bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Polymer Chemistry of Block or Random Co-Polymers for Anion Exchange Membrane Electrolyzer Membranes and Ionomers in Carbonate Electrolyte
Authors: Herring Andrew M. , Sweeney Alana Blaise , Kuo Mei-Chen , Salgado Marco , Carroll Liam
Published: December 2024

Of all the emerging electrolyzer technologies that can produce low carbon hydrogen, AEM electrolysis coupled with wind, solar or other renewable electricity has the greatest potential as it combines the contactless and rapid response advantages of PEM electrolysis without the need for rare or precious metal catalysts, or per fluorinated hydrocarbons, as demonstrated in the less scalable less responsive, lower power density liquid alkaline electrolysis. Indeed, AEM electrolyzer technology has the potential to meet the DOEs hydrogen earth shot goal of $1/kg H2. Practical AEM electrolysis with pure water has so far proved elusive. It has been easily shown that adding a small amount of supporting electrolyte, 0.5 - 1 M hydroxide or carbonate, to the circulating aqueous feed facilitates practical current densities. While adding 0.5 M hydroxide gives the highest performance, the use of hydroxide necessitates the use of higher cost, more caustic stable components, and the isolation of the hydroxide from air. Using 0.5 M potassium or sodium carbonate electrolytes only increases the over potential by 100 mV versus hydroxide allowing excellent performance to be achieved and saves significant system costs while excellent durability is simultaneously obtained. We utilize a scalable and versatile triblock co-polymer, ABA, polychloromethylstyrene-b-polyethylene-b-polychloromethylstyene, pCMS-pE-pCMS, polymer system that can be quaternized to give high performance and highly durable AEMs or tunable ionomers. Typically OH- conductivities are > 0.1 S cm-1 > 40°C and > 0.1 S cm-1 for all other common anions, Cl-, carbonate, bicarbonate > 70°C. In the laboratory this could easily be fabricated at high MW with complete control of A:B ratios on the 10 g scale and in the hands of a third-party it has been scaled up to >1 kg. The polymer can be processed on a tape caster to give sheets > 500 cm2 with controllable thicknesses from 10-100 ± 1μm.

Further improvements to the polymer chemistry are being investigated that will affect its performance and durability and allow us to cast higher quality thinner films. Furthermore, we are beginning to optimize the ionomer chemistry to allow ultra low loadings of Pt on the Hydrogen side and non-precious metal catalysts, such as MnO2 and Co3O4, on the Oxygen side. To achieve this we can swap the structural polyethylene for the more rubbery polymethylbutylene in our block polymers as well as make random polymers that act as excellent electrode binders. Finally we have begin to probe the effects of changing the aromatic hydrophilic group for a completely hydrocarbon polymer brush. We will present the results of testing these materials for performance and durability in an ambient pressure 5 cm2 electrolyzer at 60°C.
Advanced Polybenzimidazole Derivatives in Ion-Solvating Membrane Water Electrolysis with Low KOH Concentration
Authors: Cho Hyungkyu , Lee Byeol-Nim , KIM Bonghyun , Lim Jaemuk , Lim Tae-Hoon , Kim Hyoung-Juhn
Published: December 2024

The development of a polymer electrolyte with robust mechanical strength and exceptional electrochemical stability is crucial for alkaline water electrolysis while ensuring high hydroxide ion conductivity in low concentrations of KOH solution. The Ion-solvating Membrane Water Electrolysis (ISMWE) is gaining interest due to its adaptability to lower KOH solution concentrations, utilizing a polymer-based separator doped with KOH, resulting in a unified system consisting of polymer, water, and KOH, facilitating the use of non-platinum metal catalysts. Herin, we have employed the in-situ directing casting method to fabricate poly(2,5-benzimidazole) (ABPBI). The repeating benzimidazole units comprising the ABPBI membrane can retain significant amounts of KOH, leading to a dramatic increase in ion conductivity during electrolysis. The membrane was subjected to electrochemical evaluation through various conditions using an alkaline water electrolysis cell station, involving two different temperatures for cell operation, 60 ℃ and 70 ℃, and four different concentrations of KOH: 0.5M, 1M, 2M and 3M, utilizing both PGM catalysts and non-PGM catalysts. Additionally, we have fabricated ABPBI derivatives that exceed the mechanical and electrochemical performance of the pristine membrane. The physical characteristics of membranes are evaluated using techniques such as UTM, TGA, SEM, XRD, and XPS. From our results, the use of ABPBI polymer as Ion-solvating membrane, which allows for the utilization of high-efficiency and durable alkaline electrolysis. This study highlights the potential of ABPBI structures as the backbone and anion exchange sites for ISMWE operating with low KOH concentration solution.

