bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(fluorene)-Based Anion Exchange Membranes with an Interstitial Alkyl Chain in Polymer Backbone and Conducting Groups for Water Electrolysis
Authors: Park Taiho
Published: December 2024

The demand to reduce fossil fuel dependence has received unprecedented attention due to the generation of greenhouse gases and increase in energy consumption. Hydrogen is considered an ideal energy carrier for building a global renewable energy system owing to its numerous benefits, such as high energy efficiency and nontoxicity. However, more than 95% of hydrogen is produced by reformation of natural gas, which is a nonrenewable energy source with high carbon emissions that predominantly consists of methane. To realize hydrogen as a true alternative to fossil fuels, it must be produced in an environmentally friendly and sustainable manner, which is also known as green hydrogen. One approach to generating green hydrogen is by water electrolysis to split water, which is an essentially unlimited resource.

Current approaches to water electrolysis currently use proton exchange membranes, but anion exchange membranes (AEMs) operate under alkaline conditions and thus allow the use of platinum group metal (PGM)-free metals as electrocatalysts, which makes them a more cost-effective alternative. However, AEM water electrolysis (AEMWE) is limited by unsatisfactory cell durability and performance due to the poor physicochemical stability under alkaline conditions and low hydroxide conductivity of the AEM. Therefore, AEMs need to be improved in terms of their mechanical properties, dimensional stability, and alkaline stability to ensure cell durability and in terms of their hydroxide conductivity to ensure cell performance.

For AEMs, an important step in improving the efficiency and durability of the cell is to enhance the ion conductivity and chemical stability of these materials, which are vulnerable to hydroxide. The stable operation of AEMWE under high alkaline conditions and elevated temperatures is necessary; hence, the spacer-type cation groups anchored from the backbone and aryl ether-free based polymers are a promising candidate for tolerating harsh alkaline conditions.

Thus, we newly designed various type of aryl ether-free poly(fluorene)-based AEMs with interstitial alkyl chains in the conducting groups and a polymer backbone for water electrolysis. The rationally designed AEMs not only demonstrated excellent mechanical properties, high alkaline stability and satisfactory hydroxide conductivity, making them excellent cell performance and durability of the AEMWE. The resulting single AEMWE cell using synthesized AEM demonstrates a voltage decay rate of 2 mV kh−
1 at 1.0 A cm−
2, significantly lower than those reported for AEMWEs and Nafion-based PEMWEs. Additionally, a large-sized 1-cell AEMWE stack utilizing PFPBPF-4-QA with an active area of 63.6 cm2 acheived an energy conversion efficiency of 80.2% and a voltage decay rate of 1.5 mV kh−1 for 2,000 h,with over 90% of the initial efficiency maintained for over 49,095 h through exponential fitting calculation.
Highly Durable HT-PEMFC at 250oc Enabled By Self-Assembled Metal Phosphate Network Polymer Membrane
Authors: Lee So Young , Seong JongGeun , Gwak Gyeongseok , Hwang Sonjong , Lim Katie Heeyum , Kim Hyoung-Juhn , Nam Suk-Woo
Published: December 2024

Development of polymer electrolyte membranes (PEMs) that can be operated over 200 °C is an ideal solution for the transition to a hydrogen society. Currently used PEM fuel cells are limited by their low operating temperature, which restricts their use in a variety of applications. Here we developed a new PEM made of cerium hydrogen phosphate (CeHP) and para-polybenzimidazole (p-PBI) comprising a self-assembled network (SAN). Self-assembled, echinoid-shaped CeHP were overlapped together and well-dispersed in the PEM, outperforming proton transport above 200 °C compared to p-PBI and the conventional CeHP-PBI. SAN-CeHP-PBI reached a maximum peak power density of 2.35 W cm-2 (250 °C, dry H2/O2) with negligible degradation for 500 h (thermal cycles of 160 ~ 240 °C, H2/Air) and 4,575 h (80 ~ 160 °C, H2/Air), respectively. SAN-CeHP-PBI also demonstrates excellent CO tolerance, emphasizing its potential for integration into a combined fuel processor-fuel cell system with high energy efficiency.
Ion-Conducting Polymers with Intermolecularly Interacting Groups for Improved Cell Performance and Durability of Anion Exchange Membrane Water Electrolysis
Authors: Min Kyungwhan , Kim Tae-Hyun
Published: December 2024

Green hydrogen production technology has drawn much interest due to its high energy density and eco-friendly energy production of hydrogen. In particular, anion exchange membrane water electrolysis (AEMWE) have been at the core of recent research because of the low cost of hydrogen production by using a non-precious metal catalyst and non-fluorinated ion-conducting polymer electrolyte membranes. Nevertheless, the poor durability and low performance of AEMWE, due to chemical degradation of AEMs in alkaline conditions and the low diffusivity of OH-, need to be addressed for practical use of AEMWE.

