bluuebunny/crossref_metadata_2025_split huggingface dataset:
EIS Analysis and Optimization Using AI for Different Cathode Channel Cross-Sections for Open Cathode Fuel Cell Stack
Authors: Thapa Shikha , Agarwal Harshal , Sahu A K 
Published: December 2024

Abstract

Unlike convention polymer electrolyte fuel cell (PEMFC), open-cathode polymer electrolyte membrane fuel cells (OC-PEMFC) use oxidant supply fed directly from the atmosphere, owing to its simple balance of plant (BOP) and integration. Whereas concerns such as lower performance compared to PEMFC, needs to be studied carefully to understand mechanisms and parametric optimization for efficient operation of OC-PEMFC stack.
The performance of OC-PEMFC is restricted due to proton conductivity, reaction mechanism, and mass transport limitation1. The effective flow-field (FF) designs can mitigate the detrimental performance degradation arising from dehydration in OC-PEMFC by effective cooling rate2. The simplified designs with optimum pressure drop enhances the performance with balanced effect of parameters such as gas distribution, water removal/retention, heat removal/accumulation.
To enhance the performance of OC-PEMFC, we need to understand the physical and chemical mechanisms of the system. These mechanisms help to understand the losses involved caused due to low protonic conductivity, Oxygen reduction reaction, mass transfer, operating conditions, and nature/composition of materials3 etc. Among all electrochemical techniques, Electrochemical impedance spectroscopy (EIS) stands out as a powerful technique that provides a vast extent of information in a short period of time.
The presented work investigates the performance of three distinct novel cathode channels with various cross-section designs (CSDs) such as square, boot, and triangular for four cells OC-PEMFC stack of active area 100 cm2. The analysis incorporates EIS examination for critical parameters, including airflow rate, current, temperature, H2 gas condition (humidified and dry). Furthermore, a parametric optimization technique is developed based on EIS and Artificial intelligence (AI) random forest regression (RFR) algorithm, the flow chart illustrating the RFR algorithm is presented in Fig. 1(a).
The findings show that, for square design the minimum low frequency resistance 7 Ω cm2 is achieved at airflow rate 3 m3/sec, current 10-15 A, and stack temperature ~ 39 ̊C, as shown in Fig 1(b). Moreover, the AI algorithm successfully predicted the suitable operating condition with root mean square error value of 98%, as illustrated in Fig. 1(c).

References

J. C. Kurnia, B. A. Chaedir, A. P. Sasmito, and T. Shamim, Appl Energy, 283, 116359 (2021).

S. Thapa, V. Ganesh, H. Agarwal, and A. K. Sahu, J Power Sources, 603, 234398 (2024).

Z. Tang, Q. Huang, Y. Wang, F. Zhang, W. Li, A. Li, L. Zhang, and J. Zhang, J Power Sources, 468, 228361 (2020).

Figure 1
System Level Considerations for Lightweight Kilowatt Scale PEMFCs
Authors: Cronin Kevin , Jolley Adam , Stroman Richard 
Published: December 2024

Proton Exchange Membrane Fuel Cells (PEMFC) on the 1 kW scale can be used in unmanned air vehicles (UAVs) to extend operational runtimes. However, the limited commercial offering of fuel cells of this class drove the U.S. Naval Research Laboratory (NRL) to create its own kilowatt scale PEMFC system suitable for use in a wide range of ambient environments. The NRL PEMFC system utilizes a liquid cooled, closed cathode architecture with metal bipolar plates and achieves a specific power of 0.40 kW/kg and a power density of 0.17 kW/L. This study will discuss NRL’s research and development of this PEMFC system, including considerations for fuel cell system design, manufacturing and operation. These system level considerations serve to minimize weight while optimizing for power production and reliable operation in a wide range of ambient environmental conditions. The challenges and opportunities of commercially available balance of plant components for this class of fuel cell system will be discussed.
Distribution Statement A. Approved for public release, distribution is unlimited.
Figure 1. The Navy designed kilowatt scale PEM fuel cell system.

