Fuel Cell Program Research Articles

Mesoporous Carbon Supported Catalyst for Heavy Duty Fuel Cells

The interaction between the catalyst and the carbon support is crucial to both the performance and durability of the membrane electrode assembly (MEA) in a polymer electrolyte membrane fuel cell. Local oxygen transport resistance (RO2) has shown to be a significant contributor to the overpotential loss in the catalyst layer.1 Utilizing mesoporous carbon supports has shown to reduce RO2 compared to high surface area carbon and prevent ionomer poisoning of Pt inside the pores.2 Engineered catalyst supports (ECS) synthesized through templated organic precursor provides improved control of resulting carbon morphology.3 This work presents a detailed study of the performance and durability of the ECS supported catalyst. Effect of Pt weight percentage on the carbon support, ionomer loading, and the ionomer type on the catalyst performance and durability is presented. Figure 1 shows the performance at beginning of life (BOL) and end of life (EOL) after 90000 cycles, using US DOE’s electrocatalyst protocol, for MEAs with different ionomer loadings. Polarization curve, Pt accessibility through CO stripping, and RO2 from limiting current will be presented are measured at different intervals between BOL and EOL. Characterization of the Pt particle and catalyst layer structure performed at BOL and EOL will also be presented. This study highlights the value of the morphological and electrochemical evaluation to provide detailed insights into the catalyst and mesoporous carbon support interaction. Acknowledgement This research is supported by Technology Readiness Gross Receipts Tax Credit through New Mexico Legislature. This research is supported by U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office, through the Million Mile Fuel Cell Truck Consortium (M2FCT). References 1 Kongkanand, A. et al. Journal of Physical Chemistry Letters, 7, (7), 1127-1137, 2016.2 Ramaswamy, N. et al. Journal of The Electrochemical Society, 167, (6), 064515, 2020.3 Ramaswamy, N. US DOE Hydrogen and Fuel Cells Program: 2020 Annual Merit Review and Peer Evaluation Report, 2020. Figure 1

(Invited) Progress in Development of Platinum Group Metal-Free Electrocatalysts for Oxygen Reduction Reaction in Polymer Electrolyte Fuel Cells

Platinum group metal-free (PGM-free) catalysts for oxygen reduction reaction (ORR) in polymer electrolyte fuel cells have emerged as a promising alternative to PGM-based catalysts thanks to their abundance in the Earth crust and, consequently, low cost. Metal-nitrogen-carbon (M-N-C) catalysts possibly represent the most attractive PGM-free ORR materials. However, despite the significant progress accomplished in M-N-C catalyst development over the past two decades, this class of materials continues to face challenges that need to be overcome to narrow the performance gap to PGM-based catalysts.[1] Our team has made significant efforts to improve the activity and stability of M-N-C catalysts by developing novel synthesis approaches, such as the ‘dual-zone’ synthesis, targeting specifically improvements in catalyst stability.[2, 3] We have also established standardized protocols for the activity and stability evaluation of PGM-free catalysts under relevant operating conditions of the fuel cell.[4] Additionally, our modeling of PGM-free M-N-C ORR electrocatalysts has provided much needed insight into the materials and helped with their optimization. We have utilized machine learning methods coupled with high-throughput synthesis and characterization to optimize the conditions for a variety of synthesis approaches, which has led to substantial increase in experimentally realized activity.[5, 6] Our prior fundamental studies of ORR activity [1, 2, 7, 8] and materials stability [9] at the density functional theory (DFT) level are actively being linked to achieve simultaneously high activity and long-term stability through a Pareto optimization. Coupling machine learning and DFT efforts is presently underway.In this talk, we will summarize our recent progress in the development of PGM-free M-N-C catalysts for ORR, focusing on improvements in catalyst activity and stability from both experimental and theoretical perspectives. We will highlight various synthesis strategies for improving catalyst activity and stability, and key design principles for M-N-C catalysts, learned from DFT calculations and machine learning-driven, high-throughput catalyst synthesis. We will also discuss the challenges and opportunities in the development of PGM-free catalysts for ORR. Overall, PGM-free catalysts represent a promising pathway for the advancement of low-cost and efficient fuel cell technologies. References Martinez, U. et al., J. Electrochem. Soc., 2019. 166, F3136.Chung, H.T. et al., Science, 2017. 357, 479.Zelenay, P. and D. Myers, ElectroCat (Electrocatalysis Consortium); U.S. Department of Energy Hydrogen and Fuel Cell Program Annual Merit Review 2019. https://www.hydrogen.energy.gov/pdfs/review19/fc160_myers_zelenay_2019_o.pdf.Zhang, H. et al., Nat. Catal., 2022. 5 (5): 455.Kort-Kamp, W.J.M. et al. . J. Power Sources, 2023. 559: 232583.Karim, M.R. et al., ACS Appl. Energy Mater.. 2020. 3 (9): 9083.Holby, E.F., Curr. Opin. Electrochem., 2021. 25, 100631.Anderson, A.B. and E. F. Holby, J. Phys. Chem. C, 2019. 123 (30): 18398.Holby, E.F., G. Wang, and P. Zelenay, ACS Catal., 2020. 10 (24): 14527.