In this study, we developed a novel ion-conducting polymers with intermolecularly interacting groups as novel AEMs. This newly developed polymer-based AEMs, exhibited high ion conductivity and excellent alkaline stability, and showed good WE cell performance and durability when applied to AEMWE. The use of this polymer as an ionomer in AEMWE application also showed a promising result.

The details of the synthesis, characterization of the new polymers, and AEMWE cell performance will be detailed.
Ionomer Circularity: Current State of the Art, Advancements, and Challenges
Authors: Gould Benjamin , Karawan Blake , Park Andrew M , Sayler Franchessa
Published: December 2024

The significant environmental and ecological advancements associated with the hydrogen economy cannot be fully realized without robust and scalable recycling techniques. While current techniques are implemented for the recycling of platinum group metals (PGMs), these methodologies rely on incineration of the membrane electrode assemblies (MEAs). These methods thereby result in the destruction of the ion conducting polymer (ionomer) critical to proton exchange membrane-based technologies, as well as the generation of a large amount of hydrofluoric acid which requires significant abatement technologies and can lead to catalyst poisoning. It follows that novel technique development is required in order to realize true circularity for the entirety of the MEAs used in both fuel cells and water electrolyzers. The criticality of this innovation was recently realized by the Department of Energy resulting in a 50-million-dollar funding call, and subsequent selection of the H2CIRC consortium. This combined industrial and academic consortium targets the development of scalable techniques to recover, remanufacture, and reuse all critical components of fuel cell and water electrolysis systems. The topic of the current talk will cover previous efforts in this space, the most pressing challenges and considerations that need to be addressed to achieve circularity at scale, and recent advancements towards the realization of a truly circular hydrogen economy.
A Novel Inorganic Proton Conductor for the Catalyst Layer of HT-PEMFC
Authors: Zhai Yunfeng , Qi Jing , Bethune Keith
Published: December 2024

To develop a novel electrolyte with high proton conductivity under high temperature and low humidity for the cathode catalyst layer of high temperature proton exchange membrane fuel cells (HT-PEMFC), a multilayer structure inorganic material is synthesized with varying oxidation states transit metal complex by refluxing and hydrothermal methods. A fast proton transport pathway is established in the inorganic material by inserting H-bond ligands in the layered structure. With the preliminary tests, the electrolyte powders demonstrate a bulk conductivity of ~10-3 S cm-1 and a particles boundary conductivity of ~10-6 - 10-4 S cm-1 in the temperature range of 20 - 150 °C without humidification, as shown in Figure 1. The boundary conductivity increases with the increasing of testing temperature up to 110 °C then decreases rapidly; but the bulk conductivity barely changes within the testing temperature range. The thermal gravimetric analysis (TGA) indicates the material is stable up to 350 °C in nitrogen (N2) or helium (He). The properties and performance of the material will be further characterized and evaluated; and the structure and composition will be determined. The material will be integrated into the cathode catalyst layer of HT MEAs, and the MEA performance will be evaluated at 120 - 180 °C and low humidity.

Figure 1. The proton conductivity of the inorganic particles at temperature of 20 - 150 °C

Figure 1
(Invited) Membrane-Electrode-Assembly Design Strategy for PA-Based High Temperature Proton Exchange Membrane Fuel Cells
Authors: Lim Katie Heeyum , Lee So Young , Kim Yu Seung
Published: December 2024

High temperature proton exchange membrane fuel cells (HT-PEMFCs) have attained much attention for recent decades, as providing several merits over low temperature PEMFCs (LT-PEMFCs) such as simplified fuel cell system and wider applicable fuel options from high CO tolerance.

