bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bifunctional Electrocatalyst Materials for Improved Cell Reversal Tolerance in PEM Fuel Cell
Authors: Yoon Sooyoung , Oezaslan Mehtap , Hasché Frédéric 
Published: February 2024

For several decades, proton exchange membrane fuel cells (PEMFCs) have been a topic of zero-emission energy conversion technology research, spanning from material development to system control. Most of the PEMFC research is focused on the cost reduction of catalyst and membrane as well as the improvement of the long-term durability. Harsh and dynamic operating conditions such as rapid load changes, cold start temperatures, insufficient gas supply or flooding of the anode with water lead to a fatal damage of the very thin anode catalyst layer. [1-2] During the hydrogen starvation, the carbon corrosion occurs to supply further protons and electrons to the cathode, resulting in an increase of the anode potential. This event is well-known as cell reserval and results in a decrease of the overall PEMFC performance.
In this study, we evaluated a new catalyst concept by combining both functionalities (hydrogen oxidation reaction (HOR) and oxygen evolution reaction (OER)) in single nanoparticles. The potential of this bifunctional catalyst concept will be compared with the mostly used catalyst system prepared by a physical mixture of Pt/C and IrOx as co-catalyst. Controlling the chemical composition and structure of the bifunctional nanoparticle catalyst system allows to improve the cell reversal tolerance.

References

[1] Moore, C. E., Eastcott, J., Cimenti, M., Kremliakova, N., & Gyenge, E. L. (2019). Novel methodology for ex situ characterization of iridium oxide catalysts in voltage reversal tolerant proton exchange membrane fuel cell anodes. Journal of Power Sources, 417, 53-60. DOI: https://doi.org/10.1016/j.jpowsour.2019.02.006
[2] Marić, R., Gebauer, C., Nesselberger, M., Hasché, F., & Strasser, P. (2020). Towards a Harmonized Accelerated Stress Test Protocol for Fuel Starvation Induced Cell Reversal Events in PEM Fuel Cells: The Effect of Pulse Duration. Journal of The Electrochemical Society, 167(12), 124520. DOI: https://doi.org/10.1149/1945-7111/abad68
Towards Reliable Stability Measurements of OER Catalysts
Authors: Bornet Aline , Pitscheider Simon , Bertheussen Erlend , Pedersen Christoffer Mølleskov , Maletzko Annabelle , Seselj Nedjeljko , Wiberg Gustav Karl Henrik , Kallesøe Christian , Melke Julia , Cremers Carsten , Arenz Matthias 
Published: February 2024

Currently, significant efforts are taken to find the most active and stable electrochemical oxygen evolution reaction (OER) catalyst diverting from critical raw material. However, one also needs to consider new catalyst screening methods, especially with respect to stability investigations where rotating disk electrode (RDE) studies are not suitable.1 Recently, we introduced a gas diffusion electrode (GDE) setup as a new testing platform for OER catalysts.2 This methodology stems from fuel cell studies where carbon gas diffusion layer (GDL) is used as a transport layer to bring the reactant to the catalyst. Since carbon is not stable under the harsh OER conditions, water electrolyser uses titanium-based porous transport layers (PTLs). In the current work, we utilized the GDE setup to test the influence of the transport layer on the stability of a highly active Ir0.7Ru0.3Ox nanoparticle catalyst immobilized on homemade antimony-doped tin oxide (ATO) support. The test was conducted potentiostatically (@ 1.6 V vs RHE) for 2 h at 60 °C. The stability of the catalyst was then compared when deposited on GDL vs PTL. Rapid decline of the GDL-deposited catalyst activity was observed, while the PTL-deposited catalyst demonstrates a rather stable behavior (Fig. 1). We attribute this fast activity drop to the carbon oxidation of the GDL. Moreover, the activity at 30 °C of the PTL-deposited catalyst was compared to literature data on RDE setup [1]. In the RDE setup, a breakdown is observed after only 30 min when applying a constant current density. In contrast, PTL-deposited catalyst exhibits no activity loss during 2 h under similar conditions.
[1] H. A. El-Sayed. Journal of The Electrochemical Society, 166 (8), F458-F464 (2019)
[2] J. Schröder. JACS Au, 1, 247-251 (2021)

Figure
1
. Potentiostatic stability transients at 1.6 V vs RHE of Ir0.7Ru0.3Ox/ATO deposited on C-based GDL (green full) and on Ti-based PTL at 60 °C (black full) and 30 °C (blue dashed).

