bluuebunny/crossref_metadata_2025 huggingface dataset:
Activity and Stability of Iridium-Based Alloy Catalysts for PEM Electrolyzer
Authors: Mariappan Sakthivel , Drillet Jean-Francois
Published: December 2024

For large-scale production of green hydrogen via renewable energies, large capacities of highly performing, cost-effective water electrolyzers are needed. Polymer electrolyte electrolysis (PEMEL) operates at high current and pressure and is very compact compared to alkaline technology. However, it relies on very expensive noble catalysts such as Pt and Ir for H2 and O2 electrode, respectively. Meanwhile, unsupported Iridium black is considered as state-of-the-art in terms of corrosion stability and activity, whereas a lot of efforts aim at reducing loading by alloying or/and developing supported materials [1,2].

In this work, Ir black and bi-metal Ir-M (M = Pt, Pd, Cr, Co) black catalysts were synthesized by co-reduction of iridium chloride and M-ion containing precursor in 0.1 M sodium borohydride at 180°C for 3 h under hydrothermal condition. The nominal mass ratio of Ir:M was fixed to 3:1. The structural characterization of the as-prepared catalysts was performed by means of XRD, TEM, Raman, and BET. Electrochemical activity of Ir-M black catalyst for OER was studied in deaerated 0.5 M H2SO4 electrolyte at room temperature by using a rotating disk electrode (RDE) cell. The total catalyst loading was about 200 μgIr cm-2. Additional cyclic voltammetry measurements over the potential range of -0.1–1.4 V vs. RHE at 40 mV s-1 were performed to identify redox behavior of the catalysts (fig. 1a). The accelerated degradation tests (ADT) were performed between 1.1 and 1.6 V at dE/dt=0.5 V s-1 with RDE at 1600 rpm for 1000 cycles. A commercial Ir-black catalyst purchased from Alfa Aesar was used as reference. Based on half-wave potential value at 30 mA cm-2 (fig. 1b), the following trend in lower overpotential for OER was obtained: Ir-Cr > Ir-Pt > Ir-Pd >> Ir-Co > Ir-black.

PEMEL full cell experiments were performed in single cell with 5 cm² geometrical area in a balticFuelCells fixture at 60°C. The catalyst coated membrane (CCM) consists of 2 mgIr cm-2 anode and 1 mgIr cm-2 cathode coated on Nafion 117. Titanium felt and carbon paper were used as porous transport layers in the anode and cathode side, respectively. Accelerated stress tests (AST) were performed by using rectangular polarization signal to reflect dynamic electrolyzer operation. Thereby, the current density was varied between 0.05 and 3 A cm-2 in 10 s for at least 1000 h. After test, the cell components were post analyzed by SEM/EDX, XRD and XPS technique and anolyte/catholyte were analyzed by ICP-OES in order to evaluate the dissolved species. The electrochemical degradation performance of bi-metal alloy anode catalysts in PEMEL test will be presented as well.

References

[1] H. P. Tran, H. N. Nong, H.-S. Oh, M. Klingenhof, M. Kroschel, B. Paul, J. Hübner, D. Teschner, and P. Strasser, Chem. Mater. 2022, 34, 9350

[2] A. Hartig-Weiss, M. Miller, H. Beyer, A. Schmitt, A. Siebel, A. T. S. Freiberg, H. A. Gasteiger, and H. A. El-Sayed, ACS Appl. Nano Mater. 2020, 3, 2185

Figure 1
Ionomer Impact on Oxygen Evolution Reaction Activity and Kinetics for Ir-Based Catalysts
Authors: Li Zhao , Wang Xiaoping , Kariuki Nancy N. , Park Jaehyung , Myers Deborah J.
Published: December 2024

Renewable hydrogen generation using the low-temperature proton-exchange membrane water electrolyzer (PEMWE) represents a crucial technology for achieving global zero-carbon emissions. Iridium oxide (IrOx) stands out as a primary platinum group metal catalyst for the anode in electrochemical water splitting due to a balance in activity and stability in acidic environments.1 However, the anode catalyst performance is still predominately hampered by the sluggish kinetics of the oxygen evolution reaction (OER) compared to the hydrogen evolution reaction (HER) at the Pt cathode.2 Therefore,understanding the factors influencing the OER kinetics of Ir-based catalysts is essential for developing strategies to achieve high OER activity in the PEMWE anode electrocatalysts. This presentation will delve into our investigation of how the perfluorosulfonic acid (PFSA) binder affects the anode catalyst OER behaviors, specifically the corresponding kinetics and activity of two commercial Ir-based OER catalysts, IrOx from Alfa Aesar and TiO2-decorated IrOx (IrTiOx) from Umicore, as a function of the PFSA ionomer-to-catalyst (I/C) ratio. We combined the cavity microelectrode (CME) technique, which offers a direct approach to study OER kinetics without the ionomer,3 with the rotating disc electrode (RDE) technique, which allows to assess the impact of PFSA on OER kinetics and activity at varied I/C ratios in an acidic electrolyte. The study provided valuable insights into ionomer dependent OER mechanisms, elucidating the intricate interactions among the ionomer, catalyst, and reaction intermediates.

Acknowledgements

This research is supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office under the auspices of the H2NEW Consortium. Argonne National Laboratory is managed by the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.

Reference

S. M. Alia, M.-A. Ha, G. C. Anderson, C. Ngo, S. Pylypenko and R. E. Larsen, Journal of The Electrochemical Society, 2019, 166, F1243.

