bluuebunny/crossref_metadata_2025 huggingface dataset:
(Digital Presentation) Thermal Management for Liquid-Cooling PEMFC: From Temperature Control Scheme Towards Control Strategy Modeling
Authors: Yu Yang
Published: November 2022

Efficiency and durability of Proton-exchange membrane fuel cells (PEMFCs) relies on different interacting and coupling factors. The comfort temperature level with good homogeneity is one of the prominent factor, which significantly affects the stack-level and even on-board integrated systems confronted with frequent load changes. Featured with low-grade reaction heat generation (60~80 °C) and high proportion (~50%) accounting for entire yield, liquid-cooling PEMFC stack considerably relies on the construction of thermal management scheme to achieve temperature dynamic heat balance. Similarly, to further improves the electrical efficiency and lifetime, coordinate operation of thermal management BOP components is expected to be fully activated by advanced control-oriented strategy with modeling algorithm. Hence, this review focus on the current status, challenges and future perspectives on extensive potentials for liquid-cooling thermal management system (TMS) in PEMFCs. Firstly, the fundamental temperature control configurations with dual-control targets are introduced, followed by the viewpoint of structure-based as well as material-based, i.e., the effects of cooling channel design (such as parallel, serpentine and wave flow field) and novel coolant adoption (including single metal particles nanofluids and hybrid particles-based nanofluids) upon stack temperature profile and heat transfer performance are reported in detail. Then, the current situation of primary thermal management schemes is supported with classic proportional-integral-differential (PID) feedback control strategy and analyzed to address the necessity of decoupling the temperature parameters to improve the dynamic response for the high-power PEMFC stack. Furthermore, novel control strategies with emerging modeling algorithms (like model reference adaptive control, sliding mode control), oriented for comfort temperature grade, the robust response against varying loads and high efficiency with lower parasitic power, are discussed to evaluate the feasibility and practicality for TMS further integrated into overall energy management architecture of PEMFC system. Finally, in conclusion and perspective, it is appreciated for advanced thermal control strategy to promote single passive temperature control towards proactive thermal management implementation, which is promising and beneficial to identify its substantial potential of low-grade heat recovery and utilization for on-board PEMFC system.

Figure 1
Surface Texture Design of FBR-ALD Pt/C Catalyst to Enhance PEMFC Performance
Authors: Baek Ji-Hu , Jung Myung-Jin , Lee Sung , Jung Yu-Jin , Lee Woo-Jae , Kwon Se-Hun
Published: November 2022

Proton exchange membrane fuel cell (PEMFC) is an efficient electrochemical energy conversion device that directly generates electricity from the chemical energy of fuels without the emission of greenhouse gases. The most reliable catalyst in PEMFC is Platinum (Pt) metal nanoparticles (NPs) that exhibit excellent electrochemical activity and stability compared to other catalysts. However, using of Pt catalyst is limited due to its very high cost and low abundance on Earth. Therefore, it is important to use Pt catalyst efficiently for making the PEMFC economically viable. In this regard, several synthesis techniques have been developed to reduce the loading and uniform distribution of Pt NPs on carbon support with high electrochemically active surface area (ECSA). One of the most efficient techniques to uniformly deposit Pt NPs with a controllable size on carbon support is to use a fluidized bed reactor (FBR) atomic layer deposition (ALD). Our group recently demonstrated that FBR-ALD Pt/C catalysts can exhibit high fuel cell performance and high endurance even with low Pt NPs loading by optimizing the surface of carbon supports combined with proper ALD process parameters [1]. However, it is still challenging to further improve the fuel cell performance by rational designing the Pt NPs surfaces in order to make FBR-ALD into a viable commercial production.

In this study, a unique way to improve the fuel cell performance was suggested to design and optimize atomic scale surface textures of Pt NPs. During the FBR-ALD of Pt NPs, in-situ surface modulation of Pt NPs was applied via a proper protective oxide deposition and etching. A careful surface studies was performed to analyze the surface morphology, distribution and uniformity of Pt NPs. Electrochemical performances were evaluated and optimized by measuring cyclic voltammetry (CV) and oxygen reduction reaction (ORR). Finally, a fuel cell performance was studied through membrane electrode assembly (MEA) characteristics.

References

W. J. Lee, S. Bera, H. C. Shin, W. P. Hong, S. J. Oh, Z. wan, S. H. Kwon, Adv. Mater. Interfaces 6, 1901210 (2019).
Self-Standing MPL and Its In-Situ Liquid Water Measurement in PEFC
Authors: Ishikawa Yudai , Aihara Rikuo , Naito Hiroshi , Sakai Katsunori , Sasabe Takashi , Tanioka Akihiko , Hirai Shuichiro
Published: November 2022

In order to achieve high current density in PEFCs, it is necessary to suppress the increase in concentration overvoltage caused by the liquid water in the gas diffusion layer (GDL), especially in substrate layer. This study aims to reduce the liquid water by removing the substrate layer to form by thin self-standing MPL which is made by specially arranged carbon mesh filled with carbon particles. Thickness of MPL is 50 mm to reduce oxygen transport resistance. Performance of the self-standing MPL was shown in the Fig.1. In-situ liquid water measurements using soft-Xray of self-standing MPL (Fig. (a)) and SGL-25BC (Fig. (b)) are compared. Self-standing MPL shows a drastic suppression of liquid compared with that of SGL-25BC.