Figure 1
Effect of Superhydrophobic Catalyst Layers on PEMFC Durability
Authors: Folgado M. Antonia , Duque Luis , Diaz-Alvarez Ester , Chaparro Antonio M , Merino Susana , Plaza Daniel , de Diego Gonzalo , Hernández Rebeca , Serrano Marta 
Published: February 2024

High durability of proton exchange membrane fuel cells (PEMFCs) is one main objective of this technology nowadays. Among different ways, the use of a superhydrophobic catalyst layer in the cathode may help to increase the stability of the cell under operation. Superhydrophobic cathodic layers improve water management in the cell by enhancing the back-diffusion transport from cathode to anode. As a consequence, anode humidification is favored whereas flooding of the cathode is avoided, leading to higher cell response at intermediate and high current densities [1]. Superhydrophobic catalyst layers can be obtained by adding specific agents to the precursor ink that is later deposited together with the catalyst and the ionomer. Another possibility is the use of electrospray deposition, which does not require additives. Electrospray is a dry deposition method where the ink is deposited under an electric field, yielding particular ionomer distribution inside the pores of the layer as a consequence of electrostatic interactions.
Accelerated stress tests (AST) are well stablished protocols to analyze durability of PEMFCs in a systematic and reduced time frame [2]. Protocols for stressing different components of the cell have been proposed. In this work, different cell configurations have been mounted, using electrosprayed catalyst layers in cathode, anode, and both. The cells have been submitted to an AST that affects mainly the cathodic catalyst layer. The study is complemented with microscopy analysis (cross-sectional) and local mechanical properties (small-punch) (Fig. 1).
The results show the effect of superhydrophobic cathodic catalyst layers on the durability of a PEMFC.
Acknowledgements
Funding by PORHYDRO2 project (TED2021-131620B-C22, ‘Preparation and characterisation of catalyst layers fabricated by electrospray for proton exchange fuel cells with passive gas feed’) by the Spanish Ministry of Science and Innovation.
[1] M.A. Folgado, J.J. Conde, P. Ferreira-Aparicio, A.M. Chaparro, Single Cell Study of Water Transport in PEMFCs with Electrosprayed Catalyst Layers, Fuel Cells. 18 (2018) 602–612. https://doi.org/10.1002/fuce.201700217.
[2] S. Stariha, N. Macauley, B.T. Sneed, D. Langlois, K.L. More, R. Mukundan, R.L. Borup, Recent Advances in Catalyst Accelerated Stress Tests for Polymer Electrolyte Membrane Fuel Cells, J. Electrochem. Soc. 165 (2018) F492–F501. https://doi.org/10.1149/2.0881807jes.
[3] R. Hernández, S. Merino, D. Plaza, L. Duque, M.A. Folgado, A.M. Chaparro, M. Serrano, G. de Diego, Study of Mechanical Properties of Membrane-Electrode Assemblies for Proton Exchange Membrane Fuel Cells By the Small-Punch Technique, ECS Meet. Abstr. MA2022-02 (2022) 1426–1426. https://doi.org/10.1149/ma2022-02391426mtgabs.

Figure 1
Design and Operation of PEM-Electrolyzers Considering Cost and Efficiency
Authors: Scheepers Fabian , Staehler Markus , Burdzik Andrea , Müller Martin 
Published: February 2024

The design and operation of electrolyzers are always a trade-off between parameters that contrarily affect performance and operational goals. This talk will discuss some of those.
Compression of the product gases within an electrochemical process is often discussed as an alternative to subsequent mechanical compression. On the one hand, the electrochemical compression is advantageous in terms of energy efficiency; on the other hand, elevated gas pressure is responsible for increased gas loss due to permeation across the membrane. This can be prevented by using thicker membranes; in return, it impairs the proton transport in the electrolyzer and ultimately reduces its performance. It is therefore advisable to discuss an energetically sensible gas pressure level. As gas permeation is a crucial impact on this trade-off, it needs to be discussed how it is affected through operating conditions. Aside from the gas pressure difference between anode and cathode, the diffusion rate increases exponentially with temperature. However, lowering the stack temperature diminishes the electrochemical reaction kinetics as well as the ion conductivity of the ionomer. Hence, the influence of gas pressure, stack temperature and polarization curves on the plant efficiency are inextricably linked. Simulation results indicate that the energetically optimal design and operating conditions are functions of the applied cell voltage. As the design of the electrolysis plant is determined by its installation, only the operating conditions can be chosen flexibly. Economically, investment costs are best allocated to the cost of hydrogen when using high current density in order to have a high production capacity. On the contrary, a high current density also means a high cell voltage, which in turn results in a low plant efficiency and is responsible for high operating costs. Considering all these effects, the complexity of dependencies between parameters will be illustrated in this talk and how modeling can be used to access them. The results will outline challenges as well as directions how the technology can be further developed in future.