E. Oakton, D. Lebedev, M. Povia, D. F. Abbott, E. Fabbri, A. Fedorov, M. Nachtegaal, C. Copéret and T. J. Schmidt, Acs Catalysis, 2017, 7, 2346-2352.

J. Behnken, M. Yu, X. Deng, H. Tüysüz, C. Harms, A. Dyck and G. Wittstock, ChemElectroChem, 2019, 6, 3460-3467.
Highly Gas Permeable Partially Fluorinated Aromatic Ionomers Containing Cyclohexyl Groups for Fuel Cell Cathode Binders
Authors: Zou Yiyang , Miyatake Kenji
Published: December 2024

Novel aromatic polymer-based ionomers (SBAFC6) with high gas permeability and high proton conductivity were designed as electrode binders in proton exchange membrane fuel cells. The target terpolymers containing sulfophenyelene (SP), hexafluorobiphenyelne (BAF) or perfluorohexylene (PAF), and cyclohexyl (C6) groups were synthesized by Ni-promoted polycondensation reaction of the corresponding chlorinated monomers, in which composition of the C6 component was controlled from 17 to 50 mol%. The terpolymers obtained as high molecular weight (M
n = 19.2 - 95.0 kDa and M
w = 64.8 – 159.0 kDa) were evaluated as thin membranes by solution casting. SBAFC6 membranes exhibited similar proton conductivity and higher gas permeability compared to those of the sulfonated copolymer (SBAF) without C6 groups and commercial proton conductive perfluorinated ionomer (Nafion) membranes. The highest gas permeability was achieved with SBAFC650 (50 mol% C6 group); hydrogen and oxygen permeability at 80 ºC was 8.58 × 10-9 cm3 cm cm-2 sec-1 cmHg-1 and 4.49 × 10-9 cm3 cm cm-2 sec-1 cmHg-1, respectively. A fuel cell was fabricated using SBAFC650 as the cathode binder with Pt/C catalyst. Unfortunately, the cathode showed larger activation overpotential compared to the Nafion-basedn cathode but smaller oxygen diffusion overpotential. The SBAFC650 binder cell showed 1.5 A cm-2 of the current density at 0.32 V of the cell voltage while that of the Nafion cell was lower than 0.3 V. The results suggest that the highly gas-permeable SBAFC650 ionomer as the cathode was suitable for high current density operation.

Figure 1
Mechanical Durability of Water Electrolysis Membranes in a Liquid Environment Under Differential Pressure Mode
Authors: Ueda Eijun , Okada Hideyuki , Kato Ryogo
Published: December 2024

A perfluorinated sulfonic acid polymer (PFSA) membrane is extensively used in proton exchange membrane（PEM）water electrolyzers for the production of green hydrogen. It is crucial to ensure the membrane’s chemical stability and mechanical durability for long-term performance. PEM is typically assembled with a porous transport layer (PTL), which supports the membrane electrode assembly (MEA), collects current, facilitates water diffusion to catalysts, and must withstand high compressive deformation in a harsh liquid environment over extended periods.

It is known that high pressure applied to polymer materials commonly leads to compressive creep. It has been reported that due to such compressive creep deformation, the catalyst layer applied on the PFSA membrane undergoes significant deformation, resulting in the formation of cracks that degrade the performance1-2). Therefore, it is necessary to investigate the creep response of PFSA membranes on PTLs with various diameters and roughness under different pressure modes in order to understand their mechanical durability for long-term performance.

In this study, a thermal mechanical analyzer (TMA) was utilized in a hydrated environment with water at 80℃ and 6.2 MPa for over 100 hours. Initially, the PEM was placed on the PTL at 23℃ and immersed in the water chamber. The sample was then heated from 23℃ to 80℃, and once the experimental temperature stabilized at 80℃, a load corresponding to 6.2 MPa was continuously applied to the membrane during measurement. As a result, the membrane thickness rapidly decreased from its initial thickness due to the high pressure, and the membrane deformation gradually slowed down. After over 100 hours of measurement, observations using an optical microscope showed that the membrane in contact with the PTL gradually flowed and penetrated into the pore of the PTL. The relationship between the creep behavior and the penetration of the membrane into the PTL pore, considering various PTLs and membranes, will be presented during the poster session.

Reference

T, Schuler. et al., J.
Electrochem. Soc.
166 (10) F555-F565 (2019)

J, Liu. et al., ACS Cent. Sci.
DOI: 10.1021/acscentsci.4c00037
Development of High Proton Conductive Membrane Using the Nano Cellulose Fibers for Polymer Electrolyte Fuel Cells
Authors: Katoh Takashi , Matsuo Yoshimasa , Masuhara Akito
Published: December 2024

Recently, woody biomass has been used in multiple ways as a carbon-neutral and renewable resource. Among them, cellulose nanofibers (CNFs) are attracting attention as a new nanomaterial derived from cellulose, which is one of the major components of trees. We established a unique CNF production method by introducing phosphate groups to the hydroxyl groups in the wood pulp. The obtained phosphorylated CNFs were completely nanofibrillated (approximately 3 nm in width) with high yield, and their aqueous dispersion was highly transparent, viscous, and stable at pH 3−11. An aqueous dispersion of phosphorylated CNFs can be dehydrated and dried to form transparent CNFs sheet with densely-packed CNFs. This sheet has high transparency, strength, and thermal dimensional stability, and at the same time, it has paper-like flexibility. To promote the practical use of this technology, we have currently been operating a demonstration plant for the production of CNFs aqueous dispersion and CNFs sheet.

