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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A Tandem Electrolysis Process for Multi-Carbon Chemical Production from Carbon Dioxide (Final Technical Report)

a two-step CO 2 electroreduction process for selective production of acetate and ethylene was successfully developed at the kW-scale. The CO 2 and CO electrolyzers were first investigated individually on the Watt-scale to achieve high current densities and more durable operation by using a reinforced GDL. High CO 2 conversion was obtained in the first CO 2 electrolyzer to produce a CO-dominant gas stream with minimal CO 2 , and highly pure acetate stream was produced in the second CO electrolyzer by using NiFe anode, which promoted alcohol oxidation to carboxylates. The two-step process operated stably for 200 h with acetate and ethylene as the major C 2+ products. Degradation mechanism study revealed that the flooding and the salt formation in the GDL is likely the biggest contributor to the performance degradation for both CO 2 and CO electrolyzers. A 1,000 cm 2 CO electrolyzer stack was then designed, fabricated, and operated up to a total current of 300 A along with a 500 cm 2 CO 2 electrolyzer stack which was operated up to a total current of 100 A. The CO electrolyzer stack demonstrated good stability at 300 A for at least 125 h at a carbon selectivity >96%. The impact of CO 2 , O 2 , N 2 , SO x , and NO x gas impurities on the CO electrolyzer stack was studied and a relatively high resistance to these contaminants was demonstrated. Electroreduction of CO 2 into acetic acid was also demonstrated to be environmentally favorable when compared to the traditional production of acetic acid when powered by renewable electricity. Additionally, electricity cost was identified as the primary source of cost sensitivity indicating substantial economic improvements could be achieved by continuing to drive down the cost of renewable electricity. Overall, the presented approach demonstrates the feasibility of the two-step electrochemical CO 2 reduction process for the effective production of C 2+ products at the kW-scale which should inspire future scaling efforts accelerating commercialization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

CalTestBed - Twelve Benefit Co - Understanding Degradation of Water Management Properties in Gas Diffusion Layers (CRADA Final Report)

The research between Lawrence Berkeley National Lab and Twelve Benefit Co. enhanced Twelve’s understanding of how chemical changes to the gas diffusion layer lead to failure of their CO 2 electrolyzers. During the CRADA period, LBNL team tested Twelve’s gas diffusion layer samples (GDL), some with microporous layer (MPL) and some without MPL using the water-air capillary pressure setup. LBNL team also tested microporous layer samples using the fuel cell test stands and compared those results with commercial GDL and MPL. Understanding the hydrophobicity of the material, along with electrochemical performance is the key to determining Twelve’s ability to scale their platform. Further improvements to Twelve’s CO 2 electrolyzer can enhance the net zero emissions with their technology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

Gasdynamic lasers and photon machines.

The basic operational highlights of CO2-N2 gasdynamic lasers (GDL's) are described. Features common to powerful gas lasers are indicated. A simplified model of the vibrational kinetics of the system is presented, and the importance of rapid expansion nozzles is shown from analytic solutions of the equations. A high-power pulsed GDL is described, along with estimations of power extraction. A closed-cycle laser is suggested, leading to a description of a photon generator/engine. Thermodynamic analysis of the closed-cycle laser illustrates in principle the possibility of direct conversion of laser energy to work.

Christiansen, W. H.↗
NASA NTRS1976

Preheated, combustion-driven gasdynamic lasers

The effect of preheated nitrogen on the available laser specific energy is examined for two classes of combustion-driven gasdynamic lasers (GDLs). The analysis combines a nonequilibrium model of the relevant GDL processes with a simplified nondissociating combustion model handling a variety of candidate GDL fuels. For a more comprehensive evaluation of the capabilities of preheating, an optimization routine is added to the combined laser/combustion models. The effectiveness of preheating to enhance laser specific energy is demonstrated, although preheating may impose unacceptable hardware requirements. The application of numerical optimization techniques appears to offer a means to improve laser design.

