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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Dual function materials (Ru+Na 2 O/Al 2 O 3 ) for direct air capture of CO 2 and in situ catalytic methanation: The impact of realistic ambient conditions

Here a dual function material (DFM) comprised of 1% Ru, 10% Na 2 O/γ–Al 2 O 3 was studied for combined direct air capture (DAC) of CO 2 and catalytic methanation in a temperature swing operation. In the newly proposed operation, the DFM captures CO 2 (400 ppm) from air at ambient conditions. The material is then heated in H 2 to a temperature sufficient for catalytic conversion of the captured CO 2 to renewable natural gas. In this study, we demonstrate high CO 2 adsorption capacity and rates at ambient conditions (25 °C); the adsorbed CO 2 is then successfully catalytically methanated upon heating in H 2 . Adsorption was also carried out in humid conditions, more closely simulating ambient air. Adsorption and methane production were greatly improved with stable initial performance. The rate of adsorption is shown to be flowrate-dependent, which is critical for future reactor design.

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

Measured catalycities of various candidate space shuttle thermal protection system coatings at low temperatures

Atom recombination catalytic rates for surface coatings of various candidate thermal protection system materials for the space shuttle vehicle were obtained from measurements in arc jet, air flow. The coatings, chrome oxides, siliconized carbon/carbon, hafnium/tantalum carbide on carbon/carbon, and niobium silicide, were bonded to the sensitive surface of transient slug calorimeters that measured the heat transfer rates to the coatings. The catalytic rates were inferred from these heat transfer rates Surface temperatures of the calorimeters varied from approximately 300 to 410 K.

Scott, C. D.↗
DOE OSTI2024

Hydrocoals from waste biomass via catalytic hydrothermal carbonization processing

This study investigates how operating conditions (temperature and residence time) and benzoyl chloride impact hydrochar production from almond shells through hydrothermal carbonization. Carbon content rises while volatile matter decreases with increasing temperature, yielding a hydrochar with an estimated heating value of 28 MJ/kg. Elevated temperatures lower the O/C and H/C atomic ratios of hydrochars. Even at the lowest temperature under scrutiny, catalytic experiments using benzoyl chloride enhance carbonization and fuel ratio across all temperatures. Hydrochars produced through catalytic runs demonstrate elevated fuel ratios relative to those generated through noncatalytic runs, despite operating under the same conditions. These insights reveal the capacity of benzoyl chloride as a catalyst to improve hydrochar properties, suggesting its utility for advancing both the efficiency and effectiveness of hydrothermal carbonization processes.

09 BIOMASS FUELS↗
DOE OSTI2021

Synthesis of Yttrium Superhydride Superconductor with a Transition Temperature up to 262 K by Catalytic Hydrogenation at High Pressures

The recent observation of room-temperature superconductivity will undoubtedly lead to a surge in the discovery of new, dense, hydrogen-rich materials. The rare earth metal superhydrides are predicted to have very high-T c superconductivity that is tunable with changes in stoichiometry or doping. Here we report the synthesis of an yttrium superhydride that exhibits superconductivity at a critical temperature of 262 K at 182±8 GPa. A palladium thin film assists the synthesis by protecting the sputtered yttrium from oxidation and promoting subsequent hydrogenation. Phonon-mediated superconductivity is established by the observation of zero resistance, an isotope effect and the reduction of T c under an external magnetic field. Furthermore, the upper critical magnetic field is 103 T at zero temperature.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Acetylene ligands stabilize atomically dispersed supported rhodium complexes under harsh conditions

Facile sintering of atomically dispersed supported noble metal catalysts at catalytically relevant temperatures, particularly under reducing conditions, poses a challenge for their practical applications. Some ligands, such as carbonyls, aid in improving the stability at the expense of severely suppressing the catalytic activity. In this work, we demonstrate that substitution of the carbonyl ligands with reactive acetylene ligands can maintain the atomic dispersion of the supported mononuclear rhodium complex under harsh reducing conditions (>573 K), as confirmed by in-situ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies. In contrast, the supported rhodium carbonyl complex aggregates into nanoclusters under identical conditions. Furthermore, our results indicate that the acetylene ligands provide this anti-sintering ability while retaining the hydrogenation activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