Oxygen Reduction Reaction Activity of Platinum Nanosheets Derived from Layered Platinic Acid

Platinum nanoparticles are mainly utilized as the cathode catalyst for polymer electrolyte fuel cells. However, the utilization of platinum for the oxygen reduction reaction (ORR) is insufficient and one must tackle the trade-off between high surface area and high stability. We have previously shown that metallic nanosheets such as ruthenium nanosheets exhibit high electrocatalytic activity and stability owing to the two-dimensional structure with an atomic scale thickness.1, 2 Platinum nanosheets, if available, should also have the potential to increase the utilization of the atoms and durability. While a few studies have reported the synthesis of platinum nanosheets,3 the thickness of the nanosheets is more than 1 nm, and the utilization of platinum has so far been lower than that of the Pt nanoparticles.In this study, we report double-layered platinum nanosheets derived from layered platinic acid.4 Layered platinic acid was synthesized through a solid-state-reaction and subsequent acid treatment. From the layered platinic acid, platinum oxide nanosheets were obtained as a colloid via chemical exfoliation. The thickness of the platinum oxide nanosheet was ~0.9 nm, consistent with the thickness of a single PtO6 octahedron. The platinum oxide nanosheets on silicon wafer were topotactically reduced to platinum nanosheets by mild thermal treatment in hydrogen. The thickness of the platinum nanosheet was ~0.5 nm, corresponding to a two atomic layer platinum nanosheet.Carbon supported platinum nanosheets were prepared by the reduction of platinum oxide nanosheets supported on carbon. The electrochemically active surface area (ECSA) of the carbon supported platinum nanosheets was 100 to 120 m2 (g-Pt)-1, which was considerably larger than that of 3 nm platinum nanoparticle (80 m2 (g-Pt)-1). In addition, the platinum nanosheet showed 1.7 times higher mass activity towards the oxygen reduction reaction compared to that of 3 nm platinum nanoparticles.Various methods for the topotactic reduction of platinum oxide nanosheets on carbon was studied. In addition to the mild thermal treatment in hydrogen gas, electrochemical reduction was also conducted. The ECSA of the platinum nanosheet prepared by electrochemical reduction at constant potential was 100 to 120 m2 (g-Pt)-1, which was almost same as the platinum nanosheet reduced by the mild thermal treatment in hydrogen. The specific activity was 1.2 to 1.3 times higher than that of the platinum nanosheet reduced by the mild thermal treatment in hydrogen. Therefore, the platinum nanosheet reduced by electrochemical reduction showed high mass activity for ORR.AcknowledgementThis work was supported as part of the “Polymer Electrolyte Fuel Cell Program” and the FC-Platform projects from the New Energy and Industrial Technology Development Organization (NEDO) of Japan (20001201-0, 22101136-0).

(Energy Technology Division Walter van Schalkwijk Award in Sustainable Energy Technology Address) Exploring New Electrode Designs with Nanofibers

