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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Oxygen Reduction on Platinum-Nickel and Platinum-Cobalt Alloy Based Catalysts for High Temperature Proton Exchange Membrane Fuel Cells

Catalyst layers, with commercial PtNi/TKK (TECNiE52; platinum 46.5 wt%), PtCo/TKK (TEC36E52; platinum 45.8 wt%) catalysts, and an in-house catalyst PtNi-NC (platinum 38.4 wt%), synthesised using acoustic mixer and a tube furnace, are prepared using three different ionomers: 20 wt% Nafion®, 60 wt% polytetrafluoroethylene (PTFE), and an in-house 5 wt% ionomer (‘Ionomer X’). These inks are bar-coated onto carbon paper gas diffusion layers (GDLs), which are cut into 3 cm × 5 cm pieces. The coated layers are tested for oxygen reduction in a commercial gas diffusion electrode (GDE) test cell, FlexCell® (Gaskatel GmbH, Germany), using 85 wt% phosphoric acid at both room temperature and at 155°C. This study evaluates the polynorbornene (PNB)-based in-house ionomer performance as binder and in-house catalyst oxygen reduction reaction (ORR) activity in comparison to commercial products. The catalyst layers are characterised using X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Among the catalyst layers prepared with PTFE ionomer and tested at 155°C, the in-house catalyst demonstrates the highest ORR activity. Ionomer X proves to be a good candidate to be used as a per- and polyfluoroalkyl-free binder for high-temperature (HT) proton exchange membrane fuel cell (PEMFC) applications.

85 wt% phosphoric acid↗
DOE OSTI2020

Atomic Layer Deposition for Enhanced Reactivity and Stability of Biomass Conversion Catalysts

Heterogeneous catalysts are an essential tool in the transition towards a sustainable, bio-based economy for fuels and chemicals. However, the harsh conditions (e.g., high temperatures, acidity, oxidizing/reducing environments) of many key biomass conversion processes give rise to nanoparticle sintering, support collapse, and metal leaching in conventional PGM catalysts. Active site poisoning due to the relatively high sulfur content of most biomass feedstocks further compounds these durability problems. Next-generation catalysts must be developed to address these stability challenges. In this work, we used a scalable atomic layer deposition (ALD) process to modify conventional Pd-based hydrogenation catalysts to generate significant performance improvements. TiO2 ALD coatings were found to increase the activity of Pd/Al2O3 catalysts towards naphthalene hydrogenation; additionally, these coatings improved the catalyst's resistance to sulfur poisoning and thermal stability under oxidative calcination. Additional work in which Al2O3 ALD coatings were applied to Pd/TiO2 catalysts for muconic acid hydrogenation found similar stability benefits, including improved resistance to Pd leaching in the acidic environment. ALD technology holds great potential in the development of next-generation catalysts for biofuels and bioproducts and this work constitutes an important examination of applying ALD coatings to supported Pd hydrogenation catalysts.

ALD↗
DOE OSTI2021

Process model for multilayer slide coating of polymer electrolyte membrane fuel cells

Slide coating is a precision method suitable for depositing multiple liquid-film layers simultaneously. Originally developed in the photographic film industry, it has been deployed for manufacturing of other products that benefit from multilayer coatings. One emerging application is the manufacture of polymer electrolyte membrane fuel cells (PEMFCs), which are used to produce electricity through electrochemical reactions of hydrogen and oxygen gas. The membrane-electrode assembly (MEA), in which key electrochemical reactions occur, consists of three layers that are typically deposited separately in serial fashion and then laminated together to form the three-layer MEA, i.e., three sequential steps of coat and dry. Adapting the process to simultaneous, multilayer slide coating of all three layers will save equipment cost and space while minimizing possible exposure to contaminants during transition between the steps. We are developing a three-layer slide coating model to aid the manufacturing process design of PEMFC. The model accounts for rheology of each layer, which typically exhibit shear thinning behavior. Model predictions are used to investigate simultaneous coatability of catalyst inks and to determine the best layer-by-layer ink selection.

