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

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Thermal analysis of combustion synthesis of FeAlxOy catalysts for dehydrogenation of fossil fuels

The growing demand for hydrogen as a clean energy carrier highlights the need for its alternative production method with reduced CO₂ emissions. Microwave-assisted thermocatalytic dehydrogenation of fossil fuels offers a promising solution for clean hydrogen production, with FeAlxOy nanocomposites acting as efficient catalysts due to their thermal stability, catalytic activity, and microwave-absorption properties. FeAlxOy nanocomposites, fabricated by solution combustion synthesis (SCS), have shown good microwave-absorption and catalytic properties. However, the effects of synthesis parameters such as fuel type and Fe:Al molar ratio on the SCS process and properties of the final material are not well understood. The SCS process involves vaporization of water, thermal decomposition of the mixture components, and oxidation – reduction reactions. In the present work, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were utilized to study the SCS mechanism, with a focus on understanding decomposition processes. TGA provided insights into the thermal stability and mass loss profiles of the mixtures, while DSC quantified the heat release and identified reaction onset temperatures. Results demonstrated that the choice of fuel significantly influenced the thermal behavior and properties of FeAlxOy nanocomposites. Glycine-based mixtures exhibited superior thermal stability and complete decomposition in a single step with high heat release compared to citric acid-based mixtures, which required higher synthesis temperatures and experienced slower, two-step decomposition processes. These findings emphasize the effectiveness of glycine-fueled SCS in producing thermally stable and catalytically active FeAlxOy nanocomposites.

Martinez Espinoza, Laura Alejandra↗
DOE OSTI2023

Toward Quantum Chemical Free Energy Simulations of Platinum Nanoparticles on Titania Support

Platinum nanoparticles (Pt-NPs) supported on titania surfaces are costly but indispensable heterogeneous catalysts because of their highly effective and selective catalytic properties. Therefore, it is vital to understand their physicochemical processes during catalysis to optimize their use and to further develop better catalysts. However, simulating these dynamic processes is challenging due to the need for a reliable quantum chemical method to describe chemical bond breaking and bond formation during the processes but, at the same time, fast enough to sample a large number of configurations required to compute the corresponding free energy surfaces. Density functional theory (DFT) is often used to explore Pt-NPs; nonetheless, it is usually limited to some minimum-energy reaction pathways on static potential energy surfaces because of its high computational cost. In this work, we report a combination of the density functional tight binding (DFTB) method as a fast but reliable approximation to DFT, the steered molecular dynamics (SMD) technique, and the Jarzynski equality to construct free energy surfaces of the temperature-dependent diffusion and growth of platinum particles on a titania surface. In particular, we present the parametrization for Pt-X (X = Pt, Ti, or O) interactions in the framework of the second-order DFTB method, using a previous parametrization for titania as a basis. The optimized parameter set was used to simulate the surface diffusion of a single platinum atom (Pt 1 ) and the growth of Pt 6 from Pt 5 and Pt 1 on the rutile (110) surface at three different temperatures (T = 400, 600, 800 K). The free energy profile was constructed by using over a hundred SMD trajectories for each process. We found that increasing the temperature has a minimal effect on the formation free energy; nevertheless, it significantly reduces the free energy barrier of Pt atom migration on the TiO 2 surface and the transition state (TS) of its deposition. In a concluding remark, the methodology opens the pathway to quantum chemical free energy simulations of Pt-NPs’ temperature-dependent growth and other transformation processes on the titania support.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Reconstructing Oxygen-Deficient Zirconia with Ruthenium Catalyst on Atomic-Scale Interfaces toward Hydrogen Production

Downsizing a catalyst nanoparticle (NP) to a single atom (SA) has proven to be highly effective in increasing catalytic activity and decreasing the amount of catalyst required for various electrochemical reactions. However, insufficient stability of the single-atom site catalysts (SACs) is still a significant challenge for their practical application. Here, SACs firmly bound to stable metal oxide NPs are proposed to dramatically increase the electrochemical activity and stability of SA-based catalysts for hydrogen evolution reaction (HER). Starting from a Ru-infiltrated, Zr-based metal-organic framework (MOF), the tetragonal zirconium oxide (ZrO 2-x ) NPs-embedded carbon matrix is fabricated as support through facile pyrolysis. Simultaneously, Ru SAs as active sites are well dispersed on the surface of ZrO 2-x NPs due to the generation of oxygen vacancies in the tetragonal ZrO 2-x . Finally, the Ru-ZrO 2-x SAC exhibits a 4–5 times higher mass activity than commercial Pt and Ru catalysts and superior durability due to strong metal-support interaction (SMSI) between Ru atoms and ZrO 2-x substrate.

