bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterned Nafion Membranes for Improved Transport in PGM-Free PEMFC Cathodes
Authors: Arman Tanvir Alam , Uddin Aman , Ding Shuo , He Yanghua , Cetinbas Cankur , Peng Jui kun , Wang Xiaohua , Ahluwalia Rajesh , Xu Hui , Wu Gang , Komini Babu Siddharth , Litster Shawn , Pasaogullari Ugur , Spendelow Jacob S. 
Published: November 2022

Substantial cost reduction is needed to commercialize polymer electrolyte fuel cells. As PGM catalysts are projected to account for ~42% cost of a fuel cell stack (1), replacement of PGMs with PGM-free catalysts is an attractive route to cost reduction. Over the past decade, extensive research efforts have led to significant improvements in kinetic activity (2), but conventional PGM-free catalyst continues to have lower volumetric activity than PGM catalysts. The lower volumetric activity requires use of a thicker cathode catalyst layer (CL), resulting in significant proton and oxygen transport losses (3). Therefore, along with kinetic improvements in oxygen reduction reaction, improved transport of H+ and O2 is needed to achieve performance comparable to PGM catalyst. In this study, we adopt a micro-patterning technique to incorporate non-tortuous ionomer channels in the cathode to increase the ionic conductivity of the thick catalyst layer. As shown in Figure 1, cathode ionomer channels enable rapid transportation of H+ throughout the catalyst layer, compared to thin and tortuous ionomer films in the conventional electrode. Polarization curves obtained in H2/air show significantly higher performance for the CL with ionomer channels compared to the conventional cathode. Electrochemical impedance spectroscopy data in H2/N2 also demonstrate a significant decrease in H+ resistance in the catalyst layer. The ionomer channels lead to a reduction in the H+ transport resistance, reducing ohmic overpotential in the catalyst layer. Further improvement in performance in the mass transport region is achieved through implementing optimized design of the dedicated ionomer channel.
Acknowledgment
This research was supported by the US Department of Energy, the Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office and the LANL LDRD program.
References

D. Papageorgopoulos, DOE Hydrogen and Fuel Cells Program FY2019 Annual Merit Review Proceedings, https://www.hydrogen.energy.gov/pdfs/review19/plenary_fuel_cell_papageorgopoulos_2019.pdf (2019).

H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao and G. Wu, (2017).

S. Komini Babu, H. T. Chung, P. Zelenay and S. Litster, ACS Appl Mater Interfaces, 8, 32764-32777 (2016).

Figure 1
(Digital Presentation) Solving the Mystery of Ohmic Resistance in Zero-Gap Alkaline Water Electrolyzers Using Electrochemical Impedance Spectroscopy and Polarization Curves
Authors: Lira Garcia Barros Rodrigo , de Groot Matheus Theodorus , van der Schaaf John 
Published: November 2022