By using CNF, which have excellent water retention and film-forming properties, we developed a nanocellulose PEM that is weakly acidic, has low environmental impact, and has high proton conductivity. The PEM using cellulose nanofibers showed a high proton conductivity of >7×10-2Scm-1 under 95% RH at 80 ℃. By combining a PVPA filler in a CNF suspension, it has become possible to easily create a self-supporting membrane using CNF as a binder. This composite membrane showed an especially high proton conductivity of 9×10-2 Scm-1 under 95% RH at 80 ℃. These results suggest that CNF presents a high potential substitute for perfluorosulfonic acid polymers and serves as a pivotal component of environmentally sustainable PEMs.
Effect of Post-Heat Treatment of Catalysts Under Various Gas Conditions on the Microstructure of Catalysts Ink and Electrode for PEMFC
Authors: KIM Sungmin , Kang Yun Sik , Lim Iksung , Lee Eunjik , Woo Seunghee , Park Seok-Hee , Park Gu-Gon , Yim Sung-Dae
Published: December 2024

Polymer electrolyte membrane fuel cells (PEMFCs) directly convert the chemical energy of fuel into electrical energy, producing electricity through a high-efficiency, ecofriendly energy conversion device. While PEMFCs are commercialized now, enhancing their competitiveness compared to other energy sources is critical and requires an understanding of the microstructure of the membrane-electrode assembly. Typically, fuel cell electrodes are manufactured by coating an electrolyte membrane with catalyst inks composed of electrode catalyst, ionomer, and solvent or additives. To maximize the performance of fuel cells, the proper distribution of catalysts and ionomers within the electrode is essential, and the microstructure within the electrode is determined by the interactions between the carbon support and platinum surface, as well as the dispersion of catalysts and ionomers in the solvent. Thus, the internal microstructure of the catalyst ink, determined by the interactions among its constituents, ultimately defines the final electrode microstructure, affecting the performance and durability of the fuel cell.

This study aims to analyze the effects of post-heat treatment of catalyst in various gas atmospheres, including NH3 gas, on the surface characteristics and to examine the changes in interactions between the catalysts and ionomers within the catalyst ink following surface modification. Additionally, this research seeks to elucidate the correlation between the properties of the catalyst ink and the characteristics of the electrode produced by drying the ink. To this end, the physical properties of the thermally modified catalysts were analyzed, and the resulting catalyst ink was also manufactured and examined. The physical and rheological properties of the catalyst ink were assessed using a dispersing analyzer and rheometer to understand the interactions between the catalysts and ionomers. Furthermore, the coatability of the catalyst ink and the structural characteristics of the electrode were investigated.

Figure 1
Engineering Anode Catalyst Supports for Enhancing Anode Reversal Tolerance in Proton Exchange Membrane Fuel Cells
Authors: Li Zheng , Zhao Tianshou , Zeng Lin
Published: December 2024

The "hydrogen society" concept has emerged as a response to the increasing demand for carbon-free energy and the aim of achieving "carbon neutrality". Proton exchange membrane fuel cells (PEMFCs) are considered the most promising hydrogen energy utilization units for commercialization, despite facing challenges related to durability and cost. One of the key obstacles is anode reversal, which inevitably occurs during the operation of PEMFC and significantly reduces performance, eventually leading to failure. Therefore, it is essential to investigate the mechanisms that affect anti-reversal performance and find effective strategies to improve reversal tolerance without compromising performance.

Two approaches have been put forward. First, we aim to enhance the reversal tolerance of proton exchange membrane fuel cells (PEMFCs) by using polyaniline (PANI) coated carbon as a catalyst support. The PANI coating acts as a protective layer that isolates the carbon from the corrosive environment, resulting in improved anti-reversal performance. Moreover, the PANI coating helps to distribute the catalyst nanoparticles and ionomer uniformly, leading to enhanced polarization. We have tested various carbon supports to confirm the applicability of this coating strategy and optimized the thickness of the PANI coating to avoid any adverse effects on performance. Additionally, we have developed a high-specific-surface-area conductive oxide Ti4O7 as an anode catalyst support to overcome the negative effects of carbon corrosion. By shortening the electron transfer pathway and increasing metal coverage, we have achieved comparable polarization performance to conventional carbon-supported counterparts. Our Ir@IrOx/Pt/Ti4O7-fabricated RTA has demonstrated approximately ten times longer reversal time (6 hours) and two orders of magnitude lower degradation rate than the conventional carbon-supported counterpart. These systematic studies aim to promote the development of highly durable and reversal-tolerant anodes, providing a promising outlook for practical, high-performance, low-degradation, and cost-effective RTA fabrication.
Stem-Inspired Self-Contained Support for High-Power Proton-Exchange Membrane Fuel Cells
Authors: Zhang Ao , Wang Ran , Bazaid Mohammed , Tsai Yu-Han Joseph , Hsiao Ting-Jung , Goddard William A , Jang Seung Soon , Huang Yu
Published: December 2024