To date, most studies on HT-PEMFC have been focused on phosphoric acid-doped polybenzimidazole (PA-PBI) based system. Worth to note, the durability of this PA-PBI based system is still controversial, showing limited durability under dynamic condition, i.e. high current density, repetitive start up/shut down, thermal cycle, etc., which is due to PA loss from the membrane-electrode-assembly (MEA). To address this issue and further enhance the efficiency and durability of HT-PEMFC systems, a new concept of ion-pair HT-PEMFC was recently introduced. This concept has led to high HT-PEMFC performance with ~ 800 mW cm-2 peak power density under air condition and longer durability over 2,500 h, especially showing a superior durability to conventional HT-PEMFCs based on polybenzimidazole (PBI) membranes.1

Here, we investigate how PA works and moves in HT-PEMFC MEAs, both for PA-PBI based and ion-pair based systems. PA distribution and PA loss in MEAs, which determine the performance and durability of the system, are explored by titration before and after five different accelerated stability test conditions and a clear difference is indicated between PA-PBI system and ion-pair based system.2 Based on these analyses, we suggest our perspectives on MEA design for PA-based HT-PEMFCs.

Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S. Protonated phosphonic acid electrodes for high power heavy-duty vehicle fuel cells, Nature Energy, 7, 248 (2022).

Lim, K. H.; Matanovic, I.; Maurya, S.; Kim, Y.; Castro, E. S.; Jang, J-H.; Park, H.; Kim, Y. S. High temperature polymer electrolyte membrane fuel cells with high phosphoric acid retention, ACS Energy Letters, 8, 529 (2023).
(Invited) How to Make Fuel Cells Cheaper and More Efficient
Authors: Meyer Quentin , Zhao Chuan
Published: December 2024

Low-cost, high-performance, and durable hydrogen fuel cells are crucial for the success of the global hydrogen economy and Australia’s hydrogen roadmap. However, their large-scale commercialisation is hindered by their high costs and less than satisfactory efficiency. Hydrogen fuel cells currently rely on costly platinum to generate electricity, with a lot of active research on alternative materials using iron, manganese, and cobalt. While iron-nitrogen-carbon catalysts are very promising replacements for platinum, its hydrogen fuel cells' durability (<300 hours) is much lower than platinum (10 to 20,000 hours), suggesting complex device-level challenges. Dr Meyer's work will provide an overview of these challenges, focusing on how to capture them in real devices, with key findings recently published in Energy & Environmental Science in July 2023. Finally, Dr Meyer will introduce the world’s largest super-resolved digital twin of a hydrogen fuel cell structure generated on the world's most powerful supercomputer. This model allows the visualisation of large-scale (> 16 mm2) water transport using Lattice-Boltzmann simulations. These ground-breaking findings were published in Nature Communications in February 2023. This model will be crucial to further optimize the gas diffusion electrode and flow field structure to improve hydrogen fuel cells' performances.
(Digital Presentation) In-Situ Quantification of Individual Electrode Polarization and Depth Validation of the Distribution of Relaxation Times Methods Feasibility in PEM Fuel Cell
Authors: Li Lu
Published: December 2024

The article titled "Dynamics of anion exchange membrane electrolysis: Unravelling loss mechanisms with electrochemical impedance spectroscopy, reference electrodes and distribution of relaxation times" explores the challenges and mechanisms in anion exchange membrane water electrolysis (AEM-WE). The study by Matthias Ranz and colleagues employs electrochemical impedance spectroscopy (EIS), half-cell measurements using a reversible hydrogen electrode (RHE), and distribution of relaxation times (DRT) analysis to delve into the dynamics of AEM-WE cells.

AEM-WE is gaining attention as a promising technology for hydrogen production due to its potential cost benefits over conventional electrolysis systems. However, its adoption faces obstacles such as efficiency issues and high degradation rates. To address these challenges, the research employs detailed electrochemical characterization techniques, providing new insights into the operational dynamics of AEM-WE cells.

The study reveals five major loss mechanisms within AEM-WE systems: hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and ion transport losses, among others, occurring mostly within the catalyst layers. The findings also discuss the influence of various operating parameters on these loss mechanisms and how they can be systematically tracked and analyzed through EIS.

A significant aspect of the research is the application of DRT analysis, a method not previously used in AEM-WE studies. This analysis method helps in identifying and quantifying the different electrochemical phenomena contributing to cell losses. By correlating these phenomena with their physicochemical origins, the study enhances understanding of the underlying processes within AEM-WE cells.

