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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Impact of exposure to brine/CO 2 on the mechanical and transport properties of the Mt. Simon Sandstone

When sandstone rocks are exposed to CO 2 -saturated brine, their transport and mechanical properties can, potentially, change due to chemical reactions as a result of such exposure. This paper investigates changes in the flow-through characteristics, porosity, and the mechanical properties of Mt. Simon Sandstone samples caused by such exposure to brine/CO 2 . A core, extracted from the Mt. Simon formation, was first characterized for its porosity and relevant transport properties, and it was then aged for over 500 hr in CO 2 -saturated brine at formation-relevant pressure, temperature, and confining stress conditions. The deformation of the sample was measured in situ during aging via strain gauges attached to the core's surface. Following the aging experiment, the sample's porosity and transport properties were again analyzed. Our experiments show that both the porosity and permeability of the Mt. Simon sandstone sample increase due to exposure to brine/CO 2 , with the impact on permeability being more significant. The deformation measurements employing strain gauges indicate a weakening of the core material. Analysis of the composition of the brine at the conclusion of the testing reveals changes, specifically, an increase in the concentration of several of the cations. These changes are indicative of mineral/clay dissolution, consistent with the porosity, permeability, and strain gauge measurements.

58 GEOSCIENCES↗
DOE OSTI2021

The O K -2 V spectrum of CO: the influence of the second core-hole

Using synchrotron radiation in the tender X-ray regime, a photoelectron spectrum showing the formation of single site double-core-hole pre-edge states, involving the K shell of the O atom in CO, has been recorded by means of high-resolution electron spectroscopy. The experimentally observed structures have been simulated, interpreted and assigned, employing state-of-the-art ab initio quantum chemical calculations, on the basis of a theoretical model, accounting for their so-called direct or conjugate character. Features appearing above the double ionization threshold have been reproduced by taking into account the strong mixing between multi-excited and continuum states. The shift of the σ* resonance below the double ionization threshold, in combination with the non-negligible contributions of multi-excited configurations in the final states reached, gives rise to a series of avoided crossings between the different potential energy curves.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2026

Isolated and H 2 -reduced Anderson clusters catalyse low-temperature hydrogenation of CO 2 to methanol

CO 2 hydrogenation, especially to methanol, is crucial to establishing sustainable closed-loop systems for carbon utilization. However, the difficulties of CO 2 activation at low temperatures and the ambiguity of structure–activity correlations are obstacles to reducing the energy consumption of the hydrogenation process. Here we report that molecularly defined Anderson PtMo 6 O 24 clusters, sited within a robust metal–organic framework, are catalytic for low-temperature CO 2 hydrogenation. The performance of the cluster showed no signs of decay in either its activity or methanol selectivity over 3,600 h at 180 °C. It also achieves a per-pass yield exceeding that of state-of-the-art heterogeneous catalysts under similar conditions. Combined in situ spectroscopy and density functional theory calculations demonstrated that CH 3 OH formation is dominated by the reverse water–gas shift and subsequent CO* hydrogenation pathway, while the HCOO* pathway may serve as a supplementary route. The well-defined cluster structure offers an ideal model for elucidating structure–activity correlations and opens exciting avenues for the rational design of high-activity, low-temperature catalysts for CO 2 hydrogenation.

heterogeneous catalysis↗
NASA NTRS1984

Starbursts in Galaxies: Implications of Molecular and Far-infrared Observations

Starburst galaxies are defined in several ways (colors, optical spectroscopic signatures, and excess radio flux), and observational evidence indicating that episodes of rapid star formation occur in many galaxies with active nuclei is presented. There is a good correlation of 100 micron luminosity with CO emission, and of both quantities with excess nonthermal radio flux. This fact requires some linkage between central and global star formation rates. In addition, the presence of starbusts distorts the appearance of the molecular gas in which they occur. Using far infrared color temperatures and comparisons of CO isotopes, it is shown that the strong (12)CO emission in these galaxies does not accurately trace the H2 distribution, probably because the starburst raises the avearage temperature of the cloud ensemble.