Catalytic recombination of nitrogen and oxygen on high-temperature reusable surface insulation

The energy transfer catalytic recombination coefficient for nitrogen and oxygen recombination on the surface coating of high-temperature reusable surface insulation (HRSI) is inferred from stagnation point heat flux measurements in a high-temperature dissociated arc jet flow. The resulting catalytic recombination coefficients are correlated with an Arrhenius model for convenience, and these expressions may be used to account for catalytic recombination effects in predictions of the heat flux on the HRSI thermal protection system of the Space Shuttle Orbiter during reentry flight. Analysis of stagnation point pressure and total heat balance enthalpy measurements indicates that the arc heater reservoir conditions are not in chemical equilibrium. This is contrary to what is usually assumed for arc jet analysis and indicates the need for suitable diagnostics and analyses, especially when dealing with chemical reaction phenomena such as catalytic recombination heat transfer effects.

Scott, C. D.↗
NASA NTRS2014

Organic Analysis of Catalytic Fischer-Tropsch Synthesis Products and Ordinary Chondrite Meteorites by Stepwise Pyrolysis-GCMS: Organics in the Early Solar Nebula

Abiotic generation of complex organic compounds, in the early solar nebula that formed our solar system, is hypothesized by some to occur via Fischer-Tropsch (FT) synthesis. In its simplest form, FT synthesis involves the low temperature (<300degC) catalytic reaction of hydrogen and carbon monoxide gases to form more complex hydrocarbon compounds, primarily n-alkanes, via reactive nano-particulate iron, nickel, or cobalt, for example. Industrially, this type of synthesis has been utilized in the gas-to-liquid process to convert syngas, produced from coal, natural gas, or biomass, into paraffin waxes that can be cracked to produce liquid diesel fuels. In general, the effect of increasing reaction temperature (>300degC) produces FT products that include lesser amounts of n-alkanes and greater alkene, alcohol, and polycyclic aromatic hydrocarbon (PAH) compounds. We have begun to experimentally investigate FT synthesis in the context of abiotic generation of organic compounds in the early solar nebula. It is generally thought that the early solar nebula included abundant hydrogen and carbon monoxide gases and nano-particulate matter such as iron and metal silicates that could have catalyzed the FT reaction. The effect of FT reaction temperature, catalyst type, and experiment duration on the resulting products is being investigated. These solid organic products are analyzed by thermal-stepwise pyrolysis-GCMS and yield the types and distribution of hydrocarbon compounds released as a function of temperature. We show how the FT products vary by reaction temperature, catalyst type, and experimental duration and compare these products to organic compounds found to be indigenous to ordinary chondrite meteorites. We hypothesize that the origin of organics in some chondritic meteorites, that represent an aggregation of materials from the early solar system, may at least in part be from FT synthesis that occurred in the early solar nebula.

Locke, Darren R.↗
DOE OSTI2020

Synthesis and catalytic performance of polydopamine supported metal nanoparticles

Polydopamine (PDA) is an emerging nature-inspired biopolymer material that possesses many interesting properties including self-assembly and universal adhesion. PDA is also able to form coordination bonds with various metal ions, which can be reduced to metal nanoparticles (NPs) as a result of thermal annealing under protective environment. In this study, PDA has been utilized as a support material to synthesize Pt NPs in an aqueous solution at room temperature. The catalytic performance of the resulting PDA-Pt nanocomposite was evaluated using an electrochemical workstation which showed comparable activity to Pt/C material for hydrogen evolution reaction (HER). Furthermore, Cu, Ni, and Cu–Ni NPs supported on PDA were also obtained using this strategy with assistance of subsequent thermal annealing. The phase evolution of the NPs was studied by in-situ X-ray diffraction while the morphology of the nanoparticles was investigated using electron microscopic techniques. Preliminary results showed the NPs supported on PDA also possessed HER activity. This work demonstrates that PDA can be utilized as a potential support for synthesis of metal NPs that can be exploited in engineering applications such as catalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stable Surface Terminations of a Perovskite Oxyhydride from First-Principles