Figure 1
Fitting Scattering Profiles of Perfluorinated Sulfonic Acid Ionomer Dispersions
Authors: Jeong Eugene , Litster Shawn
Published: December 2024

Proton exchange membrane fuel cells (PEMFC) provide a path to wider adoption of hydrogen energy systems. This is because the energy density afforded by hydrogen makes PEMFC a strong candidate for the medium- and heavy-duty transportation sectors, where high allowable costs can reduce the barrier to adoption. As such, the focus of PEMFC research is toward greater efficiency and durability to reduce lifetime vehicle costs. To this end, high oxygen permeability ionomers (HOPI) are of interest, as the material has already been shown to increase mass activity in the cathode catalyst layer due to reduced anion poisoning from shorter side chains, in addition to enabling high power density through reduced oxygen transport resistance. While the performance of electrodes cast from HOPI and HOPI blended with commercial perfluorosulfonic acid (PFSA) has been documented, questions remain regarding the behavior of the novel ionomer in the dispersions and inks from which catalyst layers are fabricated. The literature on conventional PFSA ionomers devotes much attention to the effects of solvent media on interactions of ionomer backbone and side chains to form aggregates, motivated by the possible relationship between aggregates in dispersion and the structure of the cast catalyst layer, and thereby cell performance. In the present work, we probe the characteristic sizes and interactions among ionomer aggregates in dispersions by small angle x-ray scattering (SAXS). We report properties of aggregates in both HOPI and a commercial PFSA ionomer over a series of ionomer concentrations and at different ratios of water and propanol in the solvent medium. From these dispersions, aggregate spacings are estimated by fitting to the interference peak in the scattering intensity profile, and sizes are determined by form factor fitting. Next, series of blended HOPI and PFSA ionomer are prepared and studied by SAXS to understand the morphology of ionomer blends in solution. We further evaluate ionomer blends with different durations of ultrasonication, which can provide insight into the effect of sonication on ionomer blend aggregates during ink preparation.
Advancements in the Fabrication of Reinforced Proton Exchange Membranes and Exploration of Next-Generation Membrane Technologies
Authors: Chiba Yusuke , Hayabe Shintaro , Salem William , Sawada Toshiaki
Published: December 2024

Developing a polymer-electrolyte membrane (PEM) as a water electrolysis (WE) component is crucial for achieving a hydrogen-based economy while reducing CO2 production. Among proton exchange membranes, per-fluorinated sulfonic acid (PFSA) membranes are considered key components due to their high proton conductivity and chemical and thermal stability. Over the next few years, the demand for PFSA membranes in the PEM electrolysis market is expected to rapidly grow, necessitating suppliers to enhance their manufacturing capabilities and membrane quality.

Since 1975, AGC has been manufacturing PFSA membranes, contributing significantly to the electrolysis industry, including PEM water electrolysis and chlor-alkali electrolysis, among others. AGC R&D has developed FORBLUETM S-SERIES, a PFSA membrane for PEMWE, using PFSA polymers manufactured in-house from monomers. PFSA membranes possess the following properties: high proton conductivity, high mechanical strength and chemical stability, low gas permeability, and good dimensional stability. PFSA membrane properties can be optimized by adjusting the membrane thickness and the polymer’s ion exchange capacity (IEC). PFSA membrane dimensional stability can be enhanced using reinforcement, which reduces changes in the in-plane dimensions upon the water uptake and facilitates efficient MEA construction. We have developed two reinforced membranes, Sx-0935DH and Sx-1235DH. Sx-0935DH shows high proton conductivity, and Sx-1235DH exhibits low gas permeation ability. For instance, the overpotential of Sx-0935DH was reduced by >80 mV at 3 A/cm2 compared to N115, measured under ambient pressure at 80 °C. Additionally, the hydrogen concentration on the anode side of Sx-1235DH is 20% of that of N115. Currently, we are working on manufacturing the two reinforced PFSA membranes on a large scale via roll-to-roll (RtR) processing.

In the water electrolysis industry, there is a demand for thinner membranes to increase proton conductivity and reduce the energy required for hydrogen production. However, thinner membranes tend to have a higher hydrogen permeation ability. Since the lower explosive limit (LEL) for hydrogen in oxygen is only 4 vol%, reducing the hydrogen gas crossover is critical. A gas recombination catalyst (GRC) is used as a membrane component to lower the concentration of hydrogen in oxygen. AGC is developing thinner membranes, incorporating GRC as the next-generation solution.

We will present our recent efforts in manufacturing membranes through RtR processing and developing next-generation membranes for water electrolysis.
A New Archetype: Opportunities of Pemion® Fully Hydrocarbon Ionomer and Composite Membranes in Proton-Exchange Membrane Fuel Cell Applications
Authors: Britton Benjamin
Published: December 2024

Hydrogen fuel cells are a critical technology for the renewable energy transition, pairing with green hydrogen to represent the most economic and scalable power generation for many applications, in particular ‘heavy duty’ systems such as commercial trucking, aviation, shipping, remote operations such as mining, and the replacement of diesel generators. Perfluorosulfonic acid (PFSA) polymers as membrane and ionomer in the catalyst layer today represent the fundamental building blocks of proton-exchange membrane fuel cells (PEMFCs) and a broad range of electrochemical systems including PEM water electrolyzers (PEMWE). However, potential regulation and liabilities related to the production of environmentally mobile fluorinated materials represent a potential bottleneck to the scaling of these critical systems for the renewable energy economy. Acid-functionalized small molecules that are used as process aides and expelled as degradation products are particularly concerning and warrant direct or indirect replacement by non-fluorinated or ‘hydrocarbon’ chemistries. Sulfonated poly(arylene) ionomers exhibit exemplary stability and a the only presently commercialized material of this category, Pemion®, promises to enable to a long-sought step-change in system-level temperature hitherto limited by the physical properties of PFSAs as well as increase durability due to preferential chemical properties.

