA); fused filament fabrication (FFF); fused deposition modeling (FDM); printing temperature; filament color; dimensional accuracy; tensile strength; friction performance; wear (1)
- advanced persistent threats (1)
- aerosol (1)
- air hygiene (1)
- airborne infection (1)
- antecedents (1)
- artificial intelligence (1)
- assistive robotics (1)
- augmented reality (1)
- bacterial toxicity (1)
- balance (1)
- barrel cortex, cell types, multielectrode recordings, perception, psychophysics (1)
- bio-inspired functional surface (1)
- bioinspired (1)
- biomimetic (1)
- biomimetic materials (1)
- biomimetics; functional morphology; plant biomechanics; plant motion; strain analysis; structure–function relationship; 3D digital image correlation (3D-DIC); Hakea sericea; Hakea salicifolia (1)
- bipolar plate (1)
- blockchain (1)
- bloxberg (1)
- carbon nano fibres (1)
- carbon nanofibers, platinum electrodeposition, electrocatalysts (1)
- cartilage defect (1)
- cartilage regeneration (1)
- chlorinated phenols (1)
- cluster (1)
- co-based alloys; hot corrosion; solid particle erosion; microstructure; brazing (1)
- coatings (1)
- cobot (1)
- collaborative online international learning (COIL) (1)
- compassionate love (1)
- composition (1)
- conical intersection (1)
- consent banner (1)
- cookie banner (1)
- cookies (1)
- corrosion resistance (1)
- corrosion; self-fluxing alloys; NiCrBSi; WC-12Co; cavitation; hard metals (1)
- critical review (1)
- cyber kill chain (1)
- demagnetization cooling (1)
- design process (1)
- distributed software development (1)
- diversity (1)
- dlt (1)
- dynamic capabilities (1)
- education; skills; competences; pandemic; online or face-to-face (1)
- efficiency of exciton transfer (1)
- electrode preparation (1)
- empowerment (1)
- entrepreneurial diversity (1)
- entrepreneurship (1)
- ethereum (1)
- ethics (1)
- excitation energy transfer (1)
- expert interviews (1)
- face mask (1)
- farming (1)
- fused deposition modeling (FDM); fused filament fabrication (FFF); polylactic acid (PLA); layer height; layer thickness; filament color; PLA color; dimensional accuracy; tensile strength (1)
- gender stereotypes (1)
- gender-sensitive design (1)
- gender-specific design (1)
- human robot interaction (1)
- human-centered design (1)
- human-robot collaboration (1)
- hybrid sensor system (1)
- hydraulic cell compression (1)
- infrared heating panel (1)
- ingots (1)
- innovation (1)
- intercultural collaboration (1)
- interdisciplinary students project (1)
- intermolecular interaction (1)
- international comparative study (1)
- intersectionality (1)
- irritation (1)
- leak locating (1)
- leak monitoring (1)
- long-term toxicity (1)
- luminescent bacteria (1)
- machine learning (1)
- managerial vs. non-managerial actors (1)
- measurement study (1)
- media accountability (1)
- microfoundations (1)
- molecular force field (1)
- multi-level model of competence (1)
- narcissism (1)
- neutrality (1)
- nonadiabatic dynamics (1)
- noncommuting fluctuations (1)
- nonequilibrium quantum transport (1)
- normalisation (1)
- novel (1)
- open science (1)
- optical chemical structure recognition (1)
- oxygen plasma activation (1)
- pH-shift elution (1)
- participatory design (1)
- phishing (1)
- photovoltaic power systems (1)
- poa (1)
- poe (1)
- policymakers (1)
- political journalism (1)
- polymer electrolyte membrane (1)
- privacy (1)
- product development (1)
- project-based learning (1)
- projection (1)
- protein structure prediction (1)
- public policy (1)
- quality standards (1)
- quantum dissipation (1)
- reconnaissance (1)
- relevance (1)
- respiration inhibition (1)
- risk management (1)
- role identity (1)
- self-fluxing; ZrO2; NiCrBSi; vacuum post-treatment; thermal spraying (1)
- sensor fusion (1)
- servant leadership (1)
- shared user control (1)
- silicon (1)
- solar cells (1)
- solution finding (1)
- spatial policy (1)
- state machine (1)
- study and working time per week (1)
- sustainable development (1)
- television news coverage (1)
- theorising (1)
- trait self-control (1)
- transport (1)
- tree frog (1)
- user acceptance (1)
- ventilation (1)
- vibronic coupling (1)
- virtual reality (1)
- visual cues (1)
- visualization techniques (1)
- watchblogs (1)
- web measurement (1)
- Änderung (1)
Institut
- Westfälisches Institut für Gesundheit (115)
- Westfälisches Energieinstitut (61)
- Institut für Internetsicherheit (56)
- Informatik und Kommunikation (51)
- Elektrotechnik und angewandte Naturwissenschaften (50)