In recent years, electrospinning has been gaining popularity as a robust and scalable technique for the fabrication of non-woven mats of sub-micron diameter polymer fibers. Although not as well studied, the technique can also be used to prepare particle/polymer fiber networks with high intra- and inter-fiber porosity. Such fibrous mats can be used as porous electrodes in fuel cells and batteries, where a high electrode/electrolyte interfacial area is needed. In this talk, particle/polymer electrospinning will be presented as a platform technique to fabricate a variety of electrode and membrane-electrode-assembly (MEA) products with unique and desirable compositions, architectures, and performance characteristics. Laboratory results will be presented for: (1) hydrogen/air fuel cell cathodes with Pt/C and PGM-free catalysts, (2) Pt/C hydrogen electrodes in a H2/Br2 redox flow battery, and (3) Si anodes for lithium-ion batteries.High particle content fibers containing Pt/C or Pt-alloy catalyst powder and a Nafion®perfluorosulfonic acid binder have shown great promise as electrodes in H2/air fuel cells. During electrospinning, Nafion ionomer migrates to the outer edges of the fiber, effectively creating a core-shell fiber morphology, with a low I/C ratio in the fiber interior. Additionally, the interior of the fiber contains nm-size pores and the outer surface of the Nafion shell exhibits enhanced hydrophobicity, due presumably to an accumulation of the polytetrafluoroethylene backbone chains (-CF2-CF2-) of Nafion. The resulting structure is advantageous in that the majority of catalyst particles are in a low I/C environment, nanopores in the fiber interior trap electro-generated water via capillary condensation, and the hydrophobic surface of the fibers facilitates electrogenerated water removal from the mat during fuel cell operation. The fuel cell power output using fiber mat anodes and cathodes is very high for a low Pt loading (0.10 -0.20 mg/cm2), near or above 1.0 W/cm2 for H2/air feeds in the range of 60-100% relative humidity.1,2 Additionally, the fiber mat cathodes exhibit excellent durability, with minimal power loss after accelerated voltage cycling tests. The hydrophobicity of fibers can be enhanced by adding polyvinylidene fluoride (PVDF) directly to the Nafion binder. Such blended binders in fiber/particle hybrid electrodes extend the operational lifetime of fuel cells with iron-based PGM-free cathode MEAs.As an extension of the fuel cell electrode work, electrospun Pt/C-Nafion nanofiber mat hydrogen electrodes have been made and tested for a H2-Br2 redox flow battery.3 The hydrophobic surface coating of core-shell fibers effectively blocks bromine species from poisoning the hydrogen electrode. In a 6.6 M HBr electrolyte lab-scale redox flow battery, the fiber mat electrodes worked extraordinarily well, with: (i) high power at low Pt loading, e.g., 650 mW/cm2 at 0.70 Vfor a loading of 0.11 mgPt/cm2 (6.4 kW/gPt) and 550 mW/cm2 at 0.65 V for a loading of 0.048 mgPt/cm2 (11.5 kW/gPt), (ii) no loss in power for more than 170 charge/discharge cycles, and (iii) a roundtrip current efficiency of 95%at both 0.2 and 0.3 A/cm2.For Li-ion battery applications, single and dual fiber anode mats have been prepared and evaluated, where the fibers contain a polymer binder (e.g., polyacrylic acid, polyamidimide, or polyvinylidene fluoride), Si nanoparticles as the electrochemically active material, and carbon powder as an electron conductor.4 Here, the gravimetric and areal capacities of the fiber anode are considerably higher than those of a conventional carbon particle anode. Inter-fiber voids allow for volume changes in Si during lithiation/delithiation, thus minimizing capacity fade during charge/discharge cycling (up to 600 cycles).AcknowledgmentsThis work was funded by the U.S. Department of Energy, Contract No. DE-EE0007653 from the Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability Consortium (Fuel Cells Program Manager: Dimitrios Papageoropoulos) and Contract No. DE-EE0007215 from the Vehicle Technology Office.

(Digital Presentation) Modeling Water Transport in Proton Exchange Membrane Electrolyzers through First Principles

The efforts to decarbonize transportation and heavy industries, like agricultural chemicals, steel, etc., have increased over the past decade [1-2]. A practical solution to these efforts is using renewable energy (wind, solar, hydro) to produce hydrogen to replace fossil fuels in these energy-intensive applications [1]. The production of hydrogen via water electrolysis has been receiving tremendous attention over the past few years [1-3]. There are mainly three technologies that are employed for water electrolysis – alkaline, polymer electrolyte membrane (PEM), and solid oxide [3]. Intermittent renewable energy provides an advantage to PEM electrolysis due to the robustness of the technology capable of multiple start-stops and variation in applied power [4].PEM electrolyzer technology is improving and becoming market-ready in several countries [3]. The current focus on PEM electrolyzers ranges from improving lifetimes and electrical efficiency, reducing cost by the development of advanced materials/designs, and simplifying the balance of plant/systems designs [1]. The mathematical modeling of PEM electrolyzers is thus an active area of research for substantially reducing development costs and timelines and improving electrolyzer designs [3-4]. However, there are certain phenomena with PEM electrolysis where the current models are semi-empirical and simple first principles-based mechanistic quantifications are lacking.Figure 1 shows a simplified schematic of the physical and chemical phenomena during the operation of a PEM electrolyzer. The anode and cathode are divided by a membrane that is capable of exchanging cations across. The membrane is coated with catalyst layers on both sides to facilitate the reactions. Typical membranes used in electrolyzers belong to the Nafion® family and are perfluorosulfonic acid-based materials [3-7]. Porous transport layers are used to facilitate the interaction between gas and liquid phases in the cell. Water is fed to the anode side of the electrolyzer and is oxidized to produce oxygen gas. Typically, no water is fed to the cathode, since the anode is maintained at a high pressure (~3-70 bar), liquid water condenses and exits the electrolyzer with the hydrogen. The hydrogen gas is fed through a dryer before it is deemed suitable for use. The oxygen gas is also dried and used where needed.In this work, we present a first principles-based water transport model to quantify the movement of water across the electrolyzer cell and predict the quality of the hydrogen gas produced as a function of varying operating conditions and cell designs [4,8,9]. To model the movement of water on the cathode side, three sets of equations are obtained – I. material balances for hydrogen and water in the flow channel (z-direction), II. water movement across the membrane in the x-direction, and III. expressions for variable membrane properties to serve as inputs for I and II [4,5,6,8]. For water movement across the membrane, we consider the contributions from diffusion, electro-osmotic drag, and pressure-driven flow. The condensation of water at the cathode is also modeled to understand the respective transport contributions from the vapor and liquid phases. The coupled equation sets are solved using a Runge-Kutta ODE routine with appropriate boundary conditions. The results of the modeling case studies will be compared with the experimental data available for water transport [9]. References Satyapal, H2@Scale R&D Consortium Kickoff Meeting H2@Scale Overview Chicago, IL – August 1, 2018.Pivovar, 2019 DOE Hydrogen and Fuel Cells Program Review, April 30, 2019.S. Kumar and V. Himabindu, Material Science and Energy Technologies, 2, 442, (2019)Ma et al., International Journal of Hydrogen Energy, 46, 17627, (2021).E. Springer et al., Journal of the Electrochemical Society, 138, 2334, (1991).M. Bernardi and M. W. Verbrugge, AIChE Journal, 37, 1151, (1990).A. Zawodzinski et al., Journal of the Electrochemical. Society, 140, 1981, (1993).Marangio et al. International Journal of Hydrogen Energy, 34, 1143, (2009).Medina and M. Santarelli, International Journal of Hydrogen Energy, 35, 5173, (2010). Figure 1

