bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclohexanol Proportion Influence on Catalyst Paste Rheological Properties and Screen-Printed Hydrogen PEMFC Electrochemical Performance
Authors: Mendoza Pena Kassim Jose , Fukuda Takeshi , Tsuji Ryuki , Tanabe Maito , Satone Hiroshi , Ito Seigo
Published: December 2024

Nowadays environmental deterioration and global warming are among the principal concerns for humankind. One of the upstanding technologies to settle them is proton exchange membrane fuel cells (PEMFCs), where through an electrochemical reaction, oxygen and fuel (as hydrogen) are transformed into electric energy, water and heat, usually using carbon supported platinum (Pt/C) as catalyst and Nafion as proton conductive ionomer.

PEMFC production at the laboratory scale is mainly done by spray method, having some counterbacks such as catalyst wasting and slow deposition rate. Recently, the screen print method has caught attention worldwide for industrial-scale production of PEMFC since it was successfully employed in a variety of applications, such as solar cells, microelectronics, etc. This method consists of preparing a catalyst paste dispersing the catalyst with ionomer and solvents, once homogenized the paste is passed through a mesh and then deposited on a substrate in a single quick step avoiding material waste.

For an effective screen print process, a stable and workable catalyst paste is needed, being rheological properties and drying time the most important features to fit those needs. Despite water and low molecular weight alcohols being the typical solvents used for catalyst paste fabrication and the rheological properties of resulting pastes using these solvents are already reported [1], they do not fit the requirements for screen print industrial production.

On the other hand, cyclohexanol has a high viscosity and long drying time, being a promising alternative to obtain a paste suitable for the industry's needs, however, the rheological properties of a catalyst paste containing cyclohexanol remain unclear. In addition, it has been reported that this solvent has positive effects on the catalyst and ionomer interactions, enhancing the catalyst activity and improving mass transport [2].

In this research, several screen print catalyst pastes having the same final volume and different solvent proportions of water, 1 propanol, and cyclohexanol (W:1PA:CHN) were prepared. The same proportion of water and 1 propanol was kept but the proportion of cyclohexanol was gradually increased for each sample: (1:1:0), (1:1:0.5), (1:1:1), (1:1:2) and (1:1:3). Additionally, a sample containing only cyclohexanol was prepared (0,0,1) to discern the isolated effect of this solvent. From the resulting pastes, PEMFC were produced by the screen print method.

The relation between cyclohexanol content and catalyst paste rheological properties was investigated using a cone/plate rheometer, while the screen printed PEMFC electrochemical characteristics by the polarization curve, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), especially for evaluating proton conductivity.
Additives for Improving Chemical Stability of Polymer Electrolyte Membranes
Authors: Shin Dongwon , Kodir Abdul , Lee Hyejin , Bae Byungchan
Published: December 2024

Polymer electrolyte membrane (PEM) is a key component that affects the performance and durability of various electrochemical devices, including fuel cells and electrolyzers. Despite improvements in PEM performance, durability still needs to be improved. The lifetime of membranes deteriorates under operating conditions due to chemical degradation. This chemical degradation not only reduces electrochemical performance but also its mechanical integrity, ultimately leading to device failure. In recent years, many researches report that durability has been improved by synthesizing chemically stable polymers such as polyphenylenes. In addition, the incorporation of various additives into PEMs has emerged as a promising strategy to enhance chemical stability of membranes. The most commonly used additives to improve the chemical stability of PEMs are antioxidants. Since radicals are mainly generated by hydrogen crossover, additives that can reduce hydrogen crossover can also enhance the chemical stability.

In this study, we investigated the gas barrier properties of several additives and their impact on the performance and durability of PEMs. Gas barrier additives (GBA) were dispersed in polymer solution to form a membrane without phase separation or agglomeration. Composite membranes showed similar water uptake and mechanical properties to the pristine membrane. Although GBAs had excellent gas barrier properties, some of them decreased fuel cell performance. GBA effectively reduced the hydrogen permeation. We down selected GBAs that did not deteriorate fuel cell performance and conducted stability test under open circuit voltage (OCV) conditions. While monitoring OCV, hydrogen permeability and fluoride emission concentration were measured to confirm the degradation tendency of membranes. The durability of the composite membranes was improved compared to the pristine membrane. These results show that not only removing radicals using antioxidants, but also slowing down radical generation by blocking hydrogen crossover is effective in improving the chemical stability of the PEM.
Advanced Free Radical Scavenger for Proton Exchange Membrane Fuel Cells
Authors: Wang Liang , Jia Hongfei
Published: December 2024