This presentation highlights the similarities and major divergences of the properties of hydrocarbon PEM Pemion®, comparing the physical and electrochemical properties of an ePTFE-reinforced product PF1-HLF8-15-X with those of hydrocarbon-reinforced membranes of various chemistries and production methods, as well as comparing PFSA- and hydrocarbon-based ionomers. Preliminary sub-scale work determining the structure-property relationships within Pemion® ‘fully hydrocarbon’ systems preliminarily demonstrate industrially relevant performances (i.e. sub-scale peak power densities >1 W/cm²) even in ‘hot and dry’ conditions, with a substantial (>50%) reduction in measured hydrogen permeability. The potential for system impacts of higher operational temperatures, increased liquid permeation, non-annealable electrode structures, and reduced gas permeation will be discussed, and preliminary data including multi-day comparisons with PFSA-based systems at operational temperatures ≥110 °C presented.
Phosphoric Acid-Doped Ion-Pair High-Temperature Proton Exchange Membranes Based on Polyphenylene Copolymer
Authors: Park Heemin , Kim Youngkwang , Kim Yu Seung , Bae Chulsung
Published: December 2024

High-temperature proton exchange membrane fuel cell (HT-PEMFC) using hydrogen fuel has multiple advantages, such as faster reaction kinetics, high impurity tolerance to the catalyst, and simple water and thermal management than low-temperature proton exchange membrane fuel cell (LT-PEMFC). Polybenzimidazole (PBI) based phosphoric acid (PA)-doped membranes are the most common membrane for HT-PEMFC, because they have excellent chemical and thermal stability, and provide relatively usable conductivity for HT-PEMFCs. However, the PBI-based PA-doped membranes still suffer from reduction in conductivity at temperatures of 140–180 ˚C and high relative humidity due to acid leaching.

Herein, we have developed a novel polyphenylene-based ion-pair PA-doped membrane with excellent chemical and mechanical stability by functionalizing a polyphenylene-based copolymer with quaternary ammonium, followed by membrane casting. Due to a combination of the all-carbon backbone structure and high molecular weight of the polymer, it shows good chemical and mechanical stability of the membrane and great performance in HT-PEMFCs. We also fine-tuned the properties of the PA-doped membrane, such as proton conductivity and mechanical strength, by manipulating the ion exchange capacity (IEC) and crosslinking density of the polymer. The novel polyphenylene-based ion-pair PA-doped membranes were characterized in terms of IEC, PA doping level, area swelling ratio, PA uptake, proton conductivity, and mechanical properties. Overall, this study will present a new class of HT-PEMs with high fuel cell performance and excellent stability.
Benchmarking Composite Fuel Cell Membranes
Authors: Kushner Douglas I. , Kusoglu Ahmet , Lau Grace Y.
Published: December 2024

Proton-exchange membrane fuel cells (PEMFCs) are a unique clean energy technology capable of decarbonizing the transportation and energy sectors, particularly in cases where batteries are poorly suited. Of particular interest is the heavy-duty transportation sector where demanding weight and range requirements are better satisfied by PEMFC technology. One of the most technical challenges in realizing PEMFC technology for the transportation sector is the greater need for durability, with over 5x improvements in lifetime needed to achieve 1 million miles as targeted by the Million Mile Fuel Cell Truck Consortium (M2FCT). Recent strategies towards improving membrane durability include mechanical reinforcement and chemical additives to reduce the mechanical stresses due to hydration cycling and to quench hydroxyl radicals before membrane degradation occurs, respectively. Of particular interest in this work is a membrane by Chemours referred to as NC700 which encompasses mechanical reinforcement and chemical additives. NC700 is baselined to N211 membranes that have been subjected to various treatments. Herein, we discuss the trade-offs of chemical additives, mechanical reinforcement, and ionomer changes in physical and transport properties such as water mass uptake and volumetric swelling, proton conductivity, and mechanical strength across a wide range of humidities and temperatures. By combining all of these facets, an understanding of how these different inputs alter the material properties that will not only serve as a benchmark for future membranes but feed into future models and serve as a starting point for integration and durability efforts.
Controlling Flooding and Parameter Sensitivity in an Anion Exchange Membrane Fuel Cell Using a Triblock Copolymer Membrane and Matched Ionomers
Authors: Herring Andrew M. , Ponnada Srikanth , Kuo Mei-Chen
Published: December 2024

While there has been much interest in the proton exchange membrane (PEM) fuel cell, its wide spread use has been restricted by cost, durability, fuel versatility issues, and the environmental consequences of using perfluorosulfonic acid polymers as the membrane and ionomer. This is primarily because catalyst based on Pt are nessecary in a PEM fuel cell on both the anode and the cathode and reactive oxygen species chemically degrade the cell. Alkaline catalysis in fuel cells has been demonstrated with non-precious metal catalysts, and a variety of fuels beyond H2 and methanol. Alkaline fuel cells (AFCs), based on aqueous solutions of KOH, have serious drawbacks associated with system complexity, low system power densities and carbonate formation. Anion exchange membrane (AEMs) fuel cells have a number of advantages over both PEM fuel cells and traditional AFCs. Great strides have been made in ionic conductivity and durability in AEMs and fuel cells with reduced precious metal loadings have been demonstrated. However, AEM fuel cells have significant water management issues, as water is both a reactant and a product leading to flooding and control issues.

