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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Catalytic strategy for conversion of fructose to organic dyes, polymers, and liquid fuels

We illustrate a process to produce a versatile platform chemical from biomass-derived fructose for organic dye, polymer, and liquid fuel industries. An aldol-condensed chemical (HAH) is synthesized as a platform chemical from fructose by catalytic reactions in acetone/water solvent with non-noble metal catalysts (e.g., HCl, NaOH). Then, selective reactions (e.g., etherification, reduction, dimerization) of the functional groups, such as enone and hydroxyl groups, in the HAH molecule enable applications in organic dyes and polyether precursors. High yields of target products, such as 5-(hydroxymethyl) furfural (HMF) (85.9% from fructose) and HAH (86.3% from HMF) are achieved by sequential dehydration and aldol-condensation with a simple purification process (>99% HAH purity). The use of non-noble metal catalysts, the high yield of each reaction, and the simple purification of the target product allow for beneficial economics of the process. Techno-economic analysis indicates that the process produces HAH at minimum selling price (MSP) of $1958 per ton. The MSP of HAH product allows the economic viability of applications in organic dye and polyether markets by replacing its counterparts, such as anthraquinone ($3200-$3900 per ton) and bisphenol-A ($1360-$1720 per ton).

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

Aqueous-soluble bipyridine cobalt($\tiny{II}$/$\tiny{III}$) complexes act as direct redox mediators in photosystem I-based biophotovoltaic devices

Sustainable energy production is critical for meeting growing worldwide energy demands. Due to its stability and reduction potential, photosystem I (PSI) is attractive as the photosensitizer in biophotovoltaic devices. Herein, we characterize aqueous and organic solvent soluble synthetic bipyridine-based cobalt complexes as redox mediators for PSI-based biophotovoltaics applications. Cobalt-based complexes are not destructive to protein and have appropriate midpoint potentials for electron donation to PSI. We report on PSI stability in organic solvents commonly used in biophotovoltaics. We also show the effects of a mixed organic solvent phase on PSI reduction kinetics, slowing reduction rates approximately 8–38 fold as compared to fully aqueous systems, with implications for dye regeneration rates in PSI-based biophotovoltaics. Further, we show evidence of direct electron transfer from cobalt complexes to PSI. Finally, we report on photocurrent generation from Co mediator-PSI biophotovoltaic devices. Taken together, we discuss the development of novel Co complexes and our ability to fine-tune their characteristics via functional groups and counteranion choice to drive interaction with a biological electron acceptor on multiple levels from redox midpoints, spectral overlap, and solvent requirements, among others. This work suggests that fine-tuning of redox active species for interaction with a biological partner is possible for the creation and improvement of low cost, carbon-neutral energy production in the future.

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

All-atom molecular dynamics simulations of weak polyionic brushes: influence of charge density on the properties of polyelectrolyte chains, brush-supported counterions, and water molecules

All atom molecular dynamics (MD) simulations of planar Na+-counterion-neutralized polyacrylic acid (PAA) brushes are performed for varying degrees of ionization (and thereby varying charge density) and varying grafting density. Variation in the PE charge density (or degree of ionization) and grafting density leads to massive changes of the properties of the PE molecules (quantified by the changes in the height and the mobility of the PE brushes) as well as the local arrangement and distribution of the brush-supported counterions and water molecules within the brushes. The effect on the counterions is manifested by the corresponding variation of the counterion mobility, counterion concentration, extent of counterion binding to the charged site of the PE brushes, water-in-salt-like structure formation, and counterion-water–oxygen radial distribution function within the PE brushes. On the other hand, the effect on water molecules is manifested by the corresponding variation of water–oxygen–water–oxygen RDF, local water density, water–water and water–PE functional group hydrogen bond networks, static dielectric constant of water molecules, orientational tetrahedral order parameter, and water mobility. Enforcing such varying degree of ionization of weak polyelectrolytes is possible by changing the pH of the surrounding medium. Thus, our results provide insights into the changes in microstructure (at the atomistic level) of weak polyionic brushes at varying pH. Finally, we anticipate that this knowledge will prove to be vital for the efficient design of several nano-scale systems employing PE brushes such as nanomechanical gates, current rectifiers, etc.

