bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atomic-Scale Strucural Analysis of Pt-Based Nanoparticles Using Scanning Transmission Electron Microscopy
Authors: Kuwabara Akihide , Omori Yuki , Huang Hsin-Hui , Kobayashi Shunsuke 
Published: November 2022

Polymer electrolyte fuel cells (PEFCs) is proposed as an alternative to the power generation system in fuel cell vehicles. The performance of the PEFCs is significantly affected by the catalytic activity of the cathode, which contains platinum in general. Recent theoretical studies show that the Pt-Pt interatomic distance at the subsurface of the Pt-based catalysts might considerably influence the catalytic activity. However, experimental evidence remains a challenge due to the requirement of measurement accuracy in picometers at the subsurface. The present work attempts to achieve precise measurements on the Pt-Pt interatomic distance of Pt particles by high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM). Further, we also aim to understand the effects of the change in Pt-Pt interatomic distance on the catalytic activity.
A catalyst of 10 wt.% Pt-loaded on graphitized carbon (Sigma-Aldrich) was used in this work. TEM specimen was prepared by dispersing the catalyst on a carbon film supported copper grid. Structural characterizations were examined by a spherical aberration corrected scanning transmission electron microscope (JEM-2100F, JEOL) operated at 200 kV.
In order to determine the Pt atomic coordinate accurately, images were first taken under the optimized conditions. Further, a series of images were taken and integrated to form one image with high signal-to-noise ratio and minimized drifting. Finally, the Pt atomic coordinates were extracted precisely on a picometer scale by fitting of the individual atomic columns to two-dimensional Gaussian functions using a custom code developed by MatLab software. To gain insight into the atomic changes in Pt particle, a map of Pt-Pt interatomic displacement vector was constructed and superimposed on the HAADF-STEM image. Intriguingly, a significant Pt-Pt interatomic displacement occurs at the surface of the Pt particle, corresponding to changes in surface morphology and particle size.
The state-of-the-art methodology demonstrated here could greatly advance our understanding of surface chemistry of Pt-based catalysts such as Pt3Co alloys. Further understanding of the correlation between the interatomic distances on the catalyst surface and the catalytic activity may give considerable interests and guidelines for future developments of PEFCs.
Investigation of Liquid Water Behavior and Performance of PEFC Catalyst Layers Using a Microdevice and in-Operando Infrared Microscopy
Authors: Suzuki Takahiro , Kobayashi Ryota , Kakinuma Katsuyoshi , Uchida Makoto , Iiyama Akihiro , Tsushima Shohji 
Published: November 2022

Studies on water behavior in the vicinity of a catalyst layer (CL) and its effect on the cell performance are important challenges because water management is a key factor to achieve higher performance of polymer electrolyte fuel cells (PEFCs). In this study, a microdevice that contains a catalyst coated membrane (CCM) was developed (1) and in-operando infrared (IR) microscopy was conducted to visualize water behavior on the CL. Two types of CLs contain either carbon (2) or tin oxide (3) as supporting material to investigate the effects of materials on the water behavior and cell performance.
The microdevice, which was made of a silicon wafer, contains two microchannels (100 μm-width, 200 μm-pitch) and a current-collecting layer (30 μm-width) on a rib of the cathode plate. The CCM was sandwiched by two plates. The anode channel faced the rib of the cathode. The surface of a cathode catalyst layer was coated with thin Au by sputtering to enhance IR reflectance, which did not change the porous structure of the CL significantly. The surface of the cathode catalyst layer was observed by IR microscopy through the cathode plate.
Figure 1 shows liquid water generated during the constant current operation of the device. The catalyst layer contains carbon as the supporting material in this case. The effects of the materials and flow conditions on the water behavior and cell performance were investigated.
Acknowledgments
This work was supported by NEDO ECCEED’30.
References
(1) T. Suzuki et al., J. Therm. Sci. Technol., 11 (2016), 16-00370.
(2) T. Suzuki et al., Int. J. Hydrogen Energy, 41 (2016), 20326.
(3) Y. Chino et al., J. Electrochem. Soc., 162 (2015), F736.

