bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydroxide Conducting Naphthalene-Containing Polymers and Membranes Via Polyhydroxyalkylations
Authors: Luong Triet Nguyen Dai , Chen Si , Jannasch Patric
Published: February 2024

Anion exchange membranes (AEMs) are critical components of alkaline membrane water electrolyzers and fuel cells that are under development today [1,2]. Consequently, there is a strong demand for highly conductive and alkali-stable AEMs. In this context, polyhydroxyalkylation has emerged as one of the most efficient synthetic pathways to chemically resistant polymer backbones for AEMs. In these Friedel-Crafts type polycondensations, an electron-rich aromatic compound reacts with an activated ketone or aldehyde to produce an aryl-ether-free polymer. The desired quaternary ammonium cations are then usually introduced through a Menshutkin reaction [3,4].

In the current work, we have employed naphthalene-based compounds as monomers in polyhydroxyalkylations to prepare a series of high-molecular weight poly(naphthalene alkylene)s with various naphthalene contents. These polymers were then quaternized and cast into AEMs. Here, we will discuss the influence of the naphthalene monomer type and content on AEM properties such as solubility, water uptake, ion conductivity, ionic clustering, thermal and alkaline stability, and also the prospects of using these AEMs in electrochemical systems.

References:

[1] Chen, N., Wang, H.H., Kim, S.P. et al. Poly(fluorenyl aryl piperidinium) membranes and ionomers for anion exchange membrane fuel cells. Nat. Commun.
12, 2367 (2021).

[2] Li, D., Park, E.J., Zhu, W. et al. Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers. Nat. Energy
5, 378–385 (2020).

[3] Olsson, J.S., Pham, T.H., Jannasch, P., Poly(arylene piperidinium) hydroxide ion exchange membranes: synthesis, alkaline stability, and conductivity. Adv. Funct. Mater.
28, 1702758 (2017).

[4] Pan, D., Bakvand, P.M., Pham, T.H., Jannasch, P. Improving poly(arylene piperidinium) anion exchange membranes by monomer design. J. Mater. Chem. A
10, 16478–16489 (2022).
Influence of Monomer Configuration on the Performance of Poly(quaterphenyl piperidinium) Anion Exchange Membranes
Authors: Bakvand Pegah Mansouri , Pan Dong , Allushi Andrit , Jannasch Patric
Published: February 2024

Polymeric anion exchange membranes (AEM)s are crucial components in many electrochemical energy devices where the performance is strongly influenced by the ionic conductivity, mechanical robustness, and thermochemical stability of the materials.1,2 AEMs are susceptible to degradation due to the chemically aggressive nature of the hydroxide ion, which significantly restricts their long-term applicability, especially at elevated temperature.3,4 Improving the polymer backbone design by, e.g., eliminating ether linkages from the polymer backbone is an approach to improve alkaline stability.5 Moreover, by introducing multi-ring aromatic segments, the rigidity, hydrophobicity, and “blockiness” of the polymer backbone increase, leading to mechanical robustness and enhanced microphase separation (ionic clustering) of the AEM.6 Obviously, the configuration of the multi-ring aromatic segments will have an influence, which can be used to tune and improve the properties of the polymers and AEMs.7,8

In the present project, we investigated the influence of the configuration of quaterphenyl monomers in poly(quaterphenyl piperidinium)s on the corresponding AEM properties. Three different monomers (isomers) with different connectivity between the four rings were investigated: para-para, para-meta, and meta-meta. The polymers were prepared by superacid-mediated Friedel-Crafts type polycondensations (polyhydroxyalkylations) involving N-methyl piperidone and the respective quaterphenyl. Subsequently, the polymers were fully quaternized with methyl iodide to prepare a series of ether-free poly(quaterphenyl piperidinium)s with different backbone configurations and chain flexibility. In this presentation, the influence of the quaterphenyl configuration on AEM properties such as water uptake, hydroxide conductivity, ionic clustering, thermal and chemical stability will be discussed.