Figure 1
Development of Micro-Porous Layers for Unitized Reversible Fuel Cell and Water Electrolyzes
Authors: Yilmaz Abdurrahman , Komini Babu Siddharth , Ramani Vijay K , Pasaogullari Ugur , Spendelow Jacob S.
Published: November 2022

Unitized reversible fuel cells (URFCs) are a promising grid scale energy storage solution that can leverage intermittent renewable energy sources. URFCs operate in both fuel cell (FC) mode during discharge and water electrolyzer (WE) mode during recharge. Inherent disparity in the requirement of the system components of these two operational modes introduces several technical challenges that must be overcome to make URFCs competitive with other energy storage technologies. The wettability requirements of the porous transport layer (PTL) in the oxygen electrode are different for the two operation modes: hydrophilic PTLs provide optimal H2O transport in WE mode, while hydrophobic PTLs provide faster O2 transport in FC mode. PTL design needs to be optimized for both modes in order to resolve this conflicting requirement. We have previously shown that amphiphilic titanium (Ti) felt improved performance in both modes of operations. In this work, a corrosion-resistant micro-porous layer (MPL) is incorporated to facilitate further improvement in the transport of oxygen and water in both operational modes. The MPL is fabricated from corrosion-resistant powders (titanium nitride [TiN], antimony doped tin oxide [ATO], and niobium doped titanium dioxide and polytetrafluoroethylene (PTFE) dispersion. We present experimental results for cell performance and durability through accelerated stress testing of PTLs with amphiphilic MPLs.

Acknowledgment: Financial support from the US Department of Energy through the Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cells Technology Office is gratefully acknowledged.
(Digital Presentation) A Constant Deformation Modulus for the Simulation of Gas Diffusion Layer
Authors: Qitong Shi , Cong Feng , Ming Pingwen
Published: November 2022

The deformation of gas diffusion layer(GDL) directly affects gas diffusion and electron transfer in the fuel cell. The modulus of stress-strain relationship is the basic parameter in the process of deformation. In this paper, based on beam bending theory and geometric probability analysis, a nonlinear analytic model of stress-strain with physical meaning is established, and a constant deformation modulus of GDL is given. Based on the deformation modulus, we further simulate the inhomogeneous deformation of GDL within a half channel-rib model. The results indicate that the uneven deformation with deformation modulus is more significant than that with linear elastic modulus in the same condition. Finally, a shape-dependent bending radius design for the rib edge is proposed, in which the inhomogeneous deformation of GDL becomes smoother as the radius increases, thereby improving the service condition of GDL and prolonging its service life.
PBI-Membrane for High-Temperature PEMFC
Authors: Azizi Kobra , Hjuler Hans , Seselj Nedjeljko , Jensen Jens Oluf , Li Qingfeng , Cleemann Lars Nilausen
Published: November 2022

High-temperature proton exchange membrane fuel cells (PEMFCs) are particularly attractive because of the potential benefits of faster electrode kinetics, high tolerance to fuel impurities, no humidification requirements, and simplified system design.1 The present work focuses on ongoing work based on membrane electrode assemblies (MEAs) for high temperature proton exchange membrane fuel cells. HT-PEMFCs were operated at 160-170 °C using humidified synthetic reformate. We have illustrated that an increase in the pressure of the in-going gases to 2 barG increases - as expected - the performance, E.g. the power density was improved from 0.32 W/cm2 at 0 barG to 0.48 W/cm2 at 2 barG at 170 °C. More data will be shown at the meeting.

Fig 1: a) IV curves b) dependence of power density on back pressure, operating conditions: backpressure (0.4–2 barG), temperature: 170 °C, and λRef/ λAir (1.3 /2.5)

Continuous operation and more than 290 start stop cycles have been performed in order to study the degradation effects of both continuous operation and of repeated start stops. Start stop cycles led to a degradation of 0.01 mV/cycle.

The durability of HT-PEMFC can now be considered similar to low temperature PEMFC. We have proved more than 15,000 hours in single cells at 0.3 A/cm2. The degradation rate is around 4 μV/h for approx. 13,000 hours. Graphs of single cell performance during operation have shown very stable behavior for over 10,000 with an overall degradation of 9 μV/h at a current density of 0.4 A/cm2.

Reference

1) O. Jensen, D. Aili, H. A. Hjuler, Q. Li, High Temperature Polymer Electrolyte Membrane Fuel Cells - Approaches, Status and Perspective, ISBN 978-3-319-17081-7; DOI 10.1007/978-3-319-17082-4, Springer International Publishing, New York, 2015.