- Wirtschaft und Informationstechnik Bocholt (46)
- Institut für biologische und chemische Informatik (44)
- Maschinenbau Bocholt (37)
- Institut Arbeit und Technik (15)
- Wirtschaftsingenieurwesen (15)
Due to high power density and superior efficiency, polymer electrolyte membrane fuel cells (PEMFC) are believed to play a significant role for carbon dioxide emissions free electrical energy systems in the future. Unlike in Carnot processes, chemical energy in the form of hydrogen and oxygen is converted directly into electrical energy without a further process step. One issue in the development of PEMFCs for mobile or stationary applications is the utilization of rare and expensive catalyst material like platinum within the membrane electrode assembly (MEA) see figure 1. In addition, the objective is to reduce production costs and to increase the lifetime of PEMFC. One approach to improve PEMFCs is the development of intelligent electrode architectures. However, cost effective high performance materials are necessary to reach the development targets.
The wireless data logger system “Cor/log® BAN BT” (CL) allows seamless 24/7 monitoring of relevant vital sign parameters. CL covers the entire period of acute point of care inside the hospital and the recovery period, when first mobility is achieved and when the patient is released into an ambulatory or homecare environment. The CL records the relevant vital signs such as ECG, respiration, pulse oximetry with plethysmogram and movement. The vital data collected with the CL data logger is saved on a memory card for further analysis and is simultaneously transmitted in real-time to a telemedicine server via a smartphone or tablet. The smartphone also provides GPS location information. In addition Cor/log View, an Android Application for viewing recorded vital sign data originating from the CL, was developed. CL has also a connector to the generic MedM health cloud. MedM is a generic patient data management system (PDMS) consisting of a cloud portal and a mobile health app. The app runs on Android, iOS and Windows. The app can connects wirelessly to the CL physiologic monitor and stores the vital signs in the cloud.
In this experimental work we present a novel electrolyzer system for the production of hydrogen and oxygen at high pressure levels without an additional mechanical compressor. Due to its control strategies, the operation conditions for this electrolyzer can be kept optimal for each load situation of the system. Furthermore, the novel system design allows for dynamic long-term operation as well as for easy maintainability. Therefore, the device meets the requirements for prospective power-to-gas applications, especially, in order to store excess energy from renewable sources. A laboratory scale device has been developed and high-pressure operation was validated. We also studied the long-term stability of the system by applying dynamic load cycles with load changes every 30 sec. After 80 h of operation the used membrane electrode assembly (MEA) was investigated by means of SEM, EDX and XRD analysis.
An energy economy with high share of renewable but volatile energy sources is dependent on storage strategies in order to ensure sufficient energy delivery in periods of e.g. low wind and/or low solar radiation. Hydrogen as environmental friendly energy carrier is thought to be an appropriate solution for large scale energy storage. In 2011 the NOW (national organisation for hydrogen in Germany) calculated the demand for hydrogen energy systems as positive (0.8 GW to 5.25 GW) and negative supply for varying power demand (0.68 to 4.3 GW) for the German energy economy in 2025. Due to its dynamic behaviour on load changes polymer electrolyte membrane fuel cells (PEMFC) as well as water electrolyser systems (PEMEL) can play a significant role for large scale hydrogen based storage systems. In this work a novel design concept for modular fuel cell and electrolyser stacks is presented with single cells in pockets surrounded by a hydraulic medium. This hydraulic medium introduces necessary compression forces on the membrane electrode assembly (MEA) of each cell within a stack. Furthermore, ideal stack cooling is achieved by this medium. Due to its modularity and scalability the modular stack design with hydraulic compression meets the requirements for large PEMFC as well as PEMEL units. Small scale prototypes presented in this work illustrate the potential of this design concept.