Proton-exchange membrane fuel cells (PEMFCs), which utilize hydrogen and air to produce emission-free power, offer a promising avenue toward a cleaner energy future. However, for PEMFCs to become a practical and widely adopted solution, it's imperative to reduce the usage of platinum (Pt) while simultaneously enhancing cell performance significantly. The conventional cathode catalyst layer (CCL) within the membrane electrode assembly (MEA) of PEMFCs consists of the ionomer and carbon-supported Pt-based catalyst. While the ionomer provides the crucial, and currently the only means that facilitates micron-level proton conductivity which is necessary for the oxygen reduction reaction (ORR) throughout the cathode catalyst layer, it also introduces extra local (non-Fickian) resistance to oxygen transport when it covers the Pt surface. This resistance accounts for more than 40% of the total mass transport resistance of oxygen and protons in the cathode, hindering high performance. Furthermore, this local oxygen transport resistance escalates inversely with the decrease in Pt loading within the cathode, exacerbating the barrier of mass transport at ultralow Pt loadings and significantly limiting MEA power output. Additionally, the sulfonic acid group in the ionomer's side chain tends to strongly adsorb onto the Pt surface, thereby poisoning Pt activity and compromising MEA performance. Addressing these challenges is crucial to PEMFCs for widespread adoption as a clean energy solution.

Here, we developed a novel self-contained support structure (SCSS) that can synchronously conduct both electrons and protons for the ORR without ionomers. Thus, we effectively eliminate the detrimental effects of ionomer poisoning and oxygen transport resistance caused by ionomer presence in the CCL. We observed an impressive two-times higher specific activity of the PtNi in SCSS compared with the PtNi in CCL with the ionomer. Remarkably, the non-Fickian oxygen transport resistance measured from MEA fabricated with SCSS is only 5% of the conventional MEA, leading to a notable 36% increase in the peak power and demonstrating the promising future of the SCSS design, especially for MEAs with ultralow Pt loading.
X-Ray Scattering Characterization of Pt and PtCo Catalyst Inks and Electrodes for PEFC Cathodes
Authors: Park Jaehyung , Kariuki Nancy N. , Myers Deborah J. , Van Cleve Tim , Neyerlin Kenneth C.
Published: December 2024

The composition and processing of the catalyst-ionomer ink used to fabricate electrochemical energy conversion device electrodes can impact the final electrode microstructure and performance. Parameters influencing the microstructure and performance are, for example, solvent ratio, ink processing method and time, ionomer chemistry, and carbon morphology/porosity. Polymer electrolyte fuel cell (PEFC) cathodes are typically prepared by first dispersing a catalyst powder, comprised of platinum or platinum alloy nanoparticles supported on carbon blacks, with ionomer in solvents, followed by extensive mixing using a variety of methods. The electrode properties are controlled by the interactions of the ionomer with the catalyst particles and the support in the catalyst-ionomer ink, by the effect of ink solvent composition on those interactions, and by the ink mixing and coating procedures. This presentation will describe the in-situ/ex-situ ultra-small angle X-ray scattering (USAXS) combined with SAXS studies of the evolution of the cathode catalyst layer to determine the effect of ink processing variables and ink composition on the ink properties, especially on the carbon agglomerate break-up for efficient coating of catalyst layers while optimizing fuel cell performance and durability. The effect of ink formulation is examined for Pt-supported Vulcan carbon (Pt/Vu) and Pt and PtCo-supported on high surface area carbon (Pt and PtCo/HSC) with different ionomers. The results provide the fundamental understanding enabling improved membrane-electrode assembly (MEA) performance and durability. Moreover, the results of the evolution of the catalyst layer during the ink drying process as a function of solvent removal rate and solvent identity will be discussed.

Acknowledgments

This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office under the M2FCT Consortium. This work was authored in Argonne National Laboratory, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357. This research used the resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
(Invited) Durability Analysis of Meas with Reversal Tolerant Anodes Under Repeated Cell Reversal Conditions
Authors: Ahn Chi-Yeong , Kim Yunho , Park Jung-Hyung , Kim Young-Shik , Shim Hyungwon
Published: December 2024

As regulations on greenhouse gas emissions are being strengthened, polymer electrolyte fuel cells (PEFCs) are being applied as a power source in a variety of applications. Mobility such as cars, ships, trains, airplanes, etc. have dynamic operating conditions. Because these operating conditions affect the durability of fuel cells, many studies have been reported analyzing durability of the membrane electrode assemblies (MEAs) by applying repeated operating conditions. 'Cell Reversal’, where the fuel cell voltage drops below 0V, is one of these operating conditions. This phenomenon is observed when electric energy is continuously consumed under hydrogen starvation conditions at the anode or when the required electric energy suddenly increases.

In this talk, first, we attempted to find the optimal additive ratio by controlling the additive content of the electrode. Second, the durability of MEAs with three different types of electrocatalysts and additives was analyzed. Lastly, we will discuss strategies to further improve the durability of MEAs with additives in the anode.

Acknowledgements

This research was supported by a grant from Endowment project of “Development of Basic Technologies in Eco-friendly Ship Fuel Reliability and Safety Evaluation” funded by Korea Research Institute of Ships and Ocean Engineering (PES5100), and this research was also supported by a grant from “Development on operation and reliability verification technology of 1MW class eco-friendly ship fuel and power system under ocean environment (RS-2021-KS211507/PMS5950) funded by the Ministry of Oceans and Fisheries of Korea
Nanoscale in-Situ Effects of Humidity on Proton Exchange Membrane Fuel Cell Catalyst Layers Using Scanning Transmission X-Ray Microscopy
Authors: Parmar Harsharaj Birendrasingh , Seip Tess , Wang Jian , Hitchcock Adam , Bazylak Aimy
Published: December 2024

Polymer electrolyte membrane (PEM) fuel cells produce clean energy using hydrogen and oxygen with water and heat as the only byproducts. However, their widespread adoption is still hindered by high cost and low efficiency. PEM fuel cells have a proton exchange membrane (ionomer) supported by platinum (Pt) catalyst layers to facilitate the hydrogen oxidation (anode) and the oxygen reduction (cathode) reactions. While sufficient membrane hydration is necessary to maintain proton conductivity, excess water in the catalyst layer can severely inhibit electrochemical reactions, limiting efficient fuel cell operation.

