Michaela Roschger, Sigrid Wolf, Andreas Billiani, Kurt Mayer, Maša Hren, Selestina Gorgieva, Boštjan Genorio, and Viktor Hacker
This study provides a comparison of different commercially available low-cost anion exchange membranes (AEMs), a microporous separator, a cation exchange membrane (CEM), and an anionic-treated CEM for their application in the liquid-feed alkaline direct ethanol fuel cell (ADEFC). Moreover, the effect on performance was evaluated taking two different modes of operation for the ADEFC, with AEM or CEM, into consideration. The membranes were compared with respect to their physical and chemical properties, such as thermal and chemical stability, ion-exchange capacity, ionic conductivity, and ethanol permeability. The influence of these factors on performance and resistance was determined by means of polarization curve and electrochemical impedance spectra (EIS) measurements in the ADEFC. In addition, the influence of two different commercial ionomers on the structure and transport properties of the catalyst layer and on the performance were analyzed with scanning electron microscopy, single cell tests, and EIS. The applicability barriers of the membranes were pointed out, and the ideal combinations of membrane and ionomer for the liquid-feed ADEFC achieved power densities of approximately 80 mW cm–2 at 80 °C.
ACS Omega, 2023
https://doi.org/10.1021/acsomega.3c01564
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.
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.
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
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
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.
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.
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.
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Homepage University of Castilla-La Mancha
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
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
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
Visit to our cooperation partners at the University of Maribor, Faculty of Chemistry and Chemical Engineering (UM FKKT); meeting with Dean Prof. Dr. Zdravko Kravanja.
Michaela Roschger, Sigrid Wolf, Kurt Mayer, Andreas Billiani, Boštjan Genorio, Selestina Gorgieva and Viktor Hacker
Determining the optimum layer thickness, for the anode and cathode, is of utmost importance for minimizing the costs of the alkaline direct ethanol fuel cell (DEFC) without lowering the electrochemical performance. In this study, the influence of layer thickness on the performance of the ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) in an alkaline medium and resistance was investigated. The prepared gas diffusion electrodes (GDEs) were fully characterized, with scanning electron microscopy to determine the layer thickness and electrochemically in half-cell configuration. Cyclic voltammetry and polarization curve measurements were used to determine the oxidation and reduction processes of the metals, the electrochemical active surface area, and the activity towards the ORR and EOR. It was demonstrated that realistic reaction conditions can be achieved with simple and fast half-cell GDE measurements. Single cell measurements were conducted to evaluate the influence of factors, such as membrane or ethanol crossover. In addition, electrochemical impedance spectra investigation was performed to identify the effect of layer thickness on resistance. This successfully demonstrated that the optimal layer thicknesses and high maximum power density values (120 mW cm−2) were achieved with the Pt-free catalysts and membranes used.
Sustainable Energy & Fuels, 2023
DOI: 10.1039/D2SE01729F
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
CEET contributions to the MOOC "Dekarbonisierung & Nachhaltigkeitsmanagement: Der Weg zum klimaneutralen Unternehmen": https://imoox.at/course/dekarb
In kraft pulping, large quantities of biomass degradation products dissolved in the black liquor are incinerated for power generation and chemical recovery. The black liquor is, however, a promising feedstock for carboxylic acids and lignin. Efficient fractionation of black liquor can be used to isolate these compounds and recycle the pulping chemicals. The present work discusses the fractionation of industrial black liquor by a sequence of nanofiltration and bipolar membrane electrodialysis units. Nanofiltration led to retention of the majority of lignin in the retentate and to a significant concentration increase in low-molecular-weight carboxylic acids, such as formic, acetic, glycolic and lactic acids, in the permeate. Subsequent treatment with bipolar membrane electrodialysis showed the potential for simultaneous recovery of acids in the acid compartment and the pulping chemical NaOH in the base compartment. The residual lignin was completely retained by the used membranes. Diffusion of acids to the base compartment and the low current density, however, limited the yield of acids and the current efficiency. In experiments with a black liquor model solution under optimized conditions, NaOH and acid recoveries of 68–72% were achieved.