Yttrium doped cerium oxide (CeO2·Y2O3) was studied as a free radical scavenger for PEMFCs. The CeO2·Y2O3 was compared with pure CeO2 in MEAs with and without the free radical scavenger. MEAs before and after 50 hours of OCV (open circuit voltage) hold accelerated durability test (AST) show better performance retention with CeO2·Y2O3 than CeO2. Both CeO2·Y2O3 and CeO2 show slightly improved performance than pristine MEA without free radical scavenger. ECSA, MA and EIS of the MEAs were analyzed to study the effect of radical quenchers to MEA performance and durability. XRF confirmed the improved Ce ions retention with CeO2·Y2O3 than pure CeO2, indicating improved stability of Ce ions after doping with Yttrium. Effluents from the anode and cathode of the fuel cells were collected and analyzed by fluoride ion selective electrodes at 25 hours and 50 hours of the AST. The fuel cell with CeO2·Y2O3 as a free radical scavenger has the lowest fluoride emission rate (FER). Furthermore, ex-situ Fenton study with ICP-MS analysis shows better stability of Ce in CeO2·Y2O3. This study shows that yttrium-doped cerium oxide has better stability against dissolution and enhances the stability of polymer components against free radicals than CeO2, which will benefit the long-term durability of the PEMFCs.
Preparation and evaluation of composite membranes using cellulose nanofibers (CNF)
Authors: Yasuda Tatsuki , Kakinuma Katsuyoshi
Published: December 2024

Polymer Electrolyte Fuel Cells (PEFCs) have several advantages, such as high efficiency and compactness, and are suitable for residential and mobile applications. The fluorinated polymers (e.g., Nafion) are typically proton-conducting membranes, which are used as the electrolyte of PEFCs under a wide range of humidity conditions, although the operation under low-humidity, high-temperature conditions decrease the proton conductivity due to water evaporation. Nafion membranes that have been prepared by mixing with transition metal oxide nanoparticles have shown higher proton conductivities, reaching values as high as 0.12 S cm-1 (80 ℃, 80% RH)1, 2. The improvement is based upon the increased hydrophilicity of the surface, which helps to maintain the membrane water content even at elevated temperatures. In the present study, we focus on the highly hydrophilic surface of carboxymethyl cellulose nanofibers (CMCNFs) and have investigated the proton conductivity of the composite membranes. The CMCNFs were mixed with Nafion (20 wt.%, DE2020 CS, Chemours) neutralized with potassium hydroxide, and formed into films by use of a die-coater (Taku-dai Mini-50 Daimon Co., Ltd.), with a final hot-pressing (160 ℃, 3 min. TCMD-2.5: TOHO KOGYO Co.). The proton conductivities of the composite membranes obtained were measured by the AC four-probe method. The types of water (chemically bonded, intermediate, and free water) present in the composite membrane were determined by the use of differential scanning calorimetry (DSC).

The composite membranes obtained were flexible and translucent. The proton conductivity of the composite membrane was 1.4 times higher (0.15 S cm-1) than that of a commercial Nafion membrane (NRE211) at 80℃, 80% RH, and was 1.3 times even at 80 ℃, 20% RH. The improved water retention properties achieved by mixing with CMCNF is considered to increase the proton concentration and proton conductivity. DSC measurements showed that bonded water (water that does not freeze down to -55 ℃) remained constant even with variations in the CMCMF content. The intermediate water, with a higher melting point range (melting between -55 ℃ and 0 ℃) increased with increasing CMCMF content. The increase of intermediate water in the composite membrane is considered to contribute to the proton conductivity.
Thin Reinforced Composite Membranes for Efficient Anion-Exchange Membrane Water Electrolysis
Authors: Song Hyeon-Bee , Lee Ji-Hyeon , Kang Moon-Sung
Published: December 2024

Recently, as the demand for hydrogen (H2) used as a raw material or fuel in various industries increases, interest in environmentally friendly water electrolysis technology is increasing. In particular, anion-exchange membrane water electrolysis (AEMWE) is receiving great attention as it is considered a cost-effective and stable process compared to the traditional proton exchange membrane water electrolysis (PEMWE). In the AEMWE system, the anion-exchange membrane (AEM) is a core material that facilitates the movement of OH- ions and determines the reaction rates of OER and HER. The AEM must have high ionic conductivity for OH- ions and low gas permeability, and excellent physical and chemical stabilities are required for long-term operation in alkaline conditions. In this study, therefore, a reinforced composite AEMs with excellent mechanical strength even at a thin film thickness were fabricated using various porous supports and their properties were systematically analyzed. For preparing AEMs, a polymer backbone and ion exchange groups with an excellent stability under harsh alkaline conditions were introduced. Moreover, the membrane development was conducted to simultaneously increase the degree of crosslinking and ion exchange capacity. The properties of the prepared AEMs were confirmed through AEMWE experiments, and the excellent current density and long-term stability were confirmed in 1 M KOH solution conditions. This work was supported by NRF grants funded by the Government of Korea (MEST) (NRF-2022M3C1A3081178 and NRF-2022M3H4A4097521).
(ECS Edward Goodrich Acheson Award) Improvements in Anion Exchange Membrane Water Electrolysis Materials and Devices
Authors: Kohl Paul , Park Habin , Gerber Hazel , Freer W. Henry , Yang Xiaoxuan , Li Chenyu
Published: December 2024

Green hydrogen is a critical energy carrier for the future net-zero carbon emission by 2050. Anion exchange polymer electrolytes enable the use earth-abundant catalysts, non-fluorinated solid polymer electrolytes, and low-cost cell components for sustainable, low-temperature water electrolysis to produce green hydrogen. However, long-term durability of the anion exchange membrane water electrolysis (AEMWE) needs to be demonstrated at high current density (i.e., > 1 A/cm2). AEMWE can be operated with a more gentle (i.e., lower) hydroxide anolyte feed for improved chemical durability, however, the cell overpotential has shown to increase at lower pH.