Rickard, L. J.↗
DOE OSTI2020

Discovery of single-atom alloy catalysts for CO 2 -to-methanol reaction by density functional theory calculations

The transformations of CO 2 molecules into valuable products are of increasing interest due to the negative impact of anthropogenic CO 2 emissions on global warming. The CO 2 -to-methanol hydrogenation is an economically profitable reaction of carbon fixation, but it still steps away from widespread industrialization because of the lack of efficient and selective catalysts. Recently, single-atom alloy (SAA) catalysts have been developed to work remarkably in CO 2 hydrogenation reactions. Doping isolated single atoms into metallic catalyst can dramatically alter the catalytic performance of the host. Here, we have performed a screening discovery on Ru and 6 RuX (X = Fe, Co, Ni, Cu, Ir and Pt) SAAs using density functional theory (DFT) computations. We considered 13 possible elementary reactions in 4 possible reaction pathways on Ru and all RuX surfaces. In the computed mechanisms, we found that the formation of *H 2 COOH and *HCOO intermediates plays a critical role in determining catalysts’ activities. Doping Co and Pt isolated single atoms into Ru surface can thermodynamically and kinetically facilitate these intermediates formation processes, eventually promoting the production of methanol. The combination of weak binding and enhanced charge redistribution on RuCo and RuPt surfaces give them improved catalytic activities over pure Ru. This work will ultimately facilitate the discovery and development of SAAs for CO 2 to methanol, serving as guidance to experiments and theoreticians alike.

25 ENERGY STORAGE↗
DOE OSTI2022

13 C NMR study of amino acid salts in facilitated transport membranes for post-combustion carbon capture

Some of amino acid salts (AASs) have been demonstrated to be effective mobile carriers in facilitated transport membranes (FTMs) to achieve superior CO 2 permeance and CO 2 /N 2 selectivity for CO 2 capture from flue gas. Understandings of how the structures of different AASs affect the chemistry of the amine–CO 2 reaction are essential for the future development of more efficient AAS mobile carriers. In this study, the reaction chemistry of selected AASs with CO 2 was investigated by 13 C nuclear magnetic resonance (NMR) spectroscopy. The CO 2 loading and the distribution of major reaction products, including carbamate and bicarbonate products of each studied AAS were quantitatively analyzed. The positive correlation between the CO 2 loading of AAS (mol CO 2 /g AAS) and the CO 2 permeance of FTMs suggested that AAS with a higher CO 2 loading may improve the performance of FTMs. Our results also showed that increasing the steric hindrance of AAS could be a practical way to promote the bicarbonate reaction pathway and thus potentially increase the CO 2 loading (mol CO 2 /mol AAS). Moreover, 2-(1-piperazinyl)ethylamine (PZEA) was found to be a more effective multi-amine than piperazine (PZ) for synthesizing AASs due to the presence of more effective nitrogen sites per molecule. The superior CO 2 permeance of the PZEA-Sar membrane is also attributed to its more uniform membrane formation. As a result, the knowledge gained from this study will inform the rational design of more effective AAS carriers for CO 2 capture.

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

Assessment of sulfur trioxide formation due to enhanced interaction of nitrogen oxides and sulfur oxides in pressurized oxy-combustion

Pressurized oxy-combustion is emerging to be one of the best technologies for significantly decreasing the energy penalty for CO 2 capture in coal-fired power plants. However, the higher pressure boosts the formation of acid gases, including SO 3 and NO 2 , which could increase the risk of corrosion. The synergistic promotion of SO 3 and NO 2 formation in pressurized oxy-combustion is kinetically evaluated under representative conditions (1 ~ 30 atm, 600 ~ 1200 °C, NO/SO 2 = 0.1 ~ 5). We begin with a comprehensive mechanism (72 species and 428 reactions), covering nitrogen and sulfur chemistry, relying on GRI-Mech 3.0. This analysis shows that the interaction of SO X and NO X enhances the conversion rates of SO 2 → SO 3 , and this effect is more apparent at elevated pressures and lower temperatures. Mechanism analyses indicate that at elevated pressures, the formation pathways of SO 3 through HOSO 2 + O 2 = SO 3 + HO 2 , and NO 2 through HO 2 + NO = NO 2 + OH, are promoted due to the strong interaction between SO X and NO X . The intermediate between these two reactions is SO 2 + OH + M = HOSO 2 + M, resulting in a strong cycle, that can be expressed by the global reaction NO + SO 2 + O 2 = NO 2 + SO 3 . Finally, a nine-step reduced chemistry is developed and validated to accurately predict the formation of SO 3 in the post-flame region at elevated pressures.