Hydrogen can be produced using renewable energy sources through alkaline water electrolysis (AWE). Alkaline water electrolyzers are made of inexpensive materials such as nickel perforated electrodes and the Zirfon porous diaphragm. However, one of the bottlenecks of this technology is the high internal ohmic resistance compared to other technologies, which implies that the technology is traditionally operated at low current densities. To decrease the ohmic resistance advanced AWE electrolyzers use a zero-gap configuration. However, even with such a zero-gap configuration the ohmic resistance remains relatively high.
An analysis of polarization data on zero-gap alkaline electrolyzers with the commonly used Zirfon diaphragm suggests that the ohmic area resistances are significantly higher than what would be expected based on the properties of the diaphragm supplier [1]. In this study we use Electrochemical Impedance Spectroscopy (EIS) to further investigate this phenomenon [2], since EIS enables the separation of ohmic and charge transfer resistances.
EIS in combination with polarization measurements enables us to determine electrodes overpotentials, diaphragm ohmic losses and bubbles resistance and to estimate key parameters such as the reversible cell potential, the Tafel slopes and the exchange current densities of hydrogen and oxygen evolution reactions. Impedance data were fitted with an equivalent electric circuit, which consist of an ohmic resistance connected in series with two components, each including a resistance and a constant phase element (CPE) in parallel. Besides, the polarization measurements were fitted to a given correlation [1] using MATLAB as shown in Figure 1.
It was found that the ohmic resistance determined with EIS (~0.48 Ω.cm²) is lower than the fitted area resistance from the I-V curve (0.68 Ω.cm²), but is still higher than what would be expected based on the diaphragm properties for Zirfon. Obtained values for Tafel slopes and exchange current densities, both by EIS and I-V curves, are comparable to typical values from the literature. The resistance does not increase with current density suggesting that an increase of bubble volume with current density does not play a significant role in the resistance. Therefore, it still remains unclear what the origin is of the increased ohmic resistance.
[1] M.T. de Groot, A.W. Vreman. Ohmic resistance in zero gap alkaline electrolysis with a Zirfon diaphragm. Electrochimica Acta, 2021, 369, 137684. https://doi.org/10.1016/j.electacta.2020.137684
[2] Rodríguez, J.; Palmas, S.; Sánchez-Molina, M.; Amores, E.; Mais, L.; Campana, R. Simple and Precise Approach for Determination of Ohmic Contribution of Diaphragms in Alkaline Water Electrolysis. Membranes, 2019, 9, 129. https://doi.org/10.3390/membranes9100129

Figure 1
Fuel Cell Imaging with a Wolter Optics Neutron Microscope
Authors: Hussey Daniel , Daugherty Michael Cyrus , Kim Youngju , LaManna Jacob Michael , Jacobson David 
Published: November 2022

Wolter optics promise to radically transform neutron imaging by improving the time resolution of the method by at least a factor 1,000 while providing spatial resolution of order a few micrometers [1]. These optics will enable neutron tomography of operating fuel cells with a time resolution of about a few minutes, which will provide unique insight into the water transport phenomena in membrane electrode assemblies of fuel cells and electrolyzers.
Neutron imaging has played a critical role in understanding water transport in proton exchange membrane fuel cells and electrolyzers [2]. The primary limitation of the method is the inherent neutron source strength, which is about a billion times weaker than X-ray synchrotron sources. Additionally, neutrons are difficult to focus using refractive lenses so that neutron imaging beamlines heretofore can be described as pinhole cameras. In a pinhole camera, the best achievable spatial resolution (λg) is determined by the diameter of the pinhole (D ~1 cm), the pinhole-to-detector distance (L ~10 m), and the sample-to-detector distance (Z ~1 cm):
λg = Z D / (L – Z) ~ Z D / L
Returning to the source strength, the neutron fluence rate at the sample position scales as (D / L)2. This means that higher spatial resolution for finite sized objects requires sacrificing neutron intensity and incurring long exposure times. Typical measurements require about 20 minutes for a single two-dimension image of the water content in fuel cell for a spatial resolution of about 10 µm. Such time requirements preclude the use of tomography, which is required to understand the water content in real fuel cell components since the MEA cannot be considered to be planar at the few micrometer level.
We will describe Wolter optics, and the optical system that will be first available in 2022. After the NCNR cold source upgrade is anticipated to yield a time resolution gain of about 10,000 compared to a pinhole camera. We will discuss our expected image acquisition and analysis procedures guided by ray tracing simulations.
Figure 1. Proof of concept Wolter optics image of a fuel cell test section.
[1] D. S. Hussey et al., “Design of a neutron microscope based on Wolter mirrors,” Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip., vol. 987, no. October 2020, p. 164813, 2021.
[2] T. A. Trabold, J. P. Owejan, J. J. Gagliardo, D. L. Jacobson, D. S. Hussey, and M. Arif, “Use of neutron imaging for proton exchange membrane fuel cell (PEMFC) performance analysis and design,” Handb. fuel cells, vol. 6, no. Table 1, 2010.