Figure 1
Probing Heterogeneous Water Distributions within Fuel Cell Membranes Using Combined Neutron and X-Ray Tomography (NeXT)
Authors: Shrestha Pranay , LaManna Jacob Michael , Fahy Kieran , Kim Junseob , Lee ChungHyuk , Lee Keonhag Keonhag , Baltic Eli , Jacobson David , Hussey Daniel , Bazylak Aimy 
Published: November 2022

Water management in a fuel cell is an essential prerequisite for achieving high cell performance, where sufficient water is required for membrane hydration while excess liquid water leads to undesired mass transport losses. Existing heterogeneity within the fuel cell, such as those created by flow-field lands and channels create three-dimensional (3-D) heterogeneity in water distribution within the fuel cell components, which may have long term effect on the durability of fuel cell components, such as the membrane (1). 3-D visualization techniques such as X-ray (1-4) and neutron (5) tomography are powerful in revealing the effect of the existing heterogeneity on water distributions in 3-D. However, there is an opportunity to combine neutron and X-ray tomography (6) to probe into the details of these heterogenous water distributions even further and clarify their impacts on 3-D membrane hydration.
In this study, we investigate the effect of heterogeneity in fuel cells (primarily land-channel heterogeneity) on 3-D membrane hydration and membrane morphology changes during fuel cell operation using simultaneous neutron and X-ray tomography (NeXT). The fuel cell is tested at varying gas humidity conditions in a serpentine flow-field configuration. A simultaneous coupling of neutron and X-ray imaging provides high contrast across various components of the fuel cell. Specifically, neutrons are highly attenuated by hydrogen atoms; hence neutron imaging is used to accurately locate and quantify operando water distribution. X-rays are sensitive to metals; hence simultaneous X-rays imaging is used to track metal-containing components (metal flow-field) and interfaces (such as interface between Pt-containing catalyst layer and membrane). This study demonstrates how heterogeneity in fuel cells plays a role in 3-D membrane hydration and needs to be tailored to enhance cell performance.

References

Y. Singh, R. T. White, M. Najm, T. Haddow, V. Pan, F. P. Orfino, M. Dutta, and E. Kjeang, J. Power Sources., 412 (2019): 224-237.

Y. Nagai, J. Eller, T. Hatanaka, S. Yamaguchi, S. Kato, A. Kato, F. Marone, H. Xu and F. N. Büchi, J. Power Sources., 435 (2019).

S. J. Normile, D. C. Sabarirajan, O. Calzada, V. De Andrade, X. Xiao, P. Mandal, D. Y. Parkinson, A. Serov, P. Atanassov and I. V. Zenyuk, Meter. Today Energy., 9 (2018).

S. S. Alrwashdeh, I. Manke, H. Markötter, M. Klages, M. Göbel, J. Haußmann, J. Scholta and J. Banhart, ACS Nano., 11, 6 (2017).

J. M. LaManna, Y. Yue, T. A. Trabold, J. D. Fairweather, D. S. Hussey, E. Baltic and D. L. Jacobson, Meet. Abstr. - Electrochem. Soc., 32 (2017).

J. M. LaManna, D. S. Hussey, E. Baltic and D. L. Jacobson, Rev. Sci. Instrum., 88, 11 (2017).
Simultaneous Generation of Clean Water and Electricity Via Desalination Fuel Cells
Authors: Suss Matthew , Abu Khalla Shada , Asokan Arunchander , Abdalla Salman 
Published: November 2022

We will present a nascent technology which desalinates water and produces net electricity simultaneously from a single electrochemical cell, driven by the hydrogen/oxygen redox couple [1]. The cell combines hardware of PEM fuel cells, alkaline fuel cells and electrodialysis cells, and thus we term this device a "desalination fuel cell" [2]. We will describe both the operating principle and lab-scale cell results, as well as our development of the fundamental thermodynamics to predict the maximum available electricity production from our cell during its combined chemical reaction-separation process [2]. Our recent advances will be described, including the development of chloride-tolerant non-platinum group metal ORR catalysts [3], achievement of >95% thermodynamic energy efficiency [4], and establishment of system scaling rules. This technology promises to extend the concept of the hydrogen economy to water purification, and we will discuss the outlook on this technology and potential application areas.

References:
[1] Suss ME, Zhang Y, Atlas I, Gendel Y, Ruck EB, Presser V. Emerging, hydrogen-driven electrochemical water purification. Electrochemistry Communications. 2022
[2] Atlas I, Khalla SA, Suss ME. Thermodynamic energy efficiency of electrochemical systems performing simultaneous water desalination and electricity generation. Journal of The Electrochemical Society. 2020.
[3] Asokan A, Abu-Khalla S, Abdalla S, Suss ME. Chloride-Tolerant, Inexpensive Fe/N/C Catalysts for Desalination Fuel Cell Cathodes. ACS Applied Energy Materials. 2022.
[4] Abu Khalla S, Atlas I, Litster S, Suss ME. Desalination Fuel Cells with High Thermodynamic Energy Efficiency. Environmental science & technology. 2021.