New materials and operating conditions have been demonstrated which contribute to improved durability and energy-efficiency by the use of (i) stable ion conductive polymer membranes, (ii) self-adhesive electrode ionomers, and (ii) a high ionic strength anolyte without raising the pH. The increase in cathode hydration (where water is reduced to hydrogen) is critical to achieving durable, higher current performance. The cathode hydration level was improved in several ways including the use of hydrophilic ion conducting polymer in the membrane and cathode. A self-adhesive poly(norbornene) terpolymer ionomer has been developed for durable electrode fabrication where the hydrophilicity of the electrode environment was adjusted for each electrode. The ionomer was covalently bonded to a catalyst and the gas diffusion layer to achieve stable electrolysis under vigorous gas evolution. The rate of water transport through the AEM was improved by use of a lower pH, higher ionic strength anolyte. It has been shown that increasing the ionic strength of the anolyte, without increasing the pH, assists in water delivery to the cathode. The uptake of alkali cations within the AEM plasticizes the AEM (i.e., increases ion diffusivity) and migration of the hydrated cations to the cathode increases the overall water transport. Finally, improvements in the anion exchange membrane synthesis and fabrication have been found which can lower the overall electrolysis cost. Long-term AEMWE durability with the optimized electrodes and low pH/high ionic strength anolyte is demonstrated.
Characterization of Water Flux across Anion-Exchange Membranes
Authors: Weiss Catherine M. , Yan Yushan , Weber Adam Z.
Published: December 2024

The anion-exchange membrane (AEM) is the key component to optimize overall water flux in anion-exchange-membrane fuel cells (AEMFCs) for performance and durability. For alkaline hydrogen oxidation reaction (HOR) in the anode, 4 water molecules are produced for every 4 electrons, and for alkaline oxygen reduction reaction (ORR) in the cathode, 2 water molecules are consumed for every 4 electrons. Water molecules also transport across the AEM from the cathode to the anode along with the hydroxide due to electroosmosis. Due to the reactions and electroosmosis, large water concentration gradient develops, driving water transport from the anode back to the cathode which is essential for ORR and ionomer hydration. Insufficient water in the cathode catalyst layer can lead to ionomer dry-out which exacerbates ionomer degradation, so it is imperative to have an AEM with high water permeability and diffusivity. To quantify the water diffusivity for vapor-equilibrated PiperION-A AEMs of 13, 20, 40, and 80 µm thickness, we use an in-house built water flux station under inert conditions with varying degrees of water vapor, and we report the water transport resistance as a function of the average water activity at 80°C, a standard operating temperature for AEMFCs. Insights into understanding the water transport phenomena in AEMs as a function of thickness and water content is crucial for designing AEMFCs to overcome the challenging water balance for improved performance and durability.
Performance Improvement of Chemically Durable PVA Gas Barrier PEM by Optimizing the Interlayer Thickness
Authors: Gautama Zulfi , I Yang , Lyth Stephen Matthew , Sasaki Kazunari , Nishihara Masamichi
Published: December 2024

Polymer electrolyte fuel cell (PEFC) is a portable and clean power source suitable for decarbonizing the transport sector. Recently, PEFC has been developed as a power source for heavy-duty vehicles which requires further improvement on its components, such as the durability of the polymer electrolyte membrane (PEM). One of the challenging issues on PEM is suppression of chemical decomposition of PEM. Several decomposition mechanisms of PEM are proposed like the reactions of crossover oxygen to form hydrogen peroxide (H2O2) at the anode site or deposited platinum in PEM. H2O2 is a starting material of a radical which decomposes the polymer chain of PEM. To mitigate this issue, we have designed a gas barrier PEM which can suppress oxygen penetration through PEM by incorporating a gas barrier polymer layer in between two Nafion layers (Fig. 1a). In a previous study, we loaded 0.5 mg/cm2 of PVA/PVS blend (Fig. 1b) with 100:1 molar ratio as the gas barrier interlayer, which consequently improved the chemical durability by 1.7 times than Nafion under in-situ accelerated stress test (OCV holding test) [1]. However, the fuel cell performance of this gas barrier PEM could only reach 70% of the Nafion’s current density at 0.6 V. To practically use our gas barrier PEM concept as a viable mitigation strategy against chemical decomposition, the fuel cell performance must be improved.

To improve the fuel cell performance of the gas barrier PEM, we focused on optimizing the thickness of the gas barrier interlayer. The interlayer majorly affects the resistance of gas barrier PEMs due to its low proton conductivity. On the other hand, an interlayer with enough thickness is also important to achieve high chemical durability by high gas barrier property. Therefore, we developed thinner gas barrier interlayer with enough high gas barrier property and low resistance. After optimizing the interlayer thickness, we optimized the conditioning procedure for the selected gas barrier PEM to achieve similar catalytic activity with the Nafion MEA.