25 ENERGY STORAGE↗
DOE OSTI2022

Scalable Gas Diffusion Electrode Fabrication for Electrochemical CO 2 Reduction Using Physical Vapor Deposition Methods

Electrochemical CO 2 reduction (ECR) promises the replacement of fossil fuels as the source of feedstock chemicals and seasonal storage of renewable energy. While much progress has been made in catalyst development and electrochemical reactor design, few studies have addressed the effect of catalyst integration on device performance. Using a microfluidic gas diffusion electrolyzer, we systematically studied the effect of thickness and the morphology of electron beam (EB) and magnetron-sputtered (MS) Cu catalyst coatings on ECR performance. We observed that EB-Cu outperforms MS-Cu in current density, selectivity, and energy efficiency, with 400 nm thick catalyst coatings performing the best. Additionally, the superior performance of EB-Cu catalysts is assigned to their faceted surface morphology and sharper Cu/gas diffusion layer interface, which increases their hydrophobicity. Tests in a large-scale zero-gap electrolyzer yielded similar product selectivity distributions with an ethylene Faradaic efficiency of 39% at 200 mA/cm 2 , demonstrating the scalability for industrial ECR applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Degrade-Repair Cycle of a Fuel-Forming Photoelectrode

Artificial leaves that produce fuels using sunlight hold promise for sustainably powering the planet, but they require advance- ments in energetic efficiency, cost effectiveness, and operational durability. Herein, we showcase the application of combined surface- sensitive spectroscopic techniques to durability studies that characterize structural changes accompanying functional degradation and go beyond just observing changes in function over time. Further, the photoelectrodes used in this work feature a polymeric surface coating functionalized with molecular complexes that catalyze the hydrogen evolution reaction. Using a polymeric layer to interface the light-harvesting component with catalytic sites enables reassembly of catalysts that detach during operation, establishing a degrade-repair cycle.

14 SOLAR ENERGY↗
DOE OSTI2020

Spatial Atomic Layer Deposition to Scale Manufacturing of Robust Catalysts for Biomass Conversion Applications: Cooperative Research and Development Final Report, CRADA Number CRD-17-715

This CRADA will facilitate technology maturation for NREL-developed ALD-coated catalyst materials that are tailored for durability during harsh biomass conversion chemistries. This project will address optimizing process parameters for scale-up of Al2O3 ALD-coated catalysts, demonstrating ALD-coated catalyst performance for muconic acid hydrogenation, and validating economic models that project significant cost benefits for ALD-enhanced catalytic processes. This work will strengthen private-public partnerships in the area of advanced catalyst manufacturing for energy-related technology. Critical information will be collected to elevate the Technology Readiness Level and increase our competitiveness for cooperative R&D agreements and licensing. Success of this work will be crosscutting as it can facilitate advanced catalyst development for both renewable and conventional processes.

09 BIOMASS FUELS↗
DOE OSTI2024

Electrically Insulated Catalyst–Ionomer Anode Interfaces toward Durable Alkaline Membrane Electrolyzers

Anion-exchange-membrane water electrolysis (AEMWE) is an emerging technology for scalable hydrogen production. AEMWE has poor durability when operating without supporting electrolyte due to the oxidation of ionomers and membranes in contact with the anode oxygen evolution reaction (OER) catalyst. We report a new “passivated” anode architecture for AEMWE where the OER catalysts and ionomers are physically separated with a thin film amorphous oxide coating that is electrically insulating but conductive to hydroxide ions. We find that 2–3 nm of HfO x passivation layers show sufficient hydroxide ion transport to minimally limit the cell performance while suppressing ionomer degradation with both Ir (500 mA·cm –2 for 40 h) and CoO x (1.0 A·cm –2 for 100 h) model porous-transport-layer-supported catalysts in AEMWE. As a result, this interfacial engineering approach guides electrode design to improve the durability of AEMWE, particularly for systems operating with pure-water feed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Modeling Planar Electrodes and Zero–Gap Membrane Electrode Assemblies for CO 2 Electrolysis

Multiphysics modeling enables probing of conditions inside a CO 2 electrolyzer that are difficult to measure, such as local concentrations and pH, as well as rapid testing of possible design changes. A one-dimensional model for a zero-gap membrane electrode assembly (MEA) CO 2 electrolyzer was developed with the assumption that catalyst layers interact with the membrane ionomer such that the ionomer affects the underlying kinetics. The kinetics for bicarbonate reacting to form hydrogen are fit using a planar electrode model for silver with an ionomer coating. The MEA model results are validated against experimental studies for current density and product selectivity. Flooding of the cathode is modeled using saturation curves, and results show that blocked pores in the microporous layer play a significant role in limiting the mass transport at high potentials (>2.8 V). Sensitivity studies showed that CO Faradaic efficiency can be increased by decreasing catalyst layer thickness and porosity, and decreasing KHCO 3 concentration.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

Ultrathin platinum nanowire based electrodes for high-efficiency hydrogen generation in practical electrolyzer cells

Significant reduction of noble metal catalyst loading and simplification of electrode fabrication are urgently needed in order to lower the cost of proton exchange membrane electrolyzer cells (PEMECs) for large-scale hydrogen production. Herein, we report an integrated electrode design comprising in-situ grown platinum nanowires (PtNW) on ultrathin titanium liquid/gas diffusion layers (LGDLs) via a cost-effective and green chemical synthesis approach. The ultrathin integrated PtNW electrodes showed a low cell voltage of 1.643 V and high efficiency of 90.08% at 1000 mA cm -2 using about 15 times lower catalyst loadings than a conventional catalyst-coated membrane in PEMEC tests. Ex-situ electrochemical characterizations and microscale visualizations further reveal that PtNW electrodes display highly efficient hydrogen evolution reactions and excellent electrode durability due to high active surface area, favorable bubble detachment, and structural stability. This work provides new insights into catalyst layer design and facile ultrathin electrode fabrication for more compact and low-cost PEM electrolyzers, fuel cells and other systems.

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

Flexible Copper Metal Circuits via Desktop Laser Printed Masks

A novel process is demonstrated that produces patterns of electrically conductive copper on a flexible polyimide film substrate using standard desktop laser printed toner and near room temperature aqueous chemistry. The laser toner acts as a mask to selectively block the ion exchange self-metallization (IESM) reduction reaction that forms nanoscale silver or palladium coatings at the polyimide surface. The silver or palladium IESM coating is then used as a catalyst for electroless deposition of copper. Under appropriate conditions, the copper is deposited selectively on top of the catalyst layer. The resulting copper layer has a measured sheet resistance as low as 0.3 Ohms/sq. Electrical isolation was measured between copper traces spaced as close as 300 microns, and high conductivity was measured along traces with widths as low as 200 microns. The minimum pattern size appears to be limited primarily by the resolution of the laser toner pattern, as the IESM metal layer was observed to follow the contours of individual toner particles. Here, the process avoids the use of high temperature, vacuum, and organic solvents and is thus suitable for very low cost prototyping or distributed manufacturing of simple electronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Experimental and computational study of the microporous layer and hydrophobic treatment in the gas diffusion layer of a proton exchange membrane fuel cell

Enabling fuel cell operation at high current density is critical for developing competitive alternative power system to replace internal combustion engine. However, liquid water management continues to be a challenge for high humidity or high current density operation. Water condensation in the porous media hinders efficient oxygen transport to the catalyst layer, which in turns, reduces fuel cell performance. To improve water management capability, the gas diffusion layer is often impregnated with Polytetrafluoroethylene (PTFE) and coated with a thin microporous layer, which have shown to improve fuel cell performance, especially under wet conditions. However, the fundamental mechanism that drives the performance enhancement is still not well understood. In this work, the effects of PTFE impregnation and MPL were studied using both experimental and computational techniques. Both limiting current and polarization tests under dry and wet operating condition are conducted to study the oxygen transport resistance and fuel cell performance. In addition, a 2-D, two-phase, multi-physics PEMFC model is developed to simulate performance and gain a fundamental understanding of local water saturation and oxygen concentration. The combined results show that 5 wt% PTFE impregnation with MPL significantly enhances liquid water management, which enables higher current density operation of a fuel cell.

25 ENERGY STORAGE↗
DOE OSTI2022

Tuning Intermediate Bands of Protective Coatings to Reach the Bulk-Recombination Limit of Stable Water-Oxidation GaP Photoanodes

Stable photoelectrochemical solar fuel production requires protective coatings to achieve effective charge separation, transport, and injection at the semiconductor–liquid interfaces, implying that the coating should energetically align its intermediate band (IB) with both the photoabsorber's band edge and co-catalyst's potentials. Yet approaches to adjust coating IB positions to accommodate various semiconductor light absorbers for constructing efficient and stable photoelectrodes have not been developed. In this report, three types of transition metal (M = Mn 2+ , Mn 3+ , and Cr 3+ ions) alloyed TiO2 coatings are discovered using atomic layer deposition (ALD). The IB energetics of these coatings are characterized by X-ray photoelectron spectroscopy and are found to be tunable inside the TiO 2 bandgap, through varying ALD growth conditions. By applying these coatings to n-type GaP and integrating with IrO x co-catalysts, the water-oxidation J–E performance is comparable to an uncoated corroding GaP photoanode. It reaches the bulk recombination limit of the GaP and achieves ≈28% absorbed photon to current efficiency under 475-nm light excitation (6.48 mW cm -2 ) and 100-h stable water oxidation. The outstanding performance and stability are attributed to the efficient charge separation and hole transport, as allowed by the energy alignment of the coating IB and the GaP valence band edge.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Crack detection in fuel cell electrodes using a spatial filtering technique for overcoming noisy backgrounds

Image processing is a powerful tool that allows for rapid and automated data parsing in settings that occupy large variable spaces and require large data sets. Feature detection on difficultly discerned backgrounds is a subset of image processing that facilitates the extraction of quantitative metrics from otherwise subjective data. Crack detection and quantification is an important capability in polymer electrolyte membrane fuel cell quality control, failure analysis, and optimization. This work presents a technique to perform crack detection and quantification which overcomes challenges faced by commonly used image segmentation techniques. We demonstrate the use of a geometrically filtered noise‐level detection technique to select a binary threshold value from which we then quantify how cracked a sample is. Furthermore, we demonstrate the accuracy of our technique using programmatically generated test images of known crack amounts and their performance on real‐world fuel cell catalyst layer samples.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2023

Flexible and Extensive Platinum Ion Gel Condensers for Programmable Catalysis

Catalytic condensers composed of ion gels separating a metal electrode from a platinum-on-carbon active layer were fabricated and characterized to achieve more powerful, high surface area dynamic heterogeneous catalyst surfaces. Ion gels comprised of poly(vinylidene difluoride)/1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide were spin coated as a 3.8 μm film on a Au surface, after which carbon sputtering of a 1.8 nm carbon film and electron-beam evaporation of 2 nm Pt clusters created an active surface exposed to reactant gases. Electronic characterization indicated that most charge condensed within the Pt nanoclusters upon application of a potential bias, with the condenser device achieving a capacitance of ∼20 μF/cm 2 at applied frequencies of up to 120 Hz. The maximum charge of ∼10 14 |e – | cm –2 was condensed under stable device conditions at 200 °C on catalytic films with ∼10 15 sites cm –2 . Grazing incidence infrared spectroscopy measured carbon monoxide adsorption isobars, indicating a change in the CO* binding energy of ∼19 kJ mol –1 over an applied potential bias of only 1.25 V. Condensers were also fabricated on flexible, large area Kapton substrates allowing stacked or tubular form factors that facilitate high volumetric active site densities, ultimately enabling a fast and powerful catalytic condenser that can be fabricated for programmable catalysis applications.

Catalysis↗
DOE OSTI2025

Linking structure to performance: Characterization of porous transport layers for high-pressure water electrolysis

Proton exchange membrane (PEM) water electrolysis is a promising technology to produce cost-efficient hydrogen. PEM electrolyzers offer a large current density range and the ability to operate at differential pressure which can be used to minimize both capital and operational expenditures. However, directly producing pressurized hydrogen at the cathode results in pushing the membrane against the anode porous transport layer (PTL). This can lead to detrimental effects, such as membrane deformation or ruptures, which depend on membrane properties as well as PTL material properties such as pore size, structure, and morphology. In this work, a range of sinter and felt-based commercial PTLs are evaluated for their contributions to the cell's electrochemical and H 2 crossover performance at cathode pressures up to 30 bar. X-ray tomography and post-operando optical microscopy are used to assess the morphology of the PTLs, and the PTL induced deformation experienced by the catalyst coated membrane (CCM), respectively. PTL samples with lower porosity were found to reduce both the cell voltage and the amount of H 2 permeating from the cathode to the anode exhaust, which was ascribed to improved catalyst layer contact and reduced membrane deformation, respectively. The best performing PTLs improved electrolyzer efficiency by ~1.5 kWh/kg H2 . Specifically, 1 kWh/kg H2 was gained due to reducing membrane deformation and decreasing H 2 crossover. The remainder 0.5 kWh/kg H2 were achieved by improving the electrical contact at the electrode/PTL interface which decreased cell voltage.

08 HYDROGEN↗
DOE OSTI2025

Fabrication of porous transport electrodes: Development of quantitative approach for quality control

This work focuses on porous transport electrodes (PTEs), which integrate the anodic catalyst with the adjacent Ti porous transport layer (PTL). Challenges in catalyst deposition on PTLs, particularly at low loadings, motivated this study to evaluate various fabrication methods and characterization approaches. This work investigated Pt-treated PTLs coated with Ir-based catalysts using several common methods, including airbrush coating, rod coating, ultrasonic spray coating, electrodeposition, and sputter deposition, with catalyst loadings ranging from 2.9 to 0.1 mg/cm 2 , providing the opportunity for comparisons across a large set of samples produced by different methods. Two widely accessible characterization techniques: X-ray computed tomography (XCT) and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) were explored. Initial evaluation of selected samples with XCT provided qualitative insights into catalyst distribution, however comprehensive quantitative analysis was limited. SEM-EDS enabled detailed information on the catalyst distribution both qualitatively and quantitatively using two metrics. Atomic and surface area % ratios of Pt:Ir and Ti:Ir revealed trends in catalyst loading and losses into the PTL pores, as well as evaluating the homogeneity of catalyst coatings. The analysis demonstrated that ultrasonic spray coating, electrodeposition, and sputter coating produced the most homogeneous coatings, with minimal catalyst losses observed for electrodeposition and sputter coating. By adapting common techniques with novel, standardized methodologies, this work establishes a universally applicable framework for cross-study comparison of PTEs. The SEM-EDS approach provides a practical, accessible tool for PTE characterization and contributes a reference dataset supporting both research development and rapid quality control.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Binary Atomically Dispersed Metal-Site Catalysts with Core–Shell Nanostructures for O 2 and CO 2 Reduction Reactions

Engineering atomically dispersed metal site catalysts with controlled local coordination environments and 3D nanostructures effectively improves the catalytic performance for the oxygen reduction reaction (ORR) and the carbon dioxide reduction reaction (CO 2 RR), which are critical for clean energy conversion and chemical production. Herein, an innovative approach for preparing core-shell nanostructured catalysts with different single-metal sites in the core and the shell, respectively, is developed. In particular, as the shell precursors, covalent organic polymers with a thin layered structure that is polymerized in situ and coated on a metal-doped ZIF-derived carbon core are used, followed by a controlled thermal activation. The selective combination and construction of different metal sites increase active site density in the surface layers, promote structural robustness, facilitate mass/charge transfer, and yield a possible synergy of active sites in the core and the shell. The p-FeNC(shell)@CoNC(core), consisting of a polymerized FeTPPCl-derived carbon layer (p-FeNC) on a Co-doped ZIF-derived carbon (CoNC), exhibits remarkable ORR activity and stability in acidic media along with encouraging durability in H 2 –air fuel cells. Likewise, a p-FeNC(shell)@NiNC(core) catalyst demonstrates outstanding CO 2 RR activity and stability. Hence, integrating two appropriate single-metal sites in core and shell precursors, respectively, can modulate morphological and catalytic properties for a possible synergy toward different electrocatalysis processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Investigation of Rh–titanate (ATiO 3 ) interactions on high-surface-area perovskite thin films prepared by atomic layer deposition

Thin, ~1 nm films of CaTiO 3 , SrTiO 3 , and BaTiO 3 were deposited onto MgAl 2 O 4 by Atomic Layer Deposition (ALD) and studied as catalyst supports for Rh. Scanning Transmission Electron Microcopy (STEM) and X-Ray Diffraction (XRD) demonstrated that the films had the perovskite structure and formed uniform coatings stable up to 1073 K. Rh, added by ALD, interacted strongly with CaTiO 3 and somewhat less strongly with SrTiO 3 , while Rh on BaTiO 3 was similar to Rh on unmodified MgAl 2 O 4 . STEM measurements of Rh on CaTiO 3 films showed Rh remained well dispersed after repeated oxidations and reductions at 1073 K; however, the Rh was inactive for CO-oxidation. Rh formed small particles on SrTiO 3 films and was active for CO oxidation after reduction at 1073 K. The reducibility and catalytic activity of Rh/BaTiO 3 /MgAl 2 O 4 were similar to that of Rh/MgAl 2 O 4 . Evidence from CO-TPR, FTIR, and XPS all indicated that the degree of interaction between Rh and the three perovskite films can be ranked in the following order: Rh/CaTiO 3 /MgAl 2 O 4 > Rh/SrTiO 3 /MgAl 2 O 4 > Rh/BaTiO 3 /MgAl 2 O 4 . Here, bulk ex-solution catalysts, synthesized by reduction of ATi 0.98 Rh 0.02 O 3 (A = Ca, Sr, and Ba), were also examined for comparison.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