Figure 1
Gold-Reduced Graphene Oxide Composite Coating on Stainless Steel 316L As Bipolar Plate for Proton Exchange Membrane Fuel Cell
Authors: Seo Jinmyeong , Park Jung-Joon , Qing Wang , Yang Fan , Yoon Sanghwa , Yoo Bongyoung 
Published: November 2022

Proton exchange membrane fuel cell (PEMFC) are regarded as one of the most promising fuel cell types for a new generation of power source in portable application due to no harmful byproducts emission, rapid startup and low operating temperature. Although PEMFC has a low output with a single cell, it is overcome by the series of unit stack by using bipolar plate (BPP) to improve the total efficiency. BPP, which conveys electrical current, separates reactant gases and connects single stack unit in series, is one of the most important part of PEMFC, along with catalytic electrode and proton exchange membrane. In recent years, stainless steel 316L (SUS316L) has been touted to as a promising candidate material for BPP with the numerous advantages such as low cost, high machinability and ductility. However, it has critical issues such as low corrosion resistance and high electrical resistance. For this reason, a coating process must be carried out on SUS316L with non-corrosive and conducting materials such as Au, Rh, Ag, Ti etc. Because these materials are high cost or rare-earth metals, anti-corrosive coating process inevitably causes the increase of BPP manufacturing cost.
In this study, Au-reduced graphene composite coating is introduced on SUS316L to improve anti-corrosion resistance and electrical conductivity with in cost-effective manner by minimizing the consumption of Au deposit and the using electrochemical fabricated graphene with low cost. Corrosion properties and electrical properties are investigated with the as-coated samples and in simulated operating condition. By addition of graphene coating process, the consumption of Au is dramatically reduced with the outstanding performance compared to with only Au coating.
Assembly and Testing of a Hydrogen Fuel Cell System to Power an Airship
Authors: Molinero Antonio , Oller Juan Carlos , Barcala José Miguel , Duque Luis , Folgado M. Antonia , Chaparro Antonio M 
Published: November 2022

An airship, or dirigible balloon, is an aircraft that gains its lift from a gas less dense than air, like helium. For traction, airships have two or more propellers normally attached to a gondola that is suspended under the balloon. At present, they are used for hovering long times without the need for a high speed, like for aerial observation, advertising, or as camera platforms. In our laboratory, the airship is being used as a platform for testing hydrogen fuel cell systems for aerial applications.
The airship used in this communication is a 3 m3 polyurethane's inflatable zeppelin, with radio control, and three electrical propellers (Fig. 1a). A hydrogen fuel cell system has been developed and integrated with the gondola for powering the propellers and electronics. The fuel cell is a 15 W PEMFC stack prototype able to work fully under passive feeding conditions (Fig. 1b). In addition, three supercapacitors have been implemented, that are recharged by the fuel cell, for eventual larger power demands up to 40 W. Hydrogen is stored in two metal hydride canisters with 2g capacity to provide 30 W h energy enough for a few hours autonomy. In addition, for fuel cell parameters monitoring, different sensors have been implemented that provide voltages of the individual cells, current, and temperatures. The sensors are connected to Arduino board, and measurements are continuously monitored by a Labview software with wifi. Boost dc-dc conversion provides 7V voltage power to feed the motors.
The stack prototype allows for different testing configurations, using cells in series and parallel connection to change power characteristics with different voltage and current. Results of the testing are provided in this communication.
Acknowledgement: The work is partially financed by the ELHYPORT project (PID2019−110896RB-I00), Spanish Ministry of Science and Innovation.

Figure 1
Durability and Performance Study of Chemically Anchored Heteropoly Acid with Perfluorinated Sulfonic Acid-Expanded Polytetrafluoroethylene Composite Membrane for Proton Exchange Membrane Fuel Cells
Authors: Kim Chuloong (Christoph) , Kuo Mei-Chen , Carmosino Dominic , Lindell Matthew , Jiang Ruichun , Ha Phuc , Gittleman Craig S , Yandrasits Michael , Herring Andrew M. 
Published: November 2022