In this presentation, the effect of interlayer thickness reduction towards fuel cell performance of gas barrier PEM will be discussed in detail. In addition, we also observed that preparation of the gas barrier PEM affected to the MEA performance. Therefore, we optimized the conditioning procedure of the MEA. In this presentation, we selected PVA 0.1 (interlayer loading: 0.1mg/cm2, interlayer thickness: 1 mm, total PEM thickness: 17 mm, PVA: PVS =100:1 (mol)) to have the best balance between fuel cell performance (90% of Nafion’s current density at 0.6 V) (Fig. 1c) and gas barrier property (30% lower hydrogen crossover at 80°C 95% RH). From several results, we confirmed that the PVA 0.1 demonstrated higher chemical durability than Nafion with the same thickness in OCV holding test (Fig. 1d).

References

[1] Gautama, et. al, J. Membrane Science, 2022, 658, 15, 120734.

Figure 1
Transport Properties and Morphology of Cerium Oxide Composite Sulfonated(Poly Arylene Ether Sulfone) Membranes for Application in Heavy-Duty Fuel Cell Vehicles
Authors: Gangavarapu Pranathi , Foister Shane , Goenaga Gabriel , Zawodzinski Thomas A.
Published: December 2024

Fuel cells for Heavy Duty Vehicles (HDVs) offer easy scalability and the potential for critical reduction in CO2 emissions. During the drive cycles of HDVs, the fuel cells will operate over a range of temperatures, with increases while climbing up steep gradients. Operating temperatures above 90°C will be necessary, along with low relative humidity (RH) due to the need to avoid pressurization of gases. Therefore, Proton Exchange Membranes (PEMs) for HDV applications need to be suitable over this range of conditions, including functioning at high temperatures and low relative humidity. Moreover, the membranes should not swell extensively when more water is present.

In this study, sulfonated poly (arylene ether sulfone) multiblock copolymers were modified with the incorporation of clusters of modified cerium oxide nanoparticles to form composites. These synthesized novel membranes approach operational proton conductivity requirements for HDV vehicles, with conductivity of 15mS/cm at 120°C and 25% relative humidity, remarkably avoiding the typical large decrease in conductivity observed below 70% RH in non-fluorinated PEMs. One purpose of this study is to understand the water, proton, and polymer interactions within these membranes. The cerium nanoparticles and sulfonamide clusters play a critical role in the membrane, affecting conductivity, and water transport, especially at high temperatures and low relative humidity, while also suppressing swelling of the membrane. Membrane proton conductivity is also strongly influenced by physical properties such as water uptake and dimensional swelling behavior, which is further impacted by polymer morphology. To probe the dynamics of the components, the diffusion coefficient and relaxation time of water in the membrane and the protonic conductivity of the membrane as functions of membrane water content are analyzed using nuclear magnetic resonance (NMR) measurements and water uptake measurements. Film property and morphology changes are evaluated using Transmission Electron Microscopy (TEM) and Small-Angle X-ray Scattering (SAXS). This study demonstrates the advantageous and non-linear benefits of closely packed acid clusters with cerium oxide composites on membrane functionality under HDV operating conditions.
Improving the Durability of Perfluorosulfonic Acid Membrane in Pemfcs Using Cerium-Based Radical Scavengers Including Organic Ligand Group
Authors: Lee Byeol-Nim , Cho Hyungkyu , Kim Bonghyun , Lim Jaemuk , Munsur Md Abu Zafar Al , Lim Tae-Hoon , Kim Hyoung-Juhn
Published: December 2024

Polymer electrolyte membrane fuel cells (PEMFCs) are promising alternative power sources for stationary and automotive applications due to their low exhaust emissions and quick start-up and load response. However, the widespread commercialization of PEMFCs is still challenging to meet the cost and durability. Therefore, enhancing the durability of the PEMFC stack is the most important aspect of recent studies through improving the electrochemical and mechanical stability of major components such as polymer electrolyte membranes (PEM). The main factors contributing to the durability deterioration of PEM are chemical and mechanical degradation caused by the inescapable generation of hydroxyl and hydroperoxyl radical species through gas crossover during PEMFC operation.1 Several studies have proven using the cerium ions as radical scavengers effectively mitigates the chemical degradation of PEMs to solve these problems. Although cerium is an effective radical scavenger, it can be combined with sulfonic acid groups to lower the proton conductivity during cell operation.2

In this study, we aimed to mitigate the polymer electrolyte membrane chemical degradation and minimize proton conductivity deterioration by introducing an organic ligand group to cerium-based radical scavengers. The cerium-based radical scavengers were incorporated into the catalyst ink at different concentrations, and membrane electrode assemblies (MEAs) were subsequently fabricated by spray-coating onto perfluorosulfonic acid membranes using the prepared catalyst inks. The chemical stability of the MEAs including radical scavengers was evaluated by open circuit voltage (OCV) decay and electrochemical gas crossover at high temperatures and with low relative humidity (RH) reactant gases. The fuel cell performance was also conducted using the polarization curve, impedance, cyclic voltammetry, and linear sweep voltammetry at 80 °C and 100% RH conditions. The Cerium-based radical scavenger incorporated PFSA membrane showed significantly extended lifetimes during the steady-state OCV test as compared with a non-stabilized PFSA membrane. The MEA performance tests confirmed that the cerium-based radical scavenger dramatically mitigates degradation effects, which improves MEA chemical durability and minimizes performance losses.