Moreover, the use of equivalent circuit models in conjunction with EIS data provides a deeper understanding of the electrochemical behavior of the system. This combined approach allows for a more precise characterization of the impedance features and the differentiation of processes such as ion transport and electrochemical reactions.

Ultimately, the research highlights the complexity of the AEM-WE process and emphasizes the need for advanced diagnostic tools to optimize performance and stability. By pinpointing the specific causes of efficiency losses and identifying opportunities for material and process improvements, the study contributes significantly to the development of more robust and efficient AEM-WE systems.

In conclusion, the research not only elucidates the various loss mechanisms in AEM-WE but also showcases the potential of advanced electrochemical techniques like EIS and DRT in enhancing the understanding and optimization of this promising hydrogen production technology. This work sets a foundation for future studies aimed at overcoming the limitations of AEM-WE and advancing towards its commercial viability.
The Structural Profiling Method for Diagnosis of High Performance for LiFePO4 Cathode Materials Synthesized By Environmentally-Friendly Method with Low Cost Resources
Authors: Park Hyunyoung , Park Jong-Il , Kim Junghoon , Namkoong Been , Kam Dayoung
Published: December 2024

Over the past decade, commercialization technologies for olivine-structured LiFePO4 (LFP) cathode materials have been developed primarily in China, with solid-state synthesis methods based on iron phosphate dominating the market. However, there are numerous need prompting more environmentally-friendly process overcoming the production of iron phosphate precursor through co-precipitation processes leading to significant waste generation and environmental pollution issues. In this regard, a solid-state reaction process using iron oxide and lithium phosphate was developed to address this concern. High-purity iron oxide derived from the waste solution generated during the pickling process at steel plants and lithium phosphate produced by POSCO's process in Argentina were utilized in the synthesis of high-performance lithium iron phosphate. LFP cathode material was synthesized through a solid-state reaction and spray drying process, involving two rounds of annealing, resulting in an initial discharge capacity of over 160mAh/g at 0.1C and over 140mAh/g at 1C, along with excellent cycle life performance. In addition, it is also matter how the intermediate product after 1st annealing makes an effect on the performance of final product. Therefore, this research aims to introduce the method of manufacturing lithium iron phosphate and development results from a commercialization perspective, as well as structural profiling method about the product after 1st annealing process in relation with performances of final product after 2nd annealing process using synchrotron-based X-ray tool.
An Extendible Multiphysics Model of a Single Water Electrolysis Cell
Authors: Olguín Godoy Vicente , Blaabjerg Frede , Davari Pooya , Frandsen Henrik Lund
Published: December 2024

The important role that renewable hydrogen has in the energy transition is undeniable given the capability of decarbonizing sectors difficult to electrify acting as the link between electrical energy from renewable sources and molecules for future energy systems. Therefore, improvement of the efficiency, cost and durability of electrolyzer systems is key. The discovery of new materials is one of the research areas in which a lot of effort is focused given that finding more electrochemically active materials allows to reduce overvoltages improving the electrical performance of the electrolyzers. The requirement for these materials is also that they are durable under operating conditions and cheap to produce in order to achieve improvements in all relevant aspects of the technology.

In water electrolysis systems, kinetics, heat management, gas quality, among others, are relevant aspects to understand in order to achieve performance gains. In this line, computational modeling plays an important role in analyzing and understanding the performance of such systems, as well as the effect that different variables have on it. Given the nature of the water electrolysis process, a multiphysics approach is necessary to account for electrochemical, mass transfer, thermal and fluidic processes, as well as their interactions.

Computational models and digital twins are gaining great momentum in electrolysis systems applications, but its availability is limited as its development requires of deep physical knowledge of the different phenomena and their interactions, or large amounts of data. When data is available data-driven models are very useful but the results are not easy to extrapolate when a change in design or materials happens. Therefore, physics-based modelling is a useful tool, as characterization at small scale and short-term is the first step in the discovery of new materials, which allows to obtain physical parameters that act as input for the computational model. This way it is clear that the advantage of developing a physical model is that the model becomes generic, which means that by changing the corresponding design parameters, the performance of a different design can be analyzed.

The current project aims to develop an extendible physics-based model of a single water electrolysis cell. This development will allow to modify different parameters or operating conditions of the cell design and analyze the effect of those changes in the performance. Additionally, the extendible nature allows for its use as single element for analyses in 1D if desired.