We have developed a triblock copolymer Poly (vinylbenzyl-N-methylpiperidinium carbonate)-b-polyethylene-b-poly(vinylbenzyl-N-methylpiperidinium carbonate)as a robust, high performance, durable, and scalable AEM. We have modified the block ratios and ion exchange capacity of this material to show excellent performance and durability in both electro-desalination and water electrolysis. Despite the materials potential, we have only occasionally tested it as a fuel cell membrane. We have now begun to throughly evaluated the material in 5 cm2 H2/O2 fuel cell. Initial experiments showed good potential performance but were hampered by severe flooding of the electrodes. We will present a materials approach to solving this problem by investigating various related ionomers in the electrodes. Both variations of the polymer used to fabricate the membrane and a random co-polymer derived from polymethylbutylene and poly(vinylbenzyl-N-methylpiperidinium) were investigated. The effect of loading and ionomer ion exchange capacity on the performance of the fuel cell and the relationship between these properties will be reported.
Hydrocarbon Fuel Cell Membranes: Do We Need New Chemical Durability Testing Protocols?
Authors: Han Zongyi , Nemeth Tamas , Yandrasits Michael , Ren Hong , Bangay William , Gubler Lorenz
Published: December 2024

Hydrocarbon proton exchange membranes (PEMs) for fuel cells have recently received increased attention due to growing environmental concerns about the use of per- and polyfluoroalkyl substances. The chemical accelerated stress test (AST) protocol for membranes developed by the US Department of Energy (DOE), which is based on the understanding of the degradation mechanism of perfluoroalkylsulfonic acid PEMs, has been widely adopted to assess newly developed hydrocarbon PEMs. However, due to different polymer chemistry and membrane degradation mechanisms, the DOE chemical AST protocol may not be suitable for hydrocarbon PEMs.

In this study, the influence of two key operating parameters, i.e. relative humidity (RH) and O2 partial pressure (p
O2), on the chemical degradation of hydrocarbon PEMs was investigated in order to design a more suitable chemical AST protocol for hydrocarbon PEMs. Sulfonated poly(ether ether ketone) (SPEEK) was selected as a representative material for non-fluorinated hydrocarbon PEMs. Solution-cast membranes of ~22 μm thickness were wet-assembled in a single fuel cell (16 cm2 active area) for fixed time (4 days) open circuit voltage (OCV) holding tests at different RHs and p
O2. Under 100% RH, H2/O2, the membrane failed the fastest within 40 hours (Figure 1a). This could be related to higher gas crossover (Figure 1b), which leads to more oxidative radicals, such as HO•, being generated. Fuel cell effluent water was periodically collected from both the anode and cathode sides for analysis by UV-vis spectroscopy and ion chromatography (IC). Hydroquinone-like degradation products were detected by UV-vis spectroscopy. Furthermore, under 100% RH, H2/O2, the degradation products showed the strongest signal in the anodic effluent water. IC results of sulfate ion release suggested that the higher the RH (also p
O2), the more severe the membrane degradation. Post-test ion exchange capacity (IEC) measurements showed that the average IEC loss rate is the highest under 100% RH, H2/O2 (~0.15 %/h), while the lowest under 30% RH, H2/air (~0.01 %/h), again indicating that 100% RH, H2/O2 could be a promising protocol for AST of hydrocarbon PEMs.

Figure 1
Development of Highly Durable Anion Exchange Membrane and the Utility for Aemwe Cells
Authors: Yanagibashi Naoki , Nagatsuka Shinya , Ozawa Yuki , Nakano Megumi , Sato Hiroyuki , Nishikwa Keiji , Nagashima Kodai , Uchida Katsuya , Miyanishi Shoji , Yamaguchi Takeo
Published: December 2024

Anion exchange membrane water electrolysis is of great interest in terms of the environmental impact and the cost because it does not need precious metal-based catalysts and corrosion-resistant components. But, it is difficult to satisfy all the performance requirements for anion exchange membranes (AEMs). There are three major performance requirements for AEMs, high ion conductivity, high durability, and low cost and so on. Therefore, further development of AEMs is still needed.

Yamaguchi et al. have been researched the polyfluorene-based AEMs with high alkaline durability [1,2]. We are working on the practical application of their AEMs technology, and have been improving quality by optimizing the synthesis process and examining the film forming method, and examining scale-up for cost reduction. In addition, we prepared the test stand to evaluate the water electrolysis performance of AEMs, and we expanded our water electrolysis evaluation technology by introducing spray coater for the catalyst layer optimizing that of formation process, and the water electrolysis evaluation system.