Figure 1
Development and Evaluation of Accelerated Durability Tests Under Realistic Operating Conditions for PEMFC Stacks – a Systematic Approach
Authors: Koprek Miriam , Schlumberger Robert , Wachtel Christian , Wilhelm Florian , Scholta Joachim , Hölzle Markus 
Published: February 2024

Over the last decade, significant progress has been achieved in the commercialization of Polymer Electrolyte Membrane (PEM) fuel cells for mobile applications. However, long-term durability and stability of such systems still needs further improvement. To overcome today’s time-consuming long-term durability tests, the development of so-called accelerated durability tests (ADT) is urgently necessary. In this work, we present our recent results on such ADT test-protocols based on research promoting a detailed understanding of the individual aging mechanisms in PEM fuel cells.
Various stressors had been investigated separately to understand their impact on overall fuel cell ageing. Certain levels of cell potential, temperature and humidity could be identified as major stressors and were successively added to the test protocol. In addition to the electrochemical test results, additional focus was put on different in-situ and ex-situ characterization methods. This combination enables a detailed understanding of individual stressors and their interply. The PEM-stack used in this study is an automotive high-performance stack developed within the publically funded Auto Stack Industry (ASI) project. An extensive long-term test over 5,500 operating hours was carried out as baseline test using the New European Driving Cycle, but with additional features to mimic realistic automotive load-profiles. Based on the results of this reference protocol, four different ADT protocols of only 1,200 hours test duration were derived. All tests were performed using short stacks with automotive-size active area. In-situ measurements include spatially resolved current measurement, cyclic voltammetry and impedance spectroscopy. After each test, selected cells were additionally analyzed ex-situ using layer thickness measurement via SEM, IR-thermography and contact angle measurements.
The results from ex-situ investigations underline the degradation models postulated from in-site measurements. The overall data show that detailed understanding of individual stressors is necessary to successfully develop reliable accelerated ageing tests for PEM fuel cells.
Investigation of the Effect of Graphite Bipolar Plate Flow Channel Inhomogeneities and Faults on HT-PEM Fuel Cell Stack Performance
Authors: Özel Tansu , Kraft Samuel , Cremers Carsten 
Published: February 2024

Bipolar plates are a key component of fuel cell stacks. Bipolar plates have multiple functions. They connect the single cells of the stack electrically and must be therefore electrically conductive. They separate oxidant and fuel gases and distribute them on each side over the membrane-electrode-assembly (MEA). Bipolar plates separate coolant liquid too. Fuel cell stack is cooled by coolant liquid which is flowing through the cooling flow channels in the middle of bipolar plates.
Especially the bipolar plates for HT-PEM must endure a low pH environment, continuous electrical potential, and higher temperatures up to 200°C. The focus here is on investigations of anode and cathode side flow channels of graphite bipolar plates. Inhomogeneities and faults of flow channels are examined and their effects on fuel cell stack performance are analyzed. The analyses are based on optical scan data of flow channel geometry and measurement data of a HT-PEM fuel cell full stack consisting of 120 cells operated on a testbed under different variations. Inlet pressure and stoichiometry of both anode and cathode were varied, anode was fed with pure hydrogen and with different reformate gas compositions consisting of hydrogen, nitrogen, carbon dioxide and carbon monoxide. For each variation point, polarization curves between 0 A/cm2 – 0,55 A/cm2 in step of 0,05 A/cm2 were recorded.
With an on testbed installed cell voltage monitoring (CVM) system voltages of every cell were measured and logged. Enormous amount of optical scan data consisting of width and depth information of flow channels was merged to certain statistical data for anode and cathode bipolar plates. Correlations between statistical data and cell voltages are still being investigated. It is planned to repeat the measurements with another 120 cells HT-PEM fuel cell full stack and compare the results.
Modeling Electrical Conductivity of Injection-Molded Polymer Composite Bipolar Plates
Authors: Myers Maxwell T , Trimpey Jonathan K , Beevers David B , Bakis Charles E , Hollinger Adam S 
Published: February 2024

