Fuel Cell Truck Research Articles

Localization method of hydrogen leak source for hydrogen supply cabin of fuel cell truck based on emendatory trilateration and model inversion

Localization method of hydrogen leak source for hydrogen supply cabin of fuel cell truck based on emendatory trilateration and model inversion

Durability Study of Membrane Electrode Assembly for Heavy-Duty Fuel Cells

Polymer electrolyte membrane fuel cells (PEMFCs) are a zero emission replacement for heavy duty applications due to their range, energy density and fast refueling times.[1] In 2020, the U.S. Department of Energy (DOE) lunched the Million Mile Fuel Cell Truck (M2FCT) consortium to fund fuel cell R&D to meet heavy duty truck standards.[2] Durability studies focusing on heavy-duty applications for advanced materials testing under the M2FCT consortium have been extensively explored and continue to be analyzed to standardize the evaluation of next generation fuel cell materials.This study combines in situ electrochemical characterization with ex situ analysis of single cell PEMFCs membrane electrode assemblies (MEAs) to predict long-term durability for heavy-duty applications. Various accelerated stress test (AST) parameters were analyzed to determine the stressors affecting the long-term durability. Local degradation resulting from repeated high voltage to low current cycles was analyzed by testing state-of-the-art materials. High potential holds at various conditions were analyzed to determine membrane chemical degradation. Repeated wet and dry cycles were performed to test the membrane mechanical durability. In situ electrochemical analysis include mass activity, electrochemical surface area, hydrogen crossover, and polarization curves were collected and compared among the MEAs. Ex situ analysis includes quantification of membrane thinning at end of life and fluoride emission rate measurement for water effluent throughout the test was conducted to study the membrane degradation. Acknowledgement: This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy (EERE), US DOE through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.

Accelerated Stress Testing (AST) Protocol Development for Heavy-Duty Fuel Cells

: Polymer electrolyte membrane fuel cells (PEMFCs) are promising for heavy duty applications due to their unique scalability in terms of both power and energy [1], and the U.S. Department of Energy (DOE) established the Million Mile Fuel Cell Truck (M2FCT) consortium in 2020 to advance fuel cell truck R&D[2, 3]. The 2025 end-of-life (EOL) target of M2FCT is to achieve 2.5 kW/gPGM at 0.7 V after 25, 000 hour-equivalent accelerated durability test. Several novel materials have been developed and integrated into membrane electrode assemblies (MEA) and catalysts that meet the EOL target after 90,000 potential cycles in H2/N2 have been reported. However, these reports do not imply that the M2FCT 2025 target has been met since development of the durability protocol and lifetime prediction models for heavy-duty fuel cells are ongoing efforts. The tentative heavy-duty MEA accelerated stress test (AST) protocol consists of H2/Air potential cycling under elevated temperature (90 °C) [4], which the consortium is still actively refining based on the feedback received from the AST Working Group (ASTWG).In this talk, we will systematically summarize the results from the 500-hour H2/Air testing MEA AST, together with various characterization results from microscopy and X-ray analysis, as well as nondispersive infrared to measure support carbon corrosion and fluoride emission rates to measure membrane degradation. With better understanding of the degradation for each component under different testing conditions, we will illustrate the effect of RH (30%, 50%, 90%, and 100%) on the degradation rates of the membrane and catalyst and explain the rationale behind the proposed MEA AST protocol. The degradation rates from the MEA AST protocol were fit into lifetime prediction models and acceleration factors were calculated based on different RHs and cathode catalyst loadings. Refinement of the protocol based on feedback received will also be briefly introduced. Acknowledgment: We acknowledge the financial support for this work from the U.S. DOE) Hydrogen and Fuel Cell Technologies Office (HFTO) through the M2FCT consortium, technology managers Greg Kleen and Dimitrios Papageoropoulos.

Designer Electrocatalysts for the Oxygen Reduction Reaction with Controlled Platinum Nanoparticle Locality