Figure 1
Modeling Electrical Conductivity of Injection-Molded Polymer Composite Bipolar Plates
Authors: Trimpey Jonathan K , Myers Maxwell T , Beevers David B , Bakis Charles E , Hollinger Adam S 
Published: December 2024

Bipolar plates can be responsible for up to 40% of the total stack cost and 80% of the weight of a polymer electrolyte membrane fuel cell [1]. To reduce these cost and weight limitations, this work explores injection molding of polymer composites. Injection molding is well-suited for mass production and polymeric materials can significantly reduce the weight of traditional metallic bipolar plates. While polymers lack electrical conductivity, fillers can be added to fabricate conductive polymer composites. The main objective of this research is to model and injection mold polymer composites that will meet the United States Department of Energy technical target for bipolar plate electrical conductivity (> 100 S/cm).
A fiber contact model was developed to predict electrical conductivity based upon direction in the material, fiber alignment, fiber length and diameter, fiber concentration, and fiber conductivity [2]. Fiber alignment was measured experimentally by imaging cross sections of injection-molded nylon/carbon fiber composites. Imaging was performed on samples with different weight percentages of carbon fiber and from different mold designs to compare how fiber angles change based on mold geometry. To reduce the significant time required to measure fiber angles experimentally, computer recognition and processing of fiber alignment was developed. Nylon composites were injection molded with carbon fiber loadings ranging from 5 to 40 wt%. Modeling predictions show good correlation within 20% of experimental conductivity measurements. Samples with at least 20 wt% carbon fiber exceeded the US DOE technical target for bipolar plate conductivity, reaching 250 S/cm. In addition to modeling electrical conductivity, the Halpin-Tsai equations are used to model the elastic modulus and ultimate strain of the polymer composite. Tensile testing showed that the modulus of elasticity increases with carbon fiber loadings up to 30 wt%, reaching 7.3 GPa. At loadings above 30 wt%, the higher filler content can create voids which decrease the modulus of elasticity.

De Las Heras, A.; Vivas, F. J.; Segura, F.; Andujar, J. M., From the cell to the stack. A chronological walk through the techniques to manufacture the PEFCs core. Renewable & Sustainable Energy Reviews 2018, 96, 29-45.

Weber, M.; Kamal, M. R., Estimation of the volume resistivity of electrically conductive composites. Polymer Composites 1997, 18 (6), 711-725.

Figure 1
3D Printing Conductive Filament for Fuel Cell Bipolar Plates
Authors: Vandervort Zachary E , Lockhart Nicholas J , Hollinger Adam S 
Published: December 2024

Fuel cell bipolar plates are commonly manufactured from graphite or stainless steel. The current production method requires machining intricate channels into these materials which is a costly and time-consuming process. Utilizing a material other than graphite or stainless steel, while still adhering to the standards set by the U.S. Department of Energy for bipolar plate electrical conductivity, could greatly reduce production costs and time. 3D printing bipolar plates could have benefits that include weight reductions as well as ease of testing different flow field designs. However, very few 3D printing filaments are electrically conductive. In this work, conductive samples were printed with Electrifi filament (Multi3D, resistivity: 0.006 Ωcm). This filament is a proprietary metal-polymer composite that has been used to print electronic components such as resistors, capacitors, and inductors [1].
Using Electrifi filament, samples were printed at various conditions to determine optimal print settings for geometric accuracy and maximum electrical conductivity. Printing parameters such as nozzle temperature, flow rate, infill pattern, and infill percentage were varied to affect sample density and conductivity. Several combinations of print conditions led to conductivities that exceeded the US DOE technical target for bipolar plate conductivity. SEM imaging was also performed to better understand the structure of the Electrifi filament. In addition, an Energy-dispersive X-ray spectroscopy scan provided details on the elemental composition of printed samples.

F. Flowers, C. Reyes, S. Ye, M. J. Kim and B. J. Wiley, "3D printing electronic components and circuits with conductive thermoplastic filament," Additive Manufacturing, vol. 18, pp. 156-163, 2017.
(Invited) AEM Water Electrolysis: From Materials to System
Authors: Xu Hui , Stracensky Thomas , Gupta Ankur , Pilczak James , Stone Simon , Slenker Benjamin , Yang J.V. , Li Chenzhao , Pang Yiheng 
Published: December 2024