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

Metal Phosphide Nanoparticles Generated via a Molecular Precursor Route for Hydrotreatment of Methyl Laurate

Transition metal phosphide nanoparticles supported on silica were used as catalysts to investigate the hydrodeoxygenation of methyl laurate (used as a model compound for vegetable oils). Ni 2 P, Ni 1 Mo 1 P, and Ni 1.6 Mo 0.4 P were synthesized using a molecular precursor route. The nanoparticles were added to the silica support without any changes in their structure or particle size. As a reference and for comparison, MoP/SiO 2 was also prepared by the phosphite method. The prepared catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and chemical analysis. A higher conversion is reached with the MoP/SiO 2 monometallic catalyst, close to that with Ni 1 Mo 1 P/SiO 2 . However, this observation is misleading because the differences in dispersion obscure the result that the intrinsic activity (turnover frequency) of the bimetallic catalyst, prepared by a molecular precursor route, is significantly higher than that of the monometallic catalyst, prepared by the phosphite route, revealing a synergistic effect on the catalytic activity due to the formation of the bimetallic phosphide.

09 BIOMASS FUELS↗
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 OSTI2025

Zeta potential measurements of SiO 2 and TiO 2 particles in anionic and cationic surfactant solutions

Zeta potential measurements can provide valuable insights into colloidal stability and may reflect changes in the electrochemical double layer that influence electrocatalysis. In this study, we used zeta potential measurements to monitor and investigate the adsorption behavior of anionic sodium dodecyl sulfate (SDS), cationic dodecyl trimethyl ammonium bromide (DTAB), and cationic cetyl trimethyl ammonium bromide (CTAB) surfactants on SiO 2 and TiO 2 particles in DI water. The zeta potentials of SiO 2 and TiO 2 particles were measured as a function of particle concentration in 1.0 mM, 5.0 mM, and 10.0 mM surfactant solutions. Results indicate that there is no significant adsorption of DS - ions on SiO 2 particles across all SDS concentrations investigated in this study. The zeta potential of TiO 2 particles shifts from negative to positive as particle concentration increases at 1.0 mM SDS, indicating a decrease in DS - ions adsorption per TiO 2 particle. Adsorption plateaus at 5.0 mM SDS for all TiO 2 concentrations studied. In contrast, DTA + and CTA + ions showed clear adsorption on SiO 2 particles, but DTA + exhibited no apparent adsorption on TiO 2 particles. Interestingly, CTA + adsorption on TiO 2 was only evident at higher surfactant concentrations. This study presents a systematic investigation of zeta potential behavior as a function of particle and surfactant concentration, highlighting adsorption saturation and electrostatic reversal. Unlike prior work that was limited to single particle concentration measurements, our approach reveals how surfactant adsorption per particle decreases with increasing surface area. Despite the structural similarity between DTAB and CTAB, this study captured the different adsorption behaviors of both surfactants on SiO 2 and TiO 2 , emphasizing the role of the overall structure of the surfactant on surfactant adsorption behavior. These insights refine the interpretation of zeta potential data and advance understanding of surfactant adsorption on oxide particles. The insight provided in this study about surfactant adsorption on SiO 2 and TiO 2 particles could have important implications for the design of more effective colloidal and catalytic systems.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Oxidative Dehydrogenation of Propane to Propylene with Soft Oxidants via Heterogeneous Catalysis

Oxidative dehydrogenation of propane to propylene can be achieved using conventional, oxygen-assisted dehydrogenation of propane (O 2 –ODHP) or via the use of soft oxidants, such as CO 2 , N 2 O, S-containing compounds, and halogens/halides. The major roles of soft oxidants include inhibiting overoxidation and improving propylene selectivity, which are considered to be current challenges in O 2 -assisted dehydrogenation. For both CO 2 – and N 2 O–ODHP reactions, significant efforts have been devoted to developing redox-active (e.g., chromium, vanadate, iron, etc.), nonredox-type main group metal oxide (e.g., group IIIA, gallium), and other transition metal/metal oxide catalysts (e.g., molybdenum, palladium platinum, rhodium, ruthenium, etc.), as well as zeolite-based catalysts with adjustable acid–base properties, unique pore structures, and topologies. Metal sulfides have shown promising performance in DHP, whereas the development of suitable catalysts has lagged for SO 2 - or S-assisted ODHP. Recently, significant efforts have been focused on homogeneous and heterogeneous ODHP using halogens (e.g., Br 2 , I 2 , Cl 2 , etc.) and hydrogen halides (e.g., HCl and HBr) for the development of facile processes for C 3 H 6 synthesis. This work aims to provide a critical, comprehensive review of recent advances in oxidative dehydrogenation of propane with these soft oxidants, especially highlighting the current state of understanding of the following factors: (i) relationships between composition, structure, and catalytic performance, (ii) effects of the support, acidity, and promoters, (iii) reaction pathway and mechanistic insights, and (iv) the various roles of soft oxidants. Theoretical and computational insights toward understanding reaction mechanisms and catalyst design principles are also covered. Future research opportunities are discussed in terms of catalyst design and synthesis, deactivation and regeneration, reaction mechanisms, and alternative approaches.