42 ENGINEERING↗
DOE OSTI2021

DFT Mechanism Studies: Biomimetic 1,4-NADH Chemoselective, Co-factor Regeneration with [Cp*Rh(bpy)H] + , in Tandem with the Biocatalysis Pathways of a Core Model of the (HLADH)-Zn(II) Mediated Enzyme, in the Enantioselective Reduction of Achiral Ketones to Chiral S-Alcohols

In this study, Quantum Chemical (QC) calculations, utilizing Density Functional Theory (DFT), were performed to investigate the mechanistic aspects of the chemoselective catalyzed reaction of [Cp*Rh(bpy)H] + with the biomimetic NAD + analogues, N-benzylnicotinamide triflate, 1, and β-nicotinamide ribose-5'-methyl phosphate, 2, in the conversion to their 1,4-NADH analogues, 1,4-dihydro-N-benzylnicotinamide, 4, and β-1,4-dihydronicotinamide-5'-ribose methyl phosphate, 5. This reaction was in tandem with the 1,4-NADH dependent HLADH-Zn(II)- catalyzed reduction of achiral ketones to chiral S-alcohols. The [Cp*Rh(bpy)H] + complex, and not its equilibrium tautomer, [η 4 -Cp*HRh(bpy)] + , was found to control the hydride transfer during the biomimetic NAD + /1,4-NADH conversion, through the non-covalent interactions of the biomimetic co-factors with [Cp*Rh(bpy)H] + . The thermodynamics and kinetics for the chiral reduction of the Zn(II) bound ketones, 2-pentanone and 4-phenyl-2-butanone, with co-factor, 4, catalyzed by Zn(SCH 3 ) 2 (Imidazole), a core model of the Zn(II)-based catalytic center of HLADH, was also investigated by the evaluation of two possible reaction pathways: (1) formation of a ZnH from the C4-H hydride transfer of co-factor, 4, followed by reaction of the postulated ZnH with the bound 2-pentanone or 4-phenyl-2-butanone substrate, and (2), the direct C4-H transfer to the bound achiral ketone substrates, to provide the dominant chiral alcohols, S-2-pentanol or S-4-phenyl-2-butanol. The latter pathway was found most viable, and DFT calculations also revealed an essential η 2 -coordination of the 5,6 double bond of co-factor, 4, to the HLADH-Zn(II) metal ion center, upon imidazole decomplexation, providing an asymmetric differentiation of S-η 2 -5,6-1,4-NADH-Zn(II) binding. A proposed new paradigm for the Zn(II)'s non-innocent role in the HLADH-Zn(II) biocatalysis reduction mechanism, for enantioselective hydride transfer to a Zn(II) bound ketone, providing S-alcohols.

1,4 NADH co-factors↗
DOE OSTI2023

Perovskite evolution on La modified Mn 1.5 Co 1.5 O 4 spinel through thermal ageing with enhanced oxidation activity: Is sintering always an issue?

Non-precious metal oxides have great potential in catalytic deep oxidation of emitted hydrocarbons to help address various environmental pollution concerns. However, sintering issue is a stumbling block in practical application upon long-term high-temperature operation or thermal shock experience. Herein, La was applied to modify Mn 1.5 Co 1.5 O 4 spinel to get a highly active oxidation catalyst with exceptional stability against high-temperature thermal ageing treatment. With thermal ageing at 750 °C for 100 h, the La modified Mn–Co composite reached 90 % conversion in toluene oxidation at 265 °C under the high WHSV of 120,000 mL g -1 h -1 , while this value increased to 312 °C over blank Mn–Co spinel. The addition of La not only inhibited the growth of spinel nanocrystals, but also brought about perovskite formation through sintering, generating perovskite-spinel interfaces, thus enhancing both activity and stability. Meanwhile, the La modified Mn–Co spinel exhibited superior performance in presence of water or sulfur dioxide after thermal ageing treatment. In conclusion, this work offers a versatile strategy to design anti-sintering and active oxidation nanocatalysts based on non-precious metal oxides for industrial applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The State of the Molecular Gas in Post-starburst Galaxies

The molecular gas in galaxies traces both the fuel for star formation and the processes that can enhance or suppress star formation. Observations of the molecular gas state can thus point to when and why galaxies stop forming stars. In this study, we present Atacama Large Millimeter/submillimeter Array observations of the molecular gas in galaxies evolving through the post-starburst phase. These galaxies have low current star formation rates (SFRs), regardless of the SFR tracer used, with recent starbursts ending within the last 600 Myr. We present CO (3–2) observations for three post-starburst galaxies, and dense gas HCN/HCO+/HNC (1–0) observations for six (four new) post-starburst galaxies. The post-starbursts have low excitation traced by the CO spectral-line energy distribution up to CO (3–2), more similar to early-type than starburst galaxies. The low excitation indicates that lower density rather than high temperatures may suppress star formation during the post-starburst phase. One galaxy displays a blueshifted outflow traced by CO (3–2). MaNGA observations show that the ionized gas velocity is disturbed relative to the stellar velocity field, with a blueshifted component aligned with the molecular gas outflow, suggestive of a multiphase outflow. Low ratios of HCO + /CO, indicating low fractions of dense molecular gas relative to the total molecular gas, are seen throughout post-starburst phase, except for the youngest post-starburst galaxy considered here. These observations indicate that the impact of any feedback or quenching processes may be limited to low excitation and weak outflows in the cold molecular gas during the post-starburst phase.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Size-resolved Eddy-Covariance Particle Flux Measurement during the TRACER Campaign (Final Report)