To achieve global deployment of proton exchange membrane technologies, growing efforts in platinum group metals (PGM) recycling must be coupled with substantial improvements in the durability of PGM catalysts. This need for longevity is emphasized by the establishment of the Million Mile Fuel Cell Truck (M2FCT) Department of Energy consortium, devised with durability at its core. So far, improvements in the durability of Pt and Pt-alloy catalysts have focused on surface modifications by small organic molecules (such as melamine), formation of Pt skins (for alloys), and cell design [1–3]. However, the literature transpires a certain reluctance to exploring the interaction between the active material and the often not fully understood carbon support. A handful of studies directly address the effect of support morphology on durability, focusing on the ability of porous carbons to host nanoparticles inside (IN) and outside (OUT) of mesopores [4–7]. Still, the effect of IN vs. OUT is studied on different carbon supports—namely high surface area carbons (HSA) and solid carbons (such as Vulcan), respectively—thus coming short of decoupling nanoparticle locality from carbon support effects. Furthermore, the effects of nanoparticle locality on long-term durability remain unclear.To address these challenges, we present a new class of carbon supported Pt-based electrocatalysts with distinct nanoparticle localities. A methodology was developed to place nanoparticles at will on the inside or outside of carbon mesopores. Specialty carbon blacks from Cabot Corporation pre-production FCX series were used as supports. Synthesis protocols were tuned to ensure that nanoparticle size, crystallinity and loading were the same for IN and OUT catalysts; this way the effect of locality could be studied in isolation from all other parameters. Pt/C catalysts with nanoparticles IN or OUT of mesopores were prepared with Pt loadings of 20 and 40 wt% and shown to have ECSA and mass activity comparable to Pt/Vulcan (30 wt%) from Tanaka Kikinzoku (TKK). Pt-alloy catalysts with controlled nanoparticle locality were also prepared. We believe these materials can serve as model catalysts for long-term durability studies in membrane electrode assemblies. Specifically, given their carefully tailored structure, these catalysts can help address the question of whether placing nanoparticles in mesopores slows down their degradation. Especially for alloys, where degradation is more pronounced and complex, controlling parameters such as carbon structure and nanoparticle locality becomes even more important if we are to improve their durability.[1] H. Daimon, S.I. Yamazaki, M. Asahi, T. Ioroi, M. Inaba, A Strategy for Drastic Improvement in the Durability of Pt/C and PtCo/C Alloy Catalysts for the Oxygen Reduction Reaction by Melamine Surface Modification, ACS Catal. 12 (2022) 8976–8985. https://doi.org/10.1021/ACSCATAL.2C01942.[2] C. Wang, M. Chi, D. Li, D. Strmcnik, D. Van Der Vliet, G. Wang, V. Komanicky, K.C. Chang, A.P. Paulikas, D. Tripkovic, J. Pearson, K.L. More, N.M. Markovic, V.R. Stamenkovic, Design and synthesis of bimetallic electrocatalyst with multilayered Pt-skin surfaces, J Am Chem Soc. 133 (2011) 14396–14403. https://doi.org/10.1021/JA2047655/SUPPL_FILE/JA2047655_SI_001.PDF.[3] S. Liu, S. Hua, R. Lin, H. Wang, X. Cai, W. Ji, Improving the performance and durability of low Pt-loaded MEAs by adjusting the distribution positions of Pt particles in cathode catalyst layer, Energy. 253 (2022) 124201. https://doi.org/10.1016/J.ENERGY.2022.124201.[4] E. Padgett, N. Andrejevic, Z. Liu, A. Kongkanand, W. Gu, K. Moriyama, Y. Jiang, S. Kumaraguru, T.E. Moylan, R. Kukreja, D.A. Muller, Editors’ Choice—Connecting Fuel Cell Catalyst Nanostructure and Accessibility Using Quantitative Cryo-STEM Tomography, J Electrochem Soc. 165 (2018) F173. https://doi.org/10.1149/2.0541803JES.[5] E. Padgett, V. Yarlagadda, M.E. Holtz, M. Ko, B.D.A. Levin, R.S. Kukreja, J.M. Ziegelbauer, R.N. Andrews, J. Ilavsky, A. Kongkanand, D.A. Muller, Mitigation of PEM Fuel Cell Catalyst Degradation with Porous Carbon Supports, J Electrochem Soc. 166 (2019) F198–F207. https://doi.org/10.1149/2.0371904JES/XML.[6] Y.-C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida, Effects of carbon supports on Pt distribution, ionomer coverage and cathode performance for polymer electrolyte fuel cells, (2016). https://doi.org/10.1016/j.jpowsour.2016.02.091.[7] X. Tuaev, S. Rudi, P. Strasser, The impact of the morphology of the carbon support on the activity and stability of nanoparticle fuel cell catalysts, Catal Sci Technol. 6 (2016) 8276–8288. https://doi.org/10.1039/C6CY01679K. Figure 1

Rational Design of Nitrogen‐Doped Low Pt-Loading Electrocatalysts for Fuel Cells: Binary to High-Entropy Alloys and Intermetallics

