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Green hydrogen is central to the energy transition, but its production often requires expensive materials and poses environmental risks due to the perfluorinated substances used in electrolysis. This study introduces a transformative approach to green hydrogen production via chemical looping, utilizing an iron-based oxygen carrier with yttrium-stabilized zirconium oxide (YSZ). A significant innovation is the replacement of Al2O3 with SiO2 as an inert support pellet, enhancing process efficiency and reducing CO2 contamination by minimizing carbon deposition by up to 700%. The major findings include achieving a remarkable hydrogen purity of 99.994% without the need for additional purification methods. The Fe-YSZ oxygen carrier possesses a significantly higher pore volume of 323 mm³/g and pore surface area of 18.3 m²/g, increasing the pore volume in the iron matrix by up to 50%, further improving efficiency. The catalytic system exhibits a unique self-cleaning effect, substantially reducing CO2 contamination. Fe-YSZ-SiO2 demonstrated CO2 contamination levels below 100 ppm, which is particularly noteworthy. This research advances our understanding of chemical looping mechanisms and offers practical, sustainable solutions for green hydrogen production, highlighting the crucial synergy between support pellets and oxygen carriers. These findings underscore the potential of chemical looping hydrogen (CLH) technology for use in efficient and environmentally friendly hydrogen production, contributing to the transition to cleaner energy sources.

The anion exchange membrane is one of the core components that play a crucial and inseparable role in alkaline anion exchange membrane fuel cells. Anion exchange membranes (AEMs) were prepared from quaternary ammonium poly(vinyl alcohol) (QPVA) by an electrospinning method. QPVA was used both as material for electrospun fiber mats and as filler for the inter-fiber void matrix. The objective of this work is to investigate the influence of the inter-fibers void matrix filler concentration on the properties and performance of eQPVA-x AEMs. FTIR spectra were used to identify the chemical structures of the AEMs. The primary functional groups of PVA and quaternary ammonium-based ion conducting cation were detected. The surface morphology of QPVA nanofiber mats and eQPVA-x AEMs was observed using SEM. Electrospun nanofiber structures of QPVA with an average size of 100.96 nm were observed in SEM pictures. The ion exchange capacity, swelling properties, water uptake, and OH-ions conductivity were determined to evaluate the performance of eQPVA-x AEMs. By incorporating the QPVA matrix of 5 wt.% concentration, the eQPVA-5.0 AEMs attained the highest ion exchange capacity, water uptake, swelling properties, and OH− conductivity of 0.82 mmol g−1, 25.5%, 19.9%, and 2.26 m×s cm−1, respectively. Electrospun QPVA AEMs have the potential to accelerate the development of alkaline anion exchange membrane fuel cells.

After a one-year delay caused by the COVID-19 pandemic, the 8th Regional Symposium on Electrochemistry of South-East Europe was held jointly with the 9th Kurt Schwabe Symposium from July 11-15, 2022 at Graz University of Technology in Austria. This special edition of the jESE contains a collection of articles presented at this meeting. The 5-day event (including Monday’s Satellite Student Symposium) organized by the Association of South-East European Electrochemists (ASEEE) featured 5 plenaries, 15 keynotes, 71 contributed talks and 38 posters and was attended by 152 scientists and researchers from 23 countries.

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.

The sluggish kinetics of the ethanol oxidation reaction (EOR) and the related development of low-cost, highly active and stable anode catalysts still remains the major challenge in alkaline direct ethanol fuel cells (ADEFCs). In this respect, we synthesized a PdNiBi nanocatalyst on reduced graphene oxide (rGO) via a facile synthesis method. The prepared composite catalyst was physicochemically characterized by SEM, STEM, EDX, ICP-OES and XRD to analyze the morphology, particle distribution and size, elemental composition and structure. The electrochemical activity and stability towards EOR in alkaline media were examined using the thin-film rotating disk electrode technique. The results reveal well-dispersed and strongly anchored nanoparticles on the rGO support, providing abundant active sites. The PdNiBi/rGO presents a higher EOR activity and stability compared to a commercial Pd/C ascribed to a high ECSA and synergistic effects between Pd, Ni and Bi and the rGO material. These findings suggest PdNiBi/rGO as a promising anode catalyst in ADEFC applications.