Saunders, R. C., III↗
DOE OSTI2023

Bond Energies of UO + and UC + : Guided Ion Beam and Quantum Chemical Studies of the Reactions of Uranium Cation with O 2 and CO

Here, guided ion beam tandem mass spectrometry was used to examine the kinetic energy dependent reactions of U + with O 2 and CO. In the reaction of U + with O 2 , the UO + product is formed in a barrierless and exothermic process with a reaction efficiency at low energies of k/k col =1.1±0.2, but increases at higher collision energies. Formation of both UO + and UC + in the reaction of U + with CO is endothermic. 0 K bond dissociation energies (BDEs) of D 0 (U + -O)=7.88±0.09 eV and D 0 (U + -C)=4.03±0.13 eV were determined by analyzing the kinetic energy dependent cross sections in the latter endothermic reactions. These values are within experimental uncertainty of previously reported experimental values. Additionally, the electronic states of UO + and UC + and the potential energy surfaces for the reactions were explored by quantum chemical calculations. The former include a full Feller-Peterson-Dixon composite approach with correlation contributions up to CCSDT(Q) for UO and UO + , yielding D 0 (U-O)=7.82 eV and D 0 (U + -O)=7.99 eV, as well as more approximate CCSD(T) calculations where a semi-empirical model was used to estimate spin-orbit energy contributions, which are generally found to improve the agreement with experiment. Both experimental BDEs are observed to be close to those of their transition metal congeners, ScL + , YL + , and GdL + (L=O and C).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Effect of Commercial Gas Diffusion Layers on Catalyst Durability of Polymer Electrolyte Fuel Cells in Varied Cathode Gas Environment

Gas diffusion layers (GDLs) play a crucial role in heat transfer and water management of cathode catalyst layers in polymer electrolyte fuel cells (PEFCs). Thermal and water gradients can accelerate electrocatalyst degradation and therefore the selection of GDLs can have a major influence on PEFC durability. Currently, the role of GDLs in electrocatalyst degradation is poorly studied. Here, we perform electrocatalyst accelerated stress test studies on membrane electrode assemblies (MEAs) prepared using three most commonly used GDLs. The effect of GDLs on electrocatalyst degradation is evaluated in both nitrogen (non-reactive) and air (reactive) gas environments at 100% relative humidity. In situ electrochemical characterization and extensive physical characterization is performed to understand the subtle differences in electrocatalyst degradation and correlated to the use of different GDLs. Overall, no difference is observed in the electrocatalyst degradation due to GDLs based on polarization curves at the end of life. But interestingly, MEA with a cracked microporous layer (MPL) in the GDL exhibited a higher electrocatalyst loading loss, which resulted in a lower and more heterogeneous increase in the average electrocatalyst nanoparticle size.

25 ENERGY STORAGE↗
DOE OSTI2025

Innovative Method for Reliable Measurement of PEM Water Electrolyzer Component Resistances

Understanding the sheet resistance of porous electrodes is essential for improving the performance of polymer electrolyte membrane (PEM) water electrolyzers and related technologies. Despite its importance, existing methods often fail to provide reliable and comprehensive data, especially for porous materials with complex morphologies and non‐uniform thicknesses. This study introduces a robust and straightforward method for determining the sheet resistance of porous electrodes using a novel probe concept based on industrial printed circuit board (PCB) technology. This probe measures resistance across ten distances, ranging from 250 µm to 2500 µm, enabling local mapping of resistance. The study focuses on the sheet resistance of key components in PEM water electrolyzers, including the gas diffusion layer (GDL), porous transport layer (PTL), and catalyst layers deposited on a membrane. Additionally, an image‐processing‐based method is presented to obtain the thickness distribution of the studied catalyst layers, facilitating a detailed analysis of the electrical in‐plane resistivity with thickness variations. Overall, this methodology has the potential to expedite material integration and bridge the gap between electrode engineering and single‐cell testing, thereby advancing the development of PEM water electrolyzers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Probing water distribution in compressed fuel-cell gas-diffusion layers using X-ray computed tomography