Based on the report by Yamaguchi et al., we developed the AEM. The water electrolysis performance of the MEA using the AEM was below 1.75V at 1A/cm2 in 1M KOH solution at 80℃, which is equivalent to that of commercial AEMs. To compare the durability of AEMs, the water electrolysis performance was evaluated after soaking in 1M KOH solution at 80℃. Water electrolysis performance after durability test was better than that of commercial aromatic AEMs(Figure.1(a)). The performance of the AEM was slightly changed at 200 hours, but after that, there was almost no change in the performance at 2000 hours, and the increase in voltage was less than 3% compared to the initial performance(Figure.1(b)). On the other hand, the voltage of commercially available aromatic AEM increased by 140% at 1000 hours. We confirmed the high durability of the polyfluorene-based AEMs. For the future, we would like to show the superiority of the AEMs in the continuous data of the water electrolysis durability test in the cell.

References

[1] Miyanishi, T. Yamaguchi, Highly conductive mechanically robust high Mw polyfluorene anion exchange membrane for alkaline fuel cell and water electrolysis application,
Polym. Chem.
11.3812-3820, 2020, DOI: 10.1039/D0PY00334D

[2] T. Yamaguchi et al, An Extremely Low Methanol Crossover and Highly Durable Aromatic Pore-Filling Electrolyte Membrane for Direct Methanol Fuel Cells,
Advanced Materials
19, pp. 592–596 ,2007

Figure1. The water electrolysis performance measured after soaking 1M KOH solution.

(a) i-V curve after durability test (b) Voltage retention rate against durability time

Figure 1
Understanding the Mechanism of Chemical Durability Enhancement through Modeling of Electrolyte Membranes with Improved Oxygen Barriers
Authors: Fukaya Norihiro , Suzuki Takahisa , Gautama Zulfi , Sasaki Kazunari , Nishihara Masamichi
Published: December 2024

In pursuit of a carbon-neutral society, polymer electrolyte fuel cells (PEFCs) are gaining significant attention in commercial applications, particularly for heavy-duty vehicles. The system demands long-term durability to its components, especially for polymer electrolyte membranes (PEMs), which require further thinning in the future[1]. The chemical degradation of PEMs occurs because of the attack by radical species. It is posited that hydrogen peroxide, arising from the crossover of oxygen, contributes to the formation of radical species. We hypothesized that introducing a gas barrier layer (GBL) against oxygen into the PEM could suppress chemical degradation, and confirming this hypothesis through durability tests using a GBL sandwiched between PEMs [2]. In this study, we constructed a model having the GBL to understand the mechanism behind this enhanced durability.

According to the scanning electron microscopy (SEM) observations of the fabricated membrane electrode assembly (MEA) with the GBL (Fig. 1a), we constructed a 1D through-plane model of MEA (Fig. 1b). Species conservation equations were solved in each layer to calculate the potential and concentration. Reactions R1– R4 were assumed in the catalyst layers for the source terms of the conservation equations.

2H+ + 2e- → H2

(R1)

O2 + 4H+ + 4e- → 2H2O
(R2)

O2 + 2H+ + 2e- → H2O2

(R3)

H2O2 + 2H+ + 2e- → 2H2O
(R4)

We compared the distribution of hydrogen peroxide concentration in MEAs with and without the GBL by using our model. In MEAs with the GBL, a significant concentration (expressed by an equivalent partial pressure) gradient developed, leading to a reduction in oxygen concentration on the anode side (Fig. 2a) compared to those without the GBL (Fig. 2b). This indicates a lower oxygen flux towards the anode, which resulted in a reduced rate of hydrogen peroxide formation and lower concentrations in the MEA with the GBL. These results suggest that the presence of the GBL prevented degradation and enhanced the durability of the MEA.

In the presentation, we will present the details of the model and discuss strategies for further enhancing the durability of MEAs with the GBL by showing various case studies.

Figure 1
(Invited) Designing Cation Coordination from Bulk to Interface for Next-Generation Battery Electrolytes
Authors: Connell Justin G.
Published: December 2024

As demand surges for batteries that can deliver increased capacity and charging rates for electric vehicles, as well as low costs and long lifetimes for storing renewable energy on the grid, new electrolytes that can operate reversibly at increasingly aggressive conditions are essential. We have recently demonstrated that systems containing multiple anions represent a promising path forward for new electrolyte discovery. Specifically, differences in anion association strength to the working cation and the formation of mixed anion contact ion pairs (CIPs) in the electrolyte bulk via emergent solvation behavior can be used to independently tune the overpotentials for metal plating and stripping and improve overall performance. Furthermore, the addition of co-solvents can significantly modify cation coordination at the electrified interface, even in the absence of any measurable changes to bulk solvation structure. These concepts have been elaborated via a multimodal approach spanning electrochemical analysis, in situ/ex situ bulk and surface spectroscopy, and computational approaches. We have further demonstrated that cooperative anion effects are active for multiple working cations, which suggests a more general set of electrolyte design rules likely exists. Several examples will be presented where computationally guided exploration of anion combinations has led to the discovery of new, dual-anion electrolytes whose performance exceeds that of their single anion analogues.