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

A Review on the Impact of SO 2 on the Oxidation of NO, Hydrocarbons, and CO in Diesel Emission Control Catalysis

A high-efficiency after-treatment technology has been required to meet the increasingly stringent regulations on the emissions of nitrogen oxides (NO x ), hydrocarbons (HCs), and carbon monoxide (CO) exhausts from diesel engine vehicles throughout the world. The diesel oxidation catalyst (DOC) is an indispensable part of a diesel-fueled exhaust system, which mainly functions in the oxidation of unburned HCs and CO to CO 2 and H 2 O (in the case of HCs) and a proportion of NO to NO 2 . However, the DOC will unavoidably be poisoned by trace gaseous SO 2 or accumulated sulfur on the catalyst under real operational conditions and hence impair the overall purification efficiency of the aftertreatment system. There have been significant research efforts from both academia and industry involving sulfur-relevant diesel oxidation chemistry and development of robust sulfur-resistant oxidation catalysts. In this review, we focus on recent advances in the study of SO 2 effects on the catalytic oxidation of NO, HCs, and CO over DOCs, with particular attention to the fundamentals beneath apparent observations of sulfur influence on PGM-based and non-noble metal-based catalysts in the different oxidation reactions. Regeneration methods and design rationale for sulfur-resistant catalysts are also covered. Several challenges in the future research regarding microscopic insights into the SO 2 -influencing mechanism and next-generation sulfur-resistant DOC design are highlighted toward real-world practice.

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

Controlling Selective C–O and C–H Bond Scission of Methanol by Supporting Pt on TiN and Mo 2 N Model Surfaces and Powder Catalysts

Transition metal nitrides (TMNs) have been explored as effective supports for Pt due to their Pt-like electronic properties. However, there is a lack of fundamental understanding regarding the behavior of Pt on different TMNs (Pt/TMN). Herein two TMNs, Mo 2 N and TiN, were modified with Pt and compared using methanol decomposition as a probe reaction via both ultrahigh vacuum (UHV) studies on thin films and ambient-pressure batch reactor studies of powder catalysts. Temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) measurements were conducted under UHV conditions with Mo 2 N and TiN thin films. Mo 2 N was shown to favor C–H bond scission to form CO with a 56.2% selectivity, while TiN favored C–O bond scission to form CH 4 with a 74.5% selectivity. The addition of 0.9 monolayers (MLs) of Pt increased C–H bond scission selectivity to 89.7% and 49.2% for Mo 2 N and TiN respectively. Density functional theory (DFT) calculations on model surfaces revealed that the binding energy of O (BE *O ) was significantly reduced on Pt/TMNs, from −4.02 eV on Mo 2 N to −1.31 eV on Pt/Mo 2 N and −4.74 eV on TiN to −1.37 eV on Pt/TiN. As a result, C–O bond scission pathways were suppressed, leading to the preferential C–H bond scission that was observed experimentally. The C–O and C–H bond scission trends observed on thin films were then extended to powder catalysts, which demonstrated similar trends toward methanol decomposition. In conclusion, results from the current study establish that by combining UHV studies and DFT calculations over model surfaces, one can effectively predict the catalytic behavior of realistic TMN powder catalysts.