X-ray computed tomography was used to investigate geometrical land and channel effects on spatial liquid-water distribution in gas-diffusion layers (GDLs) of polymer-electrolyte fuel cells under different levels of compression. At low compression, a uniform liquid-water front was observed due to water redistribution and uniform porosity; however, at high compression, the water predominantly advanced at locations under the channel for higher liquid pressures. Lastly, at low compression, no apparent correlation between the spatial liquid water and porosity distributions was observed, whereas at high compression, a strong correlation was shown, indicating a potential for smart GDL architecture design with modulated porosity.

25 ENERGY STORAGE↗
DOE OSTI2017

Investigating Phase-Change-Induced Flow in Gas Diffusion Layers in Fuel Cells with X-ray Computed Tomography

The performance of polymer-electrolyte fuel cells is heavily dependent on proper management of liquid water. One particular reason is that liquid water can collect in the gas diffusion layers (GDLs) blocking the reactant flow to the catalyst layer. This results in increased mass-transport losses. At higher temperatures, evaporation of water becomes a dominant water-removal mechanism and specifically phase-change-induced (PCI) flow is present due to thermal gradients. This study used synchrotron based micro X-ray computed tomography (CT) to visualize and quantify the water distribution within gas diffusion layers subject to a thermal gradient. Plotting saturation as a function of through-plane distance quantitatively shows water redistribution, where water evaporates at hotter locations and condenses in colder locations. The morphology of the 2 GDLs on the micro-scale, as well as evaporating water clusters, are resolved, indicating that the GDL voids are slightly prolate, whereas water clusters are oblate. From the mean radii of water distributions and visual inspection, it is observed that larger water clusters evaporate faster than smaller ones.

25 ENERGY STORAGE↗
DOE OSTI2020

Understanding water management in platinum group metal-free electrodes using neutron imaging

Platinum group metal-free (PGM-free) catalysts are a low-cost alternative to expensive PGM catalysts for polymer electrolyte fuel cells. However, due to the low volumetric activity of PGM-free catalysts, the catalyst layer thickness of the PGM-free catalyst electrode is an order of magnitude higher than PGM based electrodes. The thick PGM-free electrodes suffer from increased transport resistance and poor water management, which ultimately limits the fuel cell performance. This manuscript presents the study of water management in the PGM-free electrodes to understand the transport limitations and improve fuel cell performance. Here, in-operando neutron imaging is performed to estimate the water content in different components across the fuel cell thickness. Water saturation in thick PGM electrodes, with similar catalyst layer thickness to PGM-free electrodes, is lower than in the PGM-free electrodes irrespective of the operating conditions, due to high water retention by PGM-free catalysts. Improvements in fuel cell performance are accomplished by enhancing water removal from the flooded PGM-free electrode in three ways: (i) enhanced water removal with a novel microporous layer with hydrophilic pathways incorporated through hydrophilic additives, (ii) water removal through anode via novel GDL in the anode, and (iii) lower water saturation in PGM-free electrode structures with increased catalyst porosity.

25 ENERGY STORAGE↗
DOE OSTI2022

Effect of Gold Catalyst Surface Morphology on Wetting Behavior and Electrochemical CO 2 Reduction Performance in a Large-Area Zero-Gap Gas Diffusion Electrolyzer