The model, developed in OpenModelica, is capable of reproducing the polarization curve of an electrolysis cell, the temperature change between inlet and outlet, the gas crossover and the pressure loss.
(Invited) Catalyst Activity and Durability Evaluations for PEM Water Electrolyzers
Authors: Ioroi Tsutomu , Nagai Tsukasa , Siroma Zyun , Akita Tomoki , Yasuda Kazuaki
Published: December 2024

To accelerate the deployment of green hydrogen, it is essential to reduce the cost of water electrolyzers in addition to reducing the cost of renewable energy. MW-class PEM electrolyzers are already beginning to be offered worldwide, but they still require many expensive materials such as precious metals, PFSA membranes, and titanium for catalysts, electrolyte membranes, PTL, and separators. Especially iridium is a very limited resource, it is necessary to develop highly active iridium oxide-based catalysts that can reduce the iridium loading of anode to sub-mg-Ir cm-2.

In catalyst development, half-cell evaluation (rotating disk electrode, RDE) is a useful method for rapid primary screening of catalytic activity [1]. To determine appropriate evaluation conditions, the effects of various RDE parameters on half-cell evaluation were examined [2]. Specifically, we searched for conditions that minimize the effects of RDE-specific phenomena such as oxygen bubbles, electrolyte solution, and measurement conditions (evaluation potential, amount of catalyst loading on disk electrode, ionomer ratio, electrode rotation speed, potential sweep rate, etc.). For comparison, the OER activity values (mass activity) were obtained under similar measurement conditions using MEA with the same catalyst. Since the activity values of both are in close agreement, the half-cell evaluation would be valid as an initial activity evaluation for iridium oxide catalysts.

The number of start-up and shutdown of electrolyzers is expected to increase significantly under renewable energy conditions, thus the PEM electrolyzer could deteriorate at an accelerated rate. For example, hydrogen crossover causes the anode potential to drop to near the hydrogen potential during shutdown period. Therefore, the potential of iridium oxide anode tends to fluctuate over a wide range from 0 V to >1.5V vs RHE as it starts and stops, which is considered one of the degradation factors. As an accelerated stress test simulating start-up and shutdown, cycle tests were conducted by repeating constant-current electrolysis (4 A cm-2) and constant-voltage holding (0.1 V) at cell temperature of 40-95℃. The results showed that degradation rate can be up to 15 times faster than that in base-line condition, constant-current electrolysis at 2 A cm-2 at 80°C. At the meeting, we would like to also discuss the degradation factors of MEAs under constant-current and accelerated test conditions.

Acknowledgement: This work was supported by a project, JPNP14021 and JPNP20003 commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

References:

S. M. Alia, G. C. Anderson, J. Electrochem. Soc., 166 (2019) F282.

T. Ioroi, T. Nagai, Z. Siroma, K. Yasuda, Int. J. Hydrogen Energy, 47 (2022) 38506.
Investigating Reverse Current Phenomena Induced by Start/Stop Cycling in Lab-Scale Single-Cell Liquid Alkaline Water Electrolyzers
Authors: Maurya Sandip , Leonard Daniel P , Kang Sun Young
Published: December 2024

Liquid alkaline water electrolyzers (LAWEs) represent one of the most mature hydrogen production technologies. Large-scale alkaline electrolysis plants have already been deployed at the 100MW scale. Developments advancing LAWEs are crucial in meeting the soaring demand for hydrogen, driven by efforts to combat carbon emissions and transition to cleaner energy sources. Integrating LAWEs with renewable energy sources like wind and solar holds the potential to facilitate the production of green hydrogen at a low cost. However, a significant challenge arises when coupling LAWE with inherently intermittent renewable energy sources. This challenge comes from the reverse current phenomenon following shutdown, which accelerates the degradation of electrolyzer components, including bipolar plates and electrodes. Typically, when an electrolyzer is shutdown, the anode and cathode on the bipolar plate of neighboring cells discharge rapidly. This causes current to flow through the bipolar plates in the opposite direction to normal electrolysis operation. This results in the oxidation of the cathode and the reduction of the anode. While this phenomenon is observed in industrial-scale electrolyzers and multi-cell stacks, it is relatively difficult to replicate in lab-scale single-cell LAWE setups, where bipolar plates are not typically utilized.