Li, C.; Baek, J. B., Nano Energy
2021,
87, 106162.

Aili, D.; Rykær Kraglund, M.; Rajappan S.C.; Serhiichuk, D.; Xia Y.; Deimede V.; Kallitsis, J.; Bae, C.; Jannasch, P.; Henkensmeier, D.; Jensen, J.O., ACS Energy Lett.
2023, 8, 1900–1910.

Mohanty, A. D.; Bae, C., Mater. Chem. A
2014,
2(41), 17314-17320.

Jeon, J. Y.: Park, S.; Han, J.; Maurya, S.; Mohanty, A. D.; Tian, D.; Saikia, N.; Hickner, M. A.; Ryu, C. Y.; Tuckerman, M. E.; Paddison, S. J.; Kim, Y. S.; Bae, C., Macromolecules
2019,
52(5), 2139–2147.

Olsson, J. S.; Pham, T. H.; Jannasch, P., Funct. Mater.
2018, 28(2), 1702758.

Liu, M.; Hu, X.; Hu, B.; Liu, L.; Li, N., Membr. Sci.
2022, 642, 119966.

Pham, T. H.; Olsson, J. S.; Jannasch, P., Mater. Chem. A
2019, 7(26), 15895-15906.

Lee, W-H;Park, E. J.; Junyoung, H.; Shin, D. W.; Kim, Y. S.; Bae, C., ACS Macro Lett.
2017, 6(5), 566–570.
Poly(arylene alkylene piperidinium)s for Anion Exchange Membrane Water Electrolyzers
Authors: Pan Dong , Hegelheimer Manuel , Bakvand Pegah Mansouri , Thiele Simon , Jannasch Patric
Published: February 2024

Anion exchange membrane (AEM) water electrolyzers have the potential to obviate the need for precious metal catalysts, and are therefore attracting an increasing attention.1 The high performance and durability of the device largely depend on the properties of the AEM with regards to hydroxide conductivity and resistance.2
,3 The development of viable AEM candidates is continuously advancing. Recently, we reported on a series of poly(arylene alkylene piperidinium)s (PAAs) prepared from a ketone monomer specifically designed for high alkaline stability.4 The PAA AEMs reached high hydroxide conductivities, comparable with the state-of-the-art poly(arylene piperidinium)-based AEMs derived from piperidione, but showed significantly higher chemical stability under harsh alkaline conditions.5

In the present study, we have further developed PAA AEMs by copolymerizations to tune the ion exchange capacity (IEC). An AEM (PpTDMP-2.0) with an IEC of 2.0 mequiv.g−1 reached a high OH− conductivity of 129 mS cm−1 at 80 °C and a controlled water uptake of 80%. This AEM was selected for evaluated in an alkaline water electrolyzer fed with 1 M KOH at 70 °C. Using a novel noble-metal free NiFe layered double hydroxide (LDH) catalyst in the anode, initial results showed a high current density of 4.5 A cm−2 at 2.2 V. The corresponding performance of the state-of the-art Aemion+® membrane was measured for benchmarking, and the PAP AEM demonstrated a lower degradation rate from the beginning of the experiment. In the current presentation, we will further discuss the performance, system stability, and the prospects of PAA AEMs for use in electrolyzers and other electrochemical energy applications.

C. Santoro, A. Lavacchi, P. Mustarelli, V. Di Noto, L. Elbaz, et al., ChemSusChem, 2022, 15, e202200027.

D. Aili, M. R. Kraglund, S. C. Rajappan, D. Serhiichuk, Y. Xia, V. Deimede, J. Kallitsis, C. Bae, P. Jannasch, D. Henkensmeier, J. O. Jensen, ACS Energy Lett., 2023,
8, 1900–1910.