Paul Demmelmayer, Lena Steiner, Hansjörg Weber and Marlene Kienberger
Reactive liquid–liquid extraction has been widely investigated as a means of isolating carboxylic acids from fermentation broths. However, commonly applied fossil-based solvent phases should be replaced by green alternatives. In this work, we investigate a thymol-menthol-based deep eutectic solvent (tmDES) as a green alternative to the commonly applied modifier 1–octanol for the extraction of lactic acid, acetic acid, and oxalic acid from a model solution and pre-treated sweet sorghum silage press juice (pSPJ); tri–n–octylamine (TOA) was used as a reactive extractant. Additionally, NMR spectroscopy was used to detect interactions between menthol and thymol molecules, as well as among these and TOA and lactic acid. NMR measurements of tmDES revealed the existence of multiple intermolecular contacts between thymol and menthol. Furthermore, nuclear Overhauser effects (NOEs) between the tmDES, TOA, and lactic acid molecules were found. Extraction experiments showed that tmDES improves the extraction efficiency when using pSPJ as the feed phase. The maximum extraction efficiency for lactic acid increased from 35.0 ± 0.8 % to 48.7 ± 0.7 % and for acetic acid from 52.4 ± 0.2 % to 82.2 ± 0.6 % when using a tmDES instead of 1–octanol at 50 °C. Furthermore, the use of tmDES resulted in higher extraction efficiencies as compared to the use of 1–octanol at equilibrium pH values ranging from five to seven, which is a common pH range for fermentation. Besides having superior biocompatibility and extraction efficiency as compared to 1–octanol, tmDES allow carboxylic acid extraction processes to be carried out at higher pH levels.
Separation and Purification Technology, 2023
DOI: 10.1016/j.seppur.2022.123060
Spin-off Fellowships are an essential impulse to prepare the environment for future spin-offs and to accelerate the practical implementation of the research results of TU Graz. The project will develop and produce membrane electrode assemblies for fuel cells and electrolyzers using a newly developed catalyst system.
Press release (OTS Presseaussendung, 20.12.2022)
TU Graz news
Sigrid Wolf, Michaela Roschger, Boštjan Genorio, Daniel Garstenauer, Josip Radić and Viktor Hacker
Electrocatalyst development for alkaline direct ethanol fuel cells is of great importance. In this context we have designed and synthesized cerium-modified cobalt manganese oxide (Ce-CMO) spinels on Vulcan XC72R (VC) and on its mixture with reduced graphene oxide (rGO). The influence of Ce modification on the activity and stability of the oxygen reduction reaction (ORR) in absence and presence of ethanol was investigated. The physicochemical characterization of Ce-CMO/VC and Ce-CMO/rGO–VC reveals CeO2 deposition and Ce doping of the CMO for both samples and a dissimilar morphology with respect to the nature of the carbon material. The electrochemical results display an enhanced ORR performance caused by Ce modification of CMO resulting in highly stable active sites. The Ce-CMO composites outperformed the CMO/VC catalyst with an onset potential of 0.89 V vs. RHE, a limiting current density of approx. −3 mA cm−2 and a remaining current density of 91% after 3600 s at 0.4 V vs. RHE. In addition, remarkable ethanol tolerance and stability in ethanol containing electrolyte compared to the commercial Pt/C catalyst was evaluated. These outstanding properties highlight Ce-CMO/VC and Ce-CMO/rGO–VC as promising, selective and ethanol tolerant ORR catalysts in alkaline media.
RSC Advances, 2022
DOI: 10.1039/d2ra06806k
The current energy crisis could be a turbo for renewable energies. So-called "green hydrogen" plays an important role in the energy transition. It can generate, store and transport electricity highly efficiently and without greenhouse gas emissions. Green hydrogen" is not yet sufficiently available and therefore cannot replace fossil fuels in the short term, but in the long term it is seen as an important player on the road to an environmentally friendly, renewable energy system.
Interview mit Viktor Hacker (Ö1, Wissen Aktuell, 6. December 2022, 13:55)
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