_______________________

The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. http://energy.gov/downloads/doe-public-access-plan
Conduction Mechanism Study of Argyrodite-Type and Polymer-Ceramic Composite Electrolyte By Solid-State and PFG NMR Spectroscopy
Authors: Lee Young Joo , KIM Dokyung , Shin Yoonju , Kim Hyun Woo , Han Ji-Hoon , Ahn Sangdoo , Cho Young Whan
Published: December 2024

Solid-state electrolytes including inorganic ceramics, polymer, and composite polymer electrolytes have been intensively investigated as a key component for next-generation rechargeable batteries due to their low risk of fire and high energy density. Several criteria are required such as high ionic conductivity, electrochemical stability, compatibility and ductility with electrodes, and processability. Our focus relies on understanding the effect of the structural changes on the ion transport properties of various solid electrolytes by utilizing solid-state NMR and PFG NMR spectroscopy. Among various inorganic electrolytes, argyrodite-type sulfide electrolyte exhibits advantages owing to the relatively high ionic conductivity and flexibility. Thus, many attempts have been made to increase the ionic conductivity such as cation and anion doping. In particular, we investigate the effect of the anion substitution on the ion transport. By tuning the type and the size of the anion, the ionic conductivity can be enhanced. There have been controversies about the ion transport mechanism, i.e., rotation of anion influencing ion transport (paddle wheel effect), altered electronic interaction between anion and Li+, and increased defects, etc. On the one hand, polymer electrolyte has the advantages of high processability and the possibility to make good interfaces with electrodes, but, the ionic conduction is still limited by the segmental motion of the polymer. By incorporating ceramic particles into the polymer, both conductivity and mechanical strength can be improved. The conduction path can be only through a polymer network or by exchanging between the polymer network and particles. To increase the Li-ion conduction of polymer composite electrolytes, understanding the Li+ ion conduction pathway is important. In this work, we will present 1D and 2D solid-state NMR and PFG NMR spectroscopic studies to investigate the transport mechanism of anion-substituted argyrodite-type electrolyte and polymer composite electrolyte. We prepared various anion-substituted argyrodite-type electrolytes and compared spin-lattice relaxation times (T1) at various temperatures, revealing information about Li-ion conduction and anion rotation. By 2D 7Li-7Li NMR experiments, the conduction path involving both polymer matrix and solid ceramic particles and exchange between these two phases will be investigated. In contrast to the solid-state NMR which is sensitive to the localized motion, PFG NMR results show long-range transport motion of Li cations of various electrolytes. Our work will demonstrate that structural and dynamic knowledge about the materials obtained by various NMR techniques can help develop new materials for all solid-state batteries.
Overvoltage Analysis of the Heterogeneous-Structure Effect of PEMFC Cathodes
Authors: Tanaka Akihisa , Inoue Gen , Nagato Keisuke
Published: December 2024

Catalyst layer (CL) design of polymer electrolyte membrane fuel cells (PEMFCs) requires an understanding of the contribution of each physicochemical process to overvoltage. In this study, the effect of the heterogeneous CL structure on the overvoltage of each process was numerically analyzed. Using a previously validated model [1], a heterogeneous CL structure was constructed based on the fabrication conditions of an actual CL. The Pt catalyst was distributed, and the effective diffusion coefficients of oxygen and vapor and the effective conductivities of protons and electrons were calculated locally based on the void, ionomer, and carbon structures. For comparison, a homogeneous CL structure with an averaged local Pt content, effective diffusion coefficients, and effective conductivities was constructed. Subsequently, the reaction and mass transport were calculated using the heterogeneous and homogeneous models, followed by overvoltage separation based on local power losses. Figure 1 shows the local current density distributions and overvoltage differences of the two models calculated at a cell temperature (Tcell) of 80 °C, relative humidity (RH) of 50%, and an oxygen partial pressure (pO2) of 0.2 atm. The local current density in heterogeneous model has a discrete distribution, while that in homogeneous model has a continuous distribution. Although the activation overvoltage is smaller in the heterogeneous model, the overvoltage difference is relatively small. In contrast, the overvoltages of oxygen and proton transport are larger in the heterogeneous model. Furthermore, these mass transport-related overvoltages increase with increasing current density. In this contribution, the effect of the heterogeneous CL structure on each overvoltage will be comprehensively discussed by varying the operating conditions.

Reference

[1] A. Tanaka, G. Inoue, K. Nagato, and M. Nakao, Available at SSRN: http://dx.doi.org/10.2139/ssrn.4745148.

