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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Effect of reacting gas flowrates and hydration on the carbonation of anion exchange membrane fuel cells in the presence of CO 2

Anion exchange membrane fuel cells (AEMFCs) have been widely touted as a low-cost alternative to existing proton exchange membrane fuel cells. However, one of the limitations of this technology has been the severe performance penalty related to the introduction of CO 2 to the cell – typically in the air cathode feed. Introduction of CO 2 into AEMFCs results in cell carbonation, which imparts thermodynamic, kinetic and Ohmic overpotentials that can add up to hundreds of millivolts. Therefore, it is important to find strategies and operational protocols for AEMFCs that minimize these overpotentials. In this paper, we reserach the impacts of the anode and cathode flowrate, as well as the cell hydration level, on the extent of cell carbonation and cell polarization. Key findings include: (1) decreasing the cathode flowrate generally decreases the total CO 2 -related voltage loss while changing the anode flowrate has a minimal effect; (2) increasing cell hydration helps to mitigate the performance loss in the presence of CO 2 ; and (3) operational combinations are found that significantly reduce the CO 2 penalty compared to the present literature.

25 ENERGY STORAGE↗
DOE OSTI2022

Enhancing Distribution System Resiliency Using Grid-Forming Fuel Cell Inverter: Preprint

Legacy inverters interfacing distributed energy re-sources are traditionally grid-following (GFL) in nature. GFL assets typically follow real power and reactive power set points. Recently, inverters with grid-forming (GFM) capability are gaining attention as GFM assets can increase the resiliency of the distribution system under stressed conditions. These GFM inverters can use photovoltaics, batteries, or fuel cells as their energy source. In this paper, we present information on inverters interfacing fuel cell assets, specifically with GFM capability. By introducing a fuel cell powered GFM coupled with hydrogen production and storage, the GFM can continuously provide GFM activities during periods of low renewable resource availability, and/or during power outages exceeding typical electric battery duration. Finally, we present information on the need for updates on interconnection and interoperability standards that can be leveraged by utilities for including fuel cell inverters in their asset mix.

fuel cell inverters↗
DOE OSTI2020

Proton exchange membrane fuel cells

Disclosed embodiments concern a membrane electrode assembly or a proton exchange membrane fuel cell comprising a phosphoric acid-doped polymeric membrane comprising a cationic functional group, such as an assembly or fuel cell having an ion exchange capacity of 0.8 to 3 mmol/gram and an operating temperature range of from 80° C. to 220° C. The cationic functional group can be any suitable functional group, such as ammonium, imidazolium, guanidinium, phosphazenium, sulfonium, oxonium, and phosphonium, with working embodiments typically using quaternary ammonium cationic functional groups tethered to the polymeric core. The polymeric material may be any suitable polymeric material, such as a material selected from polyaryl polymers, polyarylamides, polyimides, polystyrenes, polysulfones, polyethers, polyether sulfones, polyketones, polyetherketones, polyarylethers, polyolefins, and polynitriles. The membrane electrode assembly or a proton exchange membrane fuel cell can be used in any application now known or hereafter developed, such as a vehicle or a stationary power device.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Novel structured Sm 0.5 Sr 0.5 CoO 3-δ cathode for intermediate and low temperature solid oxide fuel cells

The performance of solid oxide fuel cell (SOFC) can be significantly enhanced using nanostructured cathode obtained by infiltration/impregnation method. However, this method has been limited due to multi-step preparation process and instability of the obtained nanoscale catalyst under long-term operation. We report here a simple, cost-effective and reproducible approach to fabricate nanostructured Sm 0.5 Sr 0.5 CoO 3-δ (SSC) cathode with enhanced performance and stability. The SSC powders were prepared by a freeze-drying method through a combustion route using Pluronic F-127 as the template. The SSC freeze-drying powders have unique morphology and a significant phase change at 750 °C. The oxygen non-stoichiometry (δ) of the SSC powders is 0.18 at room temperature, while the δ values are 0.66, 0.75 and 0.90 at 600 °C, 700 °C and 800 °C, respectively. The novel structured SSC cathode was prepared by screen-printing and one-step sintering process using the freeze-drying SSC powders. Maximum cell power densities of 0.83 and 1.13 W cm -2 are achieved at 550 °C and 600 °C, respectively for single cells with the novel structured SSC cathode. Moreover, single cells show excellent stability at 600 °C under a current density of 600 mA cm -2 over 250 h. This work expands opportunities to exploit nanotechnology in a wide range of intermediate and low temperature energy conversion devices.