42 ENGINEERING↗
DOE OSTI2021

Gas-phase pyrolysis of trans 3-pentenenitrile: competition between direct and isomerization-mediated dissociation

The flash pyrolysis of trans 3-pentenenitrile (3-PN, CH 3 –$CH=CH$–CH 2 –CN) was studied by combining the results of VUV photoionization mass spectra with broadband microwave spectra recorded as a function of the temperature of the pyrolysis tube. The two separated functional groups (vinyl and nitrile) open up isomerization as an initial step in competition with unimolecular dissociation. Primary products were detected by keeping the 3-PN concentration low and limiting reaction times to the traversal time of the gas in the pyrolysis tube (~100 μs). The reaction is quenched and products are cooled by expansion into vacuum before interrogation over the 8–18 GHz region using chirped-pulse broadband methods. 118 nm VUV photoionization of the same reaction mixture provides a means of detecting all products with ionization potentials below 10.5 eV with minimal fragmentation. These results are combined with a detailed computational investigation of the C 5 H 7 N and related potential energy surfaces, leading to a consistent picture of the unimolecular decomposition of 3-PN. Loss of two H-atoms to form a 79 amu product is proven from its microwave transitions to contain trans-Z-2,4-pentadienenitrile, while no pyridine is observed. Methyl loss, HCN loss, and breaking the central C(2)–C(3) bond all occur following isomerization of the position of the double bond, thereby opening up low-energy pathways to these decomposition channels.

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

Carbon dioxide and nitrogen reduction reactions using 2D transition metal dichalcogenide (TMDC) and carbide/nitride (MXene) catalysts

Improving the carbon dioxide and nitrogen reduction reactions (CO 2 RR and NRR) can reduce anthropogenic greenhouse gas emissions while selectively producing chemicals needed for the fuel, plastic, and chemical industries. Efficient CO 2 RR can be used to replace fossil fuels as well as repurpose captured CO 2 , while new NRR pathways can be used to supplement or replace the energy intensive Haber–Bosch process for NH 3 generation with no CO 2 emissions. Therefore, this review article focuses on (photo)electrocatalytic and photocatalytic conversion of CO 2 and N 2 molecules into useful products, such as carbon monoxide, methanol, formic acid, and ammonia, using 2D transition metal dichalcogenides (TMDCs) and metal carbides/nitrides (MXenes). Additionally, these highly tunable 2D catalysts will be evaluated for their ability to selectively and efficiently undergo CO 2 RR and NRR by controlling defects, phases, edge sites, interfaces, and functional groups. We first address the CO 2 RR and NRR challenges, with a particular focus on theoretical mechanisms and minimum energy pathways. We follow this discussion with a detailed review of state-of-the-art 2D TMDC and MXene experimental catalysts for CO 2 RR and NRR (photo)electrocatalytic and photocatalytic reactions, and then address areas of opportunity for these catalytic reactions.

14 SOLAR ENERGY↗
DOE OSTI2021

Identification of bioprivileged molecules: expansion of a computational approach to broader molecular space

As interest in biobased chemicals grows, and their application space expands, computational tools to navigate molecule space as a complement to experimental approaches are imperative. This work expands upon previous work that identified candidate bioprivileged molecules from the C 6 H x O y (C6) subspace. It refines the framework that was developed previously to better refine the molecules according to their biological origin and applies it to three new subspaces of chemical structure: C 4 H x O y (C4), C 5 H x O y (C5), and C 7 H x O y (C7). For C5 and C7, roughly the top 100 bioprivileged candidates were identified, and the enhanced framework was applied to recast slightly the previous list of the top 100 C6 molecules. In addition, all top candidates were analyzed for their key functional moieties using a random forest model, and this algorithm was applied to compare the functional group space occupied by bioprivileged molecules of various databases of molecules with a focus on evaluating how closely the molecules were aligned with those known to biology. Furthermore, with the present work's focus on automation and data science principles, the framework can be easily expanded to include other chemical formulae to screen for bioprivileged candidates. As a result, this in turn facilitates the retrosynthesis process inherent in the framework to identify those bioprivileged intermediates in other subspaces that lead to target molecules.