To design high performance catalyst layer nanostructures, the formation of liquid water and the ionomer swelling with humidity in PEM fuel cell catalyst layers need to be investigated. In-situ hard X-ray techniques have been used to study the incipience of water; however, the high energy hard X-rays prevent spectroscopy of the low-Z membrane elements like carbon, fluorine, oxygen, and sulfur. Soft X-ray scanning transmission X-ray microscopy (STXM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy can uniquely perform high resolution (30 nm) imaging of the chemical constituents of catalyst layers with minimal radiation damage. In this work, we report a novel in-situ characterization of ionomer swelling with humidity in fuel cell catalyst layers using STXM and NEXAFS spectroscopy to reveal the nanoscale reactant and proton transport pathways in PEM fuel cell catalyst layers. Pristine catalyst coated membrane samples were cut using an ultramicrotome to obtain 300 nm thick sections and mounted in a custom cell to observe the in-situ effects of humidity. The thickness of liquid water in the membrane and catalyst layer as a function of relative humidity was obtained by performing in-situ imaging at the oxygen K-edge. We observed that at 55% relative humidity (RH), a through-plane water accumulation of 10-20 nm on the silica nanoparticles maintained the membrane proton conductivity and at 90% relative humidity, the hydration of the sulfonic acid sidechains of Nafion promoted nanoscale proton transport in the catalyst layers. Moreover, in-situ characterization of ionomer swelling with humidity was performed for the first time using NEXAFS at the fluorine K-edge. The ionomer volume fraction increased from 28% to 36% from dry (~6% RH) to humidified conditions (~90% RH) and resulted in higher nanoscale oxygen and water diffusion resistance. From these analyses, the effects of hydration on nanoscale mass transport and proton conductivity were quantified to inform the design of next-generation proton exchange membrane fuel cells.

Figure 1
Establishing Foundational Structure-Performance Correlations for 3D Graphene Foams in PEMFCs
Authors: Brown Alexander , Garsany Yannick , Stroman Richard
Published: December 2024

An essential part of conventional proton exchange membrane fuel cells (PEMFCs) is the flow-field plate (FFP) which serves the dual purposes of collecting current and distributing reactants across the catalyst layers. A conventional PEMFC stack contains multiple FFPs which are the primary source of fuel cell weight, volume, and cost; so innovative approaches that replace the FFPs with new materials may make PEMFCs more appealing by improving those characteristics. Foundational knowledge on the performance of nickel foam, graphene-coated nickel foam, and freestanding graphene foam as gas diffusion media and reactant flow fields is established. The traditional carbon fiber diffusion media and FFPs were replaced with foams 0.3 - 1.6 mm thick and then compressed to 10 - 90% of their original thickness to alter the transport characteristics of the foams. The foams at various extents of compression were then assembled in a standard 5 cm2 single-cell test fixture with a (0.2 mgPt cm-2 TKK, TEC 10E50E with Nafion 1100 EW ionomer) catalyst coated membrane. Hydrogen and air reactants were supplied at 65°C and a range of relative humidity (100, 50, 25 RH), and the corresponding cyclic voltammograms, electrical impedance, and I-V polarization were recorded. Cell performances are correlated to the permeability, porosity, and electrical resistivity of the foams. Results are used to assess the utility of such foams for the low-cost fabrication of fuel cell components and stacks.
(Digital Presentation) The Influence of Pore Geometry on Water Transport in the Gas Diffusion Layer of PEM Fuel Cells
Authors: Herescu Alexandru
Published: December 2024

The water transport behavior in the Gas Diffusion Layer (GDL) depends on the pore characteristics, which include the pore size distribution, the wetting properties of the fibers, and the shape of the pore. In this study we investigate the impact of pore geometry on the breakthrough pressure of the GDL. The study shows the importance of the inclusion of different types of pore shapes in the analysis of the water transport behavior. The water invasion process through a pore inlet is simulated using a surface energy minimization model. In a GDL coated with a non-wetting coating such as PTFE, water makes contact with non-wetting fibers and with defects which pin the gas-liquid interface. The mixed-non-wetting (MNW) pore inlet is defined by fiber segments of varied wetting properties, in order to capture the water percolation process in the presence of coating defects. The shape of the pore is quantified according to its aspect ratio (AR). The high aspect ratio pores present the characteristics of micro-cracks. High to moderate aspect ratio pores up to a value of one, corresponding to the unskewed pore, are considered. For wetting pores with AR close to one, the changes in breakthrough pressure are minimal. The breakthrough pressure changes significantly in the case of mixed-non-wetting pores. MNW pores with few coating defects are further investigated by varying the AR and determining the corresponding Laplace pressure for each case. The breakthrough pressure and the droplet volume at breakthrough have direct implication on water management, through their influence on liquid finger formation. The changes in breakthrough pressure with the aspect ratio point to the necessity to include the pore shape distribution in porous media models, to accurately predict the water transport behavior in the GDL.
(Invited) How Interfaces Control Lithium (De)insertion Pathway: Comparing Liquid and Solid Electrolytes
Authors: Lim Jongwoo
Published: December 2024

In the realm of lithium-ion batteries, the process of lithium (de)insertion follows a two-fold pathway, encompassing (1) charge transfer occurring at the electrolyte-electrode interface and (2) solid-state lithium diffusion within electrode. Conventionally, these two transport mechanisms have been regarded as distinct and investigated separately due to their sequential occurrence during battery cycling. However, our recent research demonstrates that the kinetics of charge transfer can exert control over the spatial distribution of lithium on the surface, consequently influencing the entire lithium (de)insertion pathway.

