Merit Bodner and Joel Edjokola are working with the support of the CERIC-ERIC consortium and in close collaboration with Marco Bogar and Davide Pivetta (University of Trieste) and Heinz Amenitsch (ICTM, TU Graz) at the TUG beamline at the Elettra Synchrotron in Trieste. With the help of small-angle X-ray scattering (SAXS), factors influencing the ageing processes of electrocatalysts in fuel cells are being investigated in order to further improve the service life of fuel cells.

© TUGraz

Mechanistic study of fast performance decay of Pt-Cu alloy based catalyst layers for polymer electrolyte fuel cells through electrochemical impedance spectroscopy

Maximilian Grandi, Matija Gatalo, Ana Rebeka Kamšek, Gregor Kapun, Kurt Mayer, Francisco Ruiz-Zepeda, Martin Šala, Bernhard Marius, Marjan Bele, Nejc Hodnik, Merit Bodner, Miran Gaberšček and Viktor Hacker

In the past, platinum–copper catalysts have proven to be highly active for the oxygen reduction reaction (ORR), but transferring the high activities measured in thin-film rotating disk electrodes (TF-RDEs) to high-performing membrane electrode assemblies (MEAs) has proven difficult due to stability issues during operation. High initial performance can be achieved. However, fast performance decay on a timescale of 24 h is induced by repeated voltage load steps with H₂/air supplied. This performance decay is accelerated if high relative humidity (>60% RH) is set for a prolonged time and low voltages are applied during polarization. The reasons and possible solutions for this issue have been investigated by means of electrochemical impedance spectroscopy and distribution of relaxation time analysis (EIS–DRT). The affected electrochemical sub-processes have been identified by comparing the PtCu electrocatalyst with commercial Pt/C benchmark materials in homemade catalyst-coated membranes (CCMs). The proton transport resistance (Rpt) increased by a factor of ~2 compared to the benchmark materials. These results provide important insight into the challenges encountered with the de-alloyed PtCu/KB electrocatalyst during cell break-in and operation. This provides a basis for improvements in the catalysts’ design and break-in procedures for the highly attractive PtCu/KB catalyst system.

Materials, 2023

doi.org/10.3390/ma16093544

Wasserstoff - Rolle im Energiesystem der Zukunft (Viktor Hacker).

Die Energie- und Klimakrise macht eine dekarbonisierte Wirtschaft alternativlos. Wasserstoff kann als Energieträger einen wesentlichen Beitrag dazu leisten und seine chemische Anwendung in Brennstoffzellen ist bereits jetzt möglich.

Urania, Knittelfeld 19-20:30 Uhr

Sprachen, Nähen und Sport. Meine Interessen als Jugendliche sprechen nicht gerade für einen technischen Werdegang. Dieser war auch nie geplant. Durch das FIT-Praktikum an der TU Graz hatte ich das erste Mal die Chance, einen Monat lang Einblicke in die Verfahrenstechnik zu bekommen und danach war für mich ganz klar: „Die Technik“, die ist nichts für mich! Chemie fand ich jedoch, neben Sprachen, immer schon spannend und auch wenn ich Physik während meiner Schulzeit hasste, entschied ich mich für das Bachelorstudium Chemie. Die Physik hielt sich hierbei, zu meinen Freuden, in Grenzen. Vor allem zum Ende des Bachelors hin kam langsam die Einsicht, dass „die Technik“ viel breitgefächerter ist, als ich es mir immer vorgestellt habe. Ich stellte fest, dass mich Teilbereiche sogar interessieren. Daher begann ich das Masterstudium „Chemical and Pharmaceutical Engineering“, welches dem Institut der Verfahrenstechnik zugeordnet ist. Ich war nach all den Jahren doch wieder am Anfang angelangt, hätte ich dies doch nur gleich gewusst. Das Masterstudium hat mir sehr viel Freuden und Tränen beschert. Ich glaube, dass ich im Namen vieler TU-AbsolventInnen spreche, wenn ich sage: „Es war nicht einfach, aber das war es wert!“ Mittlerweile bewerbe ich mich als Diplomingenieurin für Jobs, die noch weiter in den technischen Bereich gehen. Der kleine, aber feine Unterschied: Ich weiß mittlerweile, was mich erwartet und sehe mich darin. Das ist etwas, was sich mein jüngeres Ich, vermutlich mangels Vorbilder, nicht vorstellen hätte können. Daher kann ich allen Frauen folgendes mitgeben: Sprachen, Nähen und Sport sind immer noch ein Teil meines Lebens und dennoch passt ein technischer Beruf zu mir.