The shelf-life of catalyst ink for fabricating polymer electrolyte fuel cells (PEFCs) is relevant for large-scale manufacturing with unforeseen production stops. In this study, the storage effects on the physicochemical characteristics of catalyst ink (Pt/C, Nafion, 2-propanol, water) and subsequently manufactured catalyst layers are investigated. Sedimentation analysis showed that catalyst particles are not fully stabilized by charge interaction induced by Nafion. Acetone was found to be an oxidation product, even in freshly prepared ink with platinum catalyzing the reaction. Rotating disk electrode analysis revealed that the electrochemically active surface area is, overall, minimally increased by storage, and the selectivity towards water formation (4-electron pathway) is unharmed within the first 48 h of storage. MEAs prepared from stored ink reach almost the same current density level after conditioning via potential cycling. The open-circuit voltage (OCV) increases due to increased catalyst availability. Scanning electron microscopy and mercury intrusion porosimetry showed that with increasing acetone content, the pore structure becomes finer, with a higher specific surface area. Electrochemical impedance spectroscopy revealed that this results in a more hindered mass transfer but lowered charge transfer resistance. The MEA with the highest OCV and power output and the lowest overall cell resistance was fabricated from catalyst ink stored for a duration of four weeks.

Crosslinked anion exchange membranes (AEMs) made from poly(vinyl alcohol) (PVA) as a backbone polymer and different approaches to functional group introduction were prepared by means of solution casting with thermal and chemical crosslinking. Membrane characterization was performed by SEM, FTIR, and thermogravimetric analyses. The performance of AEMs was evaluated by water uptake, swelling degree, ion exchange capacity, OH- conductivity, and single cell tests. A combination of quaternized ammonium poly(vinyl alcohol) (QPVA) and poly(diallyldimethylammonium chloride) (PDDMAC) showed the highest conductivity, water uptake, and swelling among other functional group sources. The AEM with a combined mass ratio of QPVA and PDDMAC of 1:0.5 (QPV/PDD0.5) has the highest hydroxide conductivity of 54.46 mS cm-1. The single fuel cell tests with QPV/PDD0.5 membrane yield the maximum power density and current density of 8.6 mW cm-2 and 47.6 mA cm-2 at 57 °C. This study demonstrates that PVA-based AEMs have the potential for alkaline direct ethanol fuel cells (ADEFCs) application.

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.

Polymer electrolyte membrane water electrolysis (PEMWE) is a leading candidate for the development of a sustainable hydrogen infrastructure. The heart of a PEMWE cell is represented by the membrane electrode assembly (MEA), which consists of a polymer electrolyte membrane (PEM) with catalyst layers (CLs), flow fields, and bipolar plates (BPPs). The weakest component of the system is the PEM, as it is prone to chemical and mechanical degradation. Membrane chemical degradation is associated with the formation of hydrogen peroxide due to the crossover of product gases (H2 and O2). In this paper, membrane failure due to H2 crossover was addressed in a membrane-focused accelerated stress test (AST). Asymmetric H2O and gas supply were applied to a test cell in OCV mode at two temperatures (60 °C and 80 °C). Electrochemical characterization at the beginning and at the end of testing revealed a 1.6-fold higher increase in the high-frequency resistance (HFR) at 80 °C. The hydrogen crossover was measured with a micro-GC, and the fluoride emission rate (FER) was monitored during the ASTs. A direct correlation between the FER and H2 crossover was identified, and accelerated membrane degradation at higher temperatures was detected.

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.

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.