Bipolar plates can be responsible for up to 40% of the total stack cost and 80% of the weight of a polymer electrolyte membrane fuel cell [1]. To reduce these cost and weight limitations, this work explores injection molding of polymer composites. Injection molding is well-suited for mass production and polymeric materials can significantly reduce the weight of traditional metallic bipolar plates. While polymers lack electrical conductivity, fillers can be added to fabricate conductive polymer composites. The main objective of this research is to model and injection mold polymer composites that will meet the United States Department of Energy technical target for bipolar plate electrical conductivity (> 100 S/cm).
A fiber contact model was developed to predict electrical conductivity based upon direction in the material, fiber alignment, fiber length and diameter, fiber concentration, and fiber conductivity [2]. Fiber alignment was measured experimentally by imaging cross sections of injection-molded nylon/carbon fiber composites. Imaging was performed on samples with different weight percentages of carbon fiber and from different mold designs to compare how fiber angles change based on mold geometry. To reduce the significant time required to measure fiber angles experimentally, computer recognition and processing of fiber alignment was developed. Nylon composites were injection molded with carbon fiber loadings ranging from 10 to 40 wt%. Modeling predictions show good correlation within 20% of experimental conductivity measurements. Samples with at least 20 wt% carbon fiber exceeded the US DOE technical target for bipolar plate conductivity, reaching 250 S/cm. In addition to modeling electrical conductivity, the Halpin-Tsai equations are used to model the elastic modulus and ultimate strain of the polymer composite. Tensile testing showed that the modulus of elasticity increases with carbon fiber loadings up to 30 wt%, reaching 7.3 GPa. At loadings above 30 wt%, the higher filler content can create voids which decrease the modulus of elasticity.

De Las Heras, A.; Vivas, F. J.; Segura, F.; Andujar, J. M., From the cell to the stack. A chronological walk through the techniques to manufacture the PEFCs core. Renewable & Sustainable Energy Reviews 2018, 96, 29-45.

Weber, M.; Kamal, M. R., Estimation of the volume resistivity of electrically conductive composites. Polymer Composites 1997, 18 (6), 711-725.

Figure 1
Water Dissociation Interfaces in Bipolar Membranes for H2 Electrolysers
Authors: Garcia-Osorio Dora Alicia , Jang Hansaem , Siritanaratkul Bhavin , Cowan Alexander 
Published: February 2024

In order to meet large scale energy demands in a more sustainable way, water electrolysers could be coupled with the well-developed photovoltaic solar cell technology to provide the energy input for green H2 production. Commercial PEM (proton exchange membranes) electrolysers operate in acidic pH which favours H2 production at the cost of using IrO2 as catalyst for oxygen production at the anode representing a significant drawback for this technology. Contrary, an AEM (anionic exchange membranes) operates in alkaline electrolytes which enables the use of low cost and highly active OER catalyst such as NiCoFeOx,1 however at the expense of including an extra overpotential to drive the H2 production in the electrolyser.2

Using bipolar membranes (BPM), where a cationic exchange membrane CEM is used alongside an anionic exchange membrane, allows the electrolyser to operate at different pHs: at the cathode in an acidic environment to favour H2 production, and alkaline for O2 production at the anode. However, a BPM induces a significant increase in resistance across the electrolyser.2 Recently, it has been demonstrated that by adding metal oxides as water dissociation catalysts, the electrolyser overpotential significantly decreased passing from 8 V to 2.2 V at 500 mA cm-2.3 This milestone in the field was accomplished by using two metal oxides with different point of zero charge (PZC) 3 and 11 for IrO2 and NiO respectively. Interestingly, a similar performance was observed when only TiO2 was used as water dissociation catalyst which PZC sits between IrO2 and NiO.4 Indeed demonstrating the necessity of better understanding of the physicochemical phenomena that governs water dissociation interfaces.
Using TiO2 as water dissociation catalyst provides a suitable platform to understand how properties such as conductivity or different doping content affect water dissociation during H2 production in the electrolyser. Therefore, in this work modifications of TiO2 were investigated and its impact on the cell voltage when used between Nafion 212 and Sustainion membranes as CEM and AEM respectively, in a commercial 5 cm2 electrolyser at 60 ⁰C that operates only with DI water. To only benchmark the performance of the BPM, Pt and IrO2 were chosen as H2 and O2 catalysts respectively.