Many researchers have proposed various start/stop cycling protocols aimed at mimicking the reverse current phenomenon to study the degradation of electrocatalysts or electrodes in lab-scale LAWE setups. These protocols often involve voltage or current cycling. However, despite these efforts, the reverse current phenomenon and start/stop cycling protocols are not yet fully understood. Additionally, there remains uncertainty on how these findings can be confidently extrapolated to industry-scale LAWE components. In this study, we have systematically examined several start/stop strategies and their impacts on LAWE performance and component durability. Furthermore, we have applied these start/stop cycling protocols to various anode and cathode catalysts to determine whether these protocols are exclusively applicable to conventional nickel electrodes or universal in nature.

The authors would like to acknowledge the support of the U.S. Department of Energy, and the Hydrogen from Next-Generation Electrolysis of Water (H2NEW) Consortium for their support.
Investigating the Suitability of Printing Metal Current Collectors Directly Onto the GDMs of PEMFCs
Authors: Garsany Yannick , Cronin Kevin , Bethune Keith , Cook Alex , Malakov Robert , Beck Patricia , Stroman Richard
Published: December 2024

Flexible electrochemical energy sources with unconventional cell materials and topologies are becoming more and more popular because they present novel design possibilities that are currently being investigated. Adopting electronics manufacturing techniques to manufacture flexible electrochemical devices can provide advantages such as conformability, high power density, high specific power, and lower costs. This study examines the feasibility of printing metal current collectors (CCs) directly onto Gas Diffusion Medium (GDM) typically used in Proton Exchange Membrane Fuel Cells (PEMFCs). In this work, we print the metal CCs directly onto the GDM using different techniques such as screen printing and ink jet printing. We also investigate the effect of varying the metal CCs geometry (square shape vs. hexagonal), opening ratio (30%, 40% and 50%) and metal thicknesses (10 µm to 50 µm thick) on the overall single cell performance and cell ohmic resistances. Techniques used to understand cell performance include I-V polarization curves, electrochemical impedance spectroscopy (EIS), and thermal imaging. The performance of the cells tested with the embedded GDM/Metal CCs is compared to the performance of a standard cell.
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.
(Invited) Understanding Chemo-Mechanical Degradation Behavior of Solid Oxide Cells in Terms of Ionic and Electronic Transport Properties across Electrode Interfaces
Authors: Lim Hyung-Tae
Published: December 2024

Solid oxide cells (SOCs) exhibit different degradation behaviors, depending on fuel cell/electrolysis cell modes. Chemo-mechanical failure, such as electrode delamination caused by the development of high chemical potential in electrolytes, is one of the critical degradation phenomena. This kind of degradation mechanism is also observed in other types of electrochemical cells, such as solid-state batteries (ASSBs). Similarities exist between reversible SOC and ASSB degradation mechanisms, from the viewpoint of the distribution of chemical potential across at the electrode/electrolyte interfaces. Therefore, it can be said that it is an effective strategy to mitigate SOC degradation through understanding the degradation mechanism of rechargeable lithium-ion batteries, or vice versa. In the present study, the mechanism of electrode delamination in SOCs was investigated with respect to operating conditions, and we determined a critical factor correlated to chemo-mechanical failure. This study also provides critical insights into the chemo-mechanical failure mechanism of a SOC through understanding its similarity to that of an ASSB.
(Invited) Predicting Surface Phase Diagrams of Complex Oxides Under Functionally Relevant Conditions
Authors: Yildiz Bilge
Published: December 2024

Understanding deduced from multiscale simulations have benefited the advancement of materials for solid oxide fuel and electrolysis cells (SOCs) over the past decades. This in particular includes ion transport and defect properties of materials. A remaining key gap is predicting the atomic structure and chemistry of the complex oxides, that is the surface phase diagrams under functional conditions of SOCs. In particular, perovskite oxides that serve as cathode and anode form complex surfaces at elevated temperatures and under varying oxygen chemical potentials. I will share perspectives and progress from the field, including our work, that integrate first principles, machine learning, thermodynamic and grand canonical Monte Carlo calculations to predict surface phases under relevant anodic and cathodic conditions. Being able to predict surface phases will allow us to also interpret and predict the performance of the material, as key reactions in SOCs (oxygen reduction/evolution, water splitting) take place at these surfaces.
Chromium Poisoning Studies on LSC Air Electrode in SOEC vs. SOFC Modes Using a Three-Electrode System
Authors: Park Jun Ho , Seo Jang Woo , Lee In-sung , Lim Hyung-Tae
Published: December 2024