In addition, in the field of all-solid-state batteries (ASSBs), the interface between solid-electrolytes and electrodes further modulates the surface charge transfer kinetics, active surface areas, and local stresses. Chemo-mechanical properties in ASSBs complicate interfacial charge transfer and further affect lithium diffusion within the electrodes. In this talk, I will present how our synchrotron-based operando X-ray diffraction and imaging could help understand such phenomena.
The Mechanical Dynamics of Lithium-Metal Battery Formation Protocols
Authors: Ponnekanti Aamani , Thorsteinsson Gunnar , Wasylowski David , Steingart Dan
Published: December 2024

Formation, the first charge of an SEI forming battery system, is well understood to affect the cycling behavior of the system. This is particularly crucial for anode-free lithium metal batteries due to the significant effect of initial Li plating morphology and SEI on subsequent plating and, therefore, long-term cyclability. Low-cost, operando tools that spatially map heterogeneities are important for the study and validation of formation protocols. Here, we use spatially-resolved ultrasound transmission during formation to study variations in gas formation and morphology of Li metal anode-free cells as a function of temperature, pressure, and current density. These non-invasive results are validated with ex situ optical and SEM imaging, and XPS is used to determine the SEI speciation. We then cycled these formed cells at increased rates while measuring the systems with one-dimensional acoustics to correlate formation with mechanical and electrochemical cycling performance.
Insights into Lithium Inventory Quantification of LiNi0.5Mn1.5O4-Graphite Full Cells
Authors: Bao Wurigumula , Meng Ying Shirley
Published: December 2024

High voltage spinel cathode LiNi0.5Mn1.5O4 (LNMO) offers higher energy density and competitive cost compared to traditional cathodes in lithium-ion batteries, making it a promising option for high-performance battery applications. However, the fast capacity decay in the full cell hindered further commercialization. Therefore, it is crucial to evaluate lithium inventory across the entire battery system. The Li inventory evolution upon cycling in the LNMO-Graphite pouch cell is systematically studied by developing Lithium quantification methods on cathode, anode, and electrolyte. All the active and inactive Li in the system after cycling were quantified. The findings reveal that active Li loss is a primary factor contributing to capacity decay, stemming from unstable anode interphase caused by crosstalk. This crosstalk primarily originates from electrolyte degradation on the cathode under high-voltage operation, leading to increased moisture and acidity, subsequently corroding the anode interphase. In response, two approaches, including an Aluminum Oxide (Al2O3) surface coating layer on the cathode and Lithium difluoro(oxalato)borate (LiDFOB) electrolyte additives, are evaluated systematically, resulting in cycling stability enhancement. This study offers a quantitative approach to understanding the Li inventory loss in the LNMO-Gr system, providing unique insights and guidance into identifying critical bottlenecks for developing high voltage (>4.4V) lithium battery technology.
Characterisation by Advanced Experimental Methods of Components in PEM Fuel Cells and PEM Electrolyses
Authors: Martinelli Anna , Schulz Dylan
Published: December 2024

Hydrogen based technologies, such as PEM fuel cells and PEM electrolyses, are attracting increasing attention and will be central for the transition to a renewable energy system. In order to be integrated part of the electricity grid and hence make an impact on society, however, the efficiency of these devices must increase as well as their durability should be assessed. Efficiency and durability are a complex result of the properties of several components, which include the gas diffusion layer, the catalyst and the proton exchange membrane, the performance of each relating closely to the conditions of operation.

In this oral, I will present our ongoing work in developing advanced experimental methods, heavily based on vibrational spectroscopy, that enable studying the degradation of proton exchange membranes (type of chemical or mechanical damage), the morphological evolution of catalytic particles during fuel cell operation (including morphologies other than spherical) as well as the correlation between PTFE content in the gas diffusion layer and electrochemical performance. The figure below, for instance, shows preliminary results on the local distribution of PTFE in a gas diffusion layer mapped by Raman spectroscopy.

Figure 1
A Lifetime Prediction Model for the Anode Catalyst Layer in PEM Electroyzers
Authors: Van-Brunt Alexander John
Published: December 2024

Electrolyzer stacks (ELY stacks) are anticipated to form a key component in the hydrogen economy by providing a clean hydrogen source which may be deployed modularly. Currently, proton-exchange-membrane (PEM) electolyzers are a promising candidate to meet this demand on account of their high performance relative other electrolysis methods. Amongst other considerations, economic barriers preventing the uptake of PEM ELY stacks are the durability and cost of the precious catalyst materials, especially iridium-loaded catalysts. Additionally, due to the ever-growing uptake of intermittent power sources, dynamic operation of the ELY stack is an attractive economic option, yet may also accelerate degradation. Taken together, a key question in the design and deployment of ELY stacks is predicting the lifetime of the anode catalyst layer under dynamic power loads.