In recent years, there has been considerable interest in anion exchange membrane fuel cells (AEMFCs) as part of fuel cell technology. Anion exchange membranes (AEMs) provide a significant contribution to the development of fuel cells, particularly in terms of performance and efficiency. Polymer composite membranes composed of quaternary ammonium poly(vinyl alcohol) (QPVA) as electrospun nanofiber mats and a combination of QPVA and poly(diallyldimethylammonium chloride) (PDDA) as interfiber voids matrix filler were prepared and characterized. The influence of various QPVA/PDDA mass ratios as matrix fillers on anion exchange membranes and alkaline fuel cells was evaluated. The structural, morphological, mechanical, and thermal properties of AEMs were characterized. To evaluate the AEMs’ performances, several measurements comprise swelling properties, ion exchange capacity (IEC), hydroxide conductivity (σ), alkaline stability, and single-cell test in fuel cells. The eQP-PDD0.5 acquired the highest hydroxide conductivity of 43.67 ms cm−1 at 80 °C. The tensile strength of the membranes rose with the incorporation of the filler matrix, with TS ranging from 23.18 to 24.95 Mpa. The peak power density and current density of 24 mW cm−2 and 131 mA cm−2 were achieved with single cells comprising eQP-PDD0.5 membrane at 57 °C.

Alkaline direct ethanol fuel cells (DEFCs) represent an efficient energy conversion device for sustainable ethanol fuel. In this study, a design with new structural parameters for the anodic flow field of the alkaline DEFC was modeled with the aid of computational fluid dynamics and was then actually constructed. Single-cell tests were performed to evaluate the impact of the developed design on fuel cell performance. The results show that fuel cell performance significantly increased when using the improved design in the low-temperature range. The higher the temperature in the cell, the lower the influence of the flow field structure on performance. In addition, the influence of external factors, such as the orientation of the cell, the preheating of the fuel, and the direction of the two fuel flows relative to each other (co-current and counter-current), are shown.

Anion exchange membrane fuel cells have unique advantages and are thus gaining increasing attention. Poly(vinyl alcohol) (PVA) is one of the potential polymers for the development of anion exchange membranes. This review provides recent studies on PVA-based membranes as alternative anion exchange membranes for alkaline fuel cells. The development of anion exchange membranes in general, including the types, materials, and preparation of anion exchange membranes in the last years, are discussed. The performances and characteristics of recently reported PVA-based membranes are highlighted, including hydroxide conductivity, water uptake, swelling degree, tensile strength, and fuel permeabilities. Finally, some challenging issues and perspectives for the future study of anion exchange membranes are discussed.

In this study, Ag-MnxOy/C composite catalysts deposited on reduced graphene oxide (rGO) and, for the first time on N-doped graphene oxide (NGO), were prepared via a facile synthesis method. The influence of the carbon support material on the activity and stability of the oxygen reduction reaction (ORR) and on the tolerance to ethanol in alkaline medium was focused and investigated. The physicochemical properties of the Ag-MnxOy/C catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) method, atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and thermogravimetric gas analysis (TGA). Electrochemical characterization was performed by rotating disk electrode (RDE) experiments. The results show that the active manganese species MnO2 was assembled as nanorods and nanospheres on rGO and NGO, respectively. Ag was assumed to be present as very small or amorphous particles. Similar redox processes for Ag-MnxOy/rGO and Ag-MnxOy/NGO were examined via cyclic voltammetry. The Ag-MnxOy/rGO resulted in a more negative diffusion limiting current density of −3.01 mA cm−2 compared to Ag-MnxOy/NGO. The onset potential of approximately 0.9 V vs. RHE and the favored 4-electron transfer pathway were independent of the support material. Ag-MnxOy/NGO exhibited a higher ORR stability, whereas Ag-MnxOy/rGO showed a better ethanol tolerance.

In the present work, nitrogen-doped reduced graphene oxide-supported (NrGO) bimetallic Pd–Ni nanoparticles (NPs), fabricated by means of the electrochemical reduction method, are investigated as an anode electrocatalyst in direct hydrazine–hydrogen peroxide fuel cells (DHzHPFCs). The surface and structural characterization of the synthesized catalyst affirm the uniform deposition of NPs on the distorted NrGO. The electrochemical studies indicate that the hydrazine oxidation current density on Pd–Ni/NrGO is 1.81 times higher than that of Pd/NrGO. The onset potential of hydrazine oxidation on the bimetallic catalyst is also slightly more negative, i.e., the catalyst activity and stability are improved by Ni incorporation into the Pd network. Moreover, the Pd–Ni/NrGO catalyst has a large electrochemical surface area, a low activation energy value and a low resistance of charge transfer. Finally, a systematic investigation of DHzHPFC with Pd–Ni/NrGO as an anode and Pt/C as a cathode is performed; the open circuit voltage of 1.80 V and a supreme power density of 216.71 mW cm−2 is obtained for the synthesized catalyst at 60 °C. These results show that the Pd–Ni/NrGO nanocatalyst has great potential to serve as an effective and stable catalyst with low Pd content for application in DHzHPFCs.