Membrane electrode assemblies (MEA) developed at the Westphalian Energy Institute for polymer electrolyte membrane fuel cells (PEMFC) are high tech systems containing various materials structured in nanoscale, at which electrochemical reactions occur on catalyst nano particle surfaces. For low reactance homogeneous compression of the MEA’s layers is necessary. A novel stack architecture for electrochemical cells, especially PEMFC as well as PEM electrolysers, has been developed according to achieve ideal cell operation conditions. Single cells of such a stack are inserted into flexible slots that are surrounded by hydraulic media. While operation the hydraulic media is pressurised which leads to an even compression and cooling of the stack’s cells. With this stack design it has been possible to construct a test facility for simultaneous characterisation of several MEA samples. As compression and temperature conditions of every single sample are equal, with the novel test system the effect of e.g. different electrode configurations can be investigated. Furthermore, the modular stack design leads to the development of hybrid energy applications combining fuel cells, electrolysers, batteries as well as metal hydride tanks in one system.
In the polymer electrolyte membrane fuel cells (PEMFC) state of the art, rare and expensive platinum group metals (PGM) or PGM alloys are used as catalyst material. Reduction of PGMs in PEMFC electrodes is strongly required to reach cost targets for this technology. An optimal catalyst utilization is achieved in case of nano-structured particles supported on carbon material with a large specific surface area. In this study, graphitic material, in form of carbon nanofibers (CNF), is decorated with Pt particles, serving as catalyst material for PEMFC electrodes with low Pt loading. As a novelty, the effect of oxygen plasma treatment of CNFs previously to platinum particle deposition has been studied. Electrodes are investigated in respect of the optimal morphology, microstructure as well as electrochemical properties. Therefore, samples are characterized by means of scanning electron microscopy combined with energy dispersive X-ray analysis, transmission electron microscopy, thermogravimetry, X-ray diffraction as well as X-ray fluorescence analysis. In order to determine the electrochemical active surface area of catalyst particles, cyclic voltammetry has been performed in 0.5 M sulphuric acid. Selected samples have been investigated in a PEMFC test bench according to their polarization behavior.
Carbon Nanofibers (CNF) are considered to be a promising catalyst support material due to their unique characteristics, excellent mechanical, electrical and structural properties, high surface area and nevertheless, good interaction with metallic catalyst particles. The possibility of preparing CNF decorated with platinum by an electrochemical method was tested, using a hexachloroplatinic bath solution. The experiments were carried out with the aid of a Potentiostat/Galvanostat Ivium Technologies Vertex, in a three – electrode cell. The aim of the present work was to determine the electrochemical surface area (ECSA) of the CNF-Pt catalysts in relation to the functionalization treatment of fibers, using an electrochemical method. ECSA for different functionalized CNF-Pt catalysts was determined by cyclic voltammetry in 0.5 M H2SO4 solution. The highest active surface of platinum was obtained for the samples with CNF functionalized by plasma treatment using 80 W for 1800 s. The obtained results correlate very well with the particles size and distribution of platinum, revealed by scanning electron microscopy (SEM) and the quantity of deposited platinum determined by thermo gravimetrical analysis (TGA) respectively. Cyclic voltammetry (CV) has been proven to be a suitable method for estimation of the ECSA of the electrocatalysts.
