SEARCH · Engineering Papers

Results for “fuel cell cathode”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14

All sources NASA NTRS DOE OSTI

DOE OSTI2020

Highly stable and ordered intermetallic PtCo alloy catalyst supported on graphitized carbon containing Co@CN for oxygen reduction reaction

A PtCo alloy catalyst was prepared by thermal diffusion of Co encapsulated with thin N-doped carbon layers on graphitic carbon into a Pt lattice (PtCo/NGC). The Co diffused up to the near-Pt surface and resulted in an intermetallic PtCo structure without the leaching process. The intermetallic PtCo structure thermally treated under optimized conditions showed 3-fold higher mass activity than the commercial Pt/C. The potential and maximum power density loss of PtCo/NGC after 30 000 potential cycles were 34 mV and 11%, respectively, which indicated that the PtCo/NGC was remarkably stable when compared to commercial Pt/C and commercial PtCo/GC catalysts. The enhanced catalytic performance and stability of the PtCo/NGC catalyst were attributed to the formation of an intermetallic structure that alleviated the Pt oxidation and Co dissolution. The outstanding performance and stability qualify the ordered intermetallic PtCo/NGC to be a promising cathode catalyst for the commercialization of fuel cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2005

NASA Tech Briefs, January 2005

Topics covered include: Fiber-Optic Sensor Would Monitor Growth of Polymer Film; Sensors for Pointing Moving Instruments Toward Each Other; Pd/CeO2/SiC Chemical Sensors; Microparticle Flow Sensor; Scattering-Type Surface-Plasmon-Resonance Biosensors; Diode-Laser-Based Spectrometer for Sensing Gases; Improved Cathode Structure for a Direct Methanol Fuel Cell; X-Band, 17-Watt Solid-State Power Amplifier; Improved Anode for a Direct Methanol Fuel Cell; Tools for Designing and Analyzing Structures; Interactive Display of Scenes with Annotations; Solving Common Mathematical Problems; Tools for Basic Statistical Analysis; Program Calculates Forces in Bolted Structural Joints; Integrated Structural Analysis and Test Program; Molybdate Coatings for Protecting Aluminum Against Corrosion; Synthesizing Diamond from Liquid Feedstock; Modifying Silicates for Better Dispersion in Nanocomposites; Powder-Collection System for Ultrasonic/Sonic Drill/Corer; Semiautomated, Reproducible Batch Processing of Soy; Hydrogen Peroxide Enhances Removal of NOx from Flue Gases; Subsurface Ice Probe; Real-Time Simulation of Aeroheating of the Hyper-X Airplane; Using Laser-Induced Incandescence To Measure Soot in Exhaust; Method of Real-Time Principal-Component Analysis; Insect-Inspired Flight Control for Unmanned Aerial Vehicles; Domain Compilation for Embedded Real-Time Planning; Semantic Metrics for Analysis of Software; Simulation of Laser Cooling and Trapping in Engineering Applications; Large Fluvial Fans and Exploration for Hydrocarbons; Doping-Induced Interband Gain in InAs/AlSb Quantum Wells; Development of Software for a Lidar-Altimeter Processor; Upgrading the Space Shuttle Caution and Warning System; and Fractal Reference Signals in Pulse-Width Modulation.

Source record↗

DOE OSTI2020

Electrochemical devices and fuel cell systems

Electrochemical devices including electrochemical pumps (ECPs) and fuel cell systems comprising a fuel cell and an ECP are disclosed. In particular, this electrochemical device can be an ECP that comprises an anode, a cathode and an anion exchange polymer separating the anode from the cathode. The ECP can be coupled to a hydroxide exchange membrane fuel cell (HEMFC) that is disclosed herein as a fuel cell system. These devices can be used in methods for removing carbon dioxide from air and for generating electricity.