Total Energy for the SOFC and SOEC

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy and Carbon Management (FECM) is currently developing low-cost SOFC and SOEC systems. This paper develops the governing Total Energy (TE) (kilowatt-hours per kilogram hydrogen) equation for the SOEC. The eight-component TE equation includes heat input, exergetic flows, enthalpy of vaporization, pressurization, heat loss, area specific resistance, etc. The eight-component TE equation developed, as it would happen, correlates well with the Idaho National Laboratory (INL) proven SOEC performance of 45 kilowatt-hours per kilogram hydrogen at 20 bars and 725K. TE is the key performance equation necessary for designing, predicting, and planning for SOEC and SOFC performance and cost. Important ramifications of TE are discussed.

(Invited) The SOFC Program at the DOE’s Office of Fossil Energy and Carbon Management (FECM) and National Energy Technology Laboratory (NETL)

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy (FE) and administered by the FE’s National Energy Technology Laboratory (NETL) is currently developing low-cost SOFC power generation systems. SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation. In addition, there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several projects on various aspects of high temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear or coal power plants.

Advanced Manufacturing of Unique Solid Oxide Fuel Cell Electrode and Electrolyte Microstructures through Aerosol Deposition

Development of various additive manufacturing technologies over the years has given an opportunity for highly customizable and unique structures to be fabricated with applications towards several different industries. For ceramic manufacturing, techniques such as direct ink writing (DIW), stereolithography (SLA), and fused deposition modeling (FDM) have been utilized to construct very complex structures. These technologies have also been developed for use towards solid oxide fuel cells (SOFCs) where they have been utilized to manufacture components greater than 200 µm in thickness. Some components of the SOFC such as the electrodes, electrolyte, and barrier layer are much smaller and consist of thicknesses from 1 µm to 50 µm. Along with the reduced thickness, the electrodes of a SOFC are often comprised of a composite material where the previously mentioned technologies struggle with achieving both the required high resolution and compositional change needed to manufacture these specific components. This project’s goal is to develop an additive manufacturing technique that suits both requirements for manufacturing the electrodes, electrolyte, and barrier layer of a SOFC.The technology that has been developed to complete the manufacturing of highly customizable electrodes along with the electrolyte and barrier layer is Aerosol Deposition. The Aerosol Deposition system contains several different elements that lead to consistently tailored microstructures for the various 3-D printed parts including the use of syringe pumps, an ultrasonic atomizing nozzle from Sonaer Ultrasonics, an infrared heater, and a flexible automation system. The ultrasonic atomizing nozzle is used to convert a stream of liquid into a fine mist via mechanical vibrations. The liquid that is supplied to our ultrasonic atomizing nozzle is low solids loading solvent-based suspension containing approximately 1 - 5 vol% of solids and polymer pore formers. Suspensions are supplied to the nozzle by mechanical pressure provided from a programmable syringe pump. This technology accompanied with a flexible automation system gives the potential for highly customizable and repeatable microstructures that can aid in evaluating variables associated with the different components of the SOFC.Development of the additive manufacturing system to fabricate the anode functional layer, electrolyte, barrier layer, and cathode active and current collector layers through an automated process have been studied. For the electrodes, a microstructure that contains approximately 30% - 40% porosity is suitable to enhance the electrochemical performance of the electrode. Sintering temperatures for the electrodes typically range from 1000 °C to 1300 °C which can typically densify the microstructure and restrict the amount of porosity present. To implement porosity within the microstructure poly(methyl methacrylate) was incorporated into electrode suspensions due to their ability to diffuse out of the electrode microstructure at temperatures of ~450 °C. The electrical and mechanical properties of the separate components have been characterized accordingly utilizing electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Acknowledgements: This work was performed in support of the US Department of Energy’s Solid Oxide Fuel Cell Program. The authors would like to acknowledge the WVU Shared Research Facilities (SRF) and thank Dr. Thomas Kalapos from Leidos Research Support Team for his assistance.

