bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Optimization of Novel Anisotropic Proton-Exchange Membranes with Enhanced through-Plane Conductivity
Authors: Li Jian , Dekel Dario R , Freger Viatcheslav 
Published: February 2024

Maximizing through-plane (TP) conductivity, as opposed to in-plane (IP), is desired for proton exchange membranes (PEMs) in fuel cells, electrolysis and electrodialysis. Nafion, the benchmark PEM material, owes conductivity to randomly oriented ion-channels. Channel alignment in electrospun nanofibers was shown to enhance conductivity along the fibres by an order of magnitude, but it proved challenging to convert this to desired stable TP conductance. Another challenge is that orientation proves unstable and returns to random after nanofiber consolidation.
Previously, we reported fabrication of electrospun nanofiber-based membrane with a stable anisotropic TP alignment of proton conducting channels prepared by co-spinning, buckling and fusion of Nafion and PVDF nanofibers (Odess, Li et al, ACS Appl Mat Interfaces, 2021), as shown in Figure 1. PVDF nanofibers serve as a mechanical reinforcement as well as a stabilizing component to safeguard Nafion TP alignment during annealing and swelling, akin to a solid template. However, the prepared 50% Nafion membrane still showed a TP conductivity slightly inferior to Nafion.
In this report, we systematically optimized the Nafion content in the 50-80% range, as well as buckling and consolidation procedure and its temperature regime, to achieve a maximal and sustained conductance, exceeding that of pure Nafion. It was found that the TP proton conductivity of the membrane with 60% Nafion already exceeded that of Nafion 117 and further increased with Nafion content (Figure 1), with decrease in anisotropy (TP/IP conductance ratio). As another attractive feature, compared with Nafion 117, the TP conductivity of aligned membranes decreased less at lower humidity, i.e., was less sensitivity to dehydration, apparently due to better channel connectivity. Anisotropic structure and nanoscopic alignment were further confirmed by TEM and SAXS. The results demonstrate the potential of the new buckling approach for making novel nanofiber-based anisotropic membranes with significantly improved performance in electromembrane applications.

Figure 1
Determination of Membrane Degradation in Polymer Electrolyte Fuel Cells with in-Situ and Ex-Situ Measurements
Authors: Heidinger Mathias , Sandu Daniel , Hacker Viktor , Bodner Merit 
Published: February 2024

Fuel cells convert chemical energy directly into electrical energy with high efficiency and without pollutants. The decomposition products in the clean exhaust gas caused by the chemical degradation of the membrane of polymer electrolyte fuel cells (PEFCs) can be used to monitor the service life of the cell. For perfluorinated sulfonic acid (PFSA)-based membranes, chemical degradation is investigated via ex situ monitoring of the effluent water. The decomposition of the PFSA backbone, which is part of the polymer electrolyte membrane (PEM), can be detected by the degradation products such as fluoride or fluorinated compounds [1]. There are multiple methods for measuring fluoride in water. We have developed a new method for the simple and precise measurement of fluoride based on the optical change caused by the quenching of a zirconium complex. This method requires only 900 µL of the sample and 100 µL of the complex [2].
We have extended the two fluoride measurement methods, namely fluoride sensitive electrode (FSE) and photometry (PM), to include ion chromatography (IC). This serves as an additional point of comparison with high accuracy and expands the measuring scope to include other ions like sulfate and their potential influence on photometric measurements.
The electrochemical characterization of the materials has been improved by adapted electrochemical impedance spectroscopy (EIS) equivalent circuits, which include a more detailed analysis of the contribution of degradation processes. Linear sweep voltammetry (LSV) was used to measure the gas crossover through the membrane. Cyclic voltammetry provides information about the change in electrochemical surface area. Electrochemical characterizations and fluoride measurements are supplemented by ex situ imaging methods to determine membrane thinning.
[1] M. A. Yandrasits, A. Komlev, K. Kalstabakken, M. J. Kurkowski, and M. J. Lindell, “Liquid Chromatography/Mass Spectrometry Analysis of Effluent Water from PFSA Membrane Fuel Cells Operated at OCV,” J. Electrochem. Soc., vol. 168, no. 2, p. 024517, Feb. 2021, doi: 10.1149/1945-7111/abe56a.
[2] M. Heidinger, E. Kuhnert, K. Mayer, D. Sandu, V. Hacker, and M. Bodner, “Photometric Method to Determine Membrane Degradation in Polymer Electrolyte Fuel Cells,” Energies 2023, Vol. 16, Page 1957, vol. 16, no. 4, p. 1957, Feb. 2023, doi: 10.3390/EN16041957.
Mechanism of Ionomer Degradation as a Consequence of Defective Anode PEMFC
Authors: Bas Corine , Dubelley Florence , Crouillere Marie , Dubau Laetitia , Chatenet Marian , Salah Touhami , Lottin Olivier , El Kaddouri Assma , Dillet Jérôme , Mainka Julia , Nayoze-Coynel Christine , Rosini Sébastien , Bultel Yann 
Published: February 2024

Defects in the various components of the membrane-electrode assembly (MEA), initially present or created during aging, are known to be responsible for the short lifetime PEMFC. Catalytic layer degradation has been identified as one of them [1]. However, the possible propagation of these defects to other components within a cell or a stack is not clear in the literature. To shed light on these phenomena, customized MEAs with a localized lack of anode active layer at two different locations -near the hydrogen inlet or outlet- were manufactured and tested with specific accelerated aging tests, combining high and low current and humidity cycles; these were specifically tailored to observe a possible propagation of the defects [2]. Local performance monitoring using a segmented cell revealed variations within the catalytic layers upstream and downstream of the defect. In order to better understand the impact of anode active layer defects on MEA components, localized physicochemical analyses were performed post mortem along the gas flow, with the main objective to identify possible degradations of the reinforced perfluorosulfonic acid (PFSA) membranes. Microscopic thickness measurements showed significant membrane thinning in the defective segments. Difference of these localized degradations between the monopolar plates rib and channel zones will be highlighted depending on the defect location i.e. at the inlet and outlet of hydrogen flow (Figure below). In the defective area, decrease of the Ion Exchange Capacity estimated by Raman analyses is pointed out for the reinforced PFSA layer. The PFSA chain degradation mechanism will be discussed, and, thus, the degradation rate will be calculated based on Raman and FTIR microscope and 19F NMR. For longer ageing time, the ionomer degradation is extended to an non-defective area. A propagation mechanism of the degradation will be proposed.
[1] L, Dubau, et al. WIREs Energy and Environ.
2014, 3, pp. 540-560.
[2] S, Touhami, et al. J. Power Sources.
2021, 481, pp. 228908-228917.

Figure 1
Heat-Treatment of a Fourteen Membered Macrocyclic Fe Complex for Electrocatalytic Oxygen Reduction
Authors: Nabae Yuta , Notsu Hideo , Nagata Shinsuke , Miyoshi Mami , Hayakawa Teruaki , Goto Ryota , Ichihara Takeo , Moriya Makoto , Honda Sotaro , Feng Zhiqing , Yoshida Hiroshi , Machida Masato , Ohyama Junya 
Published: February 2024

For the broad application of polymer electrolyte fuel cells (PEFCs), the development of non-precious-metal (NPM) catalysts for oxygen reduction is extremely important. To date, many NPM catalyst have been synthesized by pyrolyzing Fe-, N-, and C-containing precursors, but they suffer from the low density and uncertain chemical structure of their active sites. On the contrary, our research group has been studying a fourteen-membered macrocyclic Fe complex, which was inspired by the FeNx sites embed in graphene sheets (Fig. 1).
In this study, a fourteen-membered macrocyclic Fe complex was loaded on a carbon support and then heat-treated, and found to be quite active as a non-precious metal oxygen reduction catalyst. The oxygen reduction current at 0.8 V (RHE) was 13.3 A gcat
-1. The improvement is attributed to a high turnover frequency rather than the number of active sites. X-ray absorption spectroscopy and temperature programmed decomposition for the Fe complex suggested that the counter anions and the protons on the nitrogen atom in the ligand were eliminated by the heat-treatment. This change probably influenced the adsorption energy of the oxygen species during the oxygen reduction and resulted in the improved catalytic activity (Fig. 2). Simulation based-on the density functional theory well support this hypothesis.

Figure 1
Non-PGM Cathode Electrocatalysts for PEM Fuel Cells
Authors: Charalampopoulos Georgios , Maniatis Ilias , Daletou Maria 
Published: February 2024

Polymer electrolyte membrane fuel cells, PEMFCs, are considered the most ideal next generation energy conversion device, able to provide power to a broad range of applications; automotive, combined heat and power, portable electronic devices. Pt-based electrocatalysts are regarded as ideal for promoting the desired redox reactions of a fuel cell, especially the sluggish oxygen reduction at the cathode, ORR. High expense and scarcity of Pt are the greatest impediments to successful commercialization of this technology. The replacement of unsustainable noble-metal catalysts with platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) is essential for material wise and market value viable PEMFCs.
Among the different attempts towards non-PGM catalysts, incorporating atomically dispersed transition metal atoms (Fe, Mn, etc.) and heteroatoms (N, S, etc.) into carbon frameworks is the most promising [1,2]. Large specific surface area, high intrinsic ORR electrocatalytic activity, efficient porosity and sufficient stability in acid media and/or in the actual working environment are the least requirements to consider when designing the catalysts. So far, despite the tremendous efforts, many drawbacks still persist that include poor understanding of the nature of active centres and their control over the synthesis, as well as fast decay of the structure under operation.
In this work, we will present a rationally designed strategy to prepare hybrid composite catalysts by developing Fe–N–C materials onto different 2D and 3D templates [3,4] with differentiated surface chemistry (silicon and heteroatom-doped carbon structures). Despite structural and physicochemical characterization, the study includes extensive electrochemical characterization in terms of activity and durability in relative to the application conditions. An example is depicted in Figure 1 for a single atom Fe-N-C catalyst synthesized using porous silica nanotubes as the sacrificial template resulting in a hierarchically porous structure with a surface area of 370 m2/g. Electrochemical study revealed a half-wave potential of 0.72 V and an onset potential of 0.88 V with high stability in acidic environment.
Very importantly, the different findings are correlated to one another, thereby establishing a composition to function relationship to provide a pathway for the integrated engineering of novel structures with improved performance.

Acknowledgments

Funding from the Operational Program “Competitiveness, Entrepreneurship & Innovation” (EPAnEK), NSRF 2014-2020 through the project Solar2HyP Τ2ΕΔΚ-01877

References

[1] L. Osmieri, et al., Current Opinion in Electrochemistry 25 (2020) 100627.
[2] T. Asset, et al., Joule 4 (2019) 33-44.
[3] Jin-Cheng Li et al., Asia Materials 10 (2018) e461
[4] Nan Zhang et al., Energy Environ. Sci. 13 (2020) 111-118

Figure 1
(Invited) 25 Years of the Thin-Film Rotating Disk Electrode Technique
Authors: Schmidt Thomas J. , Gasteiger Hubert Andreas 
Published: February 2024

Twenty-five years ago, in summer 1998, the first paper introducing the thin-film rotating disk electrode (TFRDE) method was published in the Journal of the Electrochemical Society [1]. At this time, we demonstrated that by preparing a thin layer of a supported Pt/Vulcan catalyst mixed with a small amount of Nafion could reliably be coated on top of a glassy carbon disk, electrochemical reactions like the hydrogen oxidation reaction could be measured on an RDE taking advantage of the well-known mass-transport conditions of an RDE. By keeping the layer thickness in the range of 1 micrometer, additional mass-transport resistances induced by the catalyst layer/Nafion film became negligible. That is, all equations valid on an RDE could be applied without modification. Further work on the oxygen reduction reaction by using the TF Rotating Ring-Disk electrode allowed detecting peroxide formation on a supported catalyst [2]. Both publications grounded the path for catalyst development in fuel cell. The method has been used since then as a standard method for catalyst screening and characterization in both academia and industries. In addition, many researchers improved the TFRDE method within their research. The application span of the TFRDE developed from fuel cell research, oxidation of small organic molecules, to work on Li-O2 batteries, water electrolysis, and CO2 reduction.
This presentation will offer a journey over the last 25 years and the application of the TFRDE technique in catalyst development and characterization.
[1] T.J. Schmidt, H.A. Gasteiger, G.D. Stäb, P. Urban, D.M. Kolb, R.J. Behm

Characterization of High-Surface-Area Electrocatalysts Using a Rotating Disk Electrode Configuration

J. Electrochem. Soc.
145 (1998) 2354-2358

[2] U.A. Paulus, T.J. Schmidt, H.A. Gasteiger, R.J. Behm

Oxygen Reduction on a High-Surface Area Pt/Vulcan Carbon Catalyst: A Thin-Film Rotating Ring-Disk Study

J. Electroanal. Chem. 495 (2001) 134-145

[3] T.J. Schmidt, H.A. Gasteiger

Rotating Thin-Film Method for Supported Catalysts, in Handbook of Fuel Cells: Fundamentals, Technology and Applications, Vol. 2 Part 3, W. Vielstich, H.A. Gasteiger, A. Lamm (Eds.), John Wiley & Sons, New York, 316-333 (2003)
Effect of Dissolved Gases on Pt Nanoparticle Catalysts Investigated By in Situ SAXS, XAS Measurements
Authors: Watanabe Takeshi , Kawamoto Teppei , Nishiyama Hiromichi , Hiraoka Yuji , Wakisaka Mitsuru , Hirosawa Ichiro , Inukai Junji 
Published: February 2024

Understanding of the structural and the chemical properties of Pt catalysts in polymer electrolyte fuel cells (PEFCs) is necessary to improve the activity for the durability of the catalysts. The small-angle X-ray scattering (SAXS) and the X-ray absorption spectroscopy (XAS) measurements are widely used to investigate these properties. We developed a system that combines in situ A-SAXS/XAS measurements in the same field of observation using a channel flow electrode (CFE) cell and characterized the chemical states, average diameter and size distributions of Pt catalysts under controlled electrochemical conditions. In this study, we investigated an effect of dissolved gases on Pt nanoparticle catalysts using the system.
All experiments were carried out at SPring-8 BL19B2. A commercial Pt/carbon black catalyst (TEC10E50E, Tanaka Kikinzoku Kogyo) was used as test electrode in this experiment. Prior to SAXS and XAS measurements, the electrochemical potential was cycled between 0.6 and 1.0 V vs. the RHE in O2 or N2-saturated 0.1 M HClO4. For the XAS measurements, the Pt LⅢ edge was used. The ionization chamber and a seven-elements silicon drift detector were used to obtain the XAS spectra. For the SAXS measurements, the X-ray energy was set to 11.5 keV and 11.55 keV, which are below and near to the Pt LIII absorption edge, respectively. The scattered X-ray was detected using an area detector (PILATUS 2M). Figure 1 show the X-ray absorption near edge structure (XANES) spectra of the Pt catalyst after the potential cycles in O2-saturated 0.1 M HClO4. The white-line peak intensity increased and became higher at a higher potential cycle. This indicates the partial electron-transfer from Pt atoms or initial stage of Pt oxidation. We also will discuss the effect of dissolved gases for morphological and chemical states from SAXS and XAS data.

Figure 1
(Invited) Modeling of Catalyst Degradation in Toyota's Mirai and Its Application to Target-Setting for Future PEFC's Durability
Authors: Fukaya Norihiro , Sekine Shinobu , Katayama Shota , Amemiya Kazuki , Watanabe Takao 
Published: February 2024

To popularize Polymer electrolyte fuel cells (PEFCs) as a power source for various types of mobility, improving their durability is necessary. One of the factors that determines the durability of PEFCs is the electrochemical surface area (ECSA) loss of the cathode catalyst which causes a drop in PEFC’s output power and generation efficiency. The loss of ECSA has been modeled by a mechanism based on Ostwald ripping, and the model has been validated by accelerated stress testing (AST) [1]. Using AST, it is possible to evaluate the durability of PEFCs with short time, but in actual applications, such as mobility, the inputs for PEFCs are complex rather than simple repetitive inputs, and the relationship with AST is not clear.
In this study, we proposed a method for setting AST conditions that correspond to the stresses of actual applications. In order to correlate the AST with the real driving test, a simple model based on Ostwald ripping was developed, and the model was validated by experimental results for both actual vehicle tests and ASTs. Validation for the actual vehicle was performed between simulated values from Mirai's real driving data and post-driving measurements. Since the model represents well both the experimental results of both the AST and the actual vehicle, it is considered that the model can convert the stress intensity between the actual vehicle test and the AST.
Using this model and PEFC vehicle model [2], we set a target durability required for future heavy-duty trucks, and the AST conditions to evaluate it. In the presentation, we will discuss the details of the proposed target-setting procedure and models.
[1] R. Darling et al., J. Electrochem. Soc., 2003, 150, A1523
[2] T. Watanabe, et.al, 242nd ECS Meeting, MA2022-02, 1468 (2022)
The Durability of the Platinum/Polypyrrole Nanotubes' Catalysts in Oxygen Reduction Reaction
Authors: Lobko Yevheniia , Yakovlev Yurii , Darabut Alina Madalina , Kalinovych Viacheslav , Kopecký Dušan , Tsud Nataliia , Novakova Jaroslava , Matolínová Iva 
Published: February 2024

Platinum (Pt) catalysts supported on carbon-based materials are effective catalysts for fuel cells. However, the durability of the carbon supports in acidic media needs to be improved. Platinum/polypyrrole (PPy) nanotubes have emerged as promising catalysts for the oxygen reduction reaction (ORR) due to their high surface area and good electrocatalytic activity. Furthermore, the nitrogen atoms within the chemical structure of PPy nanotubes are expected to improve their durability.
In this study, we investigated the performance and durability of Pt catalysts during ORR by decorating different carbon-based materials with Pt nanoparticles. The catalytic activity and durability were analyzed using the rotation ring-disk electrode (RRDE) technique. We also examined the influence of the different supports on the electrochemical degradation of the catalysts.
Our results showed that Pt/PPy nanotubes exhibited high activity and durability in ORR reactions. We paid particular attention to the chemical changes of the catalysts' surfaces, including both the metal and support components, during the ex-situ electrochemical measurements. The surface of the catalysts was characterized using photoelectron X-ray spectroscopy (XPS), synchrotron radiation photoelectron spectroscopy (SRPES), and near-edge X-ray absorption fine structure (NEXAFS) analysis before and after electrochemical degradation. Based on our findings, we proposed degradation mechanisms of the Pt/PPy nanotubes catalysts.
In addition, we tested the Pt/PPy nanotubes catalysts in fuel cells and observed their high performance. These findings suggest that Pt/PPy nanotubes catalysts can serve as durable and effective catalysts for ORR reactions, even under harsh conditions. Further research is needed to optimize the synthesis conditions and operating parameters of these catalysts to improve their performance and durability.
Numerical Two-Phase Simulations of Alkaline Water Electrolyzers
Authors: Hess Steffen , Zhang Shidong , Kadyk Thomas , Lehnert Werner , Eikerling Michael , Beale Steven B. 
Published: February 2024

Alkaline water electrolyzers (AWE) have several advantages over other types of electrolyzers, including their high efficiency and especially their relatively low cost due to the usage of non-precious metal catalysts, such as nickel and iron, for the electrodes. Information about local quantities and physical phenomena such as the formation of gas bubbles, current densities, temperatures or local species concentrations within a running cell are important for their improvement. Multiphysical computational fluid dynamics (CFD) simulations of electrochemical components using detailed three-dimensional models can provide valuable insight on local behaviors and characteristics that are difficult or impossible to measure experimentally.
This work extends the CFD library openFuelCell2
1, which has been implemented using the open-source platform OpenFOAM®, to simulate AWE cells. The model considers the major transport phenomena, including two-phase fluid flow, heat and mass transfer, electrochemical reactions, species transfer and charge transfer in the various functional regions of the cell. It employs an Eulerian-Eulerian approach to characterize the behavior of each phase comprising interphase mass transport, momentum exchange and heat transfer. Appropriate mapping functions are used to couple the physically distinct regions together. A Butler-Volmer equation characterizes the electrochemical reactions that are assumed to occur in electrodes of finite thickness.
This model is used to simulate a single zero-gap AWE cell, depicted in Fig. 1, for different operating conditions such as varying temperatures and volumetric flow rates. The conducted studies provide insight into the local formation of the created gas phase (bubbles), the distribution of species within the gas and electrolyte and their impact towards the performance of the running cell. These numerically obtained results are compared to in-house available and gathered experimental data. Figure 1 demonstrates that the polarization curves obtained at various temperatures are in good agreement with the experimental data.

Figure 1