25 ENERGY STORAGE↗
DOE OSTI2024

Stabilizing alkaline fuel cells with a niobium-doped brookite titanium dioxide catalyst support

Anion-exchange membrane fuel cells represent a promising and scalable approach for hydrogen energy utilization. However, their development is hindered by the weak bonding between metal catalysts and carbon supports, along with challenges in fabricating electronically/ionically conductive electrodes. Here, we report a composite cathode of Nb-doped brookite TiO 2 nanorods that have robust stability when combined with Pt nanoscale catalysts in an alkaline fuel cell. The composite cathode, fabricated without the addition of an ionomer, delivers a power density of 419 mW cm −2 at a current density of 650 mA cm −2 and a voltage retention of 81% at 100 mA cm −2 after 25 h, substantially outperforming a cathode fabricated from commercial Pt/C. Further investigations of the chemical structure, anion exchange capacity, and mass transfer resistance reveal that a solvent residue derived from N-methylpyrrolidone plays an important role in charge transfer and mass transport in the alkaline fuel cell.

alkaline fuel cell↗
DOE OSTI2022

Modeling ammonia-fueled co-flow dual-channel protonic-ceramic fuel cells

This paper reports the model development for a dual-channel protonic-ceramic fuel cell (PCFC) operating on ammonia fuel. The model considers the coupled interactions of several physical and chemical processes, including three-dimensional heat conduction within the bipolar plates and the membrane-electrode assembly (MEA), one-dimensional flow within the fuel and air channels, detailed heterogeneous catalytic reactions within the porous composite anode structure, Butler–Volmer representation of the charge-transfer chemistry, and Nernst–Planck transport of three charged defects (protons, oxygen vacancies, and small polarons) within the dense electrolyte membrane. The membrane-electrode assembly is composed of a Ni-BCZYYb (BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3-δ ) anode, a BCZYYb electrolyte membrane, and a BCFZY (BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ ) cathode. Chemical and physical parameters for the MEA model are established using previously published button-cell data. One aspect of the study is to investigate the partial ammonia decomposition upstream of the fuel cell. Such fuel cracking increases the H 2 content of the fuel entering the PCFC, which may have benefits. However, endothermic ammonia pyrolysis within the composite anode structure assists with thermal control of the cell. The dual-channel model can be considered as the unit cell of a full fuel-cell stack.

25 ENERGY STORAGE↗
DOE OSTI2020

Mapping of Heterogeneous Catalyst Degradation in Polymer Electrolyte Fuel Cells

Pt catalysts in polymer electrolyte fuel cells degrade heterogeneously as the catalyst particles are exposed to local variations throughout the catalyst layer during operation. State-of-the-art analytical techniques for studying degradation of Pt catalysts do not possess fine spatial resolution to elucidate such non-uniform degradation behavior at a large electrode level. A new methodology is developed to spatially resolve and quantify the heterogeneous Pt catalyst degradation over a large area (several cm ) of aged MEAs based on synchrotron X-ray microdiffraction. PEFC single cells are aged using voltage cycling as an accelerated stress test and the degradation heterogeneity at a micrometer length scale is visualized by mapping Pt catalyst particle size after voltage cycling. It is demonstrated in detail that the Pt catalyst particle size growth is non-uniform and follows the flow field geometry. The Pt particle size growth is greater in the area under the flow field land, while it is minimal in the area under the flow field channel. Additional non-uniformity is observed with the Pt particle size increasing more rapidly at the air outlet area than the Pt particle size at the inlet area.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Graphitized Mesoporous Engineered Carbon Support for Fuel Cell Applications

As proton exchange membrane fuel cells mature into commercial devices capable of powering a wide range of stationary and automotive applications, they need materials with tunable properties to improve their performance and durability. Carbon supports used for platinum (Pt) nanoparticle dispersion is typically based on a furnace black-type material with a random structure, thereby hindering progress in catalyst development. To address this challenge, engineered carbons with a tunable mesoporous structure offer an opportunity to maximize catalyst performance and durability. In this article, we report on the development of a graphitized, mesoporous carbon support with a high degree of ordering, labeled here as ECS4005, for the dispersion of Pt nanoparticles. Pt/ECS4005 shows significantly improved kinetic activity due to its mesoporous structure that mitigates Pt poisoning by sulfonate functional groups in the ionomer while simultaneously enabling favorable accessibility to reactants.