Figure 1
Hydrogen Crossover Flux through Two-Dimensional Nanomaterials
Authors: Gaffrey Karli Ann , Bukola Saheed , Blackburn Jeff , Pivovar Bryan S.
Published: November 2022

Energy Storage and conversion devices require an ion-exchange membrane to accomplish high transmission of charge-balancing ions and separation of anode and cathode electrolytes/gases from mixing. These critical functions of membranes play a pivotal role in ensuring device optimum performance and higher efficiency. Most conventional membranes suffer huge ionic and molecular species cross-permeation resulting in low energy efficiency and material degradation. In this work, hydrogen permeability and proton transmission through membrane electrode assemblies (MEAs) that contain a monolayer of hexagonal boron nitride, single-layer and bi-layer graphene were investigated in a gas-phase small-scale cell and a liquid cell. We found that the hydrogen crossover flux through MEAs with 2D materials was inhibited by at least a factor of 5 as compared to the one without. Single-layer graphene and boron nitride enabled high proton transmission, but bi-layer graphene inhibited proton conduction. Defect visualization of 2D materials by chemical treatment with a low ferric chloride concentration followed by imaging using a digital microscope revealed few atomic-scale defects in graphene. These findings suggest that a monolayer of 2D material may provide good selectivity for energy conversion and storage devices by blocking species crossover while allowing high proton transmission.
Development of Pore-Filling Anion Exchange Membranes for Anion Exchange Membrane Water Electrolysis: Enhancement of Resistance
Authors: Jeong Dahye , Lee Minyoung , Akter Mahamuda , Park Jin Soo
Published: November 2022

Water electrolysis is a process that uses electricity to decompose water into oxygen and hydrogen. There are several types of ion exchange membrane can be used, anion exchange membrane, proton exchange membrane and bipolar membrane for water electrolysis. Alkaline based water electrolysis has several advantages to use non-precious electrocatalysts. However, the development of low resistance and durable anion-exchange membranes is of importance. In this study, several anion-exchange membranes were developed to enhance areal resistance, in other words, to minimize areal resistance. Pore-filling anion exchange composite membranes with different contents of cross-linkers were prepared by mixing an electrolyte having good anion conducting ability. The mixture of monomers into a porous polyethylene (PE) substrate were polymerized by UV curing. The pore-filling reinforced composite membranes have been investigated in terms of good electrochemical properties, in particular, areal resistance. The conductivity and areal specific resistance were measured in both in-plane cell and through-plane cell at 80 ℃ and at room temperature, respectively. Characterization in terms of ion exchange capacity, water uptake, swelling ratio, and mechanical strength were also investigated.

Acknowledgments

This research was supported in part by "Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ016253)" Rural Development Administration, Republic of Korea, by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2022 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.
Development of Pore-Filling Anion Exchange Membranes for Anion Exchange Membrane Water Electrolysis: Enhancement of Alkaline Stability
Authors: Lee Minyoung , Jeong Dahye , Akter Mahamuda , Park Jin Soo
Published: November 2022

Water electrolysis is a process that uses electricity to decompose water into oxygen and hydrogen. There are several types of ion exchange membrane can be used, anion exchange membrane, proton exchange membrane and bipolar membrane for water electrolysis. Alkaline based water electrolysis has several advantages to use non-precious electrocatalysts. However, the development of low resistance and durable anion-exchange membranes is of importance. In this study, several anion-exchange membranes were developed to enhance alkaline stability. Pore-filling anion exchange composite membranes with different contents of cross-linkers were prepared by mixing an electrolyte having good anion conducting ability. The mixture of monomers into a porous polyethylene (PE) substrate were polymerized by UV curing. The pore-filling reinforced composite membranes have been investigated in terms of good chemical stability properties, in particular, the variation of conductivity and mechanical strength in 1 M KOH at 60 oC. Characterization in terms of ion exchange capacity, water uptake, swelling ratio, and mechanical strength were also investigated.

Acknowledgments

This research was supported in part by "Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ016253)" Rural Development Administration, Republic of Korea, by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2022 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.
Alkyl Phosphonic Acids: An Alternative to Phosphoric Acid in HT-Pemfcs
Authors: Maurya Sandip , Lim Katie , Hu Zhendong , Jia Hongfei , Klein Jeffrey Michael , Kim Yu Seung
Published: November 2022

Phosphoric acid has received the most attention as a choice of electrolyte for a high-temperature proton exchange membrane fuel cell (HT-PEMFC). Phosphoric acid has many attractive properties such as high anhydrous conductivity, good compatibility with hydrocarbon membranes, and thermal stability [1], which enables high fuel cell performance under anhydrous and elevated operating temperatures (140-180 oC) [2-3]. However, phosphoric acid has undesirable properties such as high catalyst poisoning, high evaporation rate at > 200 oC, and low acid retention from the doped membrane. Alkyl phosphonic acid may correct some of the drawbacks of phosphoric acid, improving fuel cell performance and durability.

In this presentation, we report the technical challenges and possible resolutions for HT-PEMFCs using alkyl phosphonic acid doped membranes. We focus on the effects of alkyl phosphonic acid on hydrogen oxidation and oxygen reduction reactions of Pt-based catalysts. In addition, we discuss the membrane selection of robust operation of alkyl phosphonic acid-based HT-PEMFC.

References:

[1] A.S. Lee, Y.-K. Choe, I. Matanovic, Y.S. Kim, Journal of Materials Chemistry A, 7 (2019) 9867-9876.

[2] K.H. Lim, A.S. Lee, V. Atanasov, J. Kerres, E.J. Park, S. Adhikari, S. Maurya, L.D. Manriquez, J. Jung, C. Fujimoto, I. Matanovic, J. Jankovic, Z. Hu, H. Jia, Y.S. Kim, Nature Energy, 7 (2022) 248-259.