For this study gas diffusion electrodes (GDE) with low platinum loading are prepared for the application as anode in polymer electrolyte membrane fuel cell (PEMFC) systems based on hydraulic compression. As catalyst support material, carbon nanofibers (CNF) are investigated because of their high specific surface area and high graphitization degree. The electrode preparation is optimized by an economic and environmental friendly pre-treatment process in oxygen plasma. For GDE manufacture an ink containing oxygen plasma activated CNFs as well as hydrophilic polymer is used. After spray coating of this CNF ink on a graphitic substrate, platinum is deposited using the pulse plating technique. Preliminary results showed a considerable improvement of CNF dispersibility as well as an increased amount and an optimized morphology of the deposited platinum. Morphology and microstructure are observed by scanning electron microscopy as well as transmission electron microscopy. Platinum loading is determined by thermogravimetric analysis to be in the range of 0.01 mg cm-2 to 0.017 mg cm-2. Furthermore, MEAs are prepared from these GDEs and testing is performed in a novel modular fuel cell test stack based on hydraulic compression. Technical information about stack design and functions is given in this work.
Platinum nanoparticles electrodeposition on carbon nanofibers (CNF) support has been performed with the purpose to obtain electrodes that can be further used especially in a polymer electrolyte membrane fuel cell (PEMFC). A pretreatment of CNF is required in order to enhance the surface energy, which simultaneously improves handling and wettability as well as interaction with the platinum cations. This step was performed using oxygen plasma functionalization. To produce CNF supported Pt catalysts, an electrochemical method was applied and the deposition parameters were adjusted to obtain nanosized platinum particles with a good distribution onto the graphitic surface. The morphology and structure of the obtained particles were investigated by scanning electron microscopy combined with energy dispersive X-Ray spectroscopy. The amount of deposited platinum was established using thermogravimetrical measurements. Cyclic voltammetry performed in 0.5 M H2SO4 solution was applied for determining the electrochemical surface area (ECSA) of the obtained electrodes.The functionalization degree of the CNF outer surface has a strong influence on the structure, distribution and amount of platinum particles. Moreover, the current densities, which were set for the deposition process influenced not only the particles size but also the platinum amount. Applying an oxygen plasma treatment of 80 W for 1800 s, the necessary degree of surface functionalization is achieved in order to deposit the catalyst particles. The best electrodes were prepared using a current density of 50 mA cm-2 during the deposition process that leads to a homogenous platinum distribution with particles size under 80 nm and ECSA over 6 cm2
In this experimental work polymer electrolyte membrane fuel cell (PEMFC) electrodes are analysed, which are prepared by the use of two sorts of carbon nano fibres (CNF) serving as support material for platinum nano particles. Those CNFs, which are heat treated subsequently to their production, have a higher graphitisation degree than fibres as produced. The improved graphitisation degree leads to higher electrical conductivity, which is favourably for the use in PEMFC electrodes. Samples have been analysed, in order to determine graphitisation degree, electrical conductivity, as well as morphology and loading of the prepared electro catalyst. Membrane electrode assemblies manufactured from prepared electrodes are analysed in-situ in a PEM fuel cell test environment. It has been determined that power output for samples containing CNFs with higher graphitisation degree is increased by about 13.5%.
This work deals with the preparation and investigation of PEM fuel cell electrodes, which are obtained using graphene related material (GRM) serving as catalyst support for platinum nanoparticles. Applied GRM are used for the preparation of suspensions in four distinct mixing ratios. Two sorts of GRM have been investigated: carbon nanofibers (CNF) and graphene oxide (GO). Utilized CNFs provide a superior graphitization degree of about 100%, which leads to both high corrosion resistance and low ohmic resistance in PEM fuel cells.
For electrode preparation a GRM containing layer serving as catalyst support is applied onto a gas diffusion layer (GDL). Prior to GRM suspension and deposition onto a GDL, the graphene structures are functionalized by plasma treatment. Due to this step, an improved hydrophilic behavior for facilitating suspension preparation is achieved. In addition, a subsequent platinum nanoparticle deposition by pulsed electrodeposition process is optimized.