25 ENERGY STORAGE↗
DOE OSTI2022

Quantifying the electrochemical active site density of precious metal-free catalysts in situ in fuel cells

We report advances in the development of precious-group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes have produced active catalysts that reduce the performance gap to the incumbent Pt-based materials. However, utilization of state-of-the-art PGM-free catalysts for commercial applications is currently impeded by their relatively low durability. Methods designed to study catalyst degradation in the operation of fuel cells are therefore critical for understanding durability issues and, ultimately, their solutions. Here we report the use of Fourier-transform alternating current voltammetry as an electrochemical method for accurate quantification of the electrochemically active site density of PGM-free cathode catalysts, and to follow their degradation in situ during the operation of polymer electrolyte fuel cells. Using this method, we were able to quantify the electrochemical active site density, which will enable the elucidation of degradation mechanisms of PGM-free ORR catalysts in situ in fuel cells.

25 ENERGY STORAGE↗
DOE OSTI2022

Stable, high-performing bifunctional electrodes for anion exchange membrane-based unitized regenerative fuel cells

Anion exchange membrane unitized regenerative fuel cells (AEM-URFCs) are a promising technology for energy storage and electricity production; however, their efficiency is limited by the kinetics of the bifunctional oxygen electrode (BOE) where the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) occur. A particular concern when designing the BOE is that the OER and ORR have differing catalytic requirements, which make it challenging to develop effective bifunctional electrocatalysts with single active sites. In this study, we focus on advancing the BOE performance using Pt-IrO x and Pt-NiCoO x electrocatalysts. Here, single-layer and dual-layer Pt-IrO x BOEs were made, with the dual-layer electrode leading to improved performance due to efficient catalyst utilization in both modes. Using the dual-layer oxygen electrode paired with a PtRu/C hydrogen electrode, a round trip efficiency (RTE) as high as 50% (62 %iR-free) was achieved at 500 mA/cm 2 and operation for more than 24 h, which included five one-hour-long H 2 generation and consumption cycles followed by one eight-hour-long cycle. To the best of our knowledge, this is the highest performance for AEM-URFCs reported to date. Lastly, the approach is extended to electrodes with a Pt loading of 0.5 mg/cm 2 and the IrO x substituted by NiCoO x .

25 ENERGY STORAGE↗
DOE OSTI2024

Investigation of precooling unit design options in hydrogen refueling station for heavy-duty fuel-cell electric vehicles

Precooling gaseous hydrogen fuel to a cold temperature before refueling a heavy-duty (HD) hydrogen fuel cell electric vehicle (HFCEV) is essential to avoid overheating the vehicle tank, as well as achieving a high state of charge (SOC). Because a large volume of hydrogen is dispensed during each fill, the need for a shorter fill time amplifies the need to precool each load for refueling a HFCEV. Thus, the design and operation of a precooling unit (PCU), as well as the associated capital and operating costs, plays a pivotal role in any plans for heavy-duty hydrogen refueling stations. Here, in this paper, we present a thermodynamic and technoeconomic analysis of a PCU in a gaseous hydrogen refueling station (HRS) for HD HFCEVs. By employing Argonne National Laboratory's hydrogen station cost optimization and performance evaluation (H2SCOPE) model, the refueling of 50 kg of hydrogen on-board type IV tank at ambient temperatures of 15–45 °C and varying fill rates is simulated. The required degree of precooling temperature to obtain either 100% or the maximum possible SOC is obtained from the simulation. Additionally, the simulation results demonstrate that the average flow rate of hydrogen is approximately 40% lower than the maximum flow rate during a typical fill; which motivates further evaluation of the instantaneous hydrogen mass flow rate profile and suggests the scope of improving precooling unit design. Accordingly, a hybrid strategy of precooling hydrogen has been proposed to address the cooling load by sizing the refrigeration unit for the average flow rate of hydrogen, while supplementing the above average peak hydrogen flow cooling load through thermal buffering. The combined technique enables the downsizing of the original PCU capacity by 25–40% and demonstrates a potential cost reduction of the PCU by approximately 30%, which translates to an installed cost reduction of ∼$125,000 per dispenser.