[3] V. Atanasov, A.S. Lee, E.J. Park, S. Maurya, E.D. Baca, C. Fujimoto, M. Hibbs, I. Matanovic, J. Kerres, Y.S. Kim, Nature Materials, 20 (2021) 370-377.
Toward Improved Polymer Electrolyte Membranes in a High Temperature, Low Relative Humidity Environment
Authors: Gangavarapu Pranathi , Foister Shane , Zawodzinski Thomas A.
Published: November 2022

Previous studies on Polymer Electrolyte Membranes have shown that sulfonated polymers exhibit high thermal stability and mechanical properties. The proton conductivity of the sulfonated polymer is strongly dependent upon the degree of sulfonation, where it increases with increasing degree of sulfonation. Also, some observations suggest that densely packed sulfonate groups confer some advantages in allowing more mobile water and protons in the low water content range. In this study bisphenol-based polymers were modified by adding sulfone-amides to form a ball of sulfonates (BOS). Thin, ductile films of the membrane are fabricated by the solution casting method, which resulted in membranes with a thickness of approximately 50 mm. The synthesized copolymers and membranes are characterized by 1 H NMR, FT-IR, ion exchange capacity, water uptake, specific density and proton conductivity measurements. The water uptake and proton conductivity of the membranes are analyzed to determine the impact of varying degrees of sulfonation and side -chains groups within the modified Bisphenol based membranes. Conductivity was tested over a range of temperatures and relative humidity levels simulating potential operating conditions. Water sorption was tested over a range of relative humidity levels to gain an understanding of how relative humidity affects membrane hydration, which is one of the primary factors determining the rate of proton transport in the membrane. In addition, specific density was also measured as density offers insight into membrane hydration and polymer morphology and allows assessment of the mobility of the charge carriers. By studying membranes in this fashion, their performance can be objectively assessed in a controlled environment prior to testing in PEM fuel cells.
Cationic Ionomer Thin Films for Alkaline Electrochemical Energy Conversion
Authors: Kushner Douglas , Katzenberg Adlai , Luo Xiaoyan , Kusoglu Ahmet
Published: November 2022

Ionomers are used as the solid-electrolyte in many electrochemical energy conversion technologies where they offer many functionalities such as ion conduction, electrical insulation, and water transport. These ionomers are found as nanometer-thick electrolyte thin films within the catalyst layers of fuel cells, electrolyzers, and hydrogen-based redox flow batteries where electrochemical reactions take place. The ionomer performance and durability are strongly related to their properties governed by a myriad of parameters such as chemical structure, water uptake, and morphology, all of which are stimulated differently by the external environment. Typically, the ionomer consists of the same ion-conducting polymer used as the electrode separator but exhibit disparate properties from the bulk membrane when nanometer thickness coatings are confined to a hard substrate (as in a catalyst layer), where the behavior is influenced by the ionomer affinity with the air and hard interfaces. Two motifs of ionomers exist, one as an acidic polymer (e.g. Nafion) and the alternative, and less studied, alkaline polymer (e.g. Sustainion).

This talk will focus on filling in the gaps between the disparate properties of alkaline ionomers in the thin film motif that have been extensively studied for acidic ionomers. Aspects such as different backbones (e.g. perfluorinated, aliphatic, aromatic) and side chains (e.g. length, functional group) are explored in X-ray scattering, hydration, and transport measurements. Small-angle X-ray scattering is used to probe the morphology of these different polymer thin-films. Quartz crystal microbalance and spectroscopic ellipsometry under different states of humidity are used to probe hydration and free volume. The resulting correlations provide insights on not only how different polymer respond to the confined environment but how chemistry can be tuned to boost performance in alkaline electrochemical energy devices.
Self-Adhesive Ionomers for Durable Alkaline Water Electrolysis
Authors: Shah Parin , Chen Mengjie , Groenhout Katelyn , Tee Hui Min , Park Habin , Kohl Paul
Published: November 2022

Low-temperature water electrolysis using anion conductive polymer electrolytes has several potential advantages over acid-based polymer electrolyzers. However, the formation of durable, high surface area electrodes remains a challenge. In particular, the adhesion and connectivity of high surface area, particulate catalysts to the porous transport layer is critically important to the long-term cell lifetime.

In this study, a family of covalently bonded, self-adherent, hydroxide conducting ionomers has been synthesized and tested under alkaline electrolysis conditions. The ionomers are based on hydroxide conducting poly(norbornene) polymers used in fuel cell and electrolyzers. Ionomers used in electrolysis electrodes, especially at the oxygen gas producing anode, must provide adhesion between the catalyst particles, porous transport layer and solid polymer membrane. Simple mixtures of ionomer and catalyst can suffer from poor catalyst adhesion because only physical adhesion is used to bind the components together.