In this presentation we present a simple model for lifetime prediction of the anode catalyst layer of a PEM electrolyzer with iridium dissolution as the principal degradation mechanism. The model is parameterized from data in the literature and wind and solar profiles are used as validation. Implications in the design of accelerated stress tests are also discussed.
Modeling Gas Crossover and Recombination in Proton-Exchange Membrane Water Electrolysis
Authors: Rudnicki Paul E. , Dizon Arthur , Gawas Ramchandra , Arges Christopher G. , Ahluwalia Rajesh , Weber Adam Z.
Published: December 2024

Proton-exchange membrane water electrolysis (PEMWE) is promising method for generation of hydrogen fuels from clean electricity, and is most economical when operating at variable current densities, with thin membranes, and under high differential pressures. However, crossover of evolved hydrogen and oxygen gases through the membrane creates safety, durability, and efficiency concerns under these conditions. In this talk, we will discuss our two-dimensional multiphysics PEMWE model and use it to study gas-crossover mechanisms including the contribution of side reactions due to the crossover species and the effect of adding a gas-recombination catalyst layer within the membrane. The model is parametrized using new experiments at industrially relevant differential pressures and current densities, which will also be presented. The results demonstrate how convective gas transport is strongly coupled to current density through electroosmotic water transport, leading to mitigated hydrogen crossover at high current densities (i.e., a current dependent crossover rate). Furthermore, we will discuss how the efficacy of the recombination catalyst layer is highly dependent on its location within the membrane and performs best in the vicinity of the anode. Finally, we will compare the 2-D model results with a simplified analytic one-dimensional diffusive crossover model to identify discrepancies and operational range of the simplified model that can be used for upscaling. Overall, the model and associated insights help guide design of effective and efficient recombination catalyst layers for safe and durable PEMWE operation.
Boosting Hydrogen Production: Non-Noble Metal Catalysts Optimize Electrodes in Anion Exchange Membrane Water Electrolysis
Authors: Hesse Miriam , Pineti Enado , Kaufmann Bastian , Pilaski Moritz , Radev Ivan , Manolova Mila , Sörgel Seniz , Müller Thomas Ernst , Apfel Ulf-Peter
Published: December 2024

As the world transitions to renewable energy sources, efficient energy storage is crucial for managing power fluctuations and decarbonize crucial high temperature processes. Achieving grid balance and optimizing renewable energy capacity requires innovative solutions. One promising option is the conversion of electrical energy into hydrogen through Anion Exchange Membrane Water Electrolysis (AEM-WE).

AEM-WE combines high hydrogen production rates per electrode area and little production site footprint of Proton Exchange Membrane Water Electrolysis (PEM-WE) with cost-effectiveness of non-noble electrode materials utilized in Alkaline Water Electrolysis (A-WE). To further optimize AEM-WE, it is essential to improve hydrogen production while reducing material costs. This can be achieved through innovative approaches to electrocatalyst and electrode design. However, developing cost-effective catalysts that combine superior efficiency and robustness in aqueous environments, ideally in alkaline conditions, remains a big challenge. In this work, two electrode preparation approaches are investigated. For the anodic OER a corrosion synthesis is been developed to form highly active NiFe-layered double hydroxide (LDH) structures on nickel non-woven porous transport layers (PTL). A highly active cell can be combined with a cathodic HER catalyst, prepared by electrochemical deposition Ni-S on a stainless steel non-woven PTL.

In single cell AEM water electrolysis using 1 M KOH-solution utilizing the prepared NiFe-LDH anode and Pt/C cathode, 2.7 A/cm² at 2 V were achieved, surpassing commercially available powder catalysts like NiFe-oxide. Comparative analysis of Ni-S cathode with NiFe-LDH, integrated into a membrane electrode assembly demonstrated superior AEM-WE performance, outperforming the mentioned platinum on carbon catalysts. Electrochemical impedance spectra indicated higher charge transfer activity of Ni-S cathode compared to Pt/C. Importantly, the electrodes prepared in this study exhibited stability under accelerated electrochemical stress tests for 1000 cycles.

These approaches provide a simple, inexpensive, scalable and therefore industry-relevant fabrication method with improved active areas and excellent catalytic activity during AEM water electrolysis.

Figure 1
Reduction in Fuel Cell Break-in Duration by Accelerating the Removal of Impurities in the Electrode
Authors: Kodama Kensaku , Kajiya Shuji , Yamada Haruhiko , Ohshima Ayako , Murata Hajime , Oka Noritoshi , Nomoto Shigemitsu
Published: December 2024

For the widespread adoption of polymer electrolyte fuel cells (PEFCs), a high productivity of fuel cell stacks is required. The conditioning (also called break-in) of a PEFC is known to frequently take multiple hours and has been recognized to be a bottleneck for mass production [1]. In this study, we identify the origin of a long break-in duration in the production of Toyota Mirai stacks and demonstrate effective break-in protocols to reduce the duration.

Electrochemical measurements with a small cell and sample analyses were conducted for retrieved catalyst-coated-membranes (CCMs) after the cell assembling process in the production. Figure 1 shows the I-V curves and Tafel plots measured for the retrieved CCMs before and after a break-in, and the amounts of organic impurities in those CCMs. The results indicate that the oxygen reduction reaction activity of the cathode catalyst is suppressed by organic impurities before the break-in and that how to effectively remove those impurities is essential for reducing the break-in duration.