42 ENGINEERING↗
DOE OSTI2021

Critical role of structural order in bipolar redox-active molecules for organic redox flow batteries

Bipolar redox-active molecules (BRMs) have been suggested as a means to address crossover related issues in all-organic redox flow batteries (RFBs). In such species, electron donors (anolytes) and electron acceptors (catholytes) are linked by a chain, and the same chemical composition is used in both anode and cathode compartments to reduce chemical gradients and unbalanced ion transport. The resultant RFBs resemble the aqueous vanadium RFBs, but offer greater design flexibility and potentially more favorable electrochemical and physicochemical properties. Yet the complex trade-offs in these properties have been a complication. Here we developed a fundamental rubric to uncover the likely origins in the performance metrics of these BRMs that are salient for their use in RFBs. Methylene linked phenothiazine and phthalimide moieties were employed as model BRMs and variations in their properties and molecular conformations were evaluated by systematically varying the methylene linker. Our results revealed that even minimalistic changes in the linker length resulted in dramatic oscillations in the solubility and stability. Using crystallography, quantum chemistry, and molecular dynamics, we clarify that the seemingly fluctuating behavior is due to (1) the inter- and intra-molecular charge transfer between the donor and acceptor through bond or/and through space; (2) the formation of distinctive packing/clustering motifs. Both interactions are strongly dependent on the molecular conformation. As these structural factors modify the electronic structure of both electroactive functional groups and do not change monotonically, the structure–property response in BRMs is often complex. Finally, accordingly, these behaviors need to be taken into account in developing BRMs and knowledge of these structural factors will allow the more rational design of BRMs for grid-scale energy storage.

25 ENERGY STORAGE↗
DOE OSTI2021

Seawater Desalination Derived Entirely from Ocean Biomass

Solar-driven interfacial evaporation shows great prospects for seawater desalination with its rapid fast evaporation rate and high photothermal conversion efficiency. Here, a sustainable, biodegradable, non-toxic, and highly efficient full ocean biomass-based solar-driven evaporator is reported, which is composed of chitosan (CS) hydrogel as the hydratable skeleton and cuttlefish ink (CI) as the photothermal material. Under solar irradiation, the cuttlefish ink powder harvests solar energy and heats the surrounding water. Simultaneously, the water in the three-dimensional network of chitosan hydrogel is rapidly replenished by the interconnected porous structure and the hydrophilic functional groups attached to the polymer chains. With its enlarged evaporation surface, high solar absorptance, adequate water transportation, good salt drainage, and heat localization, the CI/CS-based evaporator achieves a remarkable evaporation rate of 4.1 kg m-2 h-1 under one sun irradiance (1 kW m-2) with high-quality freshwater yields. This full ocean biomass-based evaporator with abundant raw material availability provides new possibilities for an efficient, stable, sustainable, and environmentally friendly solar evaporator with guaranteed water quality.

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND AN↗
DOE OSTI2022

Molecular interactions in diffusion-controlled aldol condensation with mesoporous silica nanoparticles

The aldol reaction of p-nitrobenzaldehyde in amino-catalyzed mesoporous silica nanoparticles (MSN) has revealed varying catalytic activity with the size of the pores of MSN. The pore size dependence related to the reactivity indicates that the diffusion process is important. A detailed molecular-level analysis for understanding diffusion requires assessment of the noncovalent interactions of the molecular species involved in the aldol reaction with each other, with the solvent, and with key functional groups on the pore surface. Such an analysis is presented here based upon the effective fragment potential (EFP). The EFP method can calculate the intermolecular interactions, decomposed into Coulomb, polarization, dispersion, exchange-repulsion, and charge-transfer interactions. In this study, the potential energy surfaces corresponding to each intermolecular interaction are analyzed for homo- and hetero-dimers with various configurations. The monomers that compose dimers are five molecules such as p-nitrobenzaldehyde, acetone, n-hexane, propylamine, and silanol. The results illustrate that the dispersion interaction is crucial in most dimers.

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

Influence of intermolecular interactions on the infrared complex indices of refraction for binary liquid mixtures

This paper investigates the accuracy of deriving the composite optical constants of binary mixtures from only the complex indices of refraction of the neat materials. These optical constants enable the reflectance spectra of the binary mixtures to be modeled for multiple scenarios (e.g., different substrates, thicknesses, volume ratios), which is important for contact and standoff chemical detection. Using volume fractions, each mixture's complex index of refraction was approximated via three different mixing rules. To explore the impact of intermolecular interactions, these predictions are tested by experimental measurements for two representative sets of binary mixtures: (1) tributyl phosphate combined with n-dodecane, a non-polar medium, to represent mixtures which primarily interact via dispersion forces and (2) tributyl phosphate and 1-butanol to represent mixtures with polar functional groups that can also interact via dipole–dipole interactions, including hydrogen bonding. The residuals and the root-mean-square error between the experimental and calculated index values are computed and demonstrate that for miscible liquids in which the average geometry of the cross-interactions can be considered isotropic (e.g., dispersion), the refractive indices of the mixtures can be modeled using composite n and k values derived from volume fractions of the neat liquids. Conversely, in spectral regions where the geometry of the cross-interactions is more restricted and anisotropic (e.g., hydrogen bonding), the calculated n and k values vary from the measured values. The impact of these interactions on the reflectance spectra are then compared by modeling a thin film of the binary mixtures on an aluminum substrate using both the measured and the mathematically computed indices of refraction.