The terpolymer and tetrapolymer ionomers used in this work have been functionalized to provide cites for chemical bonding of bis(phenyl)-A-diglycidyl ether to the ionomer, catalyst, and porous transport layer. The resulting electrodes show excellent adhesion of the catalyst particles to the porous transport layer, as determined by adhesion measurements. Electrolyzer results show stable voltage performance over long periods of time.
Assessing Free Radical Scavenging Activity of Various Cerium Materials for Proton Exchange Membrane Fuel Cells Using Fluorescence Spectroscopy Presentation Format
Authors: Chakraborty Alisa , Arges Christopher G.
Published: November 2022

Proton-exchange membrane fuel cells (PEMFCs) are an electrochemical energy conversion device that only has water vapor as an emission. During fuel cell operation, the PEM undergoes mechanical, thermal, and chemical degradation. The chemical degradation is attributed to reactive oxygen species (ROS) that are generated in situ through both chemical and electrochemical pathways during fuel cell operation. Hydrogen peroxide (H2O2) is a reactive oxygen species (ROS) and is often an intermediate formed in the presence of transition metal ion like Fe2+ or Fe3+. The free radical ROS mainly hydroxyl and hydroperoxyl radicals initiate oxidative degradation of both the PEM backbone and the side chains that contain ionic groups that are essential for ion conduction. In this study, various types of free radical scavenger (FRS) additives’ free radical scavenging activity are assessed using ex-situ and in-situ fluorescence spectroscopy(1, 2). Some of FRS materials studied are cerium oxide and doped ceria salts. The scavenging ability of the FRS materials were related to their physio-chemical properties – which were assessed by XPS, SEM, and dynamic light scattering (zetasizer).

V. Prabhakaran, C. G. Arges and V. Ramani, Proceedings of the National Academy of Sciences of the United States of America, 109, 1029 (2012).

V. Prabhakaran, C. G. Arges and V. Ramani, Phys Chem Chem Phys, 15, 18965 (2013).
Molecular Dynamics Study on the Microscopic Mechanism of Mechanical Properties of Nafion Membrane
Authors: Wang Haoran , Mabuchi Takuya , Ji Jiayuan , Huang Sheng-Feng , Tokumasu Takashi
Published: November 2022

As the core component of new energy vehicles, the safe operation of polymer electrolyte fuel cells has become more important with the rapid development of the new energy field. Since polymer electrolyte membrane (PEM) works at a hydrated environment, the mechanical properties of its hydrated state must remain stable. At present, studies have shown that the increase of water content will reduce the mechanical properties of materials, such as the decrease of Young's modulus, but the microscopic mechanism has not been elucidated. This presents a challenge to the work to develop novel PEMs. We tried to use the method of coarse-grained (CG) molecular dynamics (MD) simulation to study the microscopic mechanism of the mechanical properties of basic PEM Nafion membrane under different water content conditions. The purpose of this study is to seek to demonstrate the microscopic mechanism by which macroscopic mechanical properties are determined from the MD perspective, thereby providing general guidance for the future development of novel PEMs. More specifically, we tested the Nafion membrane (CG model with 4 beads on the main chain and 2 beads on the side chain) under tensile and compressive stress (strain 0-0.5) at different water contents (2-14). Quantified micro-parameters make it possible to establish macro-micro relationships. Considering that our chosen Nafion is the basic model, it may have good generality to other complex models.

At the macroscopic level, our results show that increasing the water content reduces Young's modulus of the material. The decreasing rate of Young's modulus shows a slowing trend. This is in good agreement with previous research. At the microscopic level, our results show that the coordination number between any two types of atoms except water molecules within the same volume decreases with increasing water content, suggesting that the increase in water molecules forces other atoms to away from each other, thereby increasing the spacing between molecules. Therefore, the dominant force on this distance scale, that is, the electrostatic attraction between positive and negative ions is reduced. We have a reason to think that this is the main micromechanical factor to change macroscopic mechanical properties.

In addition, the results of polymer chain entanglement parameters show that the degree of entanglement of polymer chains deepened with the increase of water content. The complex entangled structure will increase the difficulty of the polymer deformation. We believe that this is one of the micromechanical factors to decrease the Young's modulus. The study of these mechanisms may help in the development of new Nafion materials.
Impact of Proton Activity in PFSA Membranes on Electrochemical Kinetics Using Microelectrodes
Authors: Anderson Grace C. , Kushner Douglas , Bell Alexis T. , Weber Adam Z.
Published: November 2022

Polymer-electrolyte fuel cells and electrolyzers (PEFC&Es) have the potential to play a prominent role in green energy technologies including transportation, chemical manufacturing, and grid-scale energy storage. PEFC&Es have made significant advancements in recent years, largely due to improvements in the catalyst layers, and especially at the ionomer/catalyst interface. However, it is not yet definitively known how this solid-state environment impacts electrochemical kinetics, especially under various operating conditions (e.g., temperature, humidity, etc.). Additionally, it is challenging to probe local conditions at the catalyst/ionomer interface using traditional analytical techniques. In this study, we explore the influence and nature of proton activity in Nafion and 3M ionomers using a specialized microelectrode setup containing a 50 μm platinum microelectrode in a solid-state three-electrode cell for hydrogen oxidation and evolution (HOR&HER) reactions. Proton activity was calculated through open circuit voltage measurements, and was found to increase with increasing water content, mirroring trends in reaction performance. The effect of proton activity on the reactions' kinetics was investigated using semi-empirical fitting with the Butler-Volmer equation, which gives insight into the reaction rate order and possible mechanism for the reactions. This study demonstrates that microelectrodes can be used to probe solid-state kinetics and can also elucidate complex ion interactions within the ionomer at the catalyst/ionomer interface.
Improved Oxygen Reduction Reaction (ORR) Kinetics Via Interfacial Engineering
Authors: Gawas Ramchandra , Snyder Joshua David , Tang Maureen
Published: November 2022