Figure 1: Schematic of a desalination fuel cell, which utilizes chemical energy to desalinate water and produce electricity simultaneously. The cell is driven by the hydrogen-oxygen redox couple.

Figure 1
Platinum Group Metal-Free ORR Catalysts for Anion Exchange Membrane Fuel Cells
Authors: Zhang Hanguang , Zelenay Piotr 
Published: November 2022

Platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) have attracted significant attention in the last two decades. These catalysts typically perform better in alkaline aqueous electrolytes than in their acidic counterparts.1, 2 However, the performance of PGM-free ORR catalysts in anion exchange membrane fuels cells (AEMFCs) have been consistently lower than in the acidic polymer electrolyte fuel cells (PEFCs). The most likely reasons for the sub-par behavior of PGM-free catalysts in AEMFCs has been often linked to difficulties in preparing electrodes with anion exchange ionomers and assuring efficient water management. These challenges have been amplified by the high-loading requirement for PGM-free ORR catalysts, resulting in electrodes by as much as an order of magnitude thicker than the PGM-based ones.
In this presentation, we will demonstrate AEMFCs with much improved performance of the PGM-free cathode (Fe-N-C catalyst-based). The performance improvement has been achieved by optimizing the electrode fabrication process, including changes to the electrode configuration and catalyst ink preparation. These changes have allowed us to elevate the AEMFC performance, including the peak power density of > 0.8 W cm-2 in H2-O2 cells, to the level comparable to that of the corresponding PEFC, operating with a PGM-free cathode under the same operating conditions.
References:
1. Li, X.; Liu, G.; Popov, B. N., Activity and stability of non-precious metal catalysts for oxygen reduction in acid and alkaline electrolytes. Journal of Power Sources
2010,
195 (19), 6373-6378.
2. Choi, C. H.; Lim, H.-K.; Chung, M. W.; Chon, G.; Ranjbar Sahraie, N.; Altin, A.; Sougrati, M.-T.; Stievano, L.; Oh, H. S.; Park, E. S.; Luo, F.; Strasser, P.; Dražić, G.; Mayrhofer, K. J. J.; Kim, H.; Jaouen, F., The Achilles' heel of iron-based catalysts during oxygen reduction in an acidic medium. Energy & Environmental Science
2018,
11 (11), 3176-3182.
Self-Supporting Ag Nanowire Mat Electrodes on PTFE Gas Diffusion Layers for Electrochemical Conversion of CO2 to CO
Authors: Raciti David , Braun Trevor Michael , Tackett Brian , Xu Heng , Cruz Mutya , Wiley Benjamin , Moffat Thomas P 
Published: November 2022

High surface area nanocatalysts combined with conductive carbon-based gas-diffusion layers (GDL) enable high CO2 flux and conversion, but can suffer from ineffective catalyst utilization and flooding of the GDL ultimately limiting the lifetime of electrolyzer operation. Herein we explore an alternative gas-diffusion electrode that incorporates a self-conducting network of Ag nanowires on a non-conductive PTFE GDL (Figure 1 a-b) as a gas-diffusion electrode (GDE) for CO2 conversion (Figure 1 c-d). Properties influenced by Ag nanowire mat thickness and durability of the Ag nanowires are explored. Furthermore a 1-D model of the electrode morphology and microstructure quantitatively captures the steady-state compositional gradients (Figure 1d) within the catalyst layer giving insight into the observed empirical differences in catalyst layer thickness. The self-conductive nanowire network and robust hydrophobic porous support structure provide an effective platform to further understanding of meso-scale properties and microenvironment present during CO2 electroreduction.
Figure Caption: (a) Top-down and (b) Cross-section electron micrographs of a Ag nanowire covered PTFE GDL. (c) Schematic depicting the utilization of the Ag NW covered PTFE GDL as an electrode for electrochemical CO2 reduction and (d) resulting relationships between catalyst layer thickness, mass activity and simulated local pH.