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

Transition-state correlations for predicting thermochemistry of adsorbates and surface reactions

Estimating thermochemical properties from linear correlations may provide a pathway to circumvent expensive density functional theory (DFT) calculations for quantities such as pre-exponentials and temperature corrections to DFT energies. Here, in this work, we construct thermochemical scaling relations between C 1 –C 6 n-alkanes in the gas phase and adsorbed alkyl chains extending from several transition metal surfaces, and examine changes in the slope and fit between metals and adsorption sites. We subsequently add –OH, –NH 2 , C$=$O, and C$=$C functional groups to the C 1 –C 6 molecules and demonstrate strong linear correlations for thermochemistry across all species. We broaden the correlations to incorporate transition states of C 1 –C 6 n-alkane dehydrogenation reactions, where thermochemistry for computationally prohibitive transition-state calculations can be quickly assessed. Additionally, we rationalize the linearity of thermochemical correlations based on the composition of the homologous series and theoretical assessments. As an application of the correlations, we estimate pre-exponentials for elementary surface reactions of ethane and propane hydrogenolysis on Ru(0001), which is of relevance to plastic hydrogenolysis. Depending on kinetically important steps, entropic contributions may be necessary to include in certain reaction mechanisms; in contrasting examples, entropies are found to be relatively insignificant for ethane hydrogenolysis but pertinent for propane hydrogenolysis.

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

Antioxidant-induced transformations of a metal-acid hydrocracking catalyst in the deconstruction of polyethylene waste

Plastics are ideal for numerous applications, as driven by the development of complex formulations containing various additives to improve performance and processability. Unfortunately, chemical valorization strategies (e.g., catalytic deconstruction) often can be challenged by the presence of small-molecule additives, and quantification of the impact of these molecular constituents on upcycling processes remains elusive. Here, this dearth of information restricts catalyst design efforts to combine the robustness and performance necessary to improve plastics circularity. In this communication, we describe a systematic study of common plastics additives—phenolic antioxidants, and we quantify the relationship between additive content and deconstruction yields of high-density polyethylene (HDPE) over a platinum on tungstated zirconium (Pt/WO 3 /ZrO 2 ) hydrocracking catalyst. In the simplest case of a base (antioxidant- and slip agent-containing) HDPE resin versus a pure (additive-stripped) HDPE polymer, a two-fold decrease in the yield of gas and liquid products is noted for base HDPE resin. Furthermore, both antioxidant chemistry and concentration strongly impact conversion and individual product selectivities. Using infrared spectroscopy, we determine that antioxidants change the effective ratio of metal to acid sites (i.e., metal-acid balance) through reactions of phenols and/or other functional groups (e.g., acids, esters) with catalyst active sites. Overall, this work demonstrates the impact of one common set of additives on plastics deconstruction, and the analysis herein provides a blueprint for quantitatively assessing the effects of additives on plastics deconstruction processes and for evaluating the development of more robust catalytic strategies or more tolerable additive formulations.

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

Design of supported organocatalysts from a biomass-derived difuran compound and catalytic assessment for lactose hydrolysis

The engineered structures and active sites of enzyme catalysts give rise to high catalytic activity and selectivity toward desired reactions. We have employed a biomass-derived difuran compound to append N-substituted maleimides with amino acid (glutamic acid) substitution by Diels–Alder reaction to mimic the chemical functional groups that comprise the active site channels in enzyme catalysts. The difunctionality of the biomass-derived difuran allows production of Diels–Alder adducts by appending two amino acid moieties to form a difunctional organocatalyst. The catalytic activity of the organocatalyst can be improved by immobilizing the organocatalyst on solid supporting materials. Accordingly, the structures of these immobilized organocatalysts can be engineered to mimic enzymatic active sites and to control the interaction between reactants, products, and transition states of catalytic reactions. Lactose hydrolysis was carried out to provide an example of industrial application of this approach to design and fabricate new supported organocatalysts as artificial enzymes.