Sluggish oxygen reduction reaction (ORR) kinetics, even on the best available catalyst (Pt), is one of the major challenges in widespread commercialization of polymer electrolyte membrane fuel cells (PEMFC).1 Significant advances have been made towards making highly active Pt catalysts through nanostructuring, alloying, size, and shape control to mitigate these kinetic losses.2 An additional strategy for ORR activity enhancement is though the targeted engineering of the electrochemical interface. For example, Ionic liquid (IL) interlayers improve the ORR kinetics on bulk and nanostructured catalysts for both Pt and alloyed-Pt materials.3 Along with the kinetic enhancement, ionic liquid interlayers also mitigate the sulfonate adsorption on Pt and improve the durability of Pt/C thin films.4,5

Despite remarkable improvement in performance at half-cell and MEA-level, the mechanism of this improvement is not completely understood. In this work, we combine single crystal voltammetry with microkinetic modeling to analyze the mechanism of ORR enhancement in presence of ionic liquids. With iterative feedback between single crystal voltammetry and microkinetic model output, we establish the importance of accounting for lateral interactions between adsorbed oxygenated species by using real data informed adsorption isotherms. With our experimentally validated model, we show that the mechanism of impact of ILs on ORR activity is through exclusion of water and reduction in electrochemical interface solvation, yielding lower spectator hydroxyl coverages and a reduced barrier for hydroxyl removal, resulting in higher surface site availability during the ORR. This improved understanding will help design Pt-interfaces to moderate the interaction of the interfacial water network with Pt active sites, providing another strategy for improving ORR kinetics.

References:

Debe, M. K. Electrocatalyst approaches and challenges for automotive fuel cells. Nature
486, 43–51 (2012).

Kulkarni, A., Siahrostami, S., Patel, A. & Nørskov, J. K. Understanding Catalytic Activity Trends in the Oxygen Reduction Reaction. Chem. Rev.
118, 2302–2312 (2018).

Snyder, J., Fujita, T., Chen, M. W. & Erlebacher, J. Oxygen reduction in nanoporous metal-ionic liquid composite electrocatalysts. Nat. Mater.
9, 904–907 (2010).

Li, Y., Hart, J. L., Profitt, L., Intikhab, S., Chatterjee, S., Taheri, M. & Snyder, J. D. Sequential Capacitive Deposition of Ionic Liquids for Conformal Thin Film Coatings on Oxygen Reduction Reaction Electrocatalysts. ACS Catal.
9, 9311–9316 (2019).

Li, Y., Intikhab, S., Malkani, A., Xu, B. & Snyder, J. Ionic Liquid Additives for the Mitigation of Nafion Specific Adsorption on Platinum. ACS Catal.
10, 7691–7698 (2020).

Figure 1
(Invited) High-Performance Nitrogen-Doped Pt-Based Core-Shell Catalyst for the Oxygen Reduction Reaction
Authors: Sasaki Kotaro , Zhao Xueru
Published: November 2022

There have been remarkable advances in both the development of promising core-shell catalysts for the oxygen reduction reaction (ORR) and the understanding of the fundamental catalytic mechanisms, and it is clear that some of the low-PGM core-shell catalysts with enhanced activity and stability have great potential for use in PEMFCs. Particularly, the Pt-Co and Pt-Ni core-shell catalysts are considered promising materials for broad deployment to fuel cell systems, even after the shift of focus from light-duty vehicle (LDV) to heavy-duty vehicle (HDV) applications. Nevertheless, there are still various issues that need to be clearly addressed for the advanced core-shell catalysts. A deeper understanding of the mechanisms of catalytic enhancement must still be necessary. In this paper, we will address the recent development of nitrogen-doped Pt-based core-shell catalysts and discuss strategies to obtain the desired ORR performance of Pt-based core-shell catalysts, particularly for HDV fuel cell applications.

Acknowledgments

This manuscript has been authored by employees/guests of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. DOE. Additional work was performed by the Million Mile Fuel Cell Truck (M2FCT) Consortium, technology manager Greg Kleen, which is supported by the U.S. DOE, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office, under Contract No. DE-SC0012704 (BNL).
Electronic Perturbation of Platinum Alloy By Transition Metal-Doping Towards Improved ORR Activity and Stability
Authors: Zaman Shahid , Xia Bao Yu
Published: November 2022

As of today, Pt-based catalysts are the predominant ORR catalysts that meet the desired activity requirements of ORR in fuel cells. However, their broader applications are still challenging due to highly sluggish ORR kinetics, limited stability and higher cost of Pt. In order to develop novel electrocatalyst materials, herein we report surface tuning of binary PtCo alloy through transition metal doping, which reveals superior ORR activity achieving a mass activity of 2.07 A mgPt
-1 at 0.9 V vs. reversible hydrogen electrode (RHE) and excellent durability with minor degradation after 30000 cycles. The ternary PtCoMn@NGNS alloy prepared through facile molten salt pyrolysis reveals a strong metal-support interaction via metal-nitrogen-graphene coordination.

Furthermore, Mn dopants alter the electronic structure of Pt alloy, which improves the oxygen-intermediate binding energy on the interface and suppress the Co dissolution through unique configuration, resulting in enhanced activity and durability of the catalyst. According to the DFT calculations, the surface Mn extensively adsorbs an OH, resulting in increased surface Co stability and overall ORR catalytic performance. Therefore, it is understandable that the development of ternary Pt alloy results in considerable changes in the structural and electrical characteristics of metal overlayer, which varies dramatically from monometallic surfaces.