Yan, Yushan↗

DOE OSTI2023

Electrochemical devices and fuel cell systems

Yan, Yushan↗

DOE OSTI2021

Achieving 5,000-h and 8,000-h Low-PGM Electrode Durability on Automotive Drive Cycles

Whereas total Pt loading in anode and cathode catalysts below 0.125 mg cm −2 is required to meet the stringent cost target for automotive fuel cell systems (FCS) for light duty vehicles, low-loaded cathode catalysts are susceptible to unacceptable aging-related performance losses at high current densities. A framework model, validated by accelerated stress test data, has identified cell voltage, relative humidity (RH) and temperature as the key operating variables that affect degradation of a high-activity d-PtCo/C cathode catalyst with 0.1 mg cm −2 Pt loading. Drive cycle simulations indicate that these can be controlled by properly selecting the minimum FCS power, compressor-expander module (CEM) turndown, and stack coolant temperature. The optimum system parameters are 4-kW e minimum power for an 80-kW e FCS, CEM turndown of 12.5, and 66 °C average coolant exit temperature that combine to limit the maximum cell voltage to 850 mV and outlet RH to 90%–100%. Depending on Pt loading, the mismatch between actual and allowable degradation for 10% power loss over 5,000-h lifetime requires the stack to be oversized by 2.4%–5%, resulting in 8.4%–41% lower Pt utilization and 7.1%–20.5% penalty in stack cost. The corresponding results for 8,000-h lifetime are 10.3%-14% stack oversizing, 23%–51.8% lower Pt utilization, and 24.1%–35.4% stack cost penalty.

08 HYDROGEN↗

DOE OSTI2021

Solid-State Synthesis of Highly Dispersed Nitrogen-Coordinated Single Iron Atom Electrocatalysts for Proton Exchange Membrane Fuel Cells

Fe–N–C with atomically dispersed Fe single atoms is the most promising candidate to replace platinum for the oxygen reduction reaction (ORR) in fuel cells. However, the conventional synthesis procedures require quantities solvents and metal precursors, sluggish adsorption process, and tedious washing, resulting in limited metal doping and uneconomical for large-scale production. Here, for the first time, Fe 2 O 3 is adopted as the Fe precursor to derive abundant single Fe atoms dispersed on carbon surfaces. The Fe–N–C catalyst synthesized by this simple method shows an excellent ORR activity with half-wave potentials of 0.82 and 0.90 V in acidic and alkaline solutions, respectively. A single fuel cell with an optimized Fe–N–C cathode shows a high peak power density of 0.84 W cm –2 . The solid-state transformation synthesis method developed in this study may shed light on mass production of single-atom-based catalysts.

25 ENERGY STORAGE↗

DOE OSTI2023

Highly durable fuel cell electrocatalyst with low-loading Pt-Co nanoparticles dispersed over single-atom Pt-Co-N-Graphene nanofiber

The limited durability of Pt electrocatalysis toward cathodic oxygen reduction reaction remains challenging, yet crucial for the development of Proton Exchange Membrane Fuel Cell. Here, we present a rational design of a robust catalyst consisting of PtCo nanoparticles supported on Pt-Co-N-graphene nanofiber prepared through electrospun Cobalt-Metal-Organic-Framework. The catalyst delivers unprecedented mass activity of 2.48 A·mgPt -1 , and retains 80% of initial value after 60,000 Accelerated-Stress-Test cycles. Operando X-ray absorption spectroscopies show that the electronic configurations of Pt sites in PtCo and Co sites in Co-N4 in the hybrid catalyst are modified toward high catalytic activities. Density Functional Theory unveils that the enhanced curvature of the substrate induced by the morphology engineering lowers the reaction thermodynamic barrier on Co-N4 sites, favoring the formation of H2O and suppressing that of H2O2. This result along with the strong affinity of PtCo nanoparticles to the Pt-Co-N-graphene fiber endows the catalyst an exceptional durability.

acidic electrolyte↗

DOE OSTI2020

Physically Based Modeling of PEMFC Cathode Catalyst Layers: Effective Microstructure and Ionomer Structure–Property Relationship Impacts