08 HYDROGEN↗
DOE OSTI2023

Functional Impact of a Cancer-Related Variant in Human Δ 1 -Pyrroline-5-Carboxylate Reductase 1

Pyrroline-5-carboxylate reductase (PYCR) is a proline biosynthetic enzyme that catalyzes the NAD(P)H-dependent reduction of Δ 1 -pyrroline-5-carboxylate (P5C) to proline. Humans have three PYCR isoforms, with PYCR1 often upregulated in different types of cancers. Here, we studied the biochemical and structural properties of the Thr171Met variant of PYCR1, which is found in patients with malignant melanoma and lung adenocarcinoma. Although PYCR1 is strongly associated with cancer progression, characterization of a PYCR1 variant in cancer patients has not yet been reported. Thr171 is conserved in all three PYCR isozymes and is located near the P5C substrate binding site. We found that the amino acid replacement does not affect thermostability but has a profound effect on PYCR1 catalytic activity. The k cat of the PYCR1 variant T171M is 100- to 200-fold lower than wild-type PYCR1 when P5C is the variable substrate, and 10- to 25-fold lower when NAD(P)H is varied. A 1.84 Å resolution X-ray crystal structure of T171M reveals that the Met side chain invades the P5C substrate binding site, suggesting that the catalytic defect is due to steric clash preventing P5C from achieving the optimal pose for hydride transfer from NAD(P)H. These results suggest that any impact on PYCR1 function associated with T171M in cancer does not derive from increased catalytic activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Continuous Directed Evolution of a Short-Lived Plant Histidinol Dehydrogenase

Enzyme protein turnover accounts for about half the maintenance energy budget in plants. Slowing turnover i.e., extending the effective working life (Catalytic Cycles till Replacement, CCR) of short-lived enzymes is thus a rational strategy to conserve energy and carbon and raise crop productivity. Arabidopsis histidinol dehydrogenase (HDH) is a short-lived enzyme that can sustain lifeshortening damage from its aminoaldehyde reaction intermediate. We used the yeast OrthoRep continuous directed evolution system in a his4 Δ strain to raise cumulative HDH function and, by proxy, lifespan as functional enzymes, by selecting for growth rate while tapering histidinol concentration and escalating that of the inhibitor histamine. Improved HDH variants carried diverse nonsynonymous mutations and ranged 20-fold in level. Improved HDH performance was associated with higher HDH abundance in some cases and with greater catalytic efficiency or histamine resistance in others. These findings indicate that OrthoRep-based directed evolution can extend enzyme working life in vivo in addition to, as expected, altering kinetic properties.

directed evolution↗
DOE OSTI2023

Twin Proliferation and Prolongation under Kinetic Control: Pd–Au Janus Icosahedra versus Pd@Au Core–Shell Starfishes

Heterogeneous bimetallic nanocrystals featuring explicit spatial configurations and abundant twin defects can simultaneously enable geometric and ligand effects to enhance catalytic and photonic applications. Herein, we report two growth patterns of Au atoms on penta-twinned Pd decahedra, involving twin proliferation to generate asymmetric Pd–Au Janus icosahedra and twin elongation to produce anisotropic Pd@Au core–shell starfishes, respectively. Mechanistic analysis indicates that the injection rate determines the lower-limit number (n low ) of Au(III) ions in the steady state and thus controls the growth pattern. When n low ≤ 5.5, the kinetic rate is slow enough to initiate asymmetrical one-side growth but fast enough to outpace surface diffusion; Au tetrahedral subunits are successively proliferated along the axial $\langle$110$\rangle$ direction of Pd decahedra to form Pd–Au Janus icosahedra. Composed of five Pd and 15 Au tetrahedral subunits, such a heterogeneous icosahedron supports high (2.2 GPa) tensile strain and high strain difference up to +21.9%. In contrast, when n low > 5.5, the fast reduction kinetics promotes symmetric growth with inadequate surface diffusion. As such, Au atoms are laterally deposited along five high-indexed $\langle$211$\rangle$ ridges of Pd decahedra to generate concave Pd@Au core–shell starfishes with tunable sizes (28–40 nm), twin elongation ratios (33.82–162.08%), and lattice expansion ratios (8.82–20.10%).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1986

Heat and mass transfer in a dissociated laminar boundary layer of air with consideration of the finite rate of chemical reaction

A numerical investigation of heat and mass transfer in a dissociated laminar boundary layer of air on an isothermal flat plate is carried out for different degrees of cooling of the wall. A finite-difference chemical model is used to study elementary reactions involving NO2 and N2O. The analysis is based on equations of continuity, momentum, energy, conservation and state for the two-dimensional viscous flow of a reacting multicomponent mixtures. Attention is given to the effects of both catalyticity and noncatalyticity of the wall.

Oyegbesan, A. O.↗
NASA NTRS1988

Stagnation flow field analysis for an aeroassist flight experiment vehicle

Continuum methods are used to analyze the stagnation flow field of the aeroassist flight experiment (AFE) vehicle. For the lower altitude portion of an AFE trajectory, the viscous shock-layer equations are employed. At higher altitudes, the full Navier-Stokes equations with chemical nonequilibrium and surface slip are used. Particular attention is given to the effect of surface catalyticity on surface heating, electron number density, and flow field structure.