© TUGraz

Electrode configurations study for alkaline direct ethanol fuel cells

Michaela Roschger, Sigrid Wolf, Andreas Billiani, Selestina Gorgieva, Boštjan Genorio and Viktor Hacker

The direct electrochemical conversion of ethanol, a sustainable fuel, is an alternative sustainable technology of the future. In this study, membrane electrode assemblies with different electrode configurations for an alkaline direct ethanol fuel cell were fabricated and tested in a fuel cell device. The configurations include a catalyst-coated substrate (CCS), a catalyst-coated membrane (CCM), and a mixture of these two fabrication options. Two different anion exchange membranes were used to perform a comprehensive analysis. The fabricated CCSs and CCMs were characterized with single cell measurements, electro­chemical impedance spectroscopy and scanning electron microscopy. In addition, the swelling behavior of the membranes in alkaline solution was investigated in order to obtain information for CCM production. The results of the experimental electrochemical tests show that the CCS approach provides higher power densities (42.4 mW cm-2) than the others, regardless of the membrane type.

Journal of Electrochemical Science and Engineering, 2023

DOI: 10.5599/jese.1623

The Role of Carbonate Formation during CO2 Hydrogenation over MgO-Supported Catalysts: A Review on Methane and Methanol Synthesis

Kamonrat Suksumrit, Sascha Kleiber and Susanne Lux

Methane and methanol are promising products for CO₂ hydrogenation for carbon capture and utilization concepts. In the search for effective, robust, easy-to-manufacture and stable catalysts, supported metal-based catalysts have proven advantageous. Whereas nickel for methane synthesis and copper for methanol synthesis stand out as efficient and cost-effective catalytically active metals, the best choice of support material is still a matter of ongoing debate. This review discusses the potential of the alkaline earth metal oxide MgO as support material for CO₂ hydrogenation catalysts. Due to its basicity, it gives access to bifunctional catalysts as it shows pronounced CO₂ adsorption capacity. Whereas carbonate formation seems to be beneficial in CO₂ methanation, it may even have an adverse effect in methanol synthesis from CO₂.

Energies 2023, 16(7), 2973

https://doi.org/10.3390/en16072973

Mixed Transition-Metal Oxides on Reduced Graphene Oxide as a Selective Catalyst for Alkaline Oxygen Reduction

Sigrid Wolf, Michaela Roschger, Boštjan Genorio, Daniel Garstenauer and Viktor Hacker

The development of highly efficient, stable, and selective non-precious-metal catalysts for the oxygen reduction reaction (ORR) in alkaline fuel cell applications is essential. A novel nanocomposite of zinc- and cerium-modified cobalt-manganese oxide on reduced graphene oxide mixed with Vulcan carbon (ZnCe-CMO/rGO-VC) was prepared. Physicochemical characterization reveals uniform distribution of nanoparticles strongly anchored on the carbon support resulting in a high specific surface area with abundant active sites. Electrochemical analyses demonstrate a high selectivity in the presence of ethanol compared to commercial Pt/C and excellent ORR activity and stability with a limiting current density of −3.07 mA cm–2, onset and half-wave potentials of 0.91 and 0.83 V vs reversible hydrogen reference electrode (RHE), respectively, a high electron transfer number, and an outstanding stability of 91%. Such a catalyst could be an efficient and cost-effective alternative to modern noble-metal ORR catalysts in alkaline media.

ACS Omega, 2023

http://doi.org/10.1021/acsomega.3c00615

Lab of Tomorrow Tunisia – UNIDO-BMK Workshop, 12–14 March 2023 in Tunis.

Prof. Merit Bodner and Prof. Viktor Hacker met with more than 80 Tunisian and Austrian stakeholders in a technical workshop on green hydrogen and water-related impacts.

This trip to Tunisia was the first time that UNIDO's cooperation under the Global Programme for Hydrogen in Industry, on the one hand, and the deepening under the Lab of Tomorrow process with the Austrian Development Agency and the German GIZ, on the other, were carried out together.

Thematically, during the two-day UNIDO BMK workshop, the topic of green hydrogen and, as a special topic, the water issues associated with electrolysis (desalination, wastewater treatment, competition for use, etc.) could be very well illuminated from several sides between Austrian and Tunisian representatives: Austria's and Tunisia's strategic vision on renewable energies and hydrogen, UNIDO's expertise, the scientific perspective, the private sector's perspective and the expertise of Austrian companies specifically on the topic of water.

www.unido.org/news/tunisia-austria-and-unido-advance-long-term-collaboration-green-hydrogen

Die Eröffnung des neuen MINKT-Labors der TU Graz, indem Kinder und Jugendliche in die Welt der Wissenschaft eintauchen können, fand am 10. März 2023 statt. Das Institut für Chemische Verfahrenstechnik und Umwelttechnik ist mit einer Station über den Taylor-Couette Disc Contactor (TCDC) und einem kleinen wasserstoffbetriebenen Fahrzeug vertreten. Am TCDC werden Trennungsprozesse von Flüssigkeiten anhand von unterschiedlich gefärbten Flüssigkeiten anschaulich erklärt. Mit dem kleinen Wasserstofffahrzeug können Kinder und Jugendliche auf spielerische Weise etwas über die Verwendung von Wasserstoff in einer Brennstoffzelle und damit über die Nutzung alternativer Energien lernen. 

© TU Graz

At the beginning of March, Prof. F. Javier Ramos from the University of Castilla-La Mancha visited the institute in order to strengthen cooperation in the field of student mobility between the two universities. During his visit, he gave an insight into his research activities in the field of perovskite solar cells and phase change materials.

© TU Graz

Homepage University of Castilla-La Mancha  

Efficiency of Neat and Quaternized-Cellulose Nanofibril Fillers in Chitosan Membranes for Direct Ethanol Fuel Cells

Maša Hren, Damjan Makuc, Janez Plavec, Michaela Roschger, Viktor Hacker, Boštjan Genorio, Mojca Božič and Selestina Gorgieva

In this work, fully polysaccharide based membranes were presented as self-standing, solid polyelectrolytes for application in anion exchange membrane fuel cells (AEMFCs). For this purpose, cellulose nanofibrils (CNFs) were modified successfully with an organosilane reagent, resulting in quaternized CNFs (CNF (D)), as shown by Fourier Transform Infrared Spectroscopy (FTIR), Carbon-13 (C13) nuclear magnetic resonance (¹³C NMR), Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC), and ζ-potential measurements. Both the neat (CNF) and CNF(D) particles were incorporated in situ into the chitosan (CS) membrane during the solvent casting process, resulting in composite membranes that were studied extensively for morphology, potassium hydroxide (KOH) uptake and swelling ratio, ethanol (EtOH) permeability, mechanical properties, ionic conductivity, and cell performance. The results showed higher Young’s modulus (119%), tensile strength (91%), ion exchange capacity (177%), and ionic conductivity (33%) of the CS-based membranes compared to the commercial Fumatech membrane. The addition of CNF filler improved the thermal stability of the CS membranes and reduced the overall mass loss. The CNF (D) filler provided the lowest (4.23 × 10⁻⁵ cm² s⁻¹) EtOH permeability of the respective membrane, which is in the same range as that of the commercial membrane (3.47 × 10⁻⁵ cm²s⁻¹). The most significant improvement (~78%) in power density at 80 °C was observed for the CS membrane with neat CNF compared to the commercial Fumatech membrane (62.4 mW cm⁻² vs. 35.1 mW cm⁻²). Fuel cell tests showed that all CS-based anion exchange membranes (AEMs) exhibited higher maximum power densities than the commercial AEMs at 25 °C and 60 °C with humidified or non-humidified oxygen, demonstrating their potential for low-temperature direct ethanol fuel cell (DEFC) applications.