Our experimental results corroborated by theoretical calculations show that electronic perturbation of PtCo by Mn doping stabilizes the Co and causes significant strain in the Pt(111), which accounts for the increased ORR performance. The strained lattice of Pt caused by Co alloying and surface segregation of Mn both play important roles in the increased ORR activity. Similarly, the Pt3CoMn-OH configuration diminishes Co dissolution and improves overall stability. It is anticipated that such a facile preparation of high-performance electrocatalysts will advance the practical applications of ORR catalysts.

Figure 1:

Figure 1
Polymer Electrolyte Fuel Cell Electrodes with Improved Durability
Authors: Liyanage Wipula Priya Rasika , Yang Gaoqiang , Komini Babu Siddharth , Spendelow Jacob S.
Published: November 2022

Proton exchange membrane fuel cells (PEMFC) are a promising clean energy conversion device for both transportation and stationary power applications. Current PEMFCs contain high loadings of expensive and rare platinum (Pt) based catalysts, which presents an obstacle to widespread commercialization in clean energy applications. While extensive efforts have been devoted to increase the catalytic activity of Pt while reducing the loading and to stabilize Pt particles1, state of the art Pt catalysts typically consist of 2-5 nm Pt nanoparticles supported on carbon (Pt/C). Small Pt particles are vulnerable to degradation due to Ostwald ripening, coalescence, and support corrosion during dynamic operation of the fuel cell. Therefore, before the broader commercialization of PEMFCs can be achieved, the durability and robustness of fuel cell electrodes need to be improved. In this work, we present an alternative novel strategy for improving fuel cell performance durability with a new electrode architecture containing carbon-free catalyst.

Acknowledgement:

We gratefully acknowledge support from the Laboratory Directed Research & Development Program at Los Alamos National Laboratory.

References:

Kim YS, Welch CF, Mack NH, Hjelm RP, Orler EB, Hawley ME, Lee KS, Yim SD, Johnston CM. Highly durable fuel cell electrodes based on ionomers dispersed in glycerol. Physical Chemistry Chemical Physics. 2014;16(13):5927-32.
High-Platinum-Content PGM Catalysts on Atomically Dispersed and Nitrogen Coordinated Single Manganese Site Carbons for Heavy-Duty Fuel Cells
Authors: Chen Mengjie , Zeng Yachao , Zhang Bingzhang , Macauley Natalia , Xu Hui , Wu Gang
Published: November 2022

Fuel cells for heavy-duty vehicles (HDVs) have attracted considerable attention because of their unique scalability, better fuel economy, the less demand for hydrogen refilling infrastructure. However, the potential application requires more stringent fuel cell durability up to 25,000 hours. Membrane electrode assemblies (MEAs) made from platinum group metal (PGM) catalyst with relatively high loading 0.3 mgPt/cm2 play a crucial role in ensuring high-power and long-term durability. Integrating fine PGM nanoparticles and robust carbon support with strengthened interactions is critical for improving MEA performance and durability. Here, a unique atomically dispersed and nitrogen coordinated single Mn site-rich carbon (M-N-C) support was developed for high content (40 wt.%) platinum catalysts for the oxygen reduction reaction (ORR) cathode with reduced thickness. Compared with two controls studied in this work (e.g., a porous graphitic carbon-supported Pt and a commercial TKK Pt/C catalysts), the Pt (40 wt.%)/Mn-N-C catalyst exhibited much enhanced catalytic activity and stability for the ORR in both aqueous acidic electrolyte and polymer electrolyte-based MEA. We carefully elucidated the promotional role of the Mn-N-C support in promoting Pt catalyst concerning its high surface area, partially graphitic structure, and nitrogen dopants, providing better Pt nanoparticle dispersion, and strengthened interactions between Pt and carbon. Consequently, the MEA from the Pt (40 wt.%)/Mn-N-C catalyst can retain 1.2 A/cm2 at 0.7 V (based on HDV conditions (0.2 mgPt/cm2 and 250 kPa air) after 150000 voltage AST cycling. Therefore, the Mn-N-C carbon-supported Pt catalyst holds great promise to meet the challenging DOE target (1.07 A/cm2 at 0.7 V after 150,000 cycles) for HDVs.
Study of Pt Alloy Catalysts for Oxygen Reduction Reaction on Rde and in MEA for High-Temperature Pemfcs
Authors: Lin Honghong , Hu Zhendong , Lim Katie , Zhou Li , Kim Yu Seung , Wang Liang , Jia Hongfei
Published: November 2022