References

[1] M. Zaton et al., Sustainable Energy Fuels 1 (2017) 409–438.

[2] B.P. Pearman et al., J. Power Sources 225 (2013) 75-83.

Figure 1
(Invited) Characterization of Atomic- and Nano-Scale Defects in Ni-Rich Layered Cathode Materials through Neutron and X-Ray Scattering Techniques
Authors: Kim Hyungsub
Published: December 2024

Ni-rich layered cathode materials have garnered significant attention as promising candidates for Li-ion batteries due to their high energy density. Although extensive research efforts focus on enhancing the structural stability of these materials through elemental doping, surface coating, and the use of electrolyte additives, the intrinsic chemical-mechanical instability caused by atomic- and nano-scale defects during the synthesis process remains a substantial challenge.

Recent studies have focused on improving the cycle life of Ni-rich layered cathodes by fundamentally enhancing Li/O insertion. These enhancements have been achieved by regulating key parameters, including excess-Li content, temperature, and oxygen atmosphere during synthesis, often without the need for additional treatments. Additionally, a pre-calcination stage at 200–500°C is typically employed during synthesis to efficiently decompose the precursor. However, the precise rationale behind Li overloading remains largely unexplored, and comprehensive studies on the impact of the pre-aging process on the crystal structure and morphologies of Ni-rich NCM materials are notably scarce.

In this study, we investigate the atomic- and nano-scale structural evolution of the Ni-rich layered cathode using X-ray/neutron scattering and electron/X-ray microscopy. Our findings reveal that excessive Li can be integrated into the transition metal layer of the layered structure by modulating the Li content and synthesis temperature. We present the first quantification of nanoscale pores in primary and secondary particles of the Ni-rich cathode using small-angle X-ray and neutron scattering analyses. Furthermore, we propose a simplified synthesis route aimed at mitigating the formation of multi-scale defects in Ni-rich layered cathodes, leading to superior electrochemical cycle stability. This research provides crucial insights into defect characterization and management, potentially driving advancements in the design and production of high-performance Ni-rich layered materials.
(Invited) Magnetic Field Imaging for Fault Diagnosis of Lithium-Ion Batteries
Authors: Lee Hongkyung
Published: December 2024

The popularity of Li-ion batteries for electric vehicles has spotlighted their importance in safety. Nonetheless, they can accidentally fail sometimes due to small, undetectable errors during manufacturing or use. Identifying these flaws and distinguishing between different types of cell failure without physically opening the cell presents a significant challenge. Although minor errors inside the cells can trigger catastrophic failures, tracing them and distinguishing cell failure modes without dissecting the cell remains difficult. Since various defects within the cell could cause abnormal current flow compared to normal cells, visualizing the current inside the battery allows us to pinpoint and track these invisible defects over large-area cells. Focusing on how the current moves inside the battery helps us uncover and address hidden defects, enhancing battery safety and ensuring the reliability of Li-ion batteries.

This talk introduces a real-time, non-invasive magnetic field imaging (MFI) tool capable of detecting the magnetic field signal induced by abnormal current flow inside fault-simulated Li-ion pouch cells. MFI offers high-speed scanning (~100 mm/min) and high spatial resolution (0.161 mm) with the benefits of simple instrumentation and the acquisition of directional information. By validating the Biot-Savart law, normal current flow patterns can be identified through cross-validating simulation studies and experimental results using MFI. To demonstrate the efficacy of current flow pattern analysis in battery fault diagnosis, the MFI study was extended to identify detectable defects among various flaws and to determine if the severity of these defects can be quantified by building experimental and simulational fault-simulated cells. Direct visualization of current distribution patterns and understanding pattern changes during operation is believed to expedite the non-destructive, immediate diagnosis of commercial cells and address safety-related challenges.
Synchrotron-Based Characterizations of Electrocatalytic Metal-Organic Frameworks and Covalent Organic Framework-Based Solid Electrolyte Interphase for Stabilizing Anode of Rechargeable Batteries
Authors: Wannapaiboon Suttipong , Aupama Vipada , Kheawhom Soorathep
Published: December 2024

Considering energy-related technologies including rechargeable batteries and water electrolysis, effective catalytic materials play a crucial role in the rise and unceasing development. Metal-organic frameworks (MOFs) have drawn attention due to their abundant and identical catalytic sites along the periodic network with tunable catalytic functionality and stability. Herein, structural information, catalytic sites, and their corresponding mechanistic pathways have been investigated by employing synchrotron-based X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The framework stability, the accessible active sites related to pre-designed metal clusters, the alteration of oxidation state of, and the coordination geometry around the active metal centers evolving along the electrochemical oxygen evolution reaction (OER) are thoroughly revealed. In addition, aqueous zinc-ion batteries (AZIBs) are promising energy storage systems due to their cost-effectiveness and eco-friendliness. However, there are some limitations restricting their practical utilizations such as the high activity of water leading to Zn corrosion and hydrogen evolution, along with the formation of dendrites on the Zn surface during repeated charge–discharge cycles. To limit parasitic side reactions, an artificial solid electrolyte interphase (ASEI) protective layer made of a covalent organic framework (COFs) is an effective strategy. Herein, grazing-incidence XAS was employed to specifically characterize the Zn speciation on the electrode surface. According to XAS results, the protective COF-ASEI layer can retard the coordination of water at the electrolyte–Zn interface, improve Zn plating/stripping kinetics, and increase the stability of the Zn anode. This presentation highlights the significance of synchrotron characterizations in energy-related technologies.
Study on Water Distribution Depending on the Cathode Gas Diffusion Layer in PEFC
Authors: Oh Ji-Hyun , Kang Yun Sik , Park Seokhee , Woo Seunghee , Yim Sung-Dae
Published: December 2024