The main goal of the TRacking Aerosol Convection interactions ExpeRiment (TRACER) campaign was to study aerosol–cloud interactions during deep convection over the Houston area. This project deployed a suite of instrumentation with the aim to (1) quantify turbulent vertical particle fluxes during at DOE-ARM sites, including TRACER, (2) assess hygroscopic growth factors and hygroscopicity parameters of the material driving modal aerosol growth during new particle formation and growth events, (3) derive turbulent aerosol mass fluxes using co-located Doppler LIDAR measurements, and (4) create quality-controlled PI data products to support future research utilizing data collected during the TRACER campaign. This report summarized the main findings from the deployments at two DOE-ARM sites. Briefly, we found that new particle formation may occur aloft, in a residual layer, near the top of the boundary layer. Small grown particles appear later due to downward mixing with daytime turbulence. The species that are responsible for aerosol modal growth had hygroscopicity parameters varying between 0.05 and 0.34. These values systematically depended on the wind sector, suggesting that the chemical composition of the precursors differed. This work demonstrated that lidar retrievals of the elastic backscatter and Doppler velocity can be used to obtain surface number emissions of particles with a diameter greater than 0.53 µm. During TRACER, emission particle number fluxes peaked near ∼ 100 cm−2 s−1. Multiple quality-controlled PI data products that will support future TRACER related science were generated and made publically available.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Concentration-tuned tetragonal strain in alloys: Application to magnetic anisotropy of $\mathrm{FeNo}_{1-x}\mathrm{Co}_x$

In this paper, we explore an opportunity to induce and control tetragonal distortion in materials. The idea involves formation of a binary alloy from parent compounds having body-centered and face-centered symmetries. The concept is illustrated in the case of $\mathrm{FeNo}_{1-x}\mathrm{Co}_x$ magnetic alloy formed by substitutional doping of the $L1_0$ FeNi magnet with Co. Using electronic structure calculations we demonstrate that the tetragonal strain in this system can be controlled by concentration and it reaches maximum for $x = 0.5$. This finding is then applied to create a large magnetocrystalline anisotropy (MAE) in $\mathrm{FeNo}_{1-x}\mathrm{Co}_x$ system by considering an interplay of the tetragonal distortion with electronic concentration and chemical anisotropy. In particular, we identify an ordered $\mathrm{FeNi_{0.5}Co_{0.5}}$ system with MAE larger by a factor 4.5 from the $L1_0$ FeNi magnet.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Sustainable Aviation Fuel Combustion, Soot, and Contrail Formation

The aviation industry stands at a crossroads, facing the dual challenge of meeting the growing global demand for air travel while mitigating its environmental impact. As concerns over climate change intensify, sustainable aviation fuels (SAFs) have emerged as a promising solution to reduce the carbon footprint of air travel. The aviation sector has long been recognized as a contributor to greenhouse gas emissions, with carbon dioxide (CO 2 ) being a primary concern. SAFs, derived from renewable feedstocks such as biomass, waste oils, or synthetic processes, offer a promising avenue for reducing the net carbon emissions associated with aviation. While SAFs have shown potential in lowering CO 2 emissions, the combustion process introduces complexities related to soot particle formation and contrail generation that require comprehensive exploration. These aspects are pivotal not only for their environmental implications but also for their influence on atmospheric climate interactions. As the aviation industry increasingly embraces SAFs to meet sustainability goals, it is imperative to assess their combustion characteristics, unravel the mechanisms of soot formation, and scrutinize the factors influencing contrail development.