PtM alloy electrocatalysts (M = Fe, Co, Ni, Cu) have been the subject of many investigations aimed at increasing their attractive properties, in particular, their oxygen reduction reaction (ORR) activity. Despite some success, these catalysts still have relatively high Pt content, unsatisfactory ORR activity, and lack the necessary durability as M metals leach out from the alloys during potential cycling. To alleviate these drawbacks, the BNL team has employed the approach to dope nitrogen (N) in PtM alloy catalysts for the last decade.1-4 The PtMN/C catalysts synthesized by nitriding the core metals through annealing in a flowing NH3 gas exhibited much higher ORR activity and stability compared to those of PtM alloy counterparts. On the other hand, PtM nanoparticles with ordered intermetallic structures are generally more stable against chemical oxidation/dissolution than solid-solution structures. We synthesized a N-doped L10-ordered intermetallic PtNiN core−shell catalyst (Int-PtNiN/C),5 and the result demonstrated that the strategy of combining N-doping and structure ordering can effectively improve the ORR performance of the PtM system in operating fuel cells.6 The Int-PtNiN/C catalyst has been evaluated for heavy-duty vehicle (HDV) applications in the Million Mile Fuel Cell Truck (M2FCT) consortium formed by DOE HFTO. During the development of Int-PtNiN/C in the M2FCT, we found that a new synthesis method using high-pressure nitriding (HPN) could further improve the durability of the catalyst (HPN-Int-PtNiN/C), which met the target under the M2FCT 90K AST protocols for HDV applications.Recently, we extended our strategy to multi-elemental systems; under the DOE L’Innovator project, we applied the N-doping and structural ordering to a quaternary PtCoNiCr system. The resultant Int-PtCoNiCrN/C catalyst showed much improved ORR activity and durability in MEA testing operating at 160ºC compared to those of commercial Pt catalysts, demonstrating that the N-doped intermetallic quaternary catalyst is promising for high-temperature (HT)-FC applications including aviation FC use. We also synthesized a N-doped high-entropy alloy (HEA) catalyst, which comprises a Pt-rich shell and a N-doped PtCoFeNiCu core on a carbon support (donated N-Pt/HEA/C).7 The N-Pt/HEA/C showed high mass activity and excellent stability in RDE and MEA testing, which could be rationalized by the formation of stable multiple M-N bonds coupled with the high-entropy effect. In the paper, we will address the recent development of HPN-Int-PtNiN/C, Int-PtCoNiCrN/C, and N-Pt/HEA/C catalysts and discuss the origins of enhanced electrocatalytic performance based on the results of operando X-ray absorption spectroscopy and scattering measurements, S/TEM/EDS analysis, and theoretical calculations.References K. A. Kuttiyiel, K. Sasaki, Y. M. Choi, D. Su, P. Liu and R. R. Adzic, Nano Lett. 12, 6266-6271 (2012).K. A. Kuttiyiel, Y. Choi, S. M. Hwang, G. G. Park, T. H. Yang, D. Su, K. Sasaki, P. Liu and R. R. Adzic, Nano Energy. 13, 442-449 (2015).E. Lee, K. A. Kuttiyiel, K.-H. Kim, J. Jang, H. J. Lee, M. H. Seo, Y. Choi, T.-H. Yang, S.-D. Y. V. Petkov, K. Sasaki, R. R. Adzic and G.-G. Park, ACS Catal. 11, 5525-5531 (2021).L. Song, Y. Cai, Y. Liu, X. Zhao, K. A. Kuttiyiel, N. Marinkovic, A. I. Frenkel, A. Kongkanand, Y. Choi, R. R. Adzic and K. Sasaki, ACS Appl. Energ. Mater. 5, 5245-5255 (2022).X. R. Zhao, C. Xi, R. Zhang, L. Song, C. Y. Wang, J. S. Spendelow, A. I. Frenkel, J. Yang, H. L. Xin and K. Sasaki, ACS Catal. 10, 10637-10645 (2020).X. R. Zhao, H. Cheng, L. Song, L. L. Han, R. Zhang, G. H. Kwon, L. Ma, S. N. Ehrlich, A. I. Frenkel, J. Yang, K. Sasaki, and H. L. Xin, ACS Catal. 11, 184-192 (2021).X. R. Zhao, H. Cheng, X. B. Chen, Q. Zhang, C. Z. Li, J. Xie, N. Marinkovic, L. Ma, J. C. Zheng and K. Sasaki, J. Am. Chem. Soc. 146, 3010-3022 (2024).