Anion exchange membrane water electrolysis (AEMWE) is an electrolysis technology that combines the advantages of alkaline liquid electrolysis (ALE) and proton exchange membrane water electrolysis (PEMWE). Specifically, AEMWE may eliminate or reduce the usage of expensive platinum metal group (PGM) catalysts, like its ALE counterpart, while also able to operate at high current density, non-balanced hydrogen pressure, and under dynamic loads, like PEMWE. However, AEMWE has not gained viability in commercial applications due to multiple challenges.
From the materials perspective, both electrodes and membrane need further development. Although the oxygen evolution reaction (OER) catalysts for the anode have been studied at a rotating disk electrode (RDE) level for decades, seeing massive improvement in activities, their applications in the real working AEMWE still needs improvement. One challenge that has not been sufficiently addressed is poor adhesion between the substrate and the catalyst coating, which may fall off due to the force of bubbles formed on the surface of electrodes. While many different catalyst coating methodologies have been tried, the pore size and microstructure of the substrates plays an essential role for the quality of the coating and thus the electrode's stability. In addition, the membrane also has some unsolved problems like poor mechanical strength and chemical stability that compromises the longevity of the electrolyzer. It was also found that the interface between the membrane and electrode is crucial to the long durability of the AEMWE. One solution to this is the development of thermally processable AEMs, which can not only elevate the electrolyzer operating temperatures, but also form a better electrode/membrane interface.
From the system point of view, the stack build needs to consider frames, sealing, pressure vessel, manifold, and shunt current, particularly when the AEMWE operates with the addition of electrolyte (e.g., KOH). Increasing the efficiency of the stack requires minimizing the shunt current, which is affected by the concentration of KOH, the manifold design, and the number of cells in a stack. Lowering electrolyte concentration is instrumental for reducing the shunt current but can be detrimental for the electrolyzer performance. Engineering solutions, such as using an extremal manifold design can tremendously reduce the shunt current, allowing for higher concentration of electrolyte and better performance. Finally, the successful non-balanced pressure operation (up to 50 bar) is not only determined by the membrane strength, but also the morphology of the supporting substrates like porous transport layers and the quality of assembly. These concepts will be validated in our 50 kW AEMWE stack and inform our 1 MW AEMWE design.
Processing of Dense BaCe0.4Zr0.4Y0.2O3-Δ Proton-Conducting Electrolyte for Direct Ammonia Fuel Cell Applications
Authors: Fung Kuan-Zong , Tsai Shu-Yi , Chen Tai-Chen , Tsai Yuan Jie 
Published: December 2024

Proton conducting oxide such as BaCe0.4Zr0.4Y0.2O3-δ(BCZY) electrolyte is known for its unique stability and high ionic conductivity due to the doping effect from the substitution of Zr and Y for Ce ions. For reaching the 2050 net-zero carbon goal, ammonia has been recognized as an important H2 carrier for ease transportation. Thus, using the proton conductor as an electrolyte for ammonia applications including conversion and synthesis provides extra advantages such as lower operation temperatures, negligible NOx emission and better kinetics. Thus, solid oxide cells based on a BCZY proton conducting electrolyte received great attention not only for green hydrogen but also ammonia fuel.
However, the densification of BCZY needs heating temperatures as high as 1400°C. Although the adoption of sintering additives such ZnO or NiO in BCZY has shown some improvement, the densification mechanism remains ambiguous. Thus, the objective of this study is to understand the role and mechanism of adding sintering additive in BCZY. The influence of composite electrode processed at lower temperature on its performance will be also discussed due to the better-densified BCZY. In additions, the resulted electrical and structural properties will be analyzed and discussed based on reactions and densification through heating process. The crystal structure and microstructure of densified BCZY was also characterized using XRD, field-emission SEM, and STEM.
Cation-Anion Engineering for Conductivity Enhancement in Fluorosulfide La2SrF4S2
Authors: Zhong Chengchao , Xu Tailei , Shintomi Yu , Tachibana Shintaro , Shimoda Keiji , Orikasa Yuki 
Published: December 2024