Figure 1
Nafion Composite Membrane Reinforced By Phosphonated Polypentafluorostyrene Nanofibers
Authors: Kerres Jochen Alfred , Solihul Muhammad Mu’min , Komma Miriam , Böhm Thomas , Wagner Maximilian , Krieger Anja , Thiele Simon 
Published: November 2022

The membrane is one of the crucial components of fuel cells. Applying composite membranes for fuel cells is a promising option due to better mechanical properties compared to membranes without reinforcement. Composite membranes can be prepared by combining ionomer with a filler which can be selected from many types of materials, such as polymers, ceramics, carbons, and metals. Filler materials exist in different nanostructures which provide flexible designs for composite membranes. However, the main issue in composite membranes is a trade-off among properties when adjusting the ratio between ionomer and filler, especially between ionic conductivity and mechanical modulus. On the one hand, maintaining high protonic conductivity is possible when small concentrations of reinforcing fillers are incorporated. On the other hand, a high amount of reinforcement can improve the mechanical properties significantly but could result in low protonic conductivity as well. Our strategy to overcome this issue is by employing protonic conductive nanofibers as reinforcement. Electrospinning is a versatile method to transform polymer solutions into long and solid nanofibers. Electrospun fibermats possess a high porosity and contain voids which can be filled with an ionomer like Nafion by spraycoating to form a dense composite membrane.
We were successful in producing electrospun nanofibers from phosphonated polypentafluorostyrene (PWN70) and unmodified polypentafluorostyrene (PPFSt). PWN70/Nafion and PPFSt/Nafion composite membranes were prepared separately by spraycoating of a Nafion solution into PWN70 and PPFSt fibermats that have comparable thickness and fiber loading. From tensile tests, we found that composite membranes made from PWN70/Nafion and PPFSt/Nafion have much higher Youngs’ modulus (E) than pure Nafion (Figure 1A). Although PWN70/Nafion is a relatively brittle membrane, it has the best Youngs’ modulus and yield stress. Protonic conductivity is also a crucial membrane property which can be determined by electrochemical impedance spectroscopy. In Figure 1B, Nafion reinforced by PPFSt fibers has a reduced conductivity due to non-ion-conductive PPFSt. Surprisingly, the protonic conductivity of a PWN70/Nafion composite membrane is similar to spraycoated Nafion. Without reducing much the protonic conductivity, the PWN70/Nafion composite membrane shows comparable ohmic resistance to the spraycoated D2020 in fuel cell operation which has also been done in this work. Since the PWN70 nanofibers are ion-conductive and electro-spinnable, the nanofibers offer benefits when designing fiber-reinforced composite membrane possessing both good mechanical stability and protonic conductivity.

Figure 1
Evaluation of High Oxygen Permeability Ionomer (HOPI) Oxygen Permeability for Proton Exchange Membrane Fuel Cells (PEMFCs)
Authors: Liu Jiawei , Braaten Jonathan , Tiwari Nicholas , Wang Xiaoxiao , Blackburn Scott , Brown Gerald , Park Andrew M , Ulissi Zachary , Litster Shawn 
Published: November 2022

The performance of proton exchange membrane fuel cells (PEMFCs) is sensitive to Pt loading in the cathode catalyst layer, with lower Pt loadings significantly increasing the oxygen transport resistance of the catalyst-ionomer interface when using perfluorosulfonic acid (PFSA) ionomers. The oxygen permeability is suspected to be locally decreased at Pt interfaces due to ionomer densification caused by the Pt-ionomer interactions. However, due to the high cost of Pt, it is important to be able to reduce Pt loadings without increasing oxygen transport resistance. With this goal in mind, new precommercial high oxygen permeability ionomers (HOPIs) with blocky backbone units are being studied. These HOPIs show significantly lower local oxygen transport resistance in fuel cells as well as greater efficiency and durability. However, there was a question of whether HOPI’s higher in-situ oxygen permeability is due solely to reduced densification or if it is also due to increased bulk permeability of the films. Here we evaluated this question using a unique oxygen permeability measurement apparatus that measures the oxygen permeability of thin-films supported on mesoporous substrates. This apparatus allows films to be characterized without the polarized Pt surfaces used in other oxygen permeability diagnostics, providing insights into the bulk permeability of cast thin-films with minimized substrate effects. This presentation will present our findings of the oxygen permeability of pristine thin-film HOPIs characterized against that of the baseline PFSA ionomer. Results show that the HOPI is significantly more oxygen permeable than the baseline. This finding is supported by our molecular dynamics simulations of these ionomer films. This increased bulk film oxygen permeability indicates that a significant portion of the decreased oxygen transport resistance in the cathodes is associated with the greater bulk permeability of these films and not just local Pt interface effects.
This material is based upon work supported by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office, Award Number DE-EE0008822.
Quantitative Analysis of H+ Transportation of Nafion film on Different Substrate using Planar Inter Digitated Electrodes
Authors: Bhardwaj Rahul , Suwansoontorn Athchaya , Hirose Daisuke , Takamura Yuzuru , Abbaszadehami Mehran , Karan Kunal , Nagao Yuki 
Published: November 2022