Chromium poisoning in the solid oxide fuel/electrolysis cell deteriorates cell performance by blocking active sites and forming poorly conducting secondary phases. Previous studies have indicated the mechanisms of chromium deposition vary between SOFC and SOEC modes. This study investigates the effects of electrochemical states (SOFC mode vs. SOEC mode) on chromium poisoning using symmetric cells consisting of LSC air electrodes. The cells were tested in the presence of Crofer mesh, both non-coated and Ni-Co coated. A voltage bias was applied to the symmetric cell to induce one electrode to be oxidized (i.e., to be SOEC air electrode) and another one to be reduced (i.e., to be SOFC air electrode). A reference electrode was added to the symmetric cell to measure the overvoltage of each electrode. By applying constant current, we assessed how chromium deposition affects cell degradation relative to the current density. Electrochemical analyses, including electrochemical impedance spectroscopy (EIS), current-voltage measurements, scanning electron microscopy (SEM), electrical dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were employed to understand the chromium migration and deposition pathways and their influences on air electrode in SOEC vs. SOFC modes. The results demonstrate diverse chromium poisoning mechanisms in each mode, influenced by electrochemical states and operational conditions.
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.
Stability Enhancement of Direct Ammonia Solid Oxide Fuel Cells By Using Barium-Modified Ni/YSZ Anodes
Authors: Lee Jun Su , Lim Hyung-Tae
Published: December 2024

Ammonia fuel is attracting interest as a hydrogen carrier gas in solid oxide fuel cells (SOFCs) due to its superior volumetric storage capacity. In this study, comparative analyses of hydrogen and ammonia fuel were conducted for SOFCs. Experiments using a Ni/YSZ-based button cell were conducted to investigate one of the major technical challenges encountered when using ammonia fuel: the nitridation of the Ni fuel electrode. We employed methods such as the addition of alkaline earth metals to prevent nitridation. Accordingly, two types of button cells were fabricated to compare their performance, including power density and ammonia conversion rates. The difference between these cells was in the composition of their anode support layer. One maintained the standard Ni/YSZ formulation, while the other was modified by adding BCZYYb to the Ni/YSZ base. This modification, specifically the addition of Ba, aims to enhance ammonia conversion and mitigate nitridation when operated with ammonia fuel. Both types of button cells were tested at 750℃. Current-voltage (IV) measurements and Electrochemical Impedance Spectroscopy (EIS) analysis were conducted to evaluate the electrochemical performance of the cells. X-Ray Diffraction (XRD) analysis was utilized to examine the presence of secondary phases. Gas Chromatography (GC) analysis was performed to measure the ammonia conversion rates.
Evaluation of Properties of La1-XCexCr0.5Ni0.5O3-Δ for Internal Dry Reforming of Solid Oxide Fuel Cells
Authors: Kim JunHo , Kim Seung Woo , Yu Se Han , Park Gwang Tae , Yun Jeong Woo
Published: December 2024

Dry reforming of methane (DRM) has environmental benefits because it uses CH4 and CO2, two major greenhouse gases that contribute to global warming. Additionally, SOFCs operate at high temperatures, so the DRM reaction can be performed directly internally without a separate reformer. However, the carbon coking generated after the reaction is produced through the pyrolysis of methane and the Boudouard reaction, which can be a major disadvantage of DRM. In this study, La1-xCexCr0.5Ni0.5O3-δ (LCCN) perovskite was investigated as a material to minimize carbon coking and improve catalytic activity for DRM inside SOFCs. LCCN was synthesized through the Pechini method, and Ce was substituted for La in the A-site. At 800℃, the conversion rates of LCCN55, LCCN64, and LCCN82 were high and stable at over 90 % for 40 hours. Oxygen vacancies were 53.3, 40.80, and 34.41 % in LCCN55, LCCN64, and LCCN82, respectively. These oxygen vacancies are important for increasing resistance to carbon deposition. Based on the results of this experiment, we plan to manufacture a fuel cell and measure its electrochemical performance, and as shown in the GC results, it is believed that LCCN55 will show excellent and stable long-term performance.