(Invited) The SOFC Program at the DOE’s Office of Fossil Energy and Carbon Management (FECM) and National Energy Technology Laboratory (NETL)

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy and Carbon Management (FECM) and administered by the FECM’s National Energy Technology Laboratory (NETL) is currently developing low-cost SOFC’s and reversible SOFC systems (rSOCFs). SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation. In addition, there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several projects on various aspects of high-temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. Development of reversible SOFC systems, rSOCFs, is the new central focus of FECM. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear power plants.

Total Energy for the SOFC and SOEC

The Solid Oxide Fuel Cell (SOFC) Program at the National Energy Technology Laboratory (NETL) managed by the U.S. Department of Energy (DOE) Office of Fossil Energy and Carbon Management (FECM) is currently developing low-cost SOFC and Solid Oxide Electrolysis Cell (SOEC) systems. This paper develops the Total Energy (TE) (kilowatt-hours per kilogram hydrogen, kWh/kgH2 ) for the SOEC and SOFC. The Total Energy includes heat input, exergetic flows, enthalpy of vaporization, pressurization, heat loss, area specific resistance, etc. The SOEC Total Energy developed at NETL, as it would happen, correlates well with the Idaho National Laboratory (INL) proven SOEC performance of forty-five kilowatt-hours per kilogram hydrogen at twenty bars, 1.3 volt and 725oC. Total Energy is necessary for designing, predicting, and planning for SOEC and SOFC performance and cost.

Patterned Nafion Membranes for Improved Transport in PGM-Free PEMFC Cathodes

Substantial cost reduction is needed to commercialize polymer electrolyte fuel cells. As PGM catalysts are projected to account for ~42% cost of a fuel cell stack (1), replacement of PGMs with PGM-free catalysts is an attractive route to cost reduction. Over the past decade, extensive research efforts have led to significant improvements in kinetic activity (2), but conventional PGM-free catalyst continues to have lower volumetric activity than PGM catalysts. The lower volumetric activity requires use of a thicker cathode catalyst layer (CL), resulting in significant proton and oxygen transport losses (3). Therefore, along with kinetic improvements in oxygen reduction reaction, improved transport of H+ and O2 is needed to achieve performance comparable to PGM catalyst. In this study, we adopt a micro-patterning technique to incorporate non-tortuous ionomer channels in the cathode to increase the ionic conductivity of the thick catalyst layer. As shown in Figure 1, cathode ionomer channels enable rapid transportation of H+ throughout the catalyst layer, compared to thin and tortuous ionomer films in the conventional electrode. Polarization curves obtained in H2/air show significantly higher performance for the CL with ionomer channels compared to the conventional cathode. Electrochemical impedance spectroscopy data in H2/N2 also demonstrate a significant decrease in H+ resistance in the catalyst layer. The ionomer channels lead to a reduction in the H+ transport resistance, reducing ohmic overpotential in the catalyst layer. Further improvement in performance in the mass transport region is achieved through implementing optimized design of the dedicated ionomer channel.AcknowledgmentThis research was supported by the US Department of Energy, the Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office and the LANL LDRD program.References D. Papageorgopoulos, DOE Hydrogen and Fuel Cells Program FY2019 Annual Merit Review Proceedings, https://www.hydrogen.energy.gov/pdfs/review19/plenary_fuel_cell_papageorgopoulos_2019.pdf (2019).H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao and G. Wu, (2017).S. Komini Babu, H. T. Chung, P. Zelenay and S. Litster, ACS Appl Mater Interfaces, 8, 32764-32777 (2016). Figure 1

Simple Polypyrrole Based Preparation for Fe-N-C Catalysts for the Oxygen Reduction Reaction

Hydrogen based fuel cells could play an imprtant role for future CO2-free energy supply, especially with respect to the transportation and automotive sector. However, efficient fuel cell catalyst mostly rely on the precious metal platinum. The contributions of platinum based catalysts and their application are estimated with up to 40% of the overall stack costs [1], [2]. Furthermore, taking into account the released CO2 equivalents, soil acidification and fresh water consumption the mining and production of precious metals leaves a great ecological foot-print [3].FeNC catalysts are a promising alternative to replace platinum for the oxygen reduction reaction. However, still several challenges need to be faced. A low voumetric activity, a poor long-term stability in the device and difficuilties during scale-up of the preparation procedure are the main issues. Especially for the high performing catalysts that are based on zeolitic imidazolate frameworks (ZIFs) [4], [5], the scale-up of the ZIF synthesis and subsequent FeNC preparation seems difficuilt while maintaining the same material properties [6], [7].Here, we present a simple prepration for FeNC catalysts that relys on nanostructured polypyrrole. Because the presented method is based on a simple polymer the scale-up seems easier in realizationWe will discuss the impact of different aspects as amount and kind of iron precursor, level and kind of doping agents, and pyrolysis temperature and their impact on fuel cell performance data and structural composition. The variation of these aspects leads to significant variation in structural composition, activity, selectivity and stability of these catalysts. For example, very low levels of hydrogen peroxide formation are found even for low catalyst loadings during RRDE [8]. Further, by an increase of the pyrolsis temperature from 800°C to 1000°C the retained current density after 50 hours of potentiastatic testing at 0.5 V could be increased by a factor of 1.6.[1] S.T. Thompson, D. Papageorgopoulos, Platinum group metal-free catalysts boost cost competitiveness of fuel cell vehicles, Nat Catal, 2 (2019) 558-561. [2] A.R. Wilson, J.P. Marcinkoski, D., Fuel Cell System Cost, DOE Hydrogen and Fuel Cells Program Record, in Departement of Energy, 2016. [3] P. Nuss and M.J. Eckelmann, PLOS one, Vol. 7 Life Cycle Assessment of Metals: A Scientific Synthesis, 2014. [4] E. Proietti, F. Jaouen, M. Lefevre, N. Larouche, J. Tian, J. Herranz, J.-P. Dodelet, Nature Commun., 2, 416, 2011. [5] D. Zhao, J.-L. Shui, L. R. Grabstanowicz, C. Chen, S. M. Comment, T. Xu, J. Lu, D.-J. Liu, Adv. Mater., 26, 7, 2013. [6] M. Hovestadt, J. Vargas Schmitz, T. Weissenberger, F. Reif, M. Kaspereit, W. Schwieger, M. Hartmann, Scale-up of the Synthesis of Zeolitic Imidazolate Framework ZIF-4, Chem-Ing-Tech, 89 (2017) 1374-1378. [7] T. Johnson, M.M. Lozinska, A.F. Orsi, P.A. Wright, S. Hindocha, S. Poulston, Improvements to the production of ZIF-94; a case study in MOF scale-up, Green Chem, 21 (2019) 5665-5670. [8] L. Ni, C. Gallenkamp, S. Paul, M. Kübler, P. Theis, S. Chabbra, K. Hofmann, E. Bill, A. Schnegg, B. Albert, V. Krewald, U. I. Kramm, Active Site Identification in FeNC Catalysts and Their Assignment to the Oxygen Reduction Reaction Pathway by In Situ 57Fe Mössbauer Spectroscopy, Adv. Energy Sustainability Res., 2, 2021

(Invited) Overview of the U.S. Department of Energy’s National Laboratory Consortia to Improve Fuel Cells for Heavy-Duty Applications

Hydrogen fuel cells are an attractive technology to power zero-emissions heavy duty vehicles, including truck, rail, and maritime applications. For heavy-duty fuel cell vehicles to be market competitive, it is necessary to improve the performance and durability of proton-exchange-membrane fuel cells (PEMFCs). Heavy-duty applications require significantly longer vehicle lifetimes (>25,000 hours/1,000,000 miles for heavy-duty trucks), and therefore require improved fuel-cell durability compared to light-duty vehicles. Furthermore, because of this extended lifetime, hydrogen fuel costs comprise a greater proportion of heavy-duty vehicle life-cycle cost, making increased efficiency a key parameter for economic viability, and reducing the constraints on upfront capital costs. Within the U.S. Department of Energy’s (DOE) Hydrogen and Fuel Cell Technologies Office (HFTO), the Fuel Cell Program supported the Fuel Cell Performance and Durability (FC-PAD) Consortium that aided in the understanding of, and improvements in, overall PEMFC performance and durability. In 2020, HFTO formed the Million Mile Fuel Cell Truck (M2FCT) Consortium that includes a core team of five primary and three affiliate national laboratories to overcome durability and efficiency challenges in PEMFCs for heavy-duty applications with an initial focus on long-haul trucks. This presentation will provide an overview of DOE’s Fuel Cell R&D approach, highlighting past and current activities of FC-PAD and M2FCT, as well as strategies to enable fuel-cell competitiveness for heavy-duty applications.

Solid Oxide Cell Materials Development at Pacific Northwest National Laboratory

Pacific Northwest National Laboratory (PNNL), a U.S. Department of Energy (DOE) laboratory, has worked with government agencies and industrial collaborators to accelerate the commercialization of SOFC power systems for distributed and central power applications. This presentation will highlight work performed for the US DOE Office of Fossil Energy’s Solid Oxide Fuel Cell program. Topics to be covered include effects of contaminants and their mitigation on electrode performance; investigating volatility from cathode materials; improved cell materials; Co-free protective interconnect/BOP coatings development; capabilities of the SOFC stack test platform; and progress on industrial collaborations including seal development in electrolyzer systems fabricated using advanced manufacturing techniques such as 3D printing and rapid electromagnetic sintering.

(Plenary) Update on the SOFC Program at the DOE’s National Energy Technology Laboratory

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy (FE) and administered by the FE’s National Energy Technology Laboratory (NETL) is currently developing low-cost SOFC power generation systems. SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation; there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several projects on various aspects of high temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear or coal power plants.

Sr and Co Vapor-Phase Transport from LSCF Cathodes

Strontium transport contributes to degradation mechanisms in SOFCs, especially strontium zirconate formation at the interface of the cathode barrier layer with the YSZ electrolyte. High temperatures required for cathode sintering lead to Sr transport during cell construction. SEM analysis of SOFCs with LSCF cathodes shows Sr at the YSZ/GDC barrier layer interface, but no Sr throughout the GDC barrier layer itself, as would be expected for solid-phase transport. Vapor-phase transport was identified as a possible mechanism that would lead to these observations. A series of tests were performed to differentiate between surface diffusion and vapor-phase diffusion of species from LSCF cathode material at typical sintering temperatures (up to 1100°C). A GDC substrate was printed with LSCF and separated by an air gap from a YSZ target substrate. First a simple spacer ring was used to create the air gap, and strontium transport was observed via SEM-EDS (energy dispersive spectroscopy). Then, various geometries with long surface paths were employed to reduce the possibility of surface transport. The target substrates were analyzed via x-ray photoelectron spectroscopy (XPS) with high sensitivity for surface species. An open air gap did not show evidence of Sr or Co transport. A refined, enclosed air gap with long surface path length did show such evidence for Sr and Co, indicating an enclosed area to maintain significant vapor pressure was necessary for transport. An SOFC with LSCF in direct contact with a barrier layer would also provide such an environment for vapor-phase transport to occur. Furthermore, spatially resolved analysis showed a relatively uniform distribution of Sr and Co across the target substrate. This supports the vapor-phase mechanism as Sr and Co transported via surface diffusion would have been fixed preferentially to the outer edge of the target substrate. These results have implications for adjusting sintering conditions and barrier layer requirements to prevent the formation of undesired strontium zirconate. This work was performed for the US DOE Office of Fossil Energy’s Solid Oxide Fuel Cell program under the Cathode Task.

(Plenary) Update on the SOFC Program at the DOE’s National Energy Technology Laboratory

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy (FE) and administered by the FE’s National Energy Technology Laboratory (NETL), is currently developing low-cost SOFC power generation systems. SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation; there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several new projects on various aspects of high temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear or coal power plants.

A personal retrospect on three decades of high temperature fuel cell research; ideas and lessons learned

In1986 the Dutch national fuel cell program started. Fuel cells were developed under the paradigm of replacing conventional technology. Coal-fired power plants were to be replaced by large-scale MCFC power plants fuelled by hydrogen in a full-scale future hydrogen economy. With today's knowledge we will reflect on these and other ideas with respect to high temperature fuel cell development including the choice for the type of high temperature fuel cell. It is explained that based on thermodynamics proton conducting fuel cells would have been a better choice and the direct carbon fuel cell even more so, with electrochemical gasification of carbon as the ultimate step. The specific characteristics of fuel cells and multisource multiproduct systems were not considered, whereas we understand now that these can provide huge driving forces for the implementation of fuel cells compared to just replacing conventional combined heat and power production technology.

Current Status of Solid Oxide Fuel Cell Technology Research and Development at National Energy Technology Laboratory

The DOE Office of Fossil Energy Solid Oxide Fuel Cell (SOFC) Program is interested in the near-term commercialization of high-temperature SOFC and solid oxide electrolyzer cell (SOEC) technologies that are robust, reliable, and resilient. A recent report delivered to the United States Congress highlighted several development recommendations including the design of pilot-scale units, continued early stage research and development, increased industrial engagement, and the exploration of reversible operation of SOFC technology.The National Energy Technology Laboratory (NETL) SOFC research group currently addresses most of these recommendations. NETL’s in-house research efforts focus on the characterization, simulation, and mitigation of high temperature degradation of fuel cell components. The capstone of these efforts is NETL’s SOFC degradation modeling framework, which uses NETL supercomputing facilities to simulate SOFC performance degradation of thousands of possible electrode configurations experiencing multiple simultaneous degradation modes under a broad array of relevant operating conditions. The models for the different degradation modes are based upon experimental data (1) generated in-house, (2) referenced from available scientific publications, and (3) shared from collaborations with other industrial, academic, and national laboratory partners within the SOFC Program. The team then employs techniques in data analytics to select optimal electrodes to maximize the SOFC performance for given operating conditions. These modeling efforts guide electrode engineering efforts in-house and through external collaborations by identifying (1) which degradation modes contribute the most to overall performance degradation for given operating conditions and (2) which electrode features will have the greatest impact on lowering cell degradation and system costs. Additionally, the development on non-invasive in situ high temperature fiber optic sensors for temperature and gas composition measurement provides valuable data for inclusion in degradation models as well as informing technology development at the commercial scale. Finally, the wealth of experience gained in development degradation models and materials for reducing the cost of SOFC technology is being readily applied to reducing the cost of SOEC technology.NETL will report on its most recent progress in the field of SOFC and SOEC development, including degradation modeling, in situ fiber optic sensor development, electrode engineering, and relevant systems-level analyses.

Performance of Fuel Cell Systems for Heavy Duty Vehicles

Polymer electrolyte membrane fuel cell (PEMFC) systems for heavy-duty vehicles (HDV) are attracting attention for several reasons including tighter emission regulations and, compared with light duty vehicles (LDVs), possibility of a gradual build-up of hydrogen infrastructure during the market introduction phase, and higher allowable cost (60 $/kWe vs. 30 $/kWe) and Pt loadings.1 However, competing with the incumbent diesel technology requires longer stack lifetimes than for LDVs (30,000 h vs. 8,000 h) and higher efficiencies to compensate for the likely price differential between diesel and hydrogen.2 Heat rejection in fuel cells for HDVs can also be an issue. We conducted simulations to compare radiator heat loads in two propulsion systems for a Class-8 HDV: a 450-hp turbocharged diesel engine, and a hybrid 275-kWe FCS with a 35-kWh battery. The simulations showed that the radiator heat load at rated power is higher for the hybrid propulsion system even though it is 20% more efficient than the diesel engine. Higher heat load combined with lower operating temperature makes heat rejection in an HDV radiator more challenging for the hybrid powertrain. We conducted system analysis to determine the stack operating conditions (cell voltage and temperature) and the radiator fan power required to reject the waste heat in the HDV radiator at rated power. Figure 1 summarizes the important results of the analysis of an FCS with a compressor-expander module (CEM) for air management, 2.5-atm stack inlet pressure, no cathode humidifier, de-alloyed PtCo cathode catalyst supported on a high surface-area carbon, and 0.25 mg/cm2 total Pt loading.3, 4 Figures 1a and 1b show that the heat load and radiator fan power are strong functions of the cell voltage and stack coolant temperature. These indicate a heat transfer limit that sets the minimum coolant temperature which only depends on the cell voltage. For example, at 0.7 V cell voltage, the minimum coolant temperature is 88oC corresponding to 265 kW radiator heat load and 30 kWe fan power. The cell voltage needs to be higher than 0.75 V for stacks that operate below 80oC. Figures 1c and 1d present the net stack power (stack power minus the parasitics including radiator fan power) density and system efficiency (net power produced divided by the lower heating value of H2 consumed) as functions of cell voltage and coolant temperature. Increasing the cell voltage at fixed coolant temperature improves the system efficiency at the expense of lower power density. For a fixed cell voltage, there is an optimum temperature at which the net power density is highest. The net power density is smaller below the optimum temperature because of higher fan power, and above it because of the adverse effects of low relative humidity on Ohmic losses and ORR kinetics. As a reference point, the stack can reach 1200 mW/cm2 gross and 1015 mW/cm2 net stack power density for 0.7 V cell voltage at rated power and 88oC optimum coolant temperature. The projected power density and operating conditions are based on a model formulated using the experimental data for d-PtCo/C cathode catalysts with 0.05, 0.1 and 0.15 mg/cm2 Pt loading. Further work is required to confirm these projections by building and optimizing electrodes with 0.2 mg/cm2 Pt loading. References Marcinkoski, R. Vijayagopal, J Adams, B. James, J. Kopsz, and R. Ahluwalia, DOE Advance Truck Technologies https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf L. Borup, A. Kusoglu, K. C. Neyerlin, R. Mukundan1, R. K. Ahluwalia, D. A. Cullen, K. L. More, A. Z. Weber, and D. J. Myers, “Recent Developments in Catalyst-related PEM Fuel Cell Durability,” Current Opinion in Electrochemistry, 21, 192–200 (2020)Ahluwalia, X. Wang and J-K Peng. "Fuel Cell System Modeling and Analysis," 2019 DOE Hydrogen and Fuel Cells Program Annual Merit Review and Peer Evaluation Meeting, Arlington, VA, April 29 - May 1, 2019.K. Ahluwalia, X. Wang, and A.J. Steinbach, “Performance of Advanced Automotive Fuel Cell Systems with Heat Rejection Constraint,” Journal of Power Sources, 309 (2016), 178-191. Figure 1