Abstract This work presents a pseudo-two-dimensional proton exchange membrane fuel cell (PEMFC) model incorporating Nafion ionomer structure–property relationships in the cathode catalyst layer (CL) to capture and explain losses at low Pt loading. Structural data from neutron reflectometry and thin film Nafion conductivity measurements predict variations in the oxygen diffusion coefficient and ionic conductivity with changing CL ionomer thickness and Pt loading. By including these structure–property relationships, predicted polarization curves agree closely with previously published experimental data from cells with Pt loadings between 0.025 and 0.2 mg/cm2. Results demonstrate that structure–property relationships based on physically measurable ionomer and CL properties provide a feasible interpretation of PEMFC CL phenomena for a range of Pt loadings and help explain previously unaccounted-for losses at low Pt. Results also show that simulations must account for surface species coverage variations in order to properly capture the kinetic losses. Finally, results suggest that an increase in ionomer thickness surrounding the C/Pt surfaces may lead to improved cell performance due to improved ionic conductivity.

Electrochemistry↗

DOE OSTI2022

Durable High-Power Membrane Electrode Assemblies with Low Pt Loading

Recent progress in developing and implementing Pt-alloy cathode catalysts and thin (10-15 micron) low resistance membranes has enabled high performance state of art (SOA) membrane electrode assembly (MEA) with low Pt loading. However, these high performing MEAs do not meet durability requirements, especially at peak power, because of complex degradation mechanisms that are sensitive to the materials, MEA design, and fuel cell operating strategy. Specifically, power degradation of the cathode occurs via Pt and Co dissolution as well as deterioration of O 2 transport properties. Additionally, thin membranes are subject to failure due to manufacturing defects in the adjacent gas diffusion media and electrodes and the formation of membrane-attacking radical species caused by high gas crossover. In this project led by General Motors LLC (GM), the objective was to enhance the durability of SOA MEA through optimization of operating conditions, instead of new materials development. Along with our project partners, we have mapped the impact of operating conditions on the durability of SOA MEA. Output of the project include a low Pt loading SOA MEA that exceeds Department of Energy (DOE) 2020 target of >1 W/cm 2 at rated power and pathway to achieve >5000 h of durability. Durability studies in the project provide a detailed understanding of failure modes and operating condition sensitivity on cathode and membrane failure, critical for defining operating conditions and hybridization strategies that can guide system controls to maximize low-Pt MEA life. The project also generated and validated degradation models that will provide future research direction, critical for guiding future cycles of automotive MEA development.

08 HYDROGEN↗

DOE OSTI2020

Eliminating dissolution of platinum-based electrocatalysts at the atomic scale

Deployment of proton-exchange membrane fuel cells is limited by the durability of Pt-nanoscale catalysts during cathodic oxygen reduction reactions. Dissolution processes on single crystalline and thin film surfaces are now correlated leading to the design of PtAu catalysts with suppressed dissolution. A remaining challenge for the deployment of proton-exchange membrane fuel cells is the limited durability of platinum (Pt) nanoscale materials that operate at high voltages during the cathodic oxygen reduction reaction. In this work, atomic-scale insight into well-defined single-crystalline, thin-film and nanoscale surfaces exposed Pt dissolution trends that governed the design and synthesis of durable materials. A newly defined metric, intrinsic dissolution, is essential to understanding the correlation between the measured Pt loss, surface structure, size and ratio of Pt nanoparticles in a carbon (C) support. It was found that the utilization of a gold (Au) underlayer promotes ordering of Pt surface atoms towards a (111) structure, whereas Au on the surface selectively protects low-coordinated Pt sites. Finally, this mitigation strategy was applied towards 3 nm Pt 3 Au/C nanoparticles and resulted in the elimination of Pt dissolution in the liquid electrolyte, which included a 30-fold durability improvement versus 3 nm Pt/C over an extended potential range up to 1.2 V.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Demonstration of Electrochemically-Driven CO 2 Separation Using Hydroxide Exchange Membranes

