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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 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Sequential oligodiacetylene formation for progressive luminescent color conversion via co-micellar strategy

Design and construction of organic systems that can enhance internal quantum efficiency to fully make use of radiative decay during the excitation process is highly desirable for the development of new-generation emissive materials. In practice, to employ those materials with an effective tuning of triplet-state involved multicolor luminescence is quite a considerable issue. This work takes advantage of a diphenyl-diacetylene- based co-micellar nano-ensemble that can undergo a sequential photocrosslinking to form a corresponding trimeric oligodiacetylene and a dimeric oligodiacetylene. Their emissive bands individually cover the visible-light spectral region and such a controllable dual band characteristic can result in a progressive luminescent color conversion from light-green to white and finally to purplish blue. In addition, the oligodiacetylenes possess an ultrafast intersystem crossing characteristic with a small S 1 –T 1 energy gap. The leading thermally activated delayed fluorescence and phosphorescence can be employed to achieve long-life broadband emissions without chromatic aberration in this single organic system, towards the creation of emitting materials with high quantum efficiency. The synthesis of the sub-components is simple and the co-micellar strategy is extremely straightforward. Such a material design and approach may find potential uses in the microfabrication of novel organic light-emitting diodes and sophisticated controllable optoelectronic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Pressure-dependent rate constants for PAH growth: formation of indene and its conversion to naphthalene

Unraveling the mechanisms for growth of polycyclic aromatic hydrocarbons (PAHs) requires accurate temperature- and pressure-dependent rate coefficients for a great variety of feasible pathways. Even the pathways for the formation of the simplest PAHs, indene and naphthalene, are fairly complex. These pathways provide important prototypes for modeling larger PAH growth. In this work we employ the ab initio RRKM theory-based master equation approach to predict the rate constants involved in the formation of indene and its conversion to naphthalene. The reactions eventually leading to indene involve C9Hx (x = 8–11) potential energy surfaces (PESs) and include C6H5 + C3H4 (allene and propyne), C6H6 + C3H3, benzyl + C2H2, C6H5 + C3H6, C6H6 + C3H5 and C6H5 + C3H5. These predictions allow us to make a number of valuable observations on the role of various mechanisms. For instance, we demonstrate that reactions which can significantly contribute to the formation of indene include phenyl + allene and H-assisted isomerization to indene of its major product, 3-phenylpropyne, benzyl + acetylene, and the reactions of the phenyl radical with propene and the allyl radical, both proceeding via the 3-phenylpropene intermediate. 3-Phenylpropene can be activated to a 1-phenylallyl radical, which in turn rapidly decomposes to indene. Next, indene can be converted to benzofulvene or naphthalene under typical combustion conditions, via its activation by H atom abstraction and methyl substitution on the five-membered ring followed by isomerization and decomposition of the resulting 1-methylindenyl radical, C10H9 → C10H8 + H. Alternatively, the same region of the C10H9 PES can be accessed through the reaction of benzyl with propargyl, C7H7 + C3H3 → C10H10 → C10H9 + H, which therefore can also contribute to the formation of benzofulvene or naphthalene. Benzofulvene easily transforms to naphthalene by H-assisted isomerization. An analysis of the effect of pressure on the reaction outcome and relative product yields is given, and modified Arrhenius fits of the rate constants are reported for the majority of the considered reactions. Ultimately, the implementation of such expressions in detailed kinetic models will help quantify the role of these reactions for PAH growth in various environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Pervaporation-assisted catalytic conversion of xylose to furfural