Interpretation of PEMFC Impedance Response Using Continuum Modeling

The proton-exchange-membrane fuel cell (PEMFC) is an energy conversion technology developed to assist in the decarbonization of our energy infrastructure. Oxygen and hydrogen are electrochemically reacted to produce electricity, which can be used to power industrial processes like transportation and manufacturing. For hydrogen viability in heavy-duty transportation applications, PEMFC stacks are required to operate over long times scales, which prompts the development of more durable PEMFCs. Improving the durability of PEMFCs relies on understanding process variables and parameters that cause degradation and performance loss. A common diagnostic tool for electrochemical characterization is electrochemical impedance spectroscopy (EIS), where the current—potential relationship of an electrochemical cell is probed using sinusoidal perturbations, which yields the transfer function known as impedance.Due to the complex physics and chemistry occurring within a PEMFC, meaningful interpretation of impedance spectra is often challenging and relies on assumed equivalent-circuit models. The objective of this work is the development of mathematical continuum first-principle cell-level models capable of providing insight on the relationship between cell properties and measured impedance spectra. The mathematical model is based on a non-isothermal multi-scale continuum model of a PEMFC that accounts for multi-phase transport, where the impedance response is simulated about a steady-state operational mode.The mathematical model was used to simulate experimental measurements obtained from accelerated-stress tests on a commercially available PEMFC membrane-electrode assembly, as shown in Figure 1. Kinetic parameters obtained from a single EIS measurement were generalized to estimate overall cell performance, which was in good agreement with experimental polarization curves. The mathematical model represents the development of descriptive diagnostic tools capable of providing insights into the underlying governing physics and chemistry. Acknowledgements This research is supported by DOE Hydrogen and Fuel Cell Technologies Office, through the Million Mile Fuel Cell Truck (M2FCT) Consortia. Figure 1

Defects in Membrane Electrode Assembly Environments: An Approach to Understanding Membrane Degradation Processes

The performance and long-term durability of polymer electrolyte membrane fuel cells (PEMFCs) are subject to different factors ––material properties, defects, assembly, maintenance and operational procedures.1 Among all the possible failure modes in a fuel cell, membrane electrode assembly (MEA) degradation is a determining factor for performance and lifetime.2 In the past few years, several studies have been developed to understand the degradation of membranes and electrocatalysts, and the corrosion of the carbon support; with a focus on the chemical aspects, rather than the physical features that could promote degradation. More studies are needed to evaluate physical factors that can compromise the MEA structure, especially the aspects that affect the membrane.3 The physical degradation of membranes can be effected by membrane intrinsic factors such as membrane creep, microcracks, and morphological changes.4 Furthermore, it is necessary to study the influence of membrane extrinsic factors ––such as roughness and imperfections at the interfaces between MEA components–– on the processes of membrane degradation. Whether morphological defects are generated before or during the assembly procedure or are intentionally introduced as strategy to improved water management, remains unclear if a defect can act as a precursor pit where membrane could start its degradation. In this sense, more efforts are needed to evaluate the influence of defects on potential and progressive membrane etching and pinholes formation.Our work is focused on understanding the influence of defects, specifically cracks present on gas diffusion layers (GDLs), on the performance and durability of PEMFCs. To control experimental variables associated with different production lots and suppliers, we designed a method to create artificial cracks on the mesoporous layers (MPLs) of commercial GDLs. This technique allows us to compare the cracked GDLs with the pristine GDL, ensuring our “network or pattern of cracks” as the only external variable introduced into the MEA environment. Also, we utilized other commercially available intentionally cracked GDLs as comparative elements. Accelerated stress test (ASTs) were performed and durability results were obtained from long-term (500 hours) fuel cell operation at elevated cell temperature (90 oC). Scanning electron microscopy (SEM) and laser profilometry, were used to characterize all the samples, before and after performance/durability tests. Mechanical and chemical durability of membranes are evaluated based on fluoride emission rates (FERs).This work enables a starting approach to understand the influence of cracks, existing on GDLs, on the membrane degradation processes. Results will give us insights for improving the membrane and GDLs technologies that we are developing in the Million Mile Fuel Cell Truck Consortium (M2FCT).Acknowledgement:This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos.

Porous Nitrogen-Doped Carbon Supported Pt Nanocatalyst for Efficient Oxygen Reduction Reactions

Oxygen reduction reaction (ORR) at catalyst surface is the key kinetic limiting step in fuel cells that influence the overall cell performance in the energy conversion process. Rational design of the carbon supports with unique morphology and controllable porosity is challenging and significant for efficient and durable oxygen reduction electrocatalysis. Nitrogen-doped carbon nanospheres with uniform size and precise control over mesopores and micropores have been derived from mussel-inspired biomimetic polydopamine through a facile colloidal synthesis method and subsequent high-temperature pyrolysis. The unique surface structure of this nitrogen-doped carbon also dictated the morphologies of the deposited platinum nanoparticles, alleviating the particle dissolution, detachment, and agglomeration issue, which are main factors for catalyst degradation in working conditions. The ORR activity and durability of this electrocatalysts were studied in both rotational disk electrode (RDE) system and membrane electrode assembly (MEA), and a detailed structure-property relationship between porosity of carbon supports, Pt morphologies and fuel cell ORR performance was uncovered. This work is informative to researchers working in electrochemical materials field for developing efficient and robust electrocatalyst supports.Acknowledgement: This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.