The development of high-performance fluoride-ion (F−) conductors is essential for the practical application of all-solid-state F− batteries, which are expected to have a high energy density (5000 W·h/L). To date, the crystal structures of the F− conductors have been mainly limited to perovskite-, fluorite- and tyssonite-type fluorides. None of these fluorides has yet been found to have high conductivity and a wide potential window at room temperature, necessitating a paradigm shift in materials development.
We found in fluorosulfides La2SrF4S2, the triple-fluorite layer La2SrF4 allows for a two-dimensional F− conduction, which is not found in single anion fluorides[1]. The presence of a sulphur layer widens the conduction space of the F− layer and promotes the F− conduction. In this study, we attempted to improve the F− conductivity in La2SrF4S2 by cation-anion engineering. Specifically, (i) La2SrF4+xS2-xClx, in which S2− was changed to Cl− and excess F− was introduced, and (ii) La2Sr1-xPbxF4S2, in which Sr2+ was changed to Pb2+ with 6s2 lone pair electrons, were synthesized and the change in F− conductivity were explored and explained from a crystallographic point of view.
Solid-state synthesis was used for all samples. The starting materials used were La2S3, LaF3, SrF2 and LaCl3 for La2SrF4+xS2-xClx and La2S3, SrF2, PbF2 and LaF3 for La2Sr1-xPbxF4S2. The raw materials were weighed in stoichiometric ratios, formed into pellets, vacuum-sealed using a Ta container and quartz tubes, and sintered at 1000 °C for 48 h. Powder X-ray diffraction was used to identify the samples, while AC impedance method was used to measure ionic conductivity. For measurements, pellets of the synthesised powder were isostatically pressed (190 MPa), re-sintered at 1000 °C for 48 h and gold deposited on both sides.
(i) The ionic conductivity of La2SrF4.1S1.9Cl0.1 at 160 °C was 6.26 × 10−6 S cm−1, which is five times higher than that of La2SrF4S2. The increase in the conductivity might attribute to the introduction of excess F− in the lattice by replacing divalent S2− with monovalent Cl−. This suggests that the use of mixed-anion compounds allows carrier control by anions, which is different from the carrier control of by cation substitution in previous F− conductors.
(ii) The ionic conductivity of La2Sr0.6Pb0.4F4S2 at 160 °C was 2.56 × 10−4 S cm−1, which are both higher than those of La2SrF4S2 and La2SrF4.1S1.9Cl0.1. 19F MAS NMR showed that the number of F− in the hetero-cationic environment increased after the introduction of Pb2+, suggesting that the distorted cationic sublattice is partly responsible for the conductivity enhancement.
In conclusion, using the mixed-anion compound La2SrF4S2 as a model, we found new strategies to improve F− conductivity by cation-anion engineering.
[1] S. Tachibana, C. Zhong, K. Ide, H. Yamasaki, T. Tojigamori, H. Miki, T. Saito, T. Kamiyama, K. Shimoda, Y. Orikasa, Chem. Mater.
2023, 35, 4235-4242.
Intermediate-Temperature Steam Electrolysis Using Phosphate-Based Thin Film Electrolytes
Authors: Nakagami Ayuka , Tada Shohei , Kikuchi Ryuji 
Published: December 2024

Hydrogen has been regarded as a key energy medium toward the realization of a carbon-neutral society. Currently, hydrogen is mostly derived from fossil fuel without capturing CO2, and does not contribute to carbon neutrality at all. Hydrogen production by water electrolysis powered by renewable electricity is attracting attention as an effective method for "green hydrogen" synthesis that does not emit CO2 in hydrogen production and utilization processes. As a water electrolysis device, we are working on solid-state electrolytic cells with a phosphate-based electrolyte operative at intermediate temperatures from ca. 100 to 300⁰C. This system offers excellent mass transfer characteristics of water (steam) in the electrode catalyst layer and superior electrode reaction kinetics due to an elevated temperature. In addition, it is applicable to electrochemical reduction of N2 and CO2 to NH3 [1] and hydrocarbons [2], respectively.
Several studies using phosphate-based electrolytic cells reported steam electrolysis in the intermediate temperature range [3, 4]. So far, thick disk-type electrolyte and composites with polymers have been employed in steam electrolysis to maintain ionic conductivity and stability under high water vapor pressures, which resulted in high applied voltage and large ohmic loss. Therefore, we aimed to develop a highly efficient steam electrolytic cell at intermediate temperature and to reduce the effective resistance of the electrolyte by developing thin film electrolyte comprising of CsH5(PO4)2/SiP2O7, which exhibits high proton conductivity in the temperature range of 100 to 300°C. Thin film of the electrolyte was synthesized on a porous substrate, and the conductivity and stability of the electrolyte have been investigated. Steam electrolysis cell was fabricated using developed thin film electrolyte, and electrochemical performance of the cell was evaluated in steam electrolysis at intermediate temperatures.
[1] Y. Yuan, S. Tada, R. Kikuchi, Mater. Adv., 2, 793 (2021).
[2] N. Fujiwara, S. Tada, R. Kikuchi, iScience, 25, 105381 (2022)
[3] N. Fujiwara, H. Nagase, S. Tada, R. Kikuchi, ChemSusChem, 14, 417 (2021)
[4] P. Bretzler, E. Christensen, R.W. Berg, N.J. Bjerrum, Ionics, 28, 3421 (2022)
Fabrication of Anode Functional Layer By Reactive Sputtering for Large Area Thin-Film Solid Oxide Cells
Authors: Ju Kyoungjae , Kim Hyong June , Shin Dong Won , Yang Byung Chan , Hong Jee Ho , Jo Sung Eun , Park Wan Woo , Son Ji-Won , An Jihwan 
Published: December 2024