25 ENERGY STORAGE↗
DOE OSTI2025

Forming Limits of Thin Ferritic Stainless Steel for Fuel Cell Application

To lower the cost of fuel cell bipolar plate (BPP), less expensive ferritic stainless steel (FSS) BPP substrate materials are investigated. A series of tensile tests and multistage microchannel-forming tests were conducted on 85-µm-thick ferritic stainless steel foils, 439L, 444, and Chromeshield® 22, to understand the effect of the forming temperatures, tooling geometry, and processes on their formability. Three microchannel-forming processes were conducted, which are 1-Hit (single-stage forming), 2-Hit (two-stage forming) with 50% preform, and 2-Hit with 80% preform. FLC o s at various microchannel-forming conditions were obtained to address the formability of the ferritic stainless steel foils under plane strain conditions. It has been found that the larger the microchannel radius, the better the formability, two-stage forming is superior to the single-stage process, and a larger draw percentage in preform (stage I) leads to a higher FLC o or better formability. It has also been found from tensile tests that the thermal effect (higher temperature) has a negative impact on the failure strains. A similar phenomenon was also observed through channel-forming tests conducted at room temperature, 100 °C, and 200 °C.

08 HYDROGEN↗
DOE OSTI2022

Active and Durable PGM-free Cathodic Electrocatalysts for Fuel Cell Application

Platinum Group Metal-free (PGM-free) Oxygen Reduction Reaction (ORR) electrocatalysts possess high intrinsic activity measured by a Rotating Disk Electrode (RDE) method. However, under fuel cell operating conditions, PGM-free ORR electrocatalysts have underperformed compared to platinum catalysts. PGM-free ORR electrocatalyst’s fuel cell performance can be improved by designing and optimizing the cathodic catalyst layer (CL) and Membrane Electrode Assembly (MEA) construction such that: 1) it efficiently provides oxygen access to ORR active sites (through catalyst morphology control); 2) it removes water from the CL (by tuning the hydrophobicity of the PGM-free catalysts and the catalyst layer structure); and 3) it increases proton conductivity (by homogeneous mixing of catalysts and ionomer). Studying the CL is complex due to the absence of well-established protocols of MEA activation, especially compared to platinum-containing catalysts. PGM-free fuel cell testing protocols would need to optimize potentiostatic vs galvanostatic measurements, scan rates, parameters of Electrochemical Impedance Spectroscopy (EIS) and Beginning of Experiment (BOE) criteria. To make the PGM-free catalyst’s fuel cell performance comparable to platinum, the synergistic effort of materials design, fine tuning of the catalyst layer and comprehensive electrochemical analysis is required.

08 HYDROGEN↗
DOE OSTI2022

Michigan Hydrogen and Fuel Cell Electric Vehicle Deployment Plan: H2 FCEV Roadmap 2022

This report describes a roadmap for hydrogen fuel cell electric vehicles in the state of Michigan. This plan provides links to relevant information to assess, plan, and initiate hydrogen and FCEV deployment to help meet the energy, economic, and environmental goals for the State of Michigan. Policies and incentives that support hydrogen and fuel cell technology will increase deployment, thus increasing production and creating jobs throughout the supply chain. As deployment increases, an economy of scale will develop and manufacturing costs will decline, positioning hydrogen and fuel cell technology to compete more effectively in a global market without incentives. Policies and incentives to purchase and support the deployment of FCEVs, FCEBs, and hydrogen refueling can be coordinated regionally to maintain this advanced clean transportation sector as a global exporter for long-term growth and economic development. Overall, the execution of this plan will maintain Michigan's role as a global showcase for regionally manufactured transportation technology while reducing NOx and CO 2 emissions and as new jobs are created for businesses and industry.