In polymer electrolyte fuel cells(PEFCs), the gas diffusion layers(GDLs) are critical in providing effective pathways for reactant gases from flow field channels to the catalyst layer surface. Moreover, these layers are crucial in managing the expulsion of water, ensuring optimal cell performance by maintaining the necessary hydration levels and preventing flooding of the catalyst layer. This dual functionality underscores the significance of GDLs in enhancing the overall efficiency and durability of PEFCs. This study investigated the water distribution within PEFC using two different types of GDL(Sigracet 39 AA and 39 BB, SGL Carbon Co.) with distinct characteristics. Utilizing a non-contact laser absorption spectroscopy detector(dew point measurement, HS-1000), we conducted in-situ measurements of water distribution under various experimental conditions. The results demonstrate variations in hydration levels, which are associated with the porosity and material composition of the GDL. Understanding of water management will improve cell efficiency and facilitate the development of effective GDL designs.
Protonic Vs. Gas Transport Resistance in Hydrocarbon-Based Catalyst Layers: A Trade-Off Analysis for PEM Fuel Cells Under Low Humidity Conditions
Authors: Liepold Hannes , Vierrath Severin , Münchinger Andreas
Published: December 2024

Recent developments in hydrocarbon-based proton exchange membrane (PEM) fuel cells have significantly narrowed the performance gap compared to state-of-the-art cells using perfluorosulfonic acid (PFSA) ionomers. However, at low relative humidity (RH), challenges persist in balancing sufficient proton conductivity and minimizing gas transport resistance in the electrodes. Understanding these limitations is essential to increase performance and enable future applications of hydrocarbon-based PEM fuel cells.

This study addresses these challenges by systematically investigating both the gas transport resistance and the influence of protonic conductivity on the performance of sulfonated phenylated polyphenylene-based electrodes. Results reveal an increased protonic resistance stemming from reduced thin film conductivity and enhanced cathode tortuosity at ionomer-to-carbon (I/C) ratios lower than 0.4. Reducing the I/C ratio and operating at relative humidities approaching automotive conditions (e.g., below I/C = 0.4 and 65% RH) led to a significant drop in electrode protonic conductivity. Subsequently, a highly non-homogeneous current distribution within the cathode catalyst layer is formed, resulting in modeled and experimentally verified low platinum (Pt) utilization.

At I/C ratios higher than or equal to 0.4, the electrode's protonic resistance approaches values of typical PFSA-based catalyst layers. Nevertheless, this leads to a notable decline in performance due to the rise in local and pore network-related gas transport resistance. Additionally, the local transport resistance was found to strongly positively correlate with the ion exchange capacity of the ionomer, complicating the trade-off between low gas transport resistance and high electrode conductivity. Reducing the catalyst layer thickness (e.g., by increasing the platinum-on-carbon ratio) offers an experimentally verified opportunity to increase overall hydrocarbon-based fuel cell performance by minimizing both gas transport resistance and protonic resistance in the electrode.

The observed trends offer valuable insights for guiding future optimization in the development of novel HC ionomers.
Development of Mesoporous Carbon Supports for PEFC
Authors: Hutapea Yasir Arafat , Doi Hiroki , Hayashi Akari
Published: December 2024

Introduction

Polymer electrolyte fuel cells (PEFCs) have been commercialized as fuel cell vehicles, but further improvement of IV performance is required for applying to heavy-duty vehicles. Regarding to TOYOTA MIRAI, 2nd generation MIRAI made a lot more improvement in comparison to 1st generation MIRAI, and mesoporous carbon (MC) supports are known to have largely contributed for such improvement. Our group have also been working on MC materials since 20061. In our recent study, with newly developed MC, IV performance at the high current density region is very much improved. However, at this moment, what factor of MC has contributed for such improvement is no clear.

In this study, the fundamental porous structures of MCs are deeply analyzed. Then, the correlation to IV performance is discussed.

Experimental

New MC was synthesized in the following. Pluronic F127 and carbon precursors, composed of phloroglucinol dihydrate, formaldehyde, and ethyl orthoacetate, were well mixed in the acidic water/ethanol solvent. Additionally, PVA solution was added and stirred. The heat treatments were done in N2 for decomposing Pluronic F127 and carbonizing carbon precursors. Resulting new MC was ball-milled into small particles and used for catalyst supports. For the use of a cathode catalyst, Pt deposition was done by using a precursor, Pt(NO2)2(NH3)2, by reducing with alcohol according to the reported method2. Also, membrane electrode assemblies (MEAs) were prepared by spray printing 0.3 mg Pt/cm² using TEC10E50E and Pt/MCs for the anode and cathode, respectively, within 1 cm² area of Nafion 212 membrane.

Results and Discussion

Resulting new MC shows a broad pore size distribution with the peak around 10 nm based on N2 sorption measurements were done for new MC. The specific surface area of mesopores and external results in 350 cm2/g. TEM observation was also done to check the mesoporous structure and the image is shown in Figure 1. Highly porous structure was confirmed. The further detail analyses on mesoporous structure are under consideration. Since several MCs have been developed in our group, the difference in mesoporous structure is discussed, and then the correlation to IV performance is studied.

References

Hayashi et al., Electrochim. Acta, 53(21), 6117 (2008).

M. Rahman et al., RSC Adv., 11, 20601 (2021).

Figure 1
Patterned Hybrid Electrodes for Improved Fuel Cell Performance
Authors: Ince Alper Can , Liyanage Wipula , Arman Tanvir Alam , Pasaogullari Ugur , Komini Babu Siddharth , Spendelow Jacob S.
Published: December 2024

Abstract

Polymer electrolyte membrane fuel cells (PEMFCs) present a promising zero carbon emissions alternative to internal combustion engines. However, PEMFCs face performance limitations, particularly in heavy-duty vehicle applications, largely attributed to cathode electrode inefficiencies. Conventional electrode structures often result in non-ideal tortuous pathways for oxygen (O2) and protons (H+), leading to decreased performance and durability. In this study, we present a novel hybrid electrode structure fabricated using patterned silicon (Si) templates. These templates, created via photolithography and deep-reactive ion etching, facilitate the formation of ordered plus-shaped electrode structures with uniform depth and width. Catalyst with a different ionomer loading/composition is deposited in-between the element of the plus-shaped electrode structure. The resulting novel arrangement in the hybrid electrode structure enables enhanced H+ transport, due to the higher ionomer content in the plus-shaped electrode structures. Additionally, strategically placed dedicated electrode regions with lower ionomer content between the plus shaped electrodes promotes effective O2 transport to reaction sites. We will present the fabrication process, the performance enhancement through this alternative electrode structure and its contribution to the improving the durability of the fuel cells compared to conventional electrode architectures.

Acknowledgement

This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos. Authors would also like to acknowledge support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) (20200200DR).
The Impact of Support Carbon Properties on Ionomer Adsorption on Pt/C in Polymer Electrolyte Fuel Cell Catalyst Ink
Authors: Yoshino Shuhei , Harada Masashi , Hasegawa Naoki , Yomo Shuji , Koiwai Akihiko , Yamakawa Shunsuke , Jinnouchi Ryosuke
Published: December 2024

In polymer electrolyte fuel cells, both the coatability and dispersion stability of catalyst inks, as well as the structure of the catalyst layers, are significantly influenced by the agglomerate structure of the platinum-supported carbon (Pt/C) in the catalyst ink. The previous study reported that the ionomer adsorbed onto the Pt/C mainly determines this agglomerate structure. The study also presented that the ionomer adsorption is promoted by enhancing the solvent polarity, via intensifying hydrophobic interactions between the carbon and the ionomer backbone [1]. However, little is known about the impact of Pt/C aggregate properties, such as size, surface area, and surface hydrophobicity. The aggregate is the indivisible building block of the agglomerate, serving as the site where the ionomer adsorbs, and is composed of primary particles.

Here, we present the impact of Pt/C properties on the ionomer adsorption. As shown in Fig. 1, the measured ionomer adsorption ratio Γ, which is defined as the ratio of the adsorbed ionomer to the total ionomer in the catalyst ink, can be accurately described as following Eq. (1),which is illustrated in Fig. 2, where Df and Ragg are the fractal dimension and radius of Pt/C aggregate, Am is the specific surface area of support carbon excluding the mesopore surface area (< 5 nm),ρacid is the surface density of the acidic functional groups on the carbon surface, and ρmax
acid
is the maximum value of at which ionomer adsorption ceases. The coefficients C0 and C1 are the parameters optimized to reproduce the measured Γ.

The function represents the relationship between Γ and each property of the Pt/C particles as depicted in Fig. 3. As the surface area of support carbon increases, support carbon becomes capable of adsorbing more ionomers. Hence, Γ is proportional to Am. On the contrary, as the Pt/C aggregate, which consists of primarily particles, becomes larger and/or exhibits higher fractal dimension, Γ decreases because ionomers cannot penetrate into the interiors of aggregates. Hence, Γ is inversely proportional to Df and Ragg. In addition, Γ is also influenced by the hydrophilicity of carbon surfaces. In ρacid < ρmax
acid, the carbon can adsorb a nearly constant amount of ionomer regardless of via hydrophobic interactions, while the amount sharply decreases in ρacid ≥ ρmax
acid. The stepwise behavior is represented by 1 / (1+C0 exp⁡{-k(1-ρacid /ρmax
acid)}). Eq. (1) reasonably represents the observed trends and is highly beneficial to design the Pt/C agglomerate structure allowing for stable processing and high performance.