High-temperature polymer electrolyte fuel cells (HT-PEMFCs) have advantages in enhanced fuel impurities tolerance, easier heat rejection, and simpler water management[1]. Low-temperature PEMFCs with perfluorosulfonic acid electrolytes (e.g., Nafion) could not provide sufficient proton conductivity in the absence of water when T > 120 °C, limiting the application when a higher temperature is desired. High-temperature (HT-) PEMFCs have been developed by using phosphoric acid (H3PO4)-doped polymer electrolyte (e.g., polybenzimidazole, quaternary ammonium biphosphate ion pair coordinated polyphenylene, etc.) [2-4], where H3PO4 can conduct proton at high temperature up to 200 °C. Such change of the reaction environment, however, also affects oxygen reduction reaction (ORR) kinetics. Despite of a facilitated reaction kinetics under high temperature, a high Pt loading is still demanded in state-of-the-art HT-PEMFCs. To enhance ORR activity and increase Pt utilization, here we employ a strategy to alloy Pt with another transition metal (M), which has been demonstrated to be effective in LT-PEMFCs. In this study, Pt and Pt-M catalysts were used to investigate the alloy effect on the adsorption strength of H3PO4 and ORR in both half-cell rotating disk electrode (RDE) and membrane electrode assembly (MEA). In RDE study, the competition adsorption of phosphoric acid has led to a suppression on ORR activity on all catalysts, with less impact on ORR at 160 °C using pure H3PO4 than RT using 1 M H3PO4. Since alloying not just affects the O binding energy, but also H3PO4 adsorption, a different trend of ORR on Pt-M alloy catalysts was resulted in the presence of H3PO4. The alloy effect was further studied in MEA at 160 °C, which also indicates the effectiveness of using HT-RDE setup for HT-ORR catalyst screening.

Reference:

[1] Gittleman, C. S.; Jia, H.; De Castro, E. S.; Chisholm, C. R. I.; Kim, Y. S. Proton Conductors for Heavy-Duty Vehicle Fuel Cells. Joule
2021, 5 (7), 1660–1677.

[2] Pingitore, A. T.; Huang, F.; Qian, G.; Benicewicz, B. C. Durable High Polymer Content m/ p-Polybenzimidazole Membranes for Extended Lifetime Electrochemical Devices. ACS Appl. Energy Mater.
2019, 2 (3), 1720–1726.

[3] Lee, K. S.; Spendelow, J. S.; Choe, Y. K.; Fujimoto, C.; Kim, Y. S. An Operationally Flexible Fuel Cell Based on Quaternary Ammonium-Biphosphate Ion Pairs. Nat. Energy
2016, 1 (9).

[4] 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. Nat. Energy
2022, 7 (3), 248–259.
(Invited) Material Requirements for PEM Fuel Cell in Heavy Duty Applications
Authors: Weidler Natascha , Vasquez Mariana , Mahmood Rafat , Jurjević Adrian , Reindl Michael
Published: November 2022

The membrane electrode assembly (MEA) is the core component of the fuel cell stack. Depending on the fuel cell application, lifetime requirements between 10 000- 20 000 hours must be met. The definition of material requirements for fuel cell operation is a big challenge due to the complexity of electrochemical degradation mechanisms and the lack of knowledge about the acceleration factors between different test integration levels. In addition, limited test capacity makes model test development necessary.

Here, we want to present our approach to generate a lifetime prediction model on basis of model stress tests. Defining so called translation factors (structural descriptors) we determine acceleration factors between single cell- stack- and system testing for specific automotive stressors such as Air-Start- Ups and Potential- Cycling. Finally, material requirements are deviated from the life-time predicting model tests.
Understanding the Electrochemical Dissolution of Polymer Electrolyte Fuel Cell Cathode Catalysts for Heavy Duty Applications Using Online ICP-MS
Authors: Kariuki Nancy N. , Wang Xiaohua , Myers Deborah J. , Ahluwalia Rajesh
Published: November 2022

Fuel cells for heavy-duty vehicles (HDVs) have attracted considerable attention because of their unique scalability, better fuel economy, and less demand for hydrogen refilling infrastructure relative to the light-duty vehicle application.1 However, the HDV application requires more stringent fuel cell durability, up to 25,000 h or 1 million miles of operation and increased efficiency. 1-2 Cathodes with relatively high Pt loading (~0.3 mg-Pt/cm2) have drawn extensive attention over initially highly active but unstable Pt-transition metal (Pt-TM) alloy3 catalysts owing to their capability of delivering high performance over long HDV lifetime. To fully exploit the potential of Pt in the HDV cathodes, new insights into the relationship between different drive cycles and operating conditions of HDVs and durability are needed with a particular emphasis on understanding the mechanisms for dissolution of Pt. Several mechanisms for dissolution of platinum have been proposed including direct Pt dissolution and electrochemical oxidation of the Pt surface atoms followed by chemical dissolution of the resulting Pt surface oxide. This presentation will outline the dissolution of Pt under various operating conditions in an electrochemical flow cell system connected to an inductively-coupled plasma-mass spectrometer (ICP-MS) capable of detecting trace concentrations (<ppb) of dissolved elements in solution. The electrochemical data combined with the ICP-MS data are used to evaluate the influence of various factors such as potential, potentiodynamic profile parameters (e.g., scan rate, upper and lower potential limits), Pt catalyst particle size, and support type on the dissolution processes in acidic electrolytes at room and elevated temperatures.

Acknowledgements

This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) through the Million Mile Fuel Cell Truck (M2FCT) Consortium. Argonne National Laboratory is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.

References

A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers, and A. Kusoglu, Nat. Energy, 6, 462 (2021).

Marcinkoski, et al. Hydrogen Class 8 Long Haul Truck Targets (US Department of Energy, 2019);https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf

L. Borup, et al., Curr. Opin. Electrochem.
21, 192–200 (2020).