E. J. Park, C. G. Arges, H. Xu and Y. S. Kim, ACS Energy Lett., 2022, 7, 3447-3457.

D. Pan, P. M. Bakvand, T. H. Pham and P. Jannasch, J. Mater.
Chem. A, 2022, 10, 16478-16489.

J. S. Olsson, T. H. Pham and P. Jannasch, Adv. Funct. Mater., 2018, 28, 1702758.

Figure 1. (a) Synthetic route and chemical structure of PpTDMP-2.0, (b) polarization curves of PpTDMP-2.0 and Aemion+ (left) after a constant current hold of 1 A cm-2 for 15 h (right). 5 cm² active area, 70 °C, 1 M KOH. Anode: 2.0 mgNiFe-LDH cm-2, Cathode 0.5 mgPt cm-2.

Figure 1
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
(Invited) Membrane Degradation in Polymer Electrolyte Membrane Fuel Cells for Heavy Duty Applications
Authors: Mukundan Rangachary , Arthurs Claire , Kusoglu Ahmet , Komini Babu Siddharth , Wang Xiaojing , Agarwal Tanya , Borup Rod L.
Published: February 2024

Polymer electrolyte membrane fuel cells (PEMFCs) are being considered for heavy duty applications, and the DOE has established various performance and durability targets to enable their adoption.1. The key differences between light and heavy-duty application of fuel cells is their increased durability and operating efficiency requirements for heavy duty applications when compared to the lower cost requirement for light duty applications. While higher catalyst loadings can be utilized to increase the fuel cell performance and catalyst lifetime, membrane durability could be a significant outstanding challenge. Membranes are expected to last 25,000 hours to 30,000 hours for heavy duty applications and the Million Mile Fuel Cell Truck Consortium (M2FCT) is evaluating various membrane technologies for use in heavy duty drive cycles. Current state of the art membranes with both mechanical and chemical stabilization have already met light-duty durability requirement of 5000+ hours and have the potential to meet 25,000+ hour lifetimes. This talk will describe the various membrane related accelerated stress tests (ASTs) developed by the consortium and will present membrane durability results obtained from long-term (500 hours) fuel cell operation at elevated temperature (90 oC). Both the mechanical and chemical durability of membranes will be discussed with particular emphasis and fluoride emission rates (FERs) and lifetime predictions.

Acknowledgement:

This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos.

References:

1.https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf
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
Polyphenols as an Alternative to Lanthanide Alloys for PFSA Oxidative Stability
Authors: Agarwal Tanya , Komini Babu Siddharth , Prasad Ajay Krishna , Advani Suresh , Borup Rod L.
Published: February 2024

The chemical durability of perfluorosulfonic acid (PFSA) membranes is becoming an increasingly investigated subject to meet the Department of Energy (DOE) durability targets for Heavy Duty Applications (HDVs). State-of-the-art membranes like NafionTM, rely on the use of cerium, heteropolyacids, and other inorganic additives for increasing PFSA chemical durability. A less explored avenue for the oxidative stabilization of PFSA and hydrocarbon membranes is the use of organic antioxidants. No reversible organic antioxidant has so far been demonstrated which can enhance membrane lifetime by factors similar or higher to cerium. Herein, we demonstrate ellagic acid as a promising radical scavenger for PFSAs. We found that the incorporation of EA enhanced the chemical durability of Nafion by 160%. EA when incorporated with cerium as an electron donor could surpass Nafion durability enhancement by 80% compared to a membrane incorporated with just cerium in DOE-defined durability tests. EA was found reversible in acidic conditions like that of fuel cells and its reversibility could be further enhanced by the use of suitable co-antioxidants. We discuss the present challenges with the system and highlight future areas of research.

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
Investigation of Catalyst Degradation in Proton Exchange Membrane Fuel Cell By Identical Location Electron Microscopy
Authors: Strandberg Linnéa , Shokhen Victor , Skoglundh Magnus , Wickman Björn
Published: February 2024

Proton exchange membrane fuel cells (PEMFCs) suffers from issues of degradation, partly due to the harsh conditions associated with an acidic environment, varying potentials and temperature cycling. To better understand and mitigate these issues, it is necessary to study the degradation of PEMFCs under realistic conditions. In this study, identical location (IL) electron microscopy was implemented in a single cell 5 cm2 PEMFC to examine the degradation of the cathodic catalyst layer at the nanoscopic scale during an accelerated stress test used to mimic start-up/shutdown conditions. IL scanning electron microscopy revealed the formation of cracks in the catalyst layer resulting in isolated islands of the catalytic layer with lifted edges and an increase in resistance due to loss of physical contact. Additionally, IL transmission electron microscopy analysis revealed that degradation of the carbon support forced Pt particles closer together, promoting Pt particle growth together with a significant decrease of electrochemical surface area. The carbon support was also observed to collapse at weak points, creating a less porous structure. These results shed light on the degradation mechanisms of the cathodic catalyst layer during start-up/shutdown events and can help with understanding the significant decrease of electrochemical performance during these conditions.

Figure 1
Performance of a Small PEMFC Stack Operated with CO/H2 Mixtures
Authors: Yazici Mehmet S , Yıldırım Ceyhun , Kilic Murat , Turk Betul Erdor , Boyaci San Fatma Gul , Okumus Emin
Published: February 2024

Hydrogen produced by reforming processes may include sulfur (S),carbon monoxide (CO) and other impurities.. Presence of ppm level impurities in hydrogen may adsorp onto Pt catalyst and lower performance and lifetime. There are efforts to overcome cost and performance issues by reducing Pt amount and utilizing new catalyst and support materials, more tolerant to CO. Ru catalyst are often added to oxidize CO before poisoning Pt. Ti0.7Mo0.3O2 was investigated as an alternative support material for anode catalyst. It has been shown that the stoichiometric ratio between Ti and Mo have significant impact on the CO tolerance. Ti0.8Mo0.2O2 was synthesized and used as anode electrode in PEM fuel cell testing. In this paper, titanium/molybdenum alloy on carbon (Ti0.8Mo0.2O2-C) is evaluated as catalyst support to prevent performance decay by CO poisoning. 3-cell stack was developed and tested for performance and degradation issues. Cell hardware with 15 cm2 active area was used for fuel cell measurements. Cathode was loaded with 0.6 mgPt/cm2 (20 wt.% Pt/C) and anode with 0.5 mgPt/cm2 (40 wt.% Pt/Ti0.8Mo0.2O2-C) onto Sigracet 29BC GDL by painting. Bipolar plates for single cell and stack were designed using Solid Works. End plates, anode bipolar plate and cathode bipolar plate with cooling channels on the other surfaces were designed and produced from graphite composite in-house. Seals from silicon was also designed and produced in-house. MEA had active area of 15 cm2. Figure 1 shows stack formation with all components put together in order. Stack was conditioned under 100% humidified hydrogen. There was no effect of stack orientation on performance. Performance for 2-cell stack was better going from atmospheric pressure to 2 bar. When polarization was 0.6V, pressurized operation provided improvement in current density going from 1300 mA/cm2 (no pressure) to 2000 mA/cm2 (15 psig). When this 2-cell stack was subjected to different concentrations of CO, polarization values of Figure 2 was obtained. Increasing concentration of CO caused decrease in current densities. Utilizing a DC/DC converter, stack has provided power to charge a cell phone. More details will be shared for 2, 3 cell stack operation under CO conditions.

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)
(Invited) Facile and Scalable Production of an Intermetallic Nanocatalyst for High-Power Proton-Exchange-Membrane Fuel Cell
Authors: Sung Yung-Eun , Lee Jongmin
Published: February 2024

With universal attention to sustainable development, the eco-friendly generation of energy has been emerging as one of the most important tasks. Proton-exchange-membrane fuel cells (PEMFC) are one of the key solutions to this urgent problem due to their clean energy generation. However, a complicated reaction environment has been limiting its power performance for industrial applications, such as 1) catalytic activity, 2) oxygen mass transfer, and 3) proton conduction at the cathode catalyst layer. To handle all these critical factors, a holistic design and elaborate synthesis of catalyst are imperative without compromising the scalability of synthesis. Here, we present a straightforward but exquisite synthetic approach that addresses the aforementioned practical issues and demonstrate an excellent PEMFC power performance. The crystalline ionic compound ([Co(bpy)3]2+[PtCl6]2-, bpy = 2,2′-bipyridine) enabled a carbon shell-protected growth of intermetallic nanoparticles with N-doping on the entire mesoporous carbon support via a simple thermal annealing process. The overall structure of the catalyst simultaneously tackled the critical issues in PEMFC, including ORR kinetics (by strained Pt-skin surface on intermetallic Pt-Co core), oxygen mass transfer (by high ECSA and mesoporous N-doped carbon support), and proton conduction (by stabilized Co species in intermetallic core and Pt-skin) with desirable durability. This study highlights the importance of meeting all the critical parameters to achieve much higher fuel cell power performance through the development of a facile and scalable production method of catalyst.
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
A Three-Dimensional, Multiphysics Model of An Alkaline Electrolyzer
Authors: Martinho Diogo Loureiro , Berning Torsten , Abdollahzadehsangroudi Mohammadmahdi , Rasmussen Anders Rønne , Hærvig Jakob , Araya Samuel Simon
Published: February 2024

During the previous years, increasing awareness of the detrimental effects of greenhouse gas emissions along with the need to supply an increasing world population with electricity has given rise to investments in the field of green energy technology. In particular, research and development has focused on the production of “green hydrogen” which can be used as a source for a sustainable energy system. Green hydrogen can be made from water electrolysis provided the electricity stems from a renewable energy source. Among the different types of water electrolysers, the alkaline electrolyzer cell (AEC) is the most mature technology. Among its advantages compared to other technologies are the low capital expenditure and the simplicity of the system with proven components. However, the detailed heat and mass transfer mechanisms that occur in an AEC are far from completely understood. It is expected that further improvements of the technology and reduction in cost can be attained through a fundamental understanding of above-mentioned phenomena.

In order to better understand the phenomena and the physics of such system, a numerical model is developed in this project. Using ANSYS Fluent 2021 R1, an isothermal, single phase, three-dimensional model is developed to replicate the phenomena in a small single cell. Equations such as Butler-Volmer and Nernst Equation are considered to describe the electrochemical part of the system. A simplified Nernst-Planck equation is also modelled to account with the diffusion and migration of charged species (in this case, the ion OH-). The flow is considered laminar, and the species conservation equation are written to solve the molar concentration of each species. The porosity of the electrodes is changed along the simulations to study its influence on the performance of the electrolyzer. Also, the initial concentration of the species is changed in order to evaluate its effect on the output of the system.

First results suggest that the polarization curve acquired shows a strong consistency with prior experimental findings and outcomes from other simulation models.

Figure 1
Bridging Li-Ion Batteries and Fuel Cells: From Cathode Leaching Residue to Atomic-Scale Catalytic System
Authors: Liu Mengjie , Lee Lawrence Yoon Suk
Published: February 2024

The direct manufacturing and cross-domain reuse of advanced functional materials locates on a higher position in the spent lithium-ion batteries (LIBs) waste management hierarchy, compared with the traditional metallurgies of spent LIBs involving the complex chemical extraction and purification. Energy conversion devices such as fuel cell (FC), share similar features with LIBs in terms of the electrode materials design principle, indicating an inherently close link between energy conversion and storage applications. Given that sustainability is the third dimension of the electrode in addition to structure and property, fabricating FC electrodes via simple modifications of spent LIBs materials would represent a paradigm-shifting concept of upcycling and break the boundary of different technologies. We report herein a case study of upcycling a typical LIBs cathode, LiFePO4 particles embedded in N-doped carbon spheres (LFP/C), to a highly efficient single atomic (SA) electrocatalyst for oxygen reduction reaction (ORR). The top-down partial leaching method was used to convert LFP/C into metal leachates and residual carbon-based precipitates, the latter appeared as Fe SA-embedded hollow carbon spheres, with the minority of FeOx nanoclusters and FePO4 nanoparticles. The FeOx/FePO4 species display low direct contribution towards catalytic activity, but adjust the charge distribution of neighboring SA, thereby optimizing the intermediate adsorption energy at the rate-determining step occurring on SA sites, boosting the alkaline ORR activity as manifested by the high E
onset of 0.97 V. Furthermore, the membrane electrode fabricated with the upcycled materials demonstrates great potentials in a practical energy conversion device, direct ammonia fuel cell. The etching strategy breaks a long-standing stereotype by innovatively constructing atomic catalytic sites via a top-down etching approach. More importantly, this work demonstrates the potential value of spent LIB electrodes in the half-cell reaction of FC, and builds a bridge between energy storage and conversion systems through the facile upcycling method.

Figure 1
Non-Precious Hydrogen Oxidation Catalysts for Anion Exchange Membrane Fuel Cells
Authors: Amigues Simon , Bibent Nicolas , Gervex Arsène , Khan Anastassiya , Zitolo Andrea , Gasmi Amir , Chattot Raphael , Dubau Laetitia , Maillard Frederic , Jaouen Frederic
Published: February 2024

Green hydrogen as an energy carrier has the potential to dramatically reduce our greenhouse gas emissions and meet the net-zero emissions targets set by the Paris Agreement countries by 2050. This hydrogen can be produced by electrolysis using water and renewable electricity, and be converted into electricity on demand in a fuel cell. Proton exchange membrane fuel cells (PEMFC) are already commercialized, but due to their acidic environment, these devices require precious metal catalysts, in particular platinum, which is an obstacle to their large-scale deployment. In contrast, anion exchange membrane fuel cells (AEMFCs) operate at high pH, facilitating the use of cost-effective and sustainable precious metal free catalysts.

To catalyze the hydrogen oxidation reaction (HOR) in alkaline media, nickel has shown interesting performances to replace precious metal catalysts at the anode of AEMFCs [1]. In order to improve the intrinsic activity of nickel-based materials and reach the performance of precious metals catalysts, two approaches are studied in the literature: optimization of intrinsic properties by alloying Ni with other earth abundant elements, or core@shell nanostructuration of Ni by a protective carbon shell. We are focused on this second approach through the mechanochemical synthesis of a nickel-based Metal-Organic Framework (MOF) from a Ni2+ salt and BTC (1,3,5-benzenetricarboxylic acid), followed by pyrolysis under different atmospheres (Figure 1.a). As already shown in the literature [2], there is a significant effect of the pyrolysis atmospheres (NH3, H2, N2, in various ratios) on the electrochemical performance of the catalysts (Figure 1.b). In this study, we employed ex situ and operando studies approaches to investigate the influence of these different atmospheres on the nanoparticles structuration and to relate them to the electrochemical performances obtained.

Our Ni-based anode materials were characterized by X-ray diffraction, electron microscopy, nitrogen adsorption, and electrochemical techniques, including AEMFC tests. Furthermore, the transformation of the MOF into an active catalyst was followed with in-situ X-ray absorption spectroscopy.

[1] Zhao, J. Chen, W. Sun, H. Pan, «Non-Platinum Group Metal Electrocatalysts toward Efficient Hydrogen Oxidation Reaction», Adv. Funct. Mater., vol. 31, no 20, 2021, p. 2010633.

[2] Ni et al., « An efficient nickel hydrogen oxidation catalyst for hydroxide exchange membrane fuel cells », Nat. Mater., vol. 21, no 7, 2022, p. 804.

Figure 1