Chemical degradation and mechanical degradation are the major challenges for heavy-duty vehicle fuel cell commercialization. Perfluorinated sulfonic acid is the benchmark material that has high proton conductivity and robust mechanical properties. However, chemical degradation can occur through radical formation during the fuel cell operation. Chemical degradation can also have a synergetic effect with mechanical degradation. Recent studies have used cerium and manganese additives to suppress the radical formation or chemical degradation caused by radicals. The limitation of the metal and metal oxide additives was the migration and agglomeration of the additives. Both migration and clustering can lead to changes in membrane morphology, resulting in a loss in proton conductivity. Our group has previously reported that immobilization of heteropoly acid to a fluoroelastomer can be used to both enhance proton conductivity and chemical degradation. The durability test has shown that the chemical durability was significantly enhanced, but the mechanical durability remained the challenge.
In this study, we hypothesized that when a heteropoly acid can be chemically bound to the perfluorinated polymer and cast on a composite membrane with expanded polytetrafluoroethylene (e-PTFE) will enhance the chemical and mechanical durability without migration. Proton conductivity was measured using impedance spectroscopy. The structure-property relationship was studied using multi-scale morphology analysis methods such as scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and small-angle x-ray scattering (SAXS). The chemical degradation will be tested under the highly accelerated standard test (HAST) condition, a more severe fuel cell operation condition than the accelerated standard condition (AST). The mechanical durability of the composite membrane will also be tested on the HAST condition with humidity cycling.
PFSA Membrane Thickness Impact on Chemical Degradation Rates
Authors: Coms Frank D. , McQuarters Ashley B. , Marks Alex , Green Zachary 
Published: November 2022

As the large-scale commercialization of proton exchange membrane fuel cells (PEMFC) for numerous applications, including heavy-duty trucks draws nearer, there is increasing interest in optimizing fuel cell membranes for both improved efficiency and durability. One of the major membrane attributes being considered for optimization is thickness. The current range of (perfluorosulfonic acid) PFSA membrane thicknesses employed for commercial applications range from 8 -25 µm. As with most adjustable materials parameters, there are a host of properties (cost, gas permeability, proton conductivity, etc.) that require co-optimization to provide the overall preferred position. For example, thin membranes will minimize proton resistance, facilitating high power densities, but will simultaneously allow increased gas crossover fluxes that can contribute to both reduced fuel efficiency and increased oxidative stress. On the other end of the spectrum, thick membranes will decrease gas crossover fluxes, offering improved fuel efficiency while simultaneously decreasing power density. A major question surrounding the tradeoffs of membrane thickness involves the chemical durability impact. Here, we report our investigations of PFSA membrane chemical durability as a function of thickness. For the studies reported here, a thickness series (8, 12 and 20 µm) of ePTFE reinforced Nafion®-like PFSA standalone membranes (SAMs) were prepared.
A two-pronged approach was taken for this study. The first involves investigation of intrinsic chemical stability of the ionomer as a function of membrane thickness using an ex-situ H2O2 vapor test. The second investigative mode, which targets the oxidative stress generated by crossover gas flux, employs OCV durability tests of full MEAs. In addition to membrane thickness, gas crossover rates are known to be functions of membrane hydration and gas pressures.1,2 Accordingly, a 3(4-1) fractional factorial experimental design was executed to probe the role of membrane thickness as well as the other factors known to affect gas crossover. The fractional factorial design allows all main effects to be determined and further allows estimation of two factor interactions, if present.
References

T. Sakai, H. Tanenaka, E, Torikai, “Gas Diffusion in Dried and Hydrated Nations” J. Electrochem. Soc., 1986, 133, 88-92

R. Jiang, T. Fuller, S. Brawn, C. Gittleman, “Perfluorocyclobutane and poly(vinylidene fluoride) blend membranes for fuel cells” Electrochimica, Acta, 2013, 110, 306-315
(Digital Presentation) Design of Metal/Metal Oxide Nanomaterials for Highly Active, Selective, and Durable Electrocatalysts
Authors: Sung Yung-Eun , Shin Heejong , Kim Jae Jeong 
Published: November 2022