Furfural produced from the biomass-derived xylose may serve as a platform molecule for sustainable fuel production. The Brønsted acid-catalyzed dehydration of xylose to furfural is plagued by side reactions that form a set of soluble and insoluble degradation products, collectively known as humins, which reduce the yield of furfural. The formation of humins can be minimized by removal of furfural, either by steam stripping or by liquid-liquid extraction (LLE). However, both these techniques are very costly. The goal of this study was to demonstrate the feasibility of using pervaporation, a membrane process, to remove furfural as it is produced. A laboratory-scale reactor/membrane system was designed, built, and tested for this purpose and its performance for furfural production was compared with that achieved by carrying out the reaction with and without furfural extraction by LLE. Furfural production assisted by pervaporation (with a commercially available membrane or a triblock copolymer membrane) or LLE produced comparable amounts of furfural, and more than could be achieved by reaction without extraction. A model of the reaction kinetics and the rate of furfural extraction was fit to the pervaporation- and LLE-assisted furfural production data and was used to predict the performances of these processes at near-complete xylose conversion. Here, pervaporation is shown to have two advantages over LLE: pervaporation extracts a greater fraction of the furfural produced and the furfural concentration in the permeate phase is significantly higher than that present in the extractant phase obtained by LLE. It is noted that further improvement in the separation of furfural from the aqueous phase where it is produced can be achieved by using a more-permeable, thinner pervaporation membrane of larger area, and by operating the membrane at the reaction temperature.

Wang, Alex↗
DOE OSTI2016

Versatile nickel–tungsten bimetallics/carbon nanofiber catalysts for direct conversion of cellulose to ethylene glycol

We herein propose a novel synthetic methodology for a series of nickel–tungsten bimetallics/carbon nanofiber catalysts (Ni, 0.37–2.08 wt%; W, 0.01–0.06 wt%) in situ fabricated by pyrolysis (950 °C) of Ni, W and Zn-containing metal organic framework (Ni0.6-x–Wx–ZnBTC, x = 0–0.6) fibers. The resulting catalysts (Ni0.6-x–Wx/CNF) have uniform particles (ca. 68 nm), evenly dispersed onto the hierarchically porous carbon nanofibers formed simultaneously. All of the Ni0.6-x–Wx/CNF catalysts prove to be highly active towards direct conversion of cellulose to ethylene glycol (EG). A large productivity ranging from 15.3 to 70.8 molEG h-1 gW-1 is shown, two orders of magnitude higher than those by using other W-based catalysts reported.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Direct conversion of CO 2 to meso/macro-porous frameworks of surface-microporous graphene for efficient asymmetrical supercapacitors

CO 2 conversion to useful materials is the most attractive approach to control its content in the atmosphere. An ideal electrode material for supercapacitors should possess suitable meso/macro-pores as electrolyte reservoirs and rich micro-pores as places for the adsorption of electrolyte ions. In this paper, we designed and synthesized such an ideal material, meso/macro-porous frameworks of surface-microporous graphene (MFSMG), from CO 2 via its one-step exothermic reaction with potassium. Furthermore, the MFSMG electrode exhibited a high gravimetric capacitance of 178 F g -1 at 0.2 A g -1 in 2 M KOH and retained 85% capacitance after increasing current density by 50 times. The combination of the MFSMG electrode and the activated carbon (AC) electrode constructed an asymmetrical AC//MFSMG capacitor, leading to a high capacitance of 242.4 F g -1 for MFSMG and 97.4 F g -1 for AC. With the extended potential, the asymmetrical capacitor achieved an improved energy density of 9.43 W h kg -1 and a power density of 3504 W kg -1 . Finally, this work provides a novel solution to solve the CO 2 issue and creates an efficient electrode material for supercapacitors.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Single-step catalytic conversion of furfural to 2-pentanol over bimetallic Co–Cu catalysts

The conversion of biomass derived furfural to 2-pentanol, a useful organic solvent and precursor for various types of fuels, was demonstrated in this work with ~71.1% yield in a single step over a Co–Cu/Al 2 O 3 catalyst at 240 °C and 45 bar H 2 pressure. The catalyst shown here sustained activity and selectivity for four subsequent recycles without regeneration. Co was proposed as the primary active site that enabled hydrodeoxygenation of furfural to produce methyl furan followed by ring opening, while Cu mitigated product degradation that occurred on pure Cu catalysts.

09 BIOMASS FUELS↗
DOE OSTI2019

Natural abundance solid-state 33 S NMR study of NbS 3 : applications for battery conversion electrodes

Here, we report ultra-wideline, high-field natural abundance solid-state 33 S NMR spectra of the Li-ion battery conversion electrode NbS 3 , the first 33 S NMR study of a compound containing disulfide (S 2 2- ) units. The large quadrupolar coupling parameters (C Q ≈ 31 MHz) are consistent with values obtained from DFT calculations, and the spectra provide evidence for the linear Peierls distortion that doubles the number of 33 S sites.