We report catalyst surface area and wetting behavior are key factors in determining the performance of gas diffusion electrode (GDE) electrolyzers for electrochemical CO 2 reduction. In this work, we report the integration of sub-1 μm thick nanoporous gold (npAu) catalyst coatings into a large-area (25 cm 2 ) zero-gap electrolyzer. The npAu coatings were prepared by magnetron sputtering (MS) of thin AgAu alloy films on the microporous carbon layer of a gas diffusion layer (GDL) followed by Ag leaching. Compared to MS Au films of the same thickness, npAu catalyst coatings enable higher Faradaic efficiencies and improved catalyst stability for CO 2 -to-CO reduction with Faradaic efficiencies of up to 88% at 100 mA/cm 2 . For a 800 nm npAu coating, the device level energy efficiency for CO 2 to CO conversion reaches 45% (52% for CO + H 2 ) at 100 mA/cm 2 with a single pass CO 2 conversion efficiency of ~12%. Contact angle measurements reveal that npAu coatings provide a more hydrophobic electrode interface compared to MS Au coatings, suggesting that the more hydrophobic interfacial environment of npAu coatings helps mitigating electrode flooding which is associated with performance deterioration over time.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Integrated Reference Electrodes in Anion-Exchange-Membrane Electrolyzers: Impact of Stainless-Steel Gas-Diffusion Layers and Internal Mechanical Pressure

Alkaline-membrane electrolyzers operating in pure water might provide scalable low-cost H 2 production but currently lag in performance and durability compared to commercial technologies. Typically, membrane–electrode assemblies (MEAs) are optimized in electrolyzers by changing one parameter at a time and assessing the resulting system performance via two-electrode polarization and impedance measurements. These approaches are limited in their ability to assign performance changes and durability to specific electrodes or processes. We integrate a reference electrode with the MEA to separate anode and cathode responses in both polarization and impedance measurements. Here we illustrate the power of the approach by showing how the fiber diameter of stainless-steel gas-diffusion layers (GDLs) affects performance solely at the anode, while changing the thickness of the cathode GDL simultaneously affects the performance of the anode and cathode due to changes in internal pressure from mechanical compression. This finding was obscured in conventional two-electrode measurements. The work thus guides both high-performance alkaline-membrane water-electrolyzer development and illustrates a useful strategy to study structure–activity relationships in the MEA.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Structure/property relationships in copolymers comprising renewable isosorbide, glucarodilactone, and 2,5-bis(hydroxymethyl)furan subunits

Carbohydrates and their derivatives have great potential as building blocks for the development of renewable materials that are cost and performance competitive with conventional petroleum-based materials. To this end, the rigid carbohydrate-derived diols, glucarodilactone and isosorbide were functionalized with a castor oil derivative, 10-undecenoic acid, forming α,ω-dienes suitable for acyclic diene metathesis (ADMET) polymerization. Equimolar copolymerizations of these two monomers, glucarodilactone undecenoate (GDLU) and isosorbide undecenoate (GDLU), transform brittle homopolymers into elastic materials with shape memory capabilities. To understand the source of these properties, a series of copolymers consisting of a range of GDLU and IU compositions (100:0, 77:23, 76:24, 52:48, 48:52, 18:82, 0:100 mol percent GDLU to IU) was synthesized. The material and chemical properties were characterized by uniaxial tensile testing, small-amplitude oscillatory shear rheology, X-ray scattering and hydrolytic degradation testing. Small compositional changes in this family were shown to have a drastic impact on the observed mechanical performance and degradability of these materials. Rheological measurements of GDLU-containing copolymers found evidence for the presence of transient networking within these materials. We posit that the transient network within this material is responsible for the elasticity and shape memory abilities of the GDL-containing materials. In confirmation of these properties, a novel α,ω-diene 2,5-bis(hydroxymethylfuran) undecenoate (BHMFU) was developed and served as a direct replacement for either GDLU or IU in copolymerizations. The replacement of GDLU resulted in a total loss of the elasticity and shape memory of the copolymers, supporting the role of GDLU in the mechanical performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Melting diamond in the diamond cell by laser-flash heating