Successful synthesis of some perovskite oxyhydrides and their unique catalytic properties have recently attracted researchers’ attention. However, their surface structure remains unclear. Here we identify stable surface terminations of a prototypical perovskite oxyhydride, BaTiO 2.5 H 0.5 , under catalytically relevant temperatures and pressures by using first-principles thermodynamics based on density functional theory. Five low-index facets, including (100), (010), (210), (011), and (211), and their various terminations for a total of 47 different surfaces have been examined for relative stability at different temperatures (700, 500, 300 K) and gas environments (10 –15 ≤ P O2 ≤ 1 atm, 10–15 ≤ PH2 ≤ 100 atm). The most stable ones are found to be (010)-Ba 2 O 2 , (210)-Ti 2 O 2 , and (211)-Ba 2 O 4 H surface terminations. These polar surfaces are stabilized by charge compensation. This work provides important insights into the stable surfaces of perovskite oxyhydrides for future studies of their catalytic properties.

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

Reversible hydrogen control of antiferromagnetic anisotropy in α-Fe 2 O 3

Antiferromagnetic insulators are a ubiquitous class of magnetic materials, holding the promise of low-dissipation spin-based computing devices that can display ultra-fast switching and are robust against stray fields. However, their imperviousness to magnetic fields also makes them difficult to control in a reversible and scalable manner. Here we demonstrate a novel proof-of-principle ionic approach to control the spin reorientation (Morin) transition reversibly in the common antiferromagnetic insulator α-Fe 2 O 3 (haematite) - now an emerging spintronic material that hosts topological antiferromagnetic spin-textures and long magnon-diffusion lengths. We use a low-temperature catalytic-spillover process involving the post-growth incorporation or removal of hydrogen from α-Fe 2 O 3 thin films. Hydrogenation drives pronounced changes in its magnetic anisotropy, Néel vector orientation and canted magnetism via electron injection and local distortions. We explain these effects with a detailed magnetic anisotropy model and first-principles calculations. Tailoring our work for future applications, we demonstrate reversible control of the room-temperature spin-state by doping/expelling hydrogen in Rh-substituted α-Fe 2 O 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2022

High Activity and Selectivity for Catalytic Alkane–Alkene Transfer (De)hydrogenation by ( tBu PPP)Ir and the Importance of Choice of a Sacrificial Hydrogen Acceptor

The triphosphorus-coordinating pincer iridium fragment ( tBu PPP)Ir was recently reported to be highly active for the catalytic dehydrogenation of n-alkanes. Dehydrogenation is calculated to be highly regioselective for the terminal position of n-alkanes. Here, the extremely high intermolecular selectivity observed in n-alkane/cycloalkane competition experiments supports the prediction of extremely high regioselectivity for dehydrogenation of n-alkanes. The use of sterically unhindered hydrogen acceptors is key to observing the high activity of the ( tBu PPP)Ir fragment. 4,4-Dimethylpent-1-ene (TBP) is found to be particularly convenient for this purpose. With the commonly used hydrogen acceptor 3,3-dimethylbut-1-ene (TBE), ( tBu PPP)Ir affords n-alkane dehydrogenation at a rate no different than that obtained with the well-known fragment ( iPr PCP)Ir. However, with the use of TBP as acceptor, ( tBu PPP)Ir shows much greater activity for n-alkane transfer dehydrogenation than previously reported catalysts, affording appreciable rates even at 50 °C, an unprecedentedly low temperature for catalytic alkane transfer dehydrogenation. Also critical to the identification of ( tBu PPP)Ir as a highly effective catalyst is the use of n-alkane substrate rather than the commonly used “model” dehydrogenation substrate, cyclooctane, with which dehydrogenation rates are much lower than those with n-alkanes.