(Invited) Fuel Cell Technologies: A U.S. Department of Energy Perspective

The U.S. Department of Energy (DOE) supports activities focused on the development of fuel cell technologies that are competitive with incumbent and emerging technologies across diverse applications. Fuel cell technologies for heavy-duty transportation applications are of particular interest as significant reductions in both carbon emissions and criteria pollutant emissions can be achieved.DOE engages in fuel cell research, development, and demonstration (RD&D), working closely with its national laboratories, universities, and industry partners to overcome critical technical barriers to fuel cell development. For heavy-duty applications, RD&D is focused on the development of direct hydrogen-fueled proton-exchange membrane fuel cells (PEMFCs). PEMFC RD&D addresses the materials, component, system, manufacturing, and supply chain challenges to accelerate the commercialization of zero-emission medium- and heavy-duty vehicles, with transferable benefits for other applications.The DOE’s RD&D strategy for fuel cell technologies is driven by application-specific targets. For long-haul fuel cell trucks, these include 2030 targets for cost ($80/kW at high volume production) and durability (25,000 hours). For comparison, the cost in 2023 of a PEMFC system for long-haul trucks based on next-generation laboratory demonstrated technology is projected to be approximately $170/kW when manufactured at a volume of 50,000 units/year.DOE supports a portfolio of RD&D projects and has established the national lab-led Million Mile Fuel Cell Truck Consortium (M2FCT) to advance durability and efficiency of PEMFCs for heavy-duty vehicle applications. M2FCT’s RD&D focuses on meeting a membrane electrode assembly (MEA) target by 2025 that combines efficiency, durability, and cost in a single goal: 2.5 kW/gPGM specific power (1.07 A/cm2 current density) at 0.7 V after 25,000 hour-equivalent accelerated durability test.Supported by the U.S. Infrastructure Investment and Jobs Act, DOE pursues advances in manufacturing and recycling of clean hydrogen technologies to bridge the gap between technology development and deployment. Enabling economies of scale will require a reliable supply of components, automation of the cell and stack assembly, and manufacturing capabilities not seen in the field to date. DOE established capacity targets for heavy-duty fuel cell component and stack production, including a target of 20,000 stacks per year in a single production line by 2030 to enable market lift-off.The DOE’s RD&D portfolio includes recently selected industry-led manufacturing and component supply chain development projects. To complement these projects, DOE relaunched the national lab-led Roll-to-Roll Consortium to advance high-throughput fuel cell and electrolyzer manufacturing, with emphasis on PEM MEA and MEA components.End-of-life challenges for fuel cells and electrolyzers are also addressed. DOE is establishing a consortium of industry, academia, and national labs to develop innovative and practical approaches to enable the recovery, recycling, and reuse of clean hydrogen materials and components, with the goal of securing long-term supply chain security and environmental sustainability.

Dihydroxyl Additives for Enhancing Activity and Durability of Pt/C Catalysts.

Fuel cells are especially attractive as a decarbonization strategy for heavy duty transportation sector. However, the durability and cost of the fuel cell components remains a major barrier for market penetration. Expensive platinum based catalysts, represent a significant portion of this challenge. Therefore, effort to enhance their durability and performance, without increasing the loading, could make a significant advancement towards commercial viability. In this study, we investigated the incorporation of dihydroxyl additive, ellagic acid (EA), in cathode catalyst layers to improve the performance and durability of the catalysts. Our observation revealed that incorporation of EA into cathode catalyst layer led to an increase in mass activity when used with a Pt catalyst supported on either vulcan and high surface area (HSC) carbon support. Increase in the overall conductivity of the catalyst layers due to the hydrophilic nature of the additive could be responsible for improved performance. Decrease in the catalyst activity inhibition by the ionomer adsorption of the platinum surfaces could also result in improved catalytic activity.Further increase in mass activity with the HSC can be achieved by the optimizing the solvent used for ink preparation for enhanced interaction of EA with the platinum inside the pores and not just the surface platinum particles. We also find enhanced durability of both Pt/Vulcan and Pt/HSC catalyst with the chosen additive in accelerated stress tests. The probable reasons for this behavior will be discussed. Acknowledgement This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos.