Hydroxide exchange membrane fuel cells (HEMFCs) are a potentially lower-cost hydrogen fuel cell technology; however, ambient levels of CO 2 in air significantly reduce HEMFCs’ performance. In this work, we demonstrate an electrochemically-driven CO 2 separator (EDCS) which can be used to remove ambient levels of CO 2 from air upstream of the HEMFC stack in fuel cell vehicles, protecting it from CO 2 -related performance losses. The EDCS operating window was explored for current density, anode flow, and cathode flow with respect to its impact on CO 2 separation performance. Additionally, gas-phase mass transport was improved by selecting flow fields and gas diffusion layers conducive to the EDCS operating regime. The use of a carbon-ionomer interlayer at the cathode was explored and improved CO 2 removal performance from 77.7% to 98.2% at 20 mA cm −2 . An analytical, 1-D model is used to explain the experimental observations and design improvements. A single-cell, 25 cm 2 EDCS using the aforementioned improved design demonstrated greater than 98% CO 2 removal at a cathode flow rate of 1300 sccm for 100 h with 2.7% hydrogen stack consumption.

Matz, Stephanie↗

DOE OSTI2021

Design concept of co-ionic conducting solid oxide electrolyte for stable operation in a cell-imbalanced fuel cell stack

A bilayer composite electrolyte comprising BaCe 0.85 Y 0.15 O 3-d (BCY15) – Gd 0.2 Ce 0.8 O 2-d (GDC20) at the anode side and BaZr 0.85 Y 0.15 O 3-d (BZY15) – Nd 0.1 Ce 0.9 O 2-d (NDC10) at the cathode side is designed for improving the stability of co-ionic conducting solid oxide fuel cells (SOFCs) in a cell imbalanced stack. Contrary to the single layer structured SOFCs, the bi-layer cell stably operates without electrode delamination under negative voltage conditions. We measure local internal p O 2 values using embedded Pt probes. Based on these values, local electronic conduction is estimated in combination with four probe DC conductivity measurements. It is found that n-type conductivity (~10 –3 Scm –1 ) and p-type conductivity (10 –5 –10 –4 Scm –1 ) are developed in the BCY15-GDC20 near the anode side and in the BZY15-NDC10 near the cathode side, respectively. Finally, the results indicate that local electronic conduction in electrolyte regions near both the anode and cathode interfaces is a crucial factor for the durability of co-ionic SOFCs under negative voltage operation. We therefore suggest the bi-layer configuration as a practical solution to protect co-ionic SOFCs in a cell-imbalanced stack.

25 ENERGY STORAGE↗

DOE OSTI2022

Cylindrical C 96 Fullertubes: A Highly Active Metal-Free O 2 -Reduction Electrocatalyst

A new isolation protocol was recently reported for highly purified metallic Fullertubes D 5h -C 90 , D 3d -C 96 , and D 5d -C 100 , which exhibit unique electronic features. Here, we report the oxygen reduction electrocatalytic behavior of C 60 , C 70 (spheroidal fullerenes), and C 90 , C 96 , and C 100 (tubular fullerenes) using a combination of experimental and theoretical approaches. C 96 (a metal-free catalyst) displayed remarkable oxygen reduction reaction (ORR) activity, with an onset potential of 0.85 V and a halfway potential of 0.75 V, which are close to the state-of-the-art Pt/C benchmark catalyst values. Here we achieved an excellent power density of 0.75 W cm −2 using C 96 as a modified cathode in a proton-exchange membrane fuel cell, comparable to other recently reported efficient metal-free catalysts. Combined band structure (experimentally calculated) and free-energy (DFT) investigations show that both favorable energy-level alignment active catalytic sites on the carbon cage are responsible for the superior activity of C 96 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Gas permeable fluoropolymers and ionomers

Novel copolymers that are fluoropolymers including a first repeat unit that is fluorinated and cyclic and a second repeat unit from a trifluorovinyl methylene ether monomer having sulfur or sulfone functionality in the pendant group are disclosed. The copolymers have relatively high gas permeability as a result of a cyclic repeat unit in the copolymer backbone and ionomers from oxidation of the sulfur containing functionality are particularity useful in the cathode structure of a proton exchange membrane fuel cell.

Lousenberg, Robert Daniel↗

DOE OSTI2023

Baselining Activity and Stability of ORR Catalysts and Electrodes for Proton Exchange Membrane Fuel Cells for Heavy-Duty Applications

Activity and stability of electrodes with Pt and PtCo alloy catalysts supported on high surface area carbon, hereafter to as a-Pt/C and d-PtCo/C, were evaluated for heavy-duty applications. Both catalysts had nearly identical Pt loading (50-wt% Pt on carbon and 0.25 mg Pt cm −2 ) and had undergone thermal treatment to stabilize them by growing the average particle size to 4–5 nm. Both were subjected to 90,000 (90 k) standard accelerated stress tests (AST) cycles consisting of 0.6–0.95 V square wave potentials, 3-s hold at upper and lower potential limits in H 2 /N 2 at 1.5 atm, 80 °C and 100% RH. Test protocols were developed to monitor the performance losses and characterize them in terms of activity for the oxygen reduction reaction (ORR), oxygen transport in the electrode and proton transport in the membrane and cathode catalyst layer. Despite the nearly double initial ORR activity, the PtCo/C electrode degraded faster due to the leaching of Co from the catalyst that had started even before the imposition of the AST potential cycles. Commensurate with Co leaching, Co poisoning of ionomer is responsible for the inferior performance of d-PtCo/C electrode at high current densities both before and after AST.

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2026

Translating Fundamental Insights into Ag-Based Bimetallic Electrocatalysts to Anion-Exchange Membrane Fuel Cells

To address challenges of high costs and scalability for fuel cells, it is essential to develop af-fordable and earth-abundant materials that are Pt-group-metal (PGM)-free. Recent advance-ments in PGM-free electrocatalysis for the oxygen reduction reaction (ORR) in alkaline media show that high catalyst loadings are needed to achieve high reaction rates; however, there are associated mass transport limitations. To address this issue, we develop low-loading ionomer-less Ag-bimetallic thin films by alloying with 3d block elements or Sn. We bridge knowledge from fundamental rotating disk electrode (RDE) studies to gas-diffusion cathodes in high-temperature anion-exchange membrane fuel cells (HT-AEMFCs), resulting in high-activity ORR catalysis and peak power densities up to 1.2 W cm-² geo for the Ag-Sn and Ag-Co alloys. Here, experimental post-characterization and theoretical calculations reveal small Co or Sn oxide nano-islands on Ag as likely active sites enhancing ORR activity, ultimately offering these low-loading PGM-free ORR materials as a viable path towards sustainable energy conversion.

Catalysts↗

NASA NTRS2009

Symmetrical, bi-electrode supported solid oxide fuel cell

The present invention is a symmetrical bi-electrode supported solid oxide fuel cell comprising a sintered monolithic framework having graded pore electrode scaffolds that, upon treatment with metal solutions and heat subsequent to sintering, acquire respective anodic and cathodic catalytic activity. The invention is also a method for making such a solid oxide fuel cell. The graded pore structure of the graded pore electrode scaffolds in achieved by a novel freeze casting for YSZ tape.

Cable, Thomas L.↗

NASA NTRS1972

Development of advanced fuel cell system

Weight, life and performance characteristics optimization of hydrogen-oxygen fuel cell power systems were considered. A promising gold alloy cathode catalyst was identified and tested in a cell for 5,000 hours. The compatibility characteristics of candidate polymer structural materials were measured after exposure to electrolyte and water vapor for 8,000 hours. Lightweight cell designs were prepared and fabrication techniques to produce them were developed. Testing demonstrated that predicted performance was achieved. Lightweight components for passive product water removal and evaporative cooling of cells were demonstrated. Systems studies identified fuel cell powerplant concepts for meeting the requirements of advanced spacecraft.

Grevstad, P. E.↗