10 SYNTHETIC FUELS↗
DOE OSTI2021

The effects of SMSI on m-Cresol Hydrodeoxygenation over Pt/Nb 2 O 5 and Pt/TiO 2

The hydrodeoxygenation (HDO) of m-cresol was studied on Pt/Nb 2 O 5 /MgAl 2 O 4 and Pt/TiO 2 /MgAl 2 O 4 catalysts to understand the effects of Strong Metal Support Interactions (SMSI). The Nb 2 O 5 and TiO 2 supports were prepared as 0.7-nm films on MgAl 2 O 4 by Atomic Layer Deposition (ALD) to ensure that the structures of the catalyst were the same. When reduced at 773 K to place Pt in the encapsulated state, Pt/Nb 2 O 5 /MgAl 2 O 4 was much less active than Pt/MgAl 2 O 4 at 573 K but much more active at 623 K. While Pt/MgAl 2 O 4 deactivated rapidly due to coking, Pt/Nb 2 O 5 /MgAl 2 O 4 showed significantly better coke tolerance and was almost 100% selective towards toluene production. Pt/Nb 2 O 5 /MgAl 2 O 4 reduced at lower temperatures exhibited intermediate catalytic properties. The effect of reduction temperature on Pt/TiO 2 /MgAl 2 O 4 was much less and this catalyst was more similar to Pt/MgAl 2 O 4 than its Nb 2 O 5 counterpart. Lastly, the implications of these results for understanding the nature of oxide promoters on HDO of m-cresol are discussed.

09 BIOMASS FUELS↗
DOE OSTI2021

New Insights into the Bulk and Surface Defect Structures of Ceria Nanocrystals from Neutron Scattering Study

Neutron diffraction and pair distribution function studies coupled with Raman spectroscopy have successfully unraveled the detailed oxygen defect structures of ceria nanocubes and nanorods. Two types of defect sites are revealed for the ceria nanocrystals: surface and bulk defects. It is proposed that the surface oxygen defects in both types of CeO 2 nanocrystals are predominantly the partially reduced Ce 3 O 5+x , with the bulk defect structures dominated by interstitial Frenkel-type oxygen vacancies. Ceria nanorods possess much higher concentration of surface oxygen defects relative to the nanocubes, albeit with only slightly higher concentration of bulk Frenkel-type oxygen vacancies. Upon annealing the nanorod sample at 600 °C under vacuum (~10 –4 to 10 –5 mbar), a partially reduced ceria phase with long-range oxygen vacancy ordering (Ce 3 O 5+x ) has been observed experimentally for the first time. This intriguing observation that surface defect phases can take on ordered defect sublattices under certain conditions is of great value in understanding the temperature-dependent catalytic performance of ceria nanocrystals. Furthermore, a drastic decrease of the surface vacancies in the ceria nanocrystals is observed upon exposure to SO 2 , especially for the nanorods, a likely origin for the sulfur poisoning effect on ceria-based materials. This study suggests that tailoring surface morphology is a promising strategy to control defect properties of ceria nanomaterials. It also provides fundamental insights to stabilize surface oxygen defects in CeO 2 nanocrystals to achieve high redox performance under corrosive environments such as under SO 2 /SO x exposure.