25 ENERGY STORAGE↗
DOE OSTI2019

Identification of the Criegee intermediate reaction network in ethylene ozonolysis: Impact on energy conversion strategies and atmospheric chemistry

The reaction network of the simplest Criegee Intermediate (CI) CH2OO has been studied experimentally during the ozonolysis of ethylene. The results provide valuable information about plasma- and ozone-assisted combustion processes and atmospheric aerosol formation. A network of CI reactions was identified, which can be described best by the sequential addition of CI with ethylene, water, formic acid, and other molecules containing hydroxy, aldehyde, and hydroperoxy functional groups. Species resulting from as many as four sequential CI addition reactions were observed, and these species are highly oxygenated oligomers that are known components of secondary organic aerosols in the atmosphere. Insights into these reaction pathways were obtained from a near-atmsopheric pressure jet-stirred reactor coupled to a high-resolution molecular-beam mass spectrometer. The mass spectrometer employs single-photon ionization with synchrotron-generated, tunable vacuum-ultraviolet radiation to minimize fragmentation via near-threshold ionization and to observe mass-selected photoionization efficiency (PIE) curves. Species identification is supported by comparisons of the mass-selected, experimentally observed photo-ionization thresholds with theoretical calculations for the ionization energies. A variety of multi-functional peroxide species are identified, including hydroxymethyl hydroperoxide (HOCH2OOH), hydroperoxymethyl formate (HOOCH2OCHO), methoxymethyl hydroperoxide (CH3OCH2OOH), ethoxymethyl hydroperoxide (C2H5OCH2OOH), 2-hydroxyethyl hydroperoxide (HOC2H4OOH), dihydroperoxy methane (HOOCH2OOH), and 1-hydroperoxypropan-2-one [CH3C(=O)CH2OOH]. A semi-quantitative analysis of the signal intensities as function of successive CI additions and temperature provides mechanistic insights and valuable information for future modeling work of the associated energy conversion processes and atmospheric chemistry. Furthermore this work provides further evidence that the CI is a key intermediate in the formation of oligomeric species via the formation of hydroperoxides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Computational screening, synthesis and testing of metal–organic frameworks with a bithiazole linker for carbon dioxide capture and its green conversion into cyclic carbonates

Computational crystal construction algorithms were used to create twelve metal–organic frameworks containing a newly synthesized [2,2'-bithiazole]-5,5'-dicarboxylic acid (H 2 TzTz) spacer and assorted transition metal nodes. Among the twelve structures, the zirconium-based MOF of general formula [Zr 6 O 4 (OH) 4 (TzTz) 6 ] (1) was found to be the best candidate for carbon dioxide uptake, as judged from the results of the grand canonical Monte Carlo (GCMC) simulations of CO 2 adsorption isotherms. Guided by the simulation results, 1 was synthesized in the laboratory and thoroughly characterized. 1 is isoreticular to its bithiophene and bis(benzene) (UiO-67) analogues; it crystallizes in the cubic Pn$\bar{3}$ with combining macron] space group with fcu topology, and it features octahedral [Zr 6 ] nodes connected by twelve carboxylate groups from six bridging TzTz 2- spacers. It is a predominantly microporous material (micropore volume = 84% of the total pore volume), with a BET area of 840 m 2 g -1 and a maximum CO 2 uptake at ambient pressure of 2.3 mmol g -1 (10.0 wt%) or 1.7 mmol g -1 (7.5 wt%) at 273 or 298 K, respectively. The CO 2 affinity (isosteric heat of adsorption Qst = 18.7 kJ mol -1 ; CO 2 /N 2 Henry selectivity = 10; CO 2 /N 2 IAST selectivity = 8.4) is similar to that of its bithiophene analogue. After partial removal of solvent (activation), 1 was tested as a heterogeneous catalyst in the reaction of CO 2 with epoxides bearