bluuebunny/crossref_metadata_2025_split huggingface dataset:
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
On the Tuning of the MPL’s Cracked Area for Optimizing the Performance of Polymer Electrolyte Fuel Cells
Authors: Galante Bruno , Herranz Juan , Buechi Felix N. , Gilardi Raffaele , Guglielmi Angelo , Buades Begona , Eller Jens 
Published: December 2024

The cracks in Micro Porous Layers (MPL) can have a significant impact on the performance of Polymer Electrolyte Fuel Cells (PEFCs) [1–4]. For such a reason, the interest in researching and understanding the crack formation processes, as well as studying their final morphology, is rapidly increasing [2-4]. In this contribution, we propose a method for tuning the MPL’s cracked area and an analysis of the superficial and intersected cracks through a combination of optical microscopy, XTM (X-ray Tomographic Microscopy), and image processing. An example of optical images of MPLs with different cracked areas and the results of the segmentation process applied to them is reported in the Figure. After segmentation, the calculation of the cracked area yields values of about 4.5%, 1%, and < 0.1%, respectively, for the images in the Figure. By having good control and thorough characterization of the cracked area, we target a conclusive correlation between the cracked area and fuel cell performance. This is made possible by testing the cells in dry and wet conditions and by analyzing how the polarization curve and the oxygen transport resistance vary for MPLs with different amounts of cracked areas. In such a way, we aim to answer two questions: “Are the cracks beneficial for fuel cell performance?”; and most importantly: “What is the amount and type of cracks that optimize the fuel cell performance?”.
References:

Z. Chen et al. “Crack evolution during the film drying process of fuel cell microporous layer ink.” In: Colloids and Surfaces A - Physicochemical and Engineering Aspects 650.129283 (2022).

J. Dai et al. “Analysis on the influence of crack structure on MPL transmission properties.” In: Journal of Power Sources 562.232790 (2023).

S. Wang et al. “Enhancing the properties of water and gas management for proton exchange membrane fuel cells via tailored intersected cracks in a microporous layer.” In: Journal of Power Sources 533.231402 (2022)

Z. Chen et al. “Interrelation between ink viscoelasticity and crack structure of fuel cell microporous layer.” In: Fuel 360.130629 (2024).

Figure 1
Method for Precise Oxygen Resistance Analysis in Polymer Electrolyte Membrane Fuel Cells Under Various Operating Conditions
Authors: Chun Hyunsoo , Lee Youngseop , Kim Jiwoong , Chang Jung Hyo , Kim Jin Young , Min Kyoungdoug 
Published: December 2024

The simultaneous changes occurring in the internal materials of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) under dynamic operating conditions make characterizing the inherent resistance of each material under different operating conditions highly complex. Therefore, the isolation of the internal resistance of components and the identification of the resistance elements that significantly affect PEMFC performance are essential, but comprehensive studies analyzing the internal resistance under different operating conditions have been scarce.
This study proposes a complex resistance analysis methodology capable of isolating the oxygen resistance of a PEMFC single cell under different operating conditions (relative humidity, temperature, supply gas). The Knudsen diffusion within the catalyst layer is calculated according to the operating conditions using a catalyst agglomerate model. This calculation is combined with the dissection of the oxygen transport resistance to distinguish between molecular diffusion, Knudsen diffusion and ionomer film resistance under limiting current density conditions. In addition, an equation has been developed that accurately predicts the ionomer film resistance as a function of changes in temperature and RH, proposing a new approach to mapping ionomer film resistance. Then, by inputting three forms of resistance from the dissection of the oxygen transport resistance analysis as percentages into the distribution of relaxation time analysis, the newly developed methodology gives insight into the contributions of seven different resistance elements at different current densities. This provides an indicator for determining ionomer resistance without the need for temperature and RH experiments. In addition, this research identifies the design of the ionomer within the catalyst layer as a key determinant of PEMFC cell performance, highlighting the significant impact that molecular or Knudsen diffusion can have depending on operating conditions. Consequently, through an in-depth analysis of oxygen stability under different operating conditions, this study will provide essential insights for future PEMFC cell design.
(Invited) In-Situ Liquid Water Visualization in PEFC and Its Application to Advanced Materials
Authors: Hirai Shuichiro , Satoh Keisuke , Sakai Katsunori , Naito Hiroshi , Sasabe Takashi 
Published: December 2024

Although water, not carbon dioxide, is the only substance that is exhausted from PEFC, water management inside PEFC is also important to improve its performance. To develop in-situ measurement techniques of water are needed to understand and control water, including water vapor. Authors first made an in-situ measurement by magnetic resonance imaging (MRI) to measure the spatial distribution of the water content within a polymer electrolyte membrane under operation1. This technique is valid for membrane only. It is extended to develop to measure water in gas diffusion layer using soft X-ray2. In-situ observation of liquid water transport in the microporous layer (MPL) and substrate layer of an operating PEFC was performed using high-resolution soft X-ray radiography.
Recently, in order to achieve high current density in PEFCs, we developed thin GDLs to allow sufficient oxygen transport with suppression of concentration overvoltage caused by the liquid water accumulation inside. A thin self-standing GDL that consists of nano-fiber as a substrate layer and MPL is developed. The cell performance was improved in the case of the new GDL at high current density as shown in figure 1 compared to the case of the SGL25BC. Moreover, results of X-ray visualization showed that liquid water accumulation of new GDL was reduced.

Tsushima, Kazuhiro Teranishi, S. Hirai, Electrochemical and Solid-State Letters, 7 , A269-A272 (2004)

Deevanhxay, T. Sasabe, S. Tsushima, S. Hirai, J. Power Sources, 230, 38 (2013).

Ishikawa, R. Aihara, H. Naito, K. Sakai, T. Sasabe, A. Tanioka, and S. Hirai, ECS Transactions, 109, 275 (2022)

Figure 1