09 BIOMASS FUELS↗
DOE OSTI2020

Hijacking Translation Initiation for Synthetic Biology

Genetic code expansion (GCE) has revolutionized the field of protein chemistry. Over the past several decades more than 150 different noncanonical amino acids (ncAAs) have been co-translationally installed into proteins within various host organisms. Further, the vast majority of these ncAAs have been incorporated between the start and stop codons within an open reading frame. This requires that the ncAA be able to form a peptide bond at the α-amine, limiting the types of molecules that can be genetically encoded. In contrast, the α-amine of the initiating amino acid is not required for peptide bond formation. Therefore, including the initiator position in GCE allows for co-translational insertion of more diverse molecules that are modified, or completely lacking an α-amine. This review explores various methods which have been used to initiate protein synthesis with diverse molecules both in vitro and in vivo.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1993

Multi-ion, multi-event test of ion cyclotron resonance heating

The multi-ion, multi-event study of ion cyclotron resonance heating has been funded to study ion energization through ion cyclotron resonance with low frequency broadband electromagnetic turbulence. The modeling algorithm for the ion cyclotron resonance heating (ICRH) of oxygen ions was presented in Crew et al. (1990). Crew and his co-authors developed a two-parameter representation of selected oxygen conic distributions and modelled the conic formation in terms of resonance heating. The first year of this study seeks to extend the work of Crew and his co-authors by testing the applicability of the ICRH mechanism to helium ion conic distributions, using data obtained from the Energetic Ion Composition Spectrometer and the Plasma Wave Instrument on Dynamics Explorer 1.

Persoon, Ann M.↗
DOE OSTI2022

Few-Atom Copper Catalyst for the Electrochemical Reduction of CO to Acetate: Synergetic Catalysis between Neighboring Cu Atoms

Single-atom catalysts (SACs) are gaining increasing recognition because of their superior catalytic properties for various reactions. However, the performance of SACs is often limited by the lack of neighboring metal centers to cooperate in catalysis. Herein, a synergetic interaction between neighboring Cu atoms of a few-atom catalyst (FAC) on graphdiyne is found to greatly enhance the production of acetate in CO electroreduction reaction relative to Cu SACs. In a 1.0 M KOH electrolyte, this Cu FAC exhibits an acetate Faradaic efficiency of 53.8±1.5 % and an ultrahigh relative purity of up to 97 wt% for liquid products, and excellent stability of over 23 h continuous electrolysis at -0.8 V versus reversible hydrogen electrode (RHE). Theoretical studies suggest that the intersite catalytic communication between two neighboring metal atoms confined in each pore of GDY facilitates the formation of acetic acid through either stepwise hydrogenation of CH 2 CO* or the direct reaction of H 2 O with CH 2 CO*. Our study demonstrates the unprecedented synergetic catalysis of Cu FAC in promoting the selective CO electroreduction toward acetate production.

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

Boosting alkaline hydrogen evolution: the dominating role of interior modification in surface electrocatalysis

The alkaline hydrogen evolution reaction (A-HER) holds great promise for clean hydrogen fuel generation but its practical utilization is severely hindered by the sluggish kinetics for water dissociation in alkaline solutions. Traditional ways to improve the electrochemical kinetics for A-HER catalysts have been focusing on surface modification, which still can not meet the demanding requirements for practical water electrolysis because of catalyst surface deactivation. In this work, we report an interior modification strategy to significantly boost the A-HER performance. Specifically, a trace amount of Pt was doped in the interior Co 2 P (Pt–Co 2 P) to introduce a stronger dopant–host interaction than that of the surface-modified catalyst. Consequently, the local chemical state and electronic structure of the catalysts were adjusted to improve the electron mobility and reduce the energy barriers for hydrogen adsorption and H–H bond formation. As a proof-of-concept, the interior-modified Pt–Co 2 P shows a reduced onset potential at near-zero volts for the A-HER, low overpotentials of 2 mV and 58 mV to achieve 10 and 100 mA cm –2 , and excellent durability for long-term utilization. The interior-modified Pt–Co 2 P delivers superior A-HER performance to Pt/C and other state-of-the-art electrocatalysts. This work will open a new avenue for A-HER catalyst design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRSDate not supplied

Energy landscape in Ni-Co-Cr and related alloys

Among multi-principal element alloys, the NiCoCr middle-entropy alloy has an outstanding combination of strength and ductility at both low and elevated temperatures. Equiatomic NiCoCr is a single-phase alloy with the face centered cubic (fcc) crystal structure. A low stacking fault energy in the fcc matrix is a cause of a relatively low creep in this alloy. The hexagonal close-packed (hcp) structure differs from the fcc by a stacking of atomic layers. The energy difference between the hcp and fcc structures is known to correlate with the stacking fault energy in the fcc phase. We compute formation and relative structural energies versus composition in the Ni-Co-Cr ternary and related quaternary systems, discuss possibilities of compositional adjustments, and compare theoretical predictions with experiment. We acknowledge funding by NASA’s Aeronautics Research Mission Directorate (ARMD) via Transformational Tools and Technologies (TTT) Project.

NiCoCr↗