Fuel starvation is a major cause of anode corrosion in low temperature polymer electrolyte fuel cells. The fuel cell start-up is a critical step, as hydrogen may not yet be evenly distributed in the active area, leading to local starvation. The present work investigates the hydrogen distribution and risk for starvation during start-up and after nitrogen purge by extending an existing computational fluid dynamic model to capture transient behavior. The results of the numerical model are compared with detailed experimental analysis on a 25 cm2 triple serpentine flow field with good agreement in all aspects and a required time step size of 1 s. This is two to three orders of magnitude larger than the time steps used by other works, resulting in reasonably quick calculation times (e.g., 3 min calculation time for 1 s of experimental testing time using a 2 million element mesh).

Electrochemical impedance spectroscopy is an important tool for fuel-cell analysis and monitoring. This study focuses on the low-AC frequencies (2–0.1 Hz) to show that the thickness of the catalyst layer significantly influences the overall resistance of the cell. By combining known models, a new equivalent circuit model was generated. The new model is able to simulate the impedance signal in the complete frequency spectrum of 105–10−2 Hz, usually used in experimental work on polymer electrolyte fuel cells (PEMFCs). The model was compared with experimental data and to an older model from the literature for verification. The electrochemical impedance spectra recorded on different MEAs with cathode catalyst layer thicknesses of approx. 5 and 12 µm show the appearance of a third semicircle in the low-frequency region that scales with current density. It has been shown that the ohmic resistance contribution (Rmt) of this third semicircle increases with the catalyst layer’s thickness. Furthermore, the electrolyte resistance is shown to decrease with increasing catalyst-layer thickness. The cause of this phenomenon was identified to be increased water retention by thicker catalyst layers.

The detrimental effects of the catalyst degradation on the overall envisaged lifetime of low-temperature proton-exchange membrane fuel cells (LT-PEMFCs) represent a significant challenge towards further lowering platinum loadings and simultaneously achieving a long cycle life. The elaborated physically based modeling of the degradation processes is thus an invaluable step in elucidating causal interaction between fuel cell design, its operating conditions, and degradation phenomena. However, many parameters need to be determined based on experimental data to ensure plausible simulation results of the catalyst degradation models, which proves to be challenging with the in situ measurements. To fill this knowledge gap, this paper demonstrates the application of a mechanistically based PEMFC modeling framework, comprising real-time capable fuel cell performance, and platinum and carbon support degradation models, to model transient CO2 release rates in the LT-PEMFCs with the consistent calibration of reaction rate parameters under multiple different accelerated stress tests at once. The results confirm the credibility of the physical and chemical modeling basis of the proposed modeling framework, as well as its prediction and extrapolation capabilities. This is confirmed by an increase of only 29% of root mean square deviations values when using a model calibrated on all three data sets at once in comparison to a model calibrated on only one data set. Furthermore, the unique identifiability and interconnection of individual model calibration parameters are determined via Fisher information matrix analysis. This analysis enables optimal reduction of the set of calibration parameters, which results in the speed up of both the calibration process and the general simulation time while retaining the full extrapolation capabilities of the framework.

A numerical study is conducted to compare the current most popular flow field configurations, porous, biporous, porous with baffles, Toyota 3D fine-mesh, and traditional rectangular flow field. Operation at high current densities is considered to elucidate the effect of the flow field designs on the overall heat transfer and liquid water removal. A comprehensive 3D, multiphase, nonisothermal computational fluid dynamics model is developed based on up-to-date heat and mass transfer sub-models, incorporating the complete formulation of the Forchheimer inertial effect and the permeability ratio of the biporous layers. The porous and baffled flow field improves the cell performance by minimizing mass transport losses, enhancing the water removal from the diffusion layers. The baffled flow field is chosen for optimization owing to the simple design and low manufacturing cost. A total of 49 configurations were mutually compared in the design of experiments to show the quantitative effect of each parameter on the performance of the baffled flow field. The results elucidate the significant influence of small geometry modifications on the overall heat and mass transfer. The results of different cases have shown that water saturation can be decreased by up to 33.59% and maximal temperature by 7.91 °C when compared to the reference case which is already characterized by very high performance. The most influencing geometry parameters of the baffles on the cell performance are revealed. The best case of the 49 studied cases is further optimized by introducing a linear scaling factor. Additional geometry modifications demonstrate that the gain in performance can be increased, but at a cost of higher pressure drop and increased design complexity. The conclusions of this work aids in the development of compact and high-performance proton exchange membrane fuel cell stacks.

Herein, we prepared a series of nanocomposite membranes based on chitosan (CS) and three compositionally and structurally different N-doped graphene derivatives. Two-dimensional (2D) and quasi 1D N-doped reduced graphene oxides (N-rGO) and nanoribbons (N-rGONRs), as well as 3D porous N-doped graphitic polyenaminone particles (N-pEAO), were synthesized and characterized fully to confirm their graphitic structure, morphology, and nitrogen (pyridinic, pyrrolic, and quaternary or graphitic) group contents. The largest (0.07%) loading of N-doped graphene derivatives impacted the morphology of the CS membrane significantly, reducing the crystallinity, tensile properties, and the KOH uptake, and increasing (by almost 10-fold) the ethanol permeability. Within direct alkaline ethanol test cells, it was found that CS/N rGONRs (0.07 %) membrane (Pmax. = 3.7 mWcm−2) outperformed the pristine CS membrane significantly (Pmax. = 2.2 mWcm−2), suggesting the potential of the newly proposed membranes for application in direct ethanol fuel cells.

A method for thermal ramp experiments on cylindrical 18650 Li-ion cells has been established. The method was applied on pristine cells as well as on devices aged by cyclisation or by storage at elevated temperature respectively. The tested cells comprise three types of LiNi0.8Co0.15Al0.05O2 cells for either high power or high energy applications. The heat flux to and from the cell was investigated. Degradation and exothermic breakdown released large amounts of heat and gas. The total gas and heat emission from cycled cells was significantly larger than emission from cells aged by storage. After aging, the low energy cell ICR18650HE4 did not transgress into thermal runaway. Gas composition changed mainly in the early stage of the experiment. The composition of the initial gas release changed from predominantly CO2 towards hydrocarbons. The thermal runaway emitted for all tests a comparable mixture of H2, CO and CO2.

Anion exchange membranes (AEMs) contribute significantly to enhance the performance and efficiency of alkaline polymer electrolyte fuel cells (APEFCs). A sequence of composite anion exchange membranes (AEMs) consisting of poly(vinyl alcohol) (PVA), poly(diallyldimethylammonium chloride) (PDDA), and nano-zirconia (NZ) has been prepared by a solution casting technique. The effect of zirconia mass ratio on attribute and performance of composite AEMs was investigated. The chemical structures, morphology, thermal, and mechanical properties of AEMs were characterized by FTIR, SEM, thermogravimetric analysis, and universal testing machine, respectively. The performance of composite AEMs was verified using water uptake, swelling degree, ion-exchange capacity, and OH− conductivity measurement. The nano-zirconia was homogeneously dispersed in the PVA/PDDA AEMs matrix. The mechanical properties of the composite AEMs were considerably enhanced with the addition of NZ. Through the introduction of 1.5 wt.% NZ, PVA/PDDA/NZ composite AEMs acquired the highest hydroxide conductivity of 31.57 mS·cm−1 at ambient condition. This study demonstrates that the PVA/PDDA/NZ AEMs are a potential candidate for APEFCs application.