Reference

[1] Yoshino, S.; Harada, M.; Hasegawa, N.; Jinnouchi, R. Effects of Solvent Composition on Agglomerate Structure in Catalyst Ink for Polymer Electrolyte Fuel Cells. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2024, 133847. DOI: https://doi.org/10.1016/j.colsurfa.2024.133847.

Figure 1
Influence of Catalyst-Layer Defects on PEMFC Degradation
Authors: Oya Hirotaka , Tanaka Akihisa , Ishikawa Seisho , Yamashita Tsubasa , Hanaki Yasunari , Mizuno Yusuke , Nakao Masayuki , Nagato Keisuke
Published: December 2024

Improving the durability of polymer electrolyte membrane fuel cells (PEMFCs) is essential for expanding their applications. Defects in the catalyst layers of PEMFCs may occur during their manufacturing or operation; however, the influence of these defects on PEMFC degradation has not yet been clarified. Carbon corrosion is a major factor affecting PEMFC degradation. It leads to the detachment of Pt, resulting in a reduction in the reaction surface area. Our study focused on the influence of the defects in the catalyst layer on carbon corrosion and performance degradation. Previous studies have reported that carbon corrosion progresses mainly under the conditions of either proton deficiency or potential fluctuations [1, 2].

Figure 1 shows two types of membrane electrode assemblies (MEAs) with the electrode areas of 1 cm2. One had no defects, whereas the other had a defect with a diameter of 6 mm at the center of the anode catalyst layer. The CO2 concentration in the cathode outlet gas was measured under several rectangular potential fluctuations to evaluate the amount of carbon corrosion. Figure 2 shows that the amount of carbon corrosion increased as the upper potential increased or the lower potential decreased in both the MEAs with and without defects. The MEA with a defect exhibited a higher amount of carbon corrosion than the MEA without defects at all potential fluctuations. The rate of increase varied for each potential fluctuation and ranged from 9% to 26%. In this study, the influence of several types of defects in the catalyst layers on the performance degradation is discussed using the amount of carbon corrosion.

References

[1] C. J. Banas et al., J. Electrochem. Soc., 165, F3015 (2018).

[2] N. Macauley et al., J. Electrochem. Soc., 165, F3148–F3160 (2018).

Figure 1
3D-Printed Gas Diffusion Layers for Enhanced Mass Transport in Polymer Electrolyte Fuel Cells
Authors: Doerenkamp Tim , Buechi Felix N. , Schmidt Thomas J. , Eller Jens
Published: December 2024

Water management in polymer electrolyte fuel cells (PEFC), particularly the accumulation of liquid product water in the gas diffusion layer (GDL) on the cathode side, which mitigates the oxygen transport towards the catalytic surface, must be optimized for ideal performance [1]. The potential of 3D-printing has recently gained interest in the field of electrochemical flow cells to investigate and improve mass transport in porous transport layers of various applications, including PEFC [2,3,4].

In this study we explore different 3D-printed structures that are used as cathode GDLs for PEFC. The objective is to guide the liquid product water through determined pathways by adjusting the throat size to form preferential percolation routes according to Young-Laplace law [5]. The GDLs are obtained from a 3D-printed polymer precursor that is subsequently carbonized in a tube furnace (Tc = 1200°C in N2 atmosphere, result shown in Figure 1a) and treated with a hydrophobic surface coating. The structures are assembled in a cell designed for X-ray diagnostics together with a commercial Freudenberg H2315C2 anode GDL and a Gore Primea CCM (A510.1/M815.15/C510.4) to form the membrane electrode assembly (MEA). The cross-section of one of these cells obtained from X-ray tomography is exemplarily shown for a “through-plane” cathode GDL in Figure 1b. To track the liquid water distribution and saturation in the GDL we perform current jumps from dry state to various current densities and employ operando X-ray radiography with a Lab CT, with a frame rate of 2 Hz. Additionally, the 3D water distribution after reaching steady state is captured by X-ray tomography at the end of each current jump experiment. Furthermore, we measure the electrochemical performance (see Figure 1c) and compare our results to a reference case (Toray, carbon paper GDL).

Figure
1
. a) SEM images of the carbonized structure b) Cross section obtained from X-ray tomography of the cell assembly with the through-plane GDL c) Polarization curves and HFR of the through-plane cell as well as a reference cell with a commercial Toray material (two TGP-090 w. 10% PTFE sandwiched together). The cell was operated with H2/Air at T=50°C, p=1bar and 100% relative humidity on both sides

References

[1] J. Ihonen et. al., Journal of the Electrochemical Society, 2004, 151, pp. A1152-A1161

[2] D. Niblett et. al., International Journal of Hydrogen Energy, 2022, 47, pp. 23393-23410

[3] M. v. d. Heijden et. al., Advanced Materials Technologies, 2023, 8, 2300611

[4] B. Huang et. al., Angewandte Chemie International Edition, 2023, e202304230

[5] D. Niblett et. al., Journal of Power Sources, 2020, 471, 228427

Figure 1