Advanced ORR Catalysts Based on Intermetallic Nanoparticles and Metal-Organic Frameworks

Metal-organic frameworks (MOFs) based catalysts are emerging as highly promising enablers for high-performance and durable fuel cells. Our novel PtCo catalyst, supported by porous carbon derived from the pyrolysis of zeolitic imidazolate framework-8 (ZIF-8), dubbed PtCo/ZIF8, demonstrates superior performance and robustness during fuel cell operations. Tested under the Million Mile Fuel Cell Truck Consortium (M2FCT) conditions—250 kPa, 85% relative humidity, 90 °C cell temperature, and 15% oxygen—the PtCo/CZIF8 consistently outperformed commercial catalysts at critical operating voltages of 0.7 V and above. Notably, it achieved a current density of 1.43 A/cm2 at 0.7 V after enduring 90,000 accelerated stress test (AST) cycles, surpassing the M2FCT's end-of-life target of over 1.07 A/cm2. Furthermore, the catalyst showed a high mass activity of 0.87 A/mgPt initially, which only declined to 0.59 A/mgPt by the end-of-life test , indicating a 32% loss. In terms of electrochemical surface area (ECSA), the PtCo/CZIF8 maintained about 64% of its initial ECSA after the 90,000 AST cycles, well within the M2FCT’s protocol of less than 40% ECSA loss1. These results establish MOF-based catalysts as front-runners for fuel cell commercialization and are crucial for global efforts to reduce greenhouse gas emissions.Acknowledgement:This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.

Chini Clusters on Oxygen Reduction Reaction (ORR) Catalysts

State-of-the-art oxygen reduction reaction (ORR) catalysts for fuel cells commonly use Pt which heavily increases cost of manufacturing and is a concern for long term sustainability due to the reliance on a precious metal. Therefore, it is clearly desirable to reduce the amount of Pt used in fuel cells. A realistic route to achieve this goal is to continue using this precious metal but minimize the size of Pt particles. In doing so, the surface-to-volume ratio of Pt in the catalyst can be maximized so that the necessary mass of Pt in the fuel cell may be reduced without compromising catalyst performance. To produce small particles (nanoparticles) of Pt with controlled, variable sizes, we developed a method of depositing platinum carbonyl clusters, commonly referred to as Chini clusters, on a carbon support.Pt Chini clusters, [Pt3n(CO)6n]2-, ranging from n = 2–8, have been reported in literature [1-3]. These clusters are synthesized and mixed with different types of carbon supports to perform incipient wetness impregnation (IWI), depositing the Chini clusters onto the support surface. For comparison, an alternative two-step polyol synthesis method is performed to grow Pt nanoparticles to a uniform size and deposit these nanoparticles onto a carbon support surface. Different carbon supports, including Vulcan XC-72R and KB EC300J, are used in synthesis to investigate if Pt Chini clusters of varying sizes and nanoparticles from the two-step polyol method can infiltrate pores and how the nature of a carbon support affects fuel cell testing performance. The as-synthesized Pt/C catalysts are systematically characterized using various techniques including, but not limited to, X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Membrane electrode assemblies are fabricated using the spray coating method and tested in a single 5 cm2 differential cell. Fuel cell performance from these catalysts is compared and electrochemical characterization techniques such as carbon monoxide stripping are employed to measure electrochemically active surface area and Pt accessibility. Our work aims to establish a means of synthesizing ORR catalysts using Pt Chini clusters and characterizing their stability under ambient and fuel cell testing conditions as well as overall performance in fuel cell testing. If the small Pt Chini clusters can be used effectively in ORR Pt/C catalysts, then this may be an effective route to improving fuel cell cost-efficiency and accessibility. Acknowledgement: This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.

Expanding the Scope of ZIF-Derived Carbons Towards Tailored Architectures and Compositions

Proton exchange membrane fuel cells (PEMFCs) represent a promising technology for clean energy conversion. The key chemical transformation within a fuel cell is conducted by catalyst nanoparticles tethered to a carbon support. Although the carbon support plays a critical role in maximizing the performance and durability of the catalyst nanoparticles and mass transport, predictably tuning the chemical environment and pore architecture of the carbon support remains a challenge. Metal–organic frameworks are a class of crystalline porous coordination polymers known for their structural and chemical tunability. Recently, metal–organic frameworks (MOFs), almost exclusively zeolitic imidazolate framework-8 (ZIF-8), have been used as precursors to generate carbon supports where the MOF architecture serves as a template to generate the carbon skeleton. As a result, these materials have an improved homogeneous porous landscape and, encouragingly, superior PEMFCs performance and durability. Herein, we leverage the vast library of MOFs and report design principles for generating precisely tuned carbon support architectures through systematic changes to the structure and chemical composition of MOFs. Advanced fuel cell testing of PEMFCs featuring these novel carbon architectures offers fine level insight into the effects of pore size, connectivity and chemistry on the performance of PEMFCs.Acknowledgement: This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.

Robust Fuel Cell Electrodes: Pt Thin Film Catalysts for Anode Reversal Tolerance

In recent years, polymer electrolyte membrane fuel cells (PEMFCs) have garnered significant attention due to their remarkable attributes including high power density, energy efficiency, and zero-emission characteristics. This surge in interest has primarily been driven by the potential of PEMFC-powered fuel cell electric vehicles (FCEVs) to substantially reduce carbon dioxide emissions in the transportation sector, thereby propelling the advancement of the hydrogen economy on a global scale. However, the widespread commercialization of FCEVs hinges upon addressing key challenges surrounding the durability and resilience of fuel cell systems.One critical issue that has emerged is the phenomenon of hydrogen starvation in the anode, particularly during start-up/shutdown or cold start scenarios, which can lead to rapid and severe degradation of PEMFC performance and durability through cell reversal. This degradation manifests quickly, often within minutes, resulting in abrupt cell failure. Extensive prior research has been devoted to unraveling the mechanisms underlying degradation induced by hydrogen starvation and cell reversal in PEMFCs, with the goal of identifying effective mitigation strategies to minimize damage to membrane electrode assembly (MEA) components.In this study, we introduce an innovative materials approach aimed at mitigating cell damage by employing a thin film Pt anode catalyst supported on Nafion nanowires in a co-axial configuration, referred to as coaxial nanowire electrode (CANE). Leveraging the high roughness of Nafion nanowires, CANE eliminates the need for conventional carbon support and exhibits exceptional tolerance to reversal-induced stress. We present a comprehensive evaluation of CANE as a reversal-tolerant anode, comparing its performance to that of conventional supported catalysts (Pt/C). Furthermore, we explore the potential for further enhancing durability by integrating iridium with the CANE anode. Finally, we will delve into our efforts to evaluate the feasibility of implementing this concept in structures that can be manufactured at scale. This research contributes to the ongoing efforts to enhance the robustness and longevity of PEMFC systems, thereby advancing the prospects of FCEVs as a sustainable and viable solution for future transportation needs.AcknowledgementThis research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos. Authors would also like to acknowledge support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) (2020200DR).

Patterned Hybrid Electrodes for Improved Fuel Cell Performance

Polymer electrolyte membrane fuel cells (PEMFCs) present a promising zero carbon emissions alternative to internal combustion engines. However, PEMFCs face performance limitations, particularly in heavy-duty vehicle applications, largely attributed to cathode electrode inefficiencies. Conventional electrode structures often result in non-ideal tortuous pathways for oxygen (O2) and protons (H+), leading to decreased performance and durability. In this study, we present a novel hybrid electrode structure fabricated using patterned silicon (Si) templates. These templates, created via photolithography and deep-reactive ion etching, facilitate the formation of ordered plus-shaped electrode structures with uniform depth and width. Catalyst with a different ionomer loading/composition is deposited in-between the element of the plus-shaped electrode structure. The resulting novel arrangement in the hybrid electrode structure enables enhanced H+ transport, due to the higher ionomer content in the plus-shaped electrode structures. Additionally, strategically placed dedicated electrode regions with lower ionomer content between the plus shaped electrodes promotes effective O2 transport to reaction sites. We will present the fabrication process, the performance enhancement through this alternative electrode structure and its contribution to the improving the durability of the fuel cells compared to conventional electrode architectures.AcknowledgementThis research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos. Authors would also like to acknowledge support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) (20200200DR).

Nafion Adsorption in Proton Exchange Membrane Catalyst Inks and Its Impact on Fuel Cell Performance

Electrochemical reactions in proton-exchange-membrane (PEM) fuel cells occur within catalyst layers (CL). The catalyst layer consists of a porous network of metal-activated catalyst particles coated with an ion-conducting polymer binder (ionomer) that enables proton transport. Nafion, a perfluorinated sulfonic-acid polymer, is the common binder used and consists of a hydrophobic backbone with negatively charged sulfonic-acid side chains. Prior studies have shown the Nafion distribution in catalyst layers is nonuniform on both the nano1 and micrometer-scale.2 This inhomogeneity is thought to impede catalyst-layer performance by limiting proton transport in Nafion-deficient regions and limiting oxygen transport in Nafion-enriched regions.The Nafion distribution in the catalyst layer is governed by the ink from which it is deposited. The catalyst ink is a colloidal slurry consisting of catalyst-activated particles and Nafion typically dispersed in a water-alcohol solvent mixture. Within this ink, some Nafion adsorbs to the surface of catalyst particles, while the remainder is dispersed in solution. Prior studies hypothesize that adsorption in the ink facilitates a more uniform Nafion distribution in the final catalyst layer, thereby improving transport in the catalyst layer.3,4 Here, we characterize Nafion adsorption in catalyst inks by sedimenting catalyst particles with adsorbed Nafion from inks. The adsorbed Nafion content of the sediment is measured using thermogravimetric analysis. Nafion adsorption to catalyst particles is irreversible and is limited by electrostatic repulsion of the negatively charged Nafion sidechains. We demonstrate that one can control the extent of adsorption by adding mineral acid to the ink to increase the ionic strength and decrease electrostatic repulsion. Through adding acid, the extent of Nafion adsorption to catalyst particles increases by more than a factor of 2 as shown in Figure 1 below.Next, the effect of Nafion adsorption in the ink is correlated to final catalyst-layer performance and properties via cell diagnostics including sheet resistance, polarization performance, and limiting-current measurements. Overall, the talk will elucidate the governing interactions that control Nafion adsorption and how this adsorption affects performance.AcknowledgementsThis work was funded under the Million Mile Fuel Cell Truck Consortium.

Benchmarking Composite Fuel Cell Membranes

Proton-exchange membrane fuel cells (PEMFCs) are a unique clean energy technology capable of decarbonizing the transportation and energy sectors, particularly in cases where batteries are poorly suited. Of particular interest is the heavy-duty transportation sector where demanding weight and range requirements are better satisfied by PEMFC technology. One of the most technical challenges in realizing PEMFC technology for the transportation sector is the greater need for durability, with over 5x improvements in lifetime needed to achieve 1 million miles as targeted by the Million Mile Fuel Cell Truck Consortium (M2FCT). Recent strategies towards improving membrane durability include mechanical reinforcement and chemical additives to reduce the mechanical stresses due to hydration cycling and to quench hydroxyl radicals before membrane degradation occurs, respectively. Of particular interest in this work is a membrane by Chemours referred to as NC700 which encompasses mechanical reinforcement and chemical additives. NC700 is baselined to N211 membranes that have been subjected to various treatments. Herein, we discuss the trade-offs of chemical additives, mechanical reinforcement, and ionomer changes in physical and transport properties such as water mass uptake and volumetric swelling, proton conductivity, and mechanical strength across a wide range of humidities and temperatures. By combining all of these facets, an understanding of how these different inputs alter the material properties that will not only serve as a benchmark for future membranes but feed into future models and serve as a starting point for integration and durability efforts.

Medium-Duty Road Freight Transport—Investigation of Consumption and Greenhouse Gas Emissions of Battery Electric and Fuel Cell Trucks with Model-Based Predictions Until 2050

The present work intends to make a scientific contribution to future drive technology in medium-duty road freight transportation that is as objective and fact-based as possible. In cooperation with a medium-sized forwarding company, 1-day transports, previously driven with diesel trucks, were examined. Using a physically based model, which was first validated by comparing simulated CNG drive data with real-world diesel data, the findings were transferred to battery electric trucks (BETs) and fuel cell trucks (FCETs) and extrapolated to 2050 based on expected technological developments. The model makes statements based on the results of the investigated application regarding specific consumption, greenhouse gas (GHG) emissions, consumption shares and recuperation. The CNG combustion technology (ICET-CNG) serves as a reference. BETs in this application have the lowest emission and consumption values: BET2050 will consume a third of the energy and emit a fifth of the GHGs of ICET-CNG2024. The weight of the battery leads to higher consumption values. FCETs have higher fuel consumption due to their longer drive trains. This is partially compensated by their lower weight: FCET2050 will consume 40% of the energy and emit a third of the GHGs of ICET2024. In long-distance traffic, aerodynamic drag is the dominant consumption factor, accounting for 40%, which should be addressed in further truck development. Recuperation extends the range by 3–7%.

Research on energy-saving optimization strategies of high-power hydrogen fuel cell power systems

Temperature regulation stand and hydrogen consumption as pivotal benchmarks in the assessment of fuel cell vehicle performance. To enhance the thermal control efficiency and fuel economy of high-power fuel cell power systems, this study formulates a model for a high-power hydrogen fuel cell power system. It meticulously scrutinizes the energy consumption of auxiliary components, notably cooling systems, and devises a power allocation strategy founded on fuzzy logic control, ensuring precise temperature control. Introducing a collaborative optimization control approach for heat and power, aimed at minimizing overall hydrogen consumption, constitutes a central aspect of this paper. Leveraging the parameters of a 115 kW fuel cell truck, the study conducts simulation analysis of control and optimization strategies utilizing the Matlab/Simulink platform. Results underscore the superiority of the collaborative optimization control strategy, demonstrating noteworthy 8.04% and 9.9% reduction in equivalent hydrogen consumption per 100 kilometers compared to the power following control strategy. These findings affirm the efficacy of the proposed strategy in optimizing energy consumption.

Model-based Development Using the Example of a Fuel Cell Truck

Model-based Development Using the Example of a Fuel Cell Truck