Electrocatalysis is a key part of renewable energy conversion in the future energy system. Sustainable energy conversion and chemical production require catalyst structure with high activity, durability, and product selectivity. In general, nanoscale electrocatalysts suffer various degradation phenomena during electrocatalysis, which leads to critical performance loss. Recently, the various hybrid nanostructures (such as ordered structure, metal/carbon encapsulation, or metal/metal oxide) have been highly investigated to achieve promising catalytic performances and enhanced stabilities.
In this presentation, we will cover three different types of nanomaterials as highly active and stable electrocatalysts for oxygen reduction reaction (ORR). First, the alloy nanoparticles with ordered structures exhibit novel catalytic properties from their unique electronic and geometric structures. In particular, Pt alloys with atomically ordered crystal structures have been found to largely improve both electrocatalytic activity and stability for ORR through increased electronic interaction between Pt and other transition metals. Similarly, we recently demonstrated that well-controlled Co-, Mn- and Fe-based ternary or binary oxide nanocatalysts have an exceptionally high ORR activity, in addition to the promising electrocatalytic stability. Therefore, it is very important to synthesize well-ordered alloy nanocrystals to obtain highly durable and active electrocatalysts with respect to their structural and compositional properties. Second, we will show the strategic employment of carbon shells on electrocatalyst surfaces to enhance stability in the electrochemical process. Carbon shells can beneficially shield catalyst surfaces from electrochemical degradation and physical agglomeration. Thus carbon shells can effectively preserve the initial active site structure during electrocatalysis. The carbon shell also provides a confined environment at interfaces, enabling unconventional electrochemical behaviors. Finally, we will suggest an effective strategy to construct metal/oxide interfaces, precisely modulating the metal/oxide interfacial interactions in the nanoscale. By controlling the interface and strain effect on catalytic activity, we can achieve high active and stable metal oxide systems for ORR. We would like to describe the details of the above results, for investigating structure-activity relationships in electrocatalytic processes. Only when we start to comprehend the fundamentals behind electrocatalysis on the structure and interface of metal/metal oxide nanocrystals, they can be further advanced to be sustainable in long-term device operation.
Stability and Degradation of Pt/C Catalysts Explored with IL-TEM
Authors: Smykała Szymon , Pawlyta Mirosława , Liszka Barbara 
Published: November 2022

Industrial application of fuel cells, while, hopefully, inevitable, is still hindered by various aspects, one of them being the issue with oxygen reduction reaction (ORR) catalysts. Current state of the art platinum catalysts, while extraordinarily active, still have a long way to go when it comes to stability. In this work we have decided to tackle this problem by employing FW200 carbon black as a support for platinum nanoparticles. The carbon support was treated in 3000 °C to obtain highly ordered, graphitic structure. We’ve discovered that our catalyst, while initially exhibiting lower electrochemical surface area (ECSA) than it’s commercial, Vulcan-based counterpart, degraded with substantially slower rate than the industrial catalyst. We’ve came to that conclusion after subjecting the catalysts to accelerated degradation tests (ADT) on the rotating ring disk electrode in various potential ranges and performing ECSA and activity measurements during and after said tests. Additionally, to explore degradation mechanisms of the catalysts we’ve used identical localization transmission electron microscopy (ILTEM). This technique allows us to track the behaviour of each platinum nanoparticle, before and after electrochemical measurements, by performing ADT on TEM grids covered with catalyst. ILTEM experiments allowed us to prove, that the crystalline structure of graphitized FW200 hinders nanoparticles’ movement across the carbon support, leading to increased resistance to agglomeration. We used inductively coupled plasma optical emission spectroscopy to investigate platinum dissolution’s part in reducing catalyst activity by measuring the amount of platinum left in electrolyte after ADT. Lastly, we’ve investigated the influence of heat treatment in 3000 °C on the structure and electronic properties of the FW200 carbon black using Raman spectroscopy and X-ray photoelectron spectroscopy.
Thorough electrochemical and structural study of platinum catalyst deposited on graphitized FW200 carbon black allowed us to confirm, that our material is highly competitive, in the terms of stability, to commercially available Vulcan-based catalysts. We also think that ILTEM, while exceptionally powerful, is still quite an underutilized technique and we would like to present how joint efforts of microscopists and electrochemists can push the boundaries of knowledge in ORR electrochemistry.