In polymer electrolyte membrane fuel cells (PEMFC) noble metal nano particles are deposited on graphitic supports serving as electrocatalysts for devices with high power density. In this study anodes are analysed with low platinum loading of about 0.1 mg cm-2. These electrodes are prepared by carbon nano fibres (CNF) decorated with platinum nano particles. For electrode manufacturing two sorts of fibres, which are produced in an industrial scale, are used with different graphitisation degree and surface area. CNF layers are applied on commercially available graphitic substrate by spray coating which leads to a porous structure with high surface area. Subsequently, platinum deposition is achieved by pulsed electroplating for an improved platinum utilisation in PEMFC electrodes. Spray coating and platinum deposition are assisted by a previous oxygen plasma activation process. Prepared anode material is characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), X-ray fluorescence spectroscopy (XRF) and thermogravimetry (TGA). Electrochemical analyses (cyclic voltammetry and corrosion test) are carried out in 0.5 M sulphuric acid. The effect of graphitisation degree of carbon nano fibres on the performance of prepared electrodes is investigated in-situ in a PEM fuel cell test bench.
Platinum is one of the most effective electro catalysts for PEMFCs (proton exchange membrane fuel cells), but because of its prohibitive price, the use of this metal in industrial purposes is limited. As a consequence, during last years, several materials have been investigated, in order to obtain an efficient catalyst for both ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction), which can replace the expensive platinum but preserving the same properties: high electrical conductivity, structural stability and good corrosion resistance. Moreover, one of the most important parameters for catalyst materials is the electrochemical surface area (real surface area), which has a strong influence on the reaction rate and also on the current density.
CNFs (carbon nanofibers) are considered to be a promising catalyst support material due to their unique characteristics, excellent mechanical, electrical and structural properties, high surface area and nevertheless, good interaction with platinum particles.
The possibility of preparing CNFs decorated with platinum by electrochemical methods was tested, using a hexachloroplatinic solution bath. The experiments were carried out with the aid of a Potentiostat/Galvanostat MMate 510, in a three – electrode cell.
The aim of the present work was to determine the electrochemical surface area of the CNFs – Pt catalysts, using an electrochemical method. The obtained results correlate very well with the particles size and distribution of platinum, analyzed by SEM (scanning electron microscopy) respectively with the quantity of deposited platinum determined by TG (thermo gravimetrical analyses). Cyclic voltammetry is a suitable method for estimation of the real surface area for catalyst particles.
In state of the art polymer electrolyte membrane fuel cells (PEMFC) rare and expensive platinum group metals (PGM) are used as catalyst material. Reduction of PGM in PEMFC electrodes is strongly required to reach cost targets for this technology. An optimal catalyst utilisation is achieved in the case of nano-structured particles supported on carbon material with a large specific surface area. In this study, graphitic material in form of carbon nanofibres (CNFs) is decorated with platinum (Pt) particles serving as catalyst material for PEMFC electrodes with low Pt loading. For electrode preparation CNFs have been previously activated by means of radio frequency induced oxygen plasma. This kind of treatment results in formation of functional groups on the CNF’s surface which directly influences the characteristics of subsequent Pt particle deposition. Different plasma parameters (plasma power, gas flow or exposure time) have to be set in order to achieve formation of oxygen containing functional groups (hydroxylic, carboxylic or carbonylic) on the CNF’s surface. In the frame of this experimental work, electrodes are investigated in respect of optimal morphology, microstructure as well as electrochemical properties. Therefore, samples were characterised by means of scanning electron microscopy combined with energy dispersive X-ray analysis, transmission electron microscopy, thermogravimetry, X-ray diffraction, X-ray fluorescence as well as polarisation measurements.
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.
To further increase platinum utilisation in PEM fuel cells CNFs are investigated as catalyst support material due to the CNF’s high specific surface area. Furthermore, CNFs provide suitable properties concerning corrosion resistance as well as electrical conductivity in contrast to conventional carbon supports.
This work presents the results of an electrode preparation procedure based on O2 plasma activated CNFs. The plasma treatment leads to CNF dispersibility in alcohol/water for a spray coating process. Furthermore, O2 plasma activation enhances metal deposition on the CNF’s surface. Pulse plating procedure as well as wet chemical metal synthesis have been used for particle deposition. For pulse plating a potentiostat/galvanostat type MMates 510 AC from Materials Mates, Italy has been used. Electrode morphology has been determined in SEM type XL 30 ESEM from Philips, The Netherlands.