References

[1] ACS Catal. 9 (2019) 7–15
[2] ACS Energy Lett. 7 (2022) 3447–3457
[3] Science 369, (2020) 1099–1103
[4] Nat. Commun. 13 (2022) 1–10
Advances in Reinforced Polymer Electrolyte Membrane Designs for Improved Direct Coated Electrodes
Authors: Kobaisy Amr , Kurokawa Akinari , Oshiro Kazushi , Tani Masaki , Maruyama Masashi , Miyake Rie , Namba Takafumi , Ueda Yurika 
Published: February 2024

In recent years, hydrogen fuel cells have become a key clean technology for the decarbonization of the transport sector. Significant investments are directed towards scaling the hydrogen infrastructure and the production of fuel cell vehicles to meet cost and climate targets set by governments across the globe. To achieve the required scale at cost, manufacturers of fuel cell components such as membrane electrode assembly (MEA) need to adopt high throughput processes while maintaining quality and performance of MEAs to meet heavy duty vehicle requirements.
Roll to roll direct coating (DC) process using slot die coating technique is proposed to deliver the lowest cost/highest throughput method for production of MEAs. Electrode ink containing catalyst, ionomer and solvents are applied directly on the membrane before drying to remove the solvents from the coating. The direct contact of solvents with PEM ionomer can create challenges resulting from ionomer swelling and shrinking to produce poor electrode quality and MEA performance.
This talk will discuss different design approaches to produce direct coated MEAs and present a novel approach in membrane design to address DC challenges to meet performance and quality targets that would enable the use of DC for scaling the fuel cell production.
Applying Gore’s knowledge in expanded poly-tetra-flour-ethylene (ePTFE) reinforcement properties and fuel cells research we developed a membrane that would reinforce the polymer electrolyte and electrode layers simultaneously while minimizing the impact of solvents used in DC processes. This results in improved MEA quality and performance compared to a traditional reinforced membrane design and enables the use of DC for high throughput/low-cost MEA manufacturing.

Figure 1
Cross-Aligned PTFE Nanofiber Reinforced Composite Membrane for PEM Fuel Cells
Authors: Yoon Ki Ro 
Published: February 2024

Polymer electrolyte membrane fuel cells (PEMFCs) have widely been considered environmental friendly alternative energy technologies due to their high energy conversion efficiency and zero emission. In the recent, the importance of performance and durability of electrolyte membrane, interfacial layer separating two electrodes, prohibiting fuel cross-over, while transporting only protons, has become much crucial for utilizing PEMFCs to the automobile applications such as fuel cell electric vehicles (FCEVs) and drones.
Unfortunately, the current state membranes, mainly composed of perfluorosulfonic acid (PFSA) ionomers, have suffered from the high cost and low proton conductivity, and low dimensional stability during dynamic humidity changes during fuel cell operation. In order to deal with these issues, recently, a reinforced composite membranes (RCMs) have been developed in which a PFSA ionomer is impregnated into a porous support matrix consisted with nanofibrous polymer materials such as polytetrafluoroethylene (PTFE) due to their thermal/mechanical robustness. The PTFE based RCMs could provide enhanced mechanical stability and electrochemical performance with a reduced use of PFSA ionomer, but low impregnation of ionomers into nanosized hydrophobic PTFE networks, resulting in phase separation and irreversible creep deformation.
Herein, we report a novel preparation of vertically alined PTFE aggregated fibers (PTFE AFs) as a reinforcement by using facile electrospinning hetero-polymer solutions containing PTFE nanoparticles and PEO (Polyethylene oxide) carrier polymer and subsequent thermal removal of PEO. Developed PTFE AF were effectively soaked by PFSA ionomers, and PTFE AF based RCMs delivered outstanding dimensional stability and proton conductivity compared to commercial RCMs. Furthermore, PTFE AF based RCMs used MEA exhibited exceptional single-cell performance and long-term stability. The enhanced performance was attributed to the facile proton conduction through the one dimensional channels between aligned fibers without fiber scattering, and effective suppression of volume expansion of hydrated PFSA ionomer by rectangular shaped PTFE fiber network. We believe the widespread use of novel PTFE fiber based membranes with an unique pattern in a variety of membrane applications where porous supports are used.

Figure 1