The phase behavior of carbon at high pressure and the search for carbon structures denser than diamond has been explored for decades showing large discrepancies, with many fundamental questions remaining unresolved. Here we show evidence of melting above the graphite-diamond-liquid (GDL) triple point (~13 GPa, 4000 K) up to 50 GPa on samples recovered from single flash-heating events using spectroscopic and electron microscopic methods. The results show that for all pressures, diamond melts below the triple point temperature contradicting previous studies, most of which predict a positive slope of the melting curve.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A Liquid–Vapor Two-Phase Model of Direct Methanol Fuel Cells With Platinum Group Metal-Free Cathode Catalyst

Abstract This study has developed a two-dimensional, two-phase transport model to investigate the transport characteristics in direct methanol fuel cells (DMFCs) using platinum group metal (PGM)-free cathode catalysts. The model considered anisotropic properties of the gas diffusion layer (GDL) caused by current collector’s mechanical compression, the interfacial mass transfer of water and methanol between liquid and vapor, and unique properties of the cathode PGM-free catalyst layer. Results showed that the liquid methanol solution from the anode could provide sufficient water to hydrate the proton exchange membrane (PEM), and the relative humidity of the cathode air did not impact the membrane hydration. Fully hydrating the cathode air may deteriorate the fuel cell performance, especially when the operating temperature is close to 100 °C because the exponential increase of the saturated water pressure with temperature decreased the partial pressure of oxygen. The optimized operating temperature increased with the increase of air pressure and was about 80 °C at 1.5 atm cathode pressure. To achieve the US Department of Energy’s performance target of 300 mW/cm2 peak power density, catalytic activities of both the anode and cathode catalysts need to be improved by one order of magnitude compared with the state-of-the-art commercial catalysts.

Electrochemistry↗
DOE OSTI2022

3D Printed Carbon Aerogels for Polymer-Electrolyte Fuel Cells

Carbon aerogels (CA) are known for ultra-low density, very high surface area, fine porous structure, and excellent electrical conductivity. Recent advances in high resolution 3D printing at LLNL enable the manufacturing of complex structured CA electrodes which have been demonstrated in electrolysis, flow battery, and supercapacitor applications. Polymer-electrolyte fuel cells (PEFC) may be an excellent candidate for these materials/methods as designers seek to optimize membrane-electrode assemblies to achieve higher efficiencies. A major challenge to PEFC design is two-phase flow due to water production which causes pore flooding and leads to cell instability and degradation. To mitigate these effects, groups have investigated the creation of liquid specific pathways in the porous layers to alleviate liquid buildup and enhance gas diffusion. While some progress has been made, traditionally manufactured GDLs, which consist of randomly distributed carbon fibers, are limiting. 3D printed CAs are a promising solution as complex macroporous electrode structures can be manufactured out of micro and nano porous filaments with a high level of control. Additionally, the process may allow for the consolidation of multiple layers (MPL, GDL, & flow channels) into a single printed architecture. In this work various CA lattice structures were printed using a direct ink write (DIW) method and liquid breakthrough pressures were measured to demonstrate the ability to tune the water pathways to achieve specific pressure thresholds. Furthermore, a discussion of the prospects for printed CA electrodes in PEFC will focus on material properties, synthesis techniques, and current challenges.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Manipulating Water in High-Performance Hydroxide Exchange Membrane Fuel Cells through Asymmetric Humidification and Wetproofing

Hydroxide exchange membrane fuel cells (HEMFCs) are an emerging low-cost alternative to conventional proton exchange membrane fuel cells. In addition to producing water at the anode, HEMFCs consume water at the cathode, leading to distinctive water transport behavior. We report that gas diffusion layer (GDL) wetproofing strictly lowers cell performance, but that the penalty is much higher when the anode side is wetproofed compared to the cathode side. We attribute this penalty primarily to mass transport losses from anode flooding, suggesting that cathode humidification may be more beneficial than anode humidification for this device. GDLs with little or no wetproofing perform best, yielding a competitive peak power density of 737 mW cm(-2). (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, hup://creativecommons.orgilicenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.

Kaspar, RB↗