Figure 1
Water Management in the Gas Diffusion Layer of PEM Fuel Cells Using a Surface Energy Minimization Model
Authors: Herescu Alexandru
Published: December 2024

The main goal of this study is to investigate the propensity of liquid finger formation in the stable displacement regime. The formation of liquid fingers is beneficial for the water management in the Gas Diffusion Layer (GDL), by allowing the reactant gas to reach the proton exchange membrane while the water produced is being removed effectively. A surface energy minimization model of the water breakthrough process in the GDL is developed. The model simulates the water invasion through a pore inlet into a pore space. The pore inlet is defined by fiber segments having varied wetting properties, capturing in this way the water transport behavior in the presence of coating defects. The surface energy, volume, and the Laplace pressure of evolving droplets are determined using the proposed 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. As water invades the pore, mixed-non-wetting fingers form as the pressure follows a law depending on both geometry and wetting conditions, reaching a maximum at breakthrough. The model shows that the water fingers formation process is governed by the pore breakthrough pressure and by the energy barrier between different morphologies adopted by water droplets in contact with fibers. The breakthrough pressure and the energy barrier are determined for varied geometrical and wetting conditions, to outline GDL configurations which are desirable for optimal water management. Relevant parameters considered are the pore inlet area versus the pore volume, the fiber diameter, the wetting properties, and the extent of the coating defects on the GDL fibers.
Regulating Assembly of Porous Electrode Catalyst Layers
Authors: Srivastav Harsh , Radke Clayton J. , Weber Adam Z.
Published: December 2024

Polymer-electrolyte fuel cells (PEFCs) demonstrate remarkable potential in replacing non-renewable energy resources in paving the way for a sustainable future. PEFCs have fairly high efficiencies and energy densities, making them feasible for applications such as transportation and energy storage. The most expensive units of the PEFCs are the catalyst layers, traditionally composed of platinum interspersed on a carbon support with a perfluorosulfonic acid (PFSA) which stabilizes the ink dispersions as well acts as a binder for the dried catalyst layers. Despite the great importance of optimizing the composition of the catalyst layer to improve the practicality of PEFCs, predicting the performance of the final structure of the fuel cell remains a challenge.

In this talk, we outline an approach to predict key properties of the catalyst layers such as the porosity and particle sizes that compose it through mathematical modeling of the ink properties. We discuss a kinetics-based algorithm based on interacting particles that simultaneously solves for the size distributions of the particles and the pH of the ink, a parameter that can be used for verification. The results of the aggregation formulation will be fed into calculations to determine fundamental properties of the catalyst layer, such as porosity through a void fraction calculation. To verify the accuracy of this approach, we will compare against experimental data for varying concentrations and solvents. The insights gained from these considerations will enable efficient design of future catalyst layers.
Utilizing Distribution of Relaxation Times Analysis for Water Content Management in Anion Exchange Membrane Fuel Cells
Authors: Haodong Huang , Zhao Tianshou , Zeng Lin
Published: December 2024

Amid escalating concerns over air pollution and energy scarcity, Anion Exchange Membrane Fuel Cells (AEMFCs) are increasingly recognized as a viable solution for power generation, offering high efficiency, and zero emissions. Water plays a critical role within these systems as a reactant, consumed at the cathode and generated at the anode. This process can lead to disparities in water content, potentially compromising the cell's performance. Therefore, it is imperative to maintain optimal water distribution to facilitate effective charge transport and enhance electrochemical reaction kinetics. Consequently, devising a robust water management strategy is essential to ensuring the sustained operation and longevity of AEMFCs.

Characterizing the water conditions at the anode and cathode under various operational states (normal, drying, or flooding) is a pivotal step underpinning effective water management strategies. Electrochemical Impedance Spectroscopy (EIS) provides a valuable tool for examining various resistances associated with kinetics, mass transport, and ohmic losses across different operational timescales, thereby facilitating a detailed assessment of water transport dynamics. Traditional analyses of EIS data often depend on equivalent circuit models, which require predefined assumptions and the selection of initial components. However, this study adopted the Distribution of Relaxation Times (DRT) methodology for its exceptional capability to disaggregate components, enabling a more nuanced analysis of the polarization processes. The DRT methodology was applied to scrutinize the patterns of loss and variation within each polarization process under varying water flooding and drying conditions at the anode and cathode. Moreover, to deepen our comprehension of how water content influences mass transport and electrochemical reaction kinetics, a three-dimensional multi-physics model for AEMFCs was developed. This model comprehensively integrates considerations of water phase transitions, heat and mass transfer, as well as the transport of liquid and dissolved water, alongside electrochemical reactions. These efforts collectively forge a comprehensive and systematic framework to advance the application of the distribution of relaxation times in optimizing fuel cell performance.
Degradation Characteristics of Carbon-Supported Pt Via CO2 Detection during Startup/Shutdown of Polymer Electrolyte Membrane Fuel Cells
Authors: Ishikawa Seisho , Tanaka Akihisa , Oya Hirotaka , Koshiba Hideto , Yamashita Tsubasa , Hanaki Yasunari , Mizuno Yusuke , Nakao Masayuki , Nagato Keisuke
Published: December 2024