36 MATERIALS SCIENCE↗
DOE OSTI2021

High-Entropy 2D Carbide MXenes: TiVNbMoC 3 and TiVCrMoC 3

Two-dimensional (2D) transition metal carbides and nitrides, known as MXenes, are a fast-growing family of 2D materials. MXenes 2D flakes have n + 1 (n = 1-4) atomic layers of transition metals interleaved by carbon/nitrogen layers, but to-date remain limited in composition to one or two transition metals. In this study, by implementing four transition metals, we report the synthesis of multi-principal-element high-entropy M 4 C 3 T x MXenes. Specifically, we introduce two high-entropy MXenes, TiVNbMoC 3 T x and TiVCrMoC 3 T x , as well as their precursor TiVNbMoAlC 3 and TiVCrMoAlC 3 high-entropy MAX phases. We used a combination of real and reciprocal space characterization (X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, and scanning transmission electron microscopy) to establish the structure, phase purity, and equimolar distribution of the four transition metals in high-entropy MAX and MXene phases. We use first-principles calculations to compute the formation energies and explore synthesizability of these high-entropy MAX phases. We also show that when three transition metals are used instead of four, under similar synthesis conditions to those of the four-transition-metal MAX phase, two different MAX phases can be formed (i.e., no pure single-phase forms). This finding indicates the importance of configurational entropy in stabilizing the desired single-phase high-entropy MAX over multiphases of MAX, which is essential for the synthesis of phase-pure high-entropy MXenes. The synthesis of high-entropy MXenes significantly expands the compositional variety of the MXene family to further tune their properties, including electronic, magnetic, electrochemical, catalytic, high temperature stability, and mechanical behavior.

2D materials↗
DOE OSTI2021

An alternative domain-swapped structure of the Pyrococcus horikoshii PolII mini-intein

Protein splicing is a post-translational process by which an intein catalyzes its own excision from flanking polypeptides, or exteins, concomitant with extein ligation. Many inteins have nested homing endonuclease domains that facilitate their propagation into intein-less alleles, whereas other inteins lack the homing endonuclease (HEN) and are called mini-inteins. The mini-intein that interrupts the DNA PolII of Pyrococcus horikoshii has a linker region in place of the HEN domain that is shorter than the linker in a closely related intein from Pyrococcus abyssi. The P. horikoshii PolII intein requires a higher temperature for catalytic activity and is more stable to digestion by the thermostable protease thermolysin, suggesting that it is more rigid than the P. abyssi intein. We solved a crystal structure of the intein precursor that revealed a domain-swapped dimer. Inteins found as domain swapped dimers have been shown to promote intein-mediated protein alternative splicing, but the solved P. horikoshii PolII intein structure has an active site unlikely to be catalytically competent.

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

PdCu Single Atom Alloys for the Selective Oxidation of Methanol to Methyl Formate at Low Temperatures

The selective catalytic oxidation of methanol to methyl formate (MF) has been considered as an attractive route to produce MF, an important precursor in the chemical industry. Although supported Pd nanoparticles are active for the selective oxidation of methanol to MF, the relatively low MF selectivity and yield remains an unsolved issue. Here in this paper, we show that adding a small amount of Pd into Cu forming PdCu single atom alloy (SAA) catalysts can catalyze the oxidation of methanol to MF selectively at low temperatures, with a high catalyst stability. The atomic dispersion of Pd atoms in the Cu matrix was confirmed by various in-situ characterization techniques. The activity and selectivity of PdCu SAA catalysts were compared to monometallic Cu and Pd catalysts, in a flow reactor at similar conditions. This work may guide the design of new SAA based catalysts for selective oxidation reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1978

Effect of inlet temperature on the performance of a catalytic reactor

A 12 cm diameter by 15 cm long catalytic reactor was tested with No. 2 diesel fuel in a combustion test rig at inlet temperatures of 700, 800, 900, and 1000 K. Other test conditions included pressures of 3 and 6 x 10 to the 5th power Pa, reference velocities of 10, 15, and 20 m/s, and adiabatic combustion temperatures in the range 1100 to 1400 K. The combustion efficiency was calculated from measurements of carbon monoxide and unburned hydrocarbon emissions. Nitrogen oxide emissions and reactor pressure drop were also measured. At a reference velocity of 10 m/s, the CO and unburned hydrocarbons emissions, and, therefore, the combustion efficiency, were independent of inlet temperature. At an inlet temperature of 1000 K, they were independent of reference velocity. Nitrogen oxides emissions resulted from conversion of the small amount (135 ppm) of fuel-bound nitrogen in the fuel. Up to 90 percent conversion was observed with no apparent effect of any of the test variables. For typical gas turbine operating conditions, all three pollutants were below levels which would permit the most stringent proposed automotive emissions standards to be met.

Anderson, D. N.↗