Polymers, 2023

DOI: 10.3390/polym15051146

Continuous fractional component Gibbs ensemble Monte Carlo

Niklas Mayr, Michael Haring, and Thomas Wallek

A continuous fractional component (CFC) approach increases the probability of particle swaps in the context of vapor-liquid equilibrium simulations using the Gibbs ensemble Monte Carlo algorithm. Two variants of the CFC approach are compared for simulations of pure Lennard-Jones (LJ) fluids and binary LJ mixtures as examples. The details of an exemplary CFC implementation are presented. Recommendations are provided to reduce the effort required for the suggested problems.

American Journal of Physics 91, 235 (2023)

DOI: 10.1119/5.0135841

Photometric Method to Determine Membrane Degradation in Polymer Electrolyte Fuel Cells

Mathias Heidinger, Eveline Kuhnert, Kurt Mayer, Daniel Sandu, Viktor Hacker and Merit Bodner

A new method for measuring membrane degradation in polymer electrolyte fuel cells (PEFCs) is proposed. The method is based on the detection of fluoride ions in effluent water from the cathode- and anode outlet of the PEFC using photometry (PM). The fluoride emission rate (FER) is an indicator of the membrane’s state of health (SoH) and can be used to measure the chemical membrane degradation. Commercial catalyst-coated membranes (CCMs) have been tested at 80 °C and 90 °C at 30% relative humidity (RH) to investigate the reliability of the developed method for fuel cell effluent samples. To verify the measurement, a mean-difference plot was created by measuring the same data with a fluorine selective electrode. The average difference was at ±0.13 nmol h⁻¹ cm⁻², which indicates good agreement between the two methods. These new findings imply that PM is a promising method for quick and simple assessment of membrane degradation in PEM technology.

Energies 2023, 16(4), 1957

DOI: 10.3390/en16041957

Deactivation of a steam reformer catalyst in chemical looping hydrogen systems: Experiments and modelling

Stoppacher B., Lonardi F., Bock S., Bele M., Bertucco A., Hacker V.

The utilization of real producer gases such as raw biogas or gasified wood for chemical looping hydrogen production implies the introduction of harmful contaminants into the process. Hydrogen sulfide represents one of the most challenging trace gases in the Reformer Steam Iron Cycle (RESC).

The aim of the present work was an in-depth investigation of steam reforming with pure methane and synthetic biogas contaminated with selective concentrations of 1, 5 and 10 ppm of hydrogen sulfide. To validate the experimental data, the fixed-bed reactor system was modelled as one‑dimensional pseudo‑homogeneous plug flow reactor by an adapted Maxted model. In a preliminary thermodynamic study, the dry equilibrium composition was determined within a deviation of 4% for SMR and 2% for synthetic biogas reforming compared to the experimental results.

The impact of hydrogen sulfide on the reactivity of the catalyst was discussed and quantified by the methane conversion. The deactivation rate and extent correlate directly to the concentration of H2S, as higher hydrogen sulfide concentrations lead to a faster deactivation and lower residual methane conversion. A comparison of the methane conversion as a function of sulfur coverage between experimental and simulated data showed good agreement. The predicted results are within <10% deviation for SMR and synthetic biogas reforming, except for sulfur coverages between 0.6 and 0.8. The temperature in the catalyst bed was monitored throughout the deactivation process to gather additional information about the reaction behavior. It was possible to visualize the shift of the reforming reaction front towards the bottom of the reactor caused by catalyst deactivation. The impact of sulfur chemisorption on the morphology of the steam reformer catalyst was analyzed by SEM/EDS and BET techniques. SEM images clearly indicated the presence of sulfur as a sort of dust on the surface of the catalyst, which was confirmed by EDS analysis with a sulfur concentration of 0.04 wt%.

Journal of Physics: Energy, 2023

DOI: 10.1088/2515-7655/acb668