We developed a new break-in protocol for effectively removing impurities, where impurities desorbed from Pt surfaces in the cathode at a low potential are expected to be immediately washed away by produced water (Fig. 2(a)). As intended, the new protocol promptly brought the cell to a state where it could demonstrate its maximum performance compared to the reference protocol (Fig. 2(b)). The concept of the new protocol was applied in the break-in process for the second-generation Mirai stacks, and the break-in duration was reduced by 70% compared to the process for the first-generation Mirai stacks [2]. In the meeting, the details of the experimental results and their mechanisms are discussed.

References:

[1] F. Van Der Linden et al., J. Power Sources, 2023, 575, 233168

[2] Toyota Technical Review, 2021, vol. 66

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New Designs and Approaches for Enabling the Large-Scale Fabrication of Gas Diffusion Electrodes
Authors: Ruiz Christian , Rockward Tommy , Allen Jabari
Published: December 2024

At the heart of the fuel cell resides two electrodes (anode and cathode) sandwiched around a proton exchange membrane. These electrodes are comprised of electrochemically active catalyst, typically platinum based and are either adhered to the membrane electrode assembly (MEA) or directly to the gas diffusion electrodes (GDE). The large-scale fabrication of MEAs or GDEs can help reduce cost and support the viability of mass emergence of fuel cell systems. This study focuses on using a slot die coater to fabricate GDEs using non-supported catalyst inks. It’s worth noting that there are challenges that emerge when using this technique. Some key challenges include ink formulation for proper catalyst suspension, surface properties of the hydrophobic substrate, and maintaining electrode uniformity during deposition. To overcome these challenges, we explore various approaches such as equipment modification, pre-treatment of the substrate, and modifying ink formulations to enhance the reliability of the coating process.
Asymmetric Diaphragms and Their Influence on Gas Crossover in Alkaline Electrolysis
Authors: Kraglund Mikkel Rykær , Gellrich Florian , Xia Yifan , Rajappan Sinu Charamchirail , Aili David , Jensen Jens Oluf
Published: December 2024

Many novel lab-scale diaphragms, as well as commercial state-of-the-art diaphragms for alkaline water electrolysis are prepared by non-solvent based phase inversion processes. On the lab-scale, the fabrication process is often asymmetric. The polymer dope is coated onto a glass plate similar to conventional film forming techniques, after which the glass substrate carrying the film is immersed into a non-solvent bath to rapidly precipitate the constituting polymer. As the film is initially only exposed to the non-solvent on the top surface, the resulting pore structure at the top surface of the film differs from that at the glass plate side.

This contribution explores a number of phase-inversion prepared diaphragms towards their pore structure, and in particular investigate how the asymmetric nature influences the electrolysis behavior at single cell level. Reference diaphragms based on polysulfone (PSU) are used as reference materials, and the investigation is extended to include diaphragms based on more novel polymers systems.

Significant differences are observed in the relative crossover of hydrogen to oxygen (HTO) as well as the oxygen to hydrogen (OTH), depending on the orientation of the diaphragm. Specifically, towards which electrode the skin layer is oriented matters. More than an order of magnitude in apparent crossover flux can be observed in some cases at otherwise identical conditions. Introducing an electrode-diaphragm gap can alleviate severe supersaturation and reduce crossover flux, whereas over compressed cells exhibit more severe degrees of crossover.
A Low-Cost Bipolar Plate Comprising a Channeled Porous Transport Layer for Proton and Anion Exchange Membrane Electrolyzers
Authors: Amrite Archis , Oliveira Alexandra M. , Yan Yushan , Prasad Ajay Krishna
Published: December 2024

Hydrogen is gaining acceptance as a viable energy vector for renewable energy and as a green molecule for chemical synthesis, but its production in a sustainable, efficient, and affordable manner requires further optimization. Proton exchange membrane electrolyzers (PEMELs) can be efficient for hydrogen production. Within the PEMEL stack, the repeating unit cell consists of a bipolar plate, two porous transport layers (PTLs), two catalyst layers, and one proton exchange membrane (PEM). The oxygen evolution reaction at the anode creates a corrosive environment, therefore, titanium is used as the anode bipolar plate material. The anode bipolar plate is typically machined from a block of titanium for small volume production or stamped for large volume production, which is time-consuming and challenging due to frequent tool breakage resulting in high cost. Furthermore, ineffective in-plane water transport within the anode PTL can cause inadequate water supply to the catalyst layer resulting in unutilized catalyst. To alleviate these problems, we have designed a novel PEMEL cell containing channeled titanium foam enclosed within a PTFE frame that functions both as the bipolar plate and the PTL, termed channeled porous transport layer (CPTL). In our design, the channels face the current collector such that the water flows through the channels and the pores of the foam in both the through-plane and in-plane directions, thereby maximizing catalyst coverage and utilization. Similarly, the pores and channels of the CPTL provide an effective pathway for the evacuation of oxygen gas evolved at the anode catalyst layer. Most importantly, the channels in the titanium foam can be formed as part of the PTL production process which could greatly reduce PEMWE manufacturing costs and lower the cost of hydrogen. The same CPTL design can also be employed in anion exchange membrane electrolyzers (AEMELs) whose anode environment permits the use of nickel foam which further reduces material costs. We will present experimental results for PEMELs and AEMELs performance with this new design and compare them with those obtained with conventional bipolar plates.