Introduction: Ionomer thin-film gained attraction because of their thickness- and morphology-dependent changes in ionic conductivity. In a fuel cell catalyst layer, ionomer thin films coating the carbon-supported Pt-based catalysts (Pt/C) is distributed in spatially heterogeneous manner with variation in thickness and connectivity. Thus, it is difficult to clarify the quantitative attribution of the true source of effective proton resistance among Pt and carbon-support. To evaluate the quantitative attribution of proton conductivity of a thin-film ionomer on relevant substrates (e.g., carbon), we have fabricated specially designed interdigitated electrodes (IDEs) to accommodate different substrates upon which ionomer film is coated. In this work, we present the Nafion (~55 nm) proton (H+) transportation over carbon and quartz substrate in N2 atmosphere. Also, we will discuss the true attribution of substrate-dependence to estimate the Nafion’s thin film conductivity.

Experimental: Interdigitated electrodes (IDEs) with and without carbon pad were fabricated in clean room facilities. To prepare IDEs, the patterned carbon structure was developed and pyrolyzed at 1000 ºC in 2% H2/N2 gas before the Pt deposition. 1.2% Nafion dispersion was spin coated and dried at 40ºC under vacuum before electrochemical impedance spectroscopy (EIS) measurement in N2 atmosphere. Relative humidity (RH) dependence of in-plane H+ resistance was obtained and discussed through EIS measurements.

Results and Discussion: Figure 1 (a) and (b) shows the side view of IDEs with (Pt_C_IDE) and without carbon pad (Pt_Q_IDE), and also Nafion’s (~55 nm) H+ resistance obtained from EIS measurement at various RH in N2 atmosphere. Nyquist plot (not shown) exhibited significant difference and ascribed film resistance (Mean value) for ionomer at carbon substrate was significantly lower (one order of magnitude) compared to that at the quartz substrate, as shown in Fig. 1 (c).
In case of H+ resistance using Pt IDE with carbon (Pt_C_IDE), approximately 90% of the IDE area between the electrodes is carbon and the rest is quartz. Therefore, the method of estimation of Nafion’s thin film conductivity from impedance response must be reviewed carefully and will be discussed later in detail.

References:

[1] Y. Nagao Sci. Tech. Adv. Mater, 21, 79 (2020).
[2] X. Gao, K. Yamamoto et al.
Solid State Ionics, 357, 115456 (2020).
[3] U. N. Shrivastava, D. Khattar et al.
J. Electrochem. Soc., 167, 134520 (2020).

Figure 1
Chemical Stability Enhancement of Aromatic Proton Exchange Membranes Using a Damage Repair Mechanism
Authors: de Wild Tym , Nemeth Tamas , Nauser Thomas , Schmidt Thomas J. , Gubler Lorenz 
Published: November 2022

Harmful radical species (HO•, HOO•) are formed during fuel cell operation. Out of these species, the highly electrophilic hydroxyl radical is the most reactive (1.8 – 2.7 V vs. NHE). Consequently, the most electron-rich constituents, aromatic rings, are preferentially attacked and undergo rapid degradation. Hydroxyl radical formation rates depend on operating conditions and cell parameters, but even with low formation rates the damage accumulates over time and can lead to thinning or embrittlement of the membrane, and will cause irreversible damage to the cell. Due to these effects, long-term operation becomes challenging. Therefore, membranes with enhanced radical stability are increasingly desirable. In our previous work, we have shown, using kinetics measurements, that it should be possible for Ce(III) to act as a repair agent for formed damaged intermediates (cf. Figure).[1] In our follow-up work we demonstrate that Ce(III) can indeed reduce degradation rates.[2] These experiments were performed in a fuel cell setup using accelerated stress tests at open circuit voltage (OCV), a cell temperature of 80 °C, 100% RH and high H2 and O2 partial pressures of 2 bar. In-situ measurements and post-test analyses unequivocally show that bound Ce(III) can mitigate degradation of poly(α-methylstyrene sulfonate)-based membranes. We believe that this approach could also be applicable for other aromatic-based polymers if a sufficiently long-lived intermediate is formed upon radical attack.
References:
[1] T. de Wild et al., J. Electrochem. Soc.
2021, 168, 054514.
[2] T. de Wild et al., J. Power Sources, submitted

Figure 1