One of the major factors that reduces the durability of polymer electrolyte membrane fuel cells (PEMFCs) is degradation of the carbon-supported Pt in the catalyst layer, which can be attributed to the aggregation of Pt and the corrosion of carbon [1]. In this study, the degradation characteristics of a PEMFC during startup/shutdown were evaluated through detection of the CO2 generated during power generation tests. Non dispersive infrared-type (NDIR) analyzers have been shown to provide immediate and accurate measurements of carbon dioxide concentrations [2], and a pathway for the immediate measurement of CO2 concentration was established by connecting an NDIR analyzer to a test bench for the power generation tests. The degradation test of the PEMFC was repeated 100 times, involving the voltage sweep to 1.5 and 1.0 V and a voltage hold at 0.6 V. The PEMFC performance was evaluated using linear sweep voltammetry before the start of the tests and after every 10 sets of degradation tests, and the CO2 concentration was measured in parallel with the tests. As a result, the generation of CO2 and degradation of the PEMFC performance were confirmed. Figure 1 shows measured CO2 concentration during the degradation test, and approximately 3 ppm of the initial value is an offset derived from the measurement system. More CO2 was generated when the voltage was raised from 0.3 to 1.5 V than when it was raised from 0.6 to 1.5 V. Furthermore, the amount of CO2 generation decreased as the degradation tests were repeated, which can be explained by the passivation of some carbon atoms on the surface above 0.6 V. The study will be extended to investigate the effects of the voltage profile and carbon support type on degradation characteristics, contributing to the improvement of the durability of PEMFCs.

References

[1] N. Macauley et al., Carbon Corrosion in PEM Fuel Cells and the Development of Accelerated Stress Tests, J Electrochem Soc, 16, F3148‒F3160 (2018).

[2] E. Niangar et al., Real-time CO2 Detection from Carbon Support Oxidation in PEM Fuel Cell Cathodes during Potential Cycling, ECS Trans, 50, 1599–1606 (2013).

Figure 1
Impedance Based Comparison of PEMFC Cathode Catalyst Layer Materials
Authors: Schwab Kersten , Weber Andre , Heider Emanuel Albert , Joos Markus
Published: December 2024

The performance of Polymer Electrolyte Membrane Fuel Cells (PEMFC) is strongly dependent on the oxygen reduction reaction and therefore the cathode catalyst layer. Different catalyst layers with the same platinum loading can achieve vastly different performances. The exact composition of ionomer, carbon support and catalyst has a big impact on important electrode characteristic. These characteristics define the contributions of the loss processes that occur in the electrode. By improving one of the performance defining features of the catalyst layer, another one is oftentimes worsened. This creates a trade-off between the loss contributions and the catalyst design parameters.

Impedance spectroscopy (EIS) is a powerful tool to make these trade-offs visible. By calculating the distribution of relaxation times (DRT) the different loss processes can be deconvoluted and by fitting the impedance spectra to a physicochemical meaningful transmission line model, the loss processes can be quantified. In addition the electrochemical active surface area (ECSA) can be determined by cyclic voltammetry (CV) and correlated to the charge transfer losses.

In this contribution PEMFCs with different cathode catalyst layers and the same anodes are compared in a wide spectrum of operating conditions by means of EIS and DRT. On the basis of these measurements a transmission line model (TLM) is fitted to the impedance spectra and the loss contributions are quantified. The results enable a direct comparison of the cathode catalyst specific loss processes in different operating conditions. By means of CV and Hydrogen Underpotential Desorption, the ECSA is estimated and correlated with the loss contributions.
Cloud-Connected Labs of Future for Green Energy Materials
Authors: Malek Kourosh
Published: December 2024

The clean energy technology sector faces a major challenge with the pace of development trailing behind commercialization targets. The root cause hampering progress towards cleaner materials and technologies is that laboratories with complementary capabilities still largely operate in separation, with a lack of coordination among their efforts. The EU-funded DECODE project (DE-centralised ClOud Labs for inDustrialisation of Energy Materials) aims to break down these barriers by creating a decentralised and adaptive cloud-connect labs concept. DECODE aims at transforming the development and innovation process for clean energy materials and technologies. The project envisions the creation of a decentralized platform that connects multiple labs to enhance the effectiveness and accelerate the progress of research and development in the field of clean energy technology. The core elements of the platform consist of the DECODE FABRIC, a matrix-like structure that facilitates collaboration, and a scoring system to assess integration readiness of methods and tools. An AI-enabled CPU orchestrates contributions from partner labs.

The objective of DECODE is to digitally connect multiple labs, boost the effectiveness, and accelerate the development and integration of materials for sustainable hydrogen technologies. At its core, DECODE strives to develop and deploy three innovative modules: 1) the DECODE Foundry, a semantic search engine for assembling methods and tools into practical workflows, 2) the DECODE FABRIC, a matrix structure that connects modelling and characterisation suites, and 3) the DECODE CPU for end-to-end orchestration of a given materials development to integration pipeline. The platform, designed for unprecedented flexibility and interoperability, harnesses AI-driven data management and ontological mapping to enable the seamless collaboration among partner labs.

Initially focusing on hydrogen technologies, DECODE's vision may be expanded to other technologies including energy harvesting, storage, clean water and more. The platform strives for an unprecedented level of flexibility and adaptability, accommodating diverse strategies and technologies. In summary, DECODE accelerates clean energy innovation through interconnected labs, fostering a sustainable and cleaner future.