Gupta, Roop N.↗
NASA NTRS1991

On the origin and early evolution of biological catalysis and other studies on chemical evolution

One of the lines of research in molecular evolution which we have developed for the past three years is related to the experimental and theoretical study of the origin and early evolution of biological catalysis. In an attempt to understand the nature of the first peptidic catalysts and coenzymes, we have achieved the non-enzymatic synthesis of the coenzymes ADPG, GDPG, and CDP-ethanolamine, under conditions considered to have been prevalent on the primitive Earth. We have also accomplished the prebiotic synthesis of histidine, as well as histidyl-histidine, and we have measured the enhancing effects of this catalytic dipeptide on the dephosphorylation of deoxyribonucleotide monophosphates, the hydrolysis of oligo A, and the oligomerization 2', 3' cAMP. We reviewed and further developed the hypothesis that RNA preceded double stranded DNA molecules as a reservoir of cellular genetic information. This led us to undertake the study of extant RNA polymerases in an attempt to discover vestigial sequences preserved from early Archean times. In addition, we continued our studies of on the chemical evolution of organic compounds in the solar system and beyond.

Oro, J.↗
NASA NTRS1993

Stagnation flowfield analysis for an aeroassisted vehicle

Hypersonic reactive flowfield results are presented for the flow about an axisymmetric representation of a three-dimensional aeroassisted vehicle using the viscous shock-layer (VSL) and Navier-Stokes (NS) equations for low- and high-altitude entry conditions, respectively. Solutions are limited to the stagnation region. The NS results have been obtained by employing the surface recombination boundary condition for an 11-species air model, whereas the VSL calculations are carried out by using a 5-species model. Three widely used surface recombination rate models are implemented with these two flowfield calculation procedures. The low-density (or high altitude) NS solutions are obtained with surface slip equations and compare quite well with the direct simulation Monte Carlo predictions. For higher densities (or lower altitudes), the no-slip VSL solutions are considered adequate. Results from this study highlight the effect of surface catalyticity on surface heating and electron number density.

Gupta, Roop N.↗
NASA NTRS1994

An implementation of a chemical and thermal nonequilibrium flow solver on unstructured meshes and application to blunt bodies

This paper presents a nonequilibrium flow solver, implementation of the algorithm on unstructured meshes, and application to hypersonic flow past blunt bodies. Air is modeled as a mixture of five chemical species, namely O2, N2, O, NO, and N, having two temperatures namely translational and vibrational. The solution algorithm is a cell centered, point implicit upwind scheme that employs Roe's flux difference splitting technique. Implementation of this algorithm on unstructured meshes is described. The computer code is applied to solve Mach 15 flow with and without a Type IV shock interference on a cylindrical body of 2.5mm radius representing a cowl lip. Adaptively generated meshes are employed, and the meshes are refined several times until the solution exhibits detailed flow features and surface pressure and heat flux distributions. Effects of a catalytic wall on surface heat flux distribution are studied. For the Mach 15 Type IV shock interference flow, present results showed a peak heat flux of 544 MW/m2 for a fully catalytic wall and 431 MW/m(exp 2) for a noncatalytic wall. Some of the results are compared with available computational data.

Prabhu, Ramadas K.↗
NASA NTRSDate not supplied

Thermochemical Instabilities at High Temperature Ceramic Surfaces

The surface of silicon-based high temperature ceramics exhibits thermochemical instabilities when exposed to oxygen-rich high enthalpy flows. These instabilities manifest as sudden temperature jumps of several hundred degrees and rapid material failure, when temperatures exceed 2000 K. Understanding and predicting these phenomena is critical to the design of thermal protection systems for sustained high speed flight vehicles. In this talk we review a series of test cases where surface temperature jumps were observed during plasmatron wind tunnel testing of ceramic materials, including ZrB2-SiC ultra-high temperature ceramics, C/SiC ceramic matrix composites, and silicone-based coatings for low-density carbon phenolic ablators. The underlying physical processes occurring when Si-containing ceramics are exposed to high enthalpy air flow include formation of passivating scales at low temperatures, passive to active oxidation transition, melting of oxide scales, changes in surface radiative properties, formation of porosity and changes in effective conductivity, surface catalytic recombination and transitions in catalytic properties, as well as high-temperature phase changes. The role of these processes in promoting thermochemical instabilities for the different material systems is discussed.

Ultra High Temperature Ceramics, UHTC↗