Solid Oxide Cells (SOCs), the electrochemical device that converts chemical to electrical energy, or electrical to chemical energy, have been highlighted for its high efficiency, fuel flexibility, and reversible operation modes between fuel cells and electrolyzers. Recent research has focused on developing intermediate-temperature SOCs (operating between 500 ~ 700°C) to address issues such as thermal durability, and cost. However, reducing the operating temperature presents challenges including decreased rates of charge and ion transport. Consequently, fabricating thin-film SOCs (TF-SOCs) constructed on porous anode supports helps maintain adequate power density even at lower temperatures.
Traditional anode supports, however, present limitations in fabricating thin electrolytes due to their rough surface topographies and large pore structures, inherent to powder-based processing methods. To overcome these challenges, vacuum deposition techniques have emerged as alternatives, offering precise control over micro to nanostructures. This precise control enables the smoother layer, referred to as anode functional layers (AFLs), characterized by finer grain sizes. The fabrication of nanostructured AFLs (n-AFLs) enhances the triple-phase boundary (TPB) length, charge transfer, and overall electrochemical kinetics of the cell.
Despite these advancements, scalability remains a critical problem that prevents the commercialization of SOCs with optimized AFLs. One of the physical vapor deposition techniques, sputtering, attracts attention due to its scalability, reproducibility, and compatibility with multilayered designs. Reactive sputtering allows the deposition of composite materials by introducing reactive gases during the deposition process.
In this study, we fabricated a large-area (12cm x 12cm) n-AFL featuring nano-sized grains via reactive sputtering. A thermal treatment at 1200°C was followed to ensure the structural integrity and stability. By optimizing sputtering power and oxygen partial pressure, we successfully suppress pore and crack formation and Ni agglomeration during the post-annealing, resulting in a durable AFL with enhanced performance characteristics.
The optimized AFL, fabricated under 3kW sputtering power and 80% oxygen partial pressure, effectively mitigates structural defects induced by the thermal process. Consequently, TF-SOCs with n-AFL exhibit impressive performance in fuel cell mode, achieving power densities of 1286mW/cm2 at 650°C and 912mW/cm2 at 600°C. In contrast, cells without the n-AFL show low open-circuit voltages (OCV) of below 0.8V. It is speculated that the gas crossover is due to the pores generated from the heat treatment.
(Invited) Input of Atomic Layer Engineering for Active and Stable Electrodes for Solid Oxide Cells
Authors: An Jihwan , Kim Hyong June , Li Haoyu , Lee Minhwan 
Published: December 2024

Reversible solid oxide cells (rSOCs), which can operate both in fuel cell and electrolysis cell modes, offer an effective solution for the conversion and storage of renewable energy with hydrogen as an energy carrier. Nonetheless, the commercialization of rSOCs remains limited due to technical challenges such as yet insufficient electrochemical performance (particularly in intermediate temperature range of 500-700 °C), short lifespan caused by degradation phenomena, and high system costs associated with the high operating temperatures. rSOCs, therefore, necessitate the appropriate designing and fabrication of highly active and thermally stable bifunctional catalysts with minimal noble metal loadings.
This study demonstrates the route to incorporate highly dense metal catalyst nanoparticles onto the electrodes’ surface of SOC with plasma-enhanced atomic layer deposition (PEALD) process that is the variant of chemical vapor deposition (CVD). For hydrogen electrode, we employed Pt nanoparticles fabricated via PEALD to a nickel-yttria stabilized zirconia (Ni-YSZ) electrode as effective catalysts in fuel cell and electrolysis modes. The superior electrochemical performance of the PEALD Pt@Ni-YSZ catalytic electrode, despite the remarkably low Pt catalyst loading (0.2 µg cm-2), the notable lack of degradation of the cell voltage for 50 h operation at 700 °C. For oxygen electrode, we present a highly effective approach to enhance air electrode performance and durability by depositing an ultra-thin layer of metallic Ru, as thin as ~7.5 Å in nominal thickness, onto (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) using PEALD. Our study uncovers the beneficial role of a newly formed perovskite, SrRuO3, which emerges from the reaction between ALD-based Ru and surface-segregated Sr species.