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

Single atoms and small clusters of atoms may accompany Au and Pd dendrimer-encapsulated nanoparticles

Here we report the presence of small clusters of atoms (<1 nm) (SCs) and single atoms (SAs) in solutions containing 1–2 nm dendrimer-encapsulated nanoparticles (DENs). Au and Pd DENs were imaged using aberration-corrected scanning transmission electron microscopy (ac-STEM), and energy dispersive spectroscopy (EDS) was used to identify and quantify the SAs/SCs. Two main findings have emerged from this work. First, the presence or absence of SAs/SCs depends on both the terminal functional group of the dendrimer (–NH 2 or –OH) and the elemental composition of the DENs (Au or Pd). Second, dialysis can be used to remove the majority of SAs/SCs in cases where a high density of SAs/SCs are present. The foregoing conclusions provide insights into the mechanisms for Au and Pd DEN synthesis and stability. Ultimately, these results demonstrate the need for careful characterization of systems containing nanoparticles to ensure that SAs/SCs, which may be below the detection limit of most analytical methods, are taken into consideration (especially for catalysis experiments).

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

A General Binary Isotherm Model for Amines Interacting with CO 2 and H 2 O

CO 2 capture by primary or secondary amines has been of great research interests for a century because of its industrial importance. Interest has grown even more, because of the need to eliminate the CO 2 emissions that drive global warming. Experimental evidence shows that CO 2 sorption in primary or secondary amines is accompanied by co-absorption of H 2 O. A quantitative analysis of such CO 2 -H 2 O co-absorption behavior is important for practical process design and theoretical understanding. Even though there is almost an experimental consensus that water enhances CO 2 uptake capacity, an analytic model to explain this phenomenon is not well established. Instead, some empirical models such as the Toth model are used to describe the isotherm without accounting for the presence of water. Recently, we have demonstrated that the isotherm equation of CO 2 sorption into strong-base anion exchange materials with quaternary ammonium can be derived from that of strong-base aqueous alkaline solutions by correcting for the drastic change in water activity and by including an appropriate parameterization of the water activity terms. In this paper, we generalize this model from quaternary ammonium to primary, secondary and tertiary amines either in solutions or as functional groups in polymer resins. For primary, secondary and tertiary amines, the isotherm equation can be derived by extending that of a weak-base aqueous alkaline solution such as aqueous ammonia. The model has been validated using experimental data of aqueous ammonia in literature. Furthermore, this general model even includes quaternary ammonium as a special limit. Hence, this general model offers a platform that can treat the isotherms of solid amines, aqueous amines and aqueous alkaline solutions in a unified way.

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

Locking water molecules via ternary O–H⋯O intramolecular hydrogen bonds in perhydroxylated closo -dodecaborate

A multitude of applications related to perhydroxylated closo-dodecaborate B 12 (OH) 12 2− in the condensed phase are inseparable from the fundamental mechanisms underlying the high water orientation selectivity based on the base B 12 (OH) 12 2− . Herein, we directly compare the structural evolution of water clusters, ranging from monomer to hexamer, oriented by functional groups in the bases B 12 H 12 2− , B 12 H 11 OH 2− and B 12 (OH) 12 2− using multiple theoretical methods. A significant revelation is made regarding B 12 (OH) 12 2− : each additional water molecule is locked into the intramolecular hydrogen bond B–O–H ternary ring in an embedded form. This new pattern of water cluster growth suggests that B–(H–O)⋯H–O interactions prevail over the competition from water–hydrogen bonds (O⋯H–O), distinguishing it from the behavior observed in B 12 H 12 2− and B 12 H 11 OH 2− bases, in which competition arises from a mixed competing model involving dihydrogen bonds (B–H⋯H–O), conventional hydrogen bonds (B–(H–O)⋯H–O) and water hydrogen bonds (O⋯H–O). Through aqueous solvation and ab initio molecular dynamics analysis, we further demonstrate the largest water clusters in the first hydrated shell with exceptional thermodynamic stability around B 12 (OH) 12 2− . These findings provide a solid scientific foundation for the design of boron cluster chemistry incorporating hydroxyl-group-modified borate salts with potential implications for various applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