08 HYDROGEN↗
DOE OSTI2020

Architecture-Based Control of Temperature Gradient-Driven Water Transport in Polymer Electrolyte Fuel Cells

Temperature gradients can move water within the porous media of a polymer electrolyte fuel cell through phase-change-induced (PCI) flow. It is critical to understand PCI flow so that control and distribution of water within a fuel cell can be accomplished. This work investigates the role of architecture, specifically anode land width, on overall cell water content and distribution in the through-plane direction. A specially-designed 4.8 cm 2 fuel cell with precise thermal boundary conditions was imaged with neutrons using two different anode flow field configurations. A new, non-dimensional thermal transport number was developed which quantifies the relative influence of PCI flow on cell water transport. It was found that anode lands larger than the cathode lands cause large thermal gradients that instigate net water flux from the cathode to the anode. An asymmetric configuration with larger anode lands was found to have large changes in water content that were strongly sensitive to cell operating conditions. The thermal transport number developed here enables deduction of the net flux condition based on operating conditions and architecture. This approach enables design of high-performance systems with balanced water management.

25 ENERGY STORAGE↗
DOE OSTI2022

Study of Cathode Gas Diffusion Architecture for Improved Oxygen Transport in Hydroxide Exchange Membrane Fuel Cells

The high pH environment in hydroxide exchange membrane fuel cells (HEMFCs) has the potential to reach lower costs than the current proton exchange membrane fuel cells (PEMFCs), the incumbent technology. A significant difference between HEMFCs and PEMFCs is the location of water production within the cell. In PEMFCs, the water is produced on the cathode, limiting oxygen transport. In HEMFCs, the water is produced on the anode where the fuel is pure hydrogen. This allows the cathode to be optimized for oxygen transport without the presence of excess liquid water. Limiting current analysis, a technique previously used in PEMFCs, is adopted in HEMFCs to evaluate the oxygen mass transport resistances for different sections of the cathode. Through elimination of the microporous layer (MPL), gas diffusion layer (GDL), and traditional flow field and using porous nickel foam for gas distribution, the transport resistance at an operating condition of 150 kPa(g) and with the cell temperature at 80 °C was decreased from 112 s m −1 to 48 s m −1 , effectively halved. The optimal configuration for performance was found with Ni foam and a GDL, eliminating the MPL and traditional flow field, which vastly improved oxygen transport while maintaining adequate electrical contact with the cathode catalyst layer.

25 ENERGY STORAGE↗
DOE OSTI2021

Computationally Assisted Design of Ion-conducting Polymers for Anion Exchange Membrane Fuel Cells (2nd Year Report) [Slides]

Phosphonated polymers have been proposed as proton conductors for fuel cells; however, the anhydride formation of phosphonic acid functional groups lowers proton conductivity and hinders their use in fuel cell applications. We used calculations to support this hypothesis by correlating calculated Gibbs free energies for the formation of the anhydride with pK values of the corresponding acid. The results showed that stronger acids are less likely to form an anhydride even at elevated temperatures and supported the design of a new polymer and the high-temperature proton exchange membrane fuel cell (HT-PEMFC) that outperformed other state-of-the-art HT-PEMFCs.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2023

Electrolyzer and Fuel Cell Recycling for a Circular Hydrogen Economy

Abstract Electrolyzers and fuel cells will be crucial for achieving global clean hydrogen and industrial decarbonization goals. However, the nascent clean hydrogen sector faces uncertainties around material supply chains and technology end‐of‐life management. This work aims to guide the transition to a circular hydrogen economy by using process modeling, techno‐economic analysis, and life cycle assessment to evaluate the material cost, energy use, greenhouse gas (GHG) emissions, toxicity, and water use of five potential recycling strategies for proton exchange membrane electrolyzers (PEMWE) and fuel cells (PEMFC). Hydrometallurgy, acid dissolution, and electrochemical dissolution are shown to offer 2–7 times improvement across all assessed metrics relative to the manufacturing of PEMWE and PEMFC from raw materials. Recycling can also lower the raw material demand, material cost, energy use, and GHG emissions associated with PEMWE and PEMFC deployment in the United States in 2050 by 23%, 19%, 21%, and 16%, respectively. This study provides key insights into the costs, benefits, and complexities of recycling strategies for PEMWE and PEMFC, aiding the development of a circular economy that is synergistic with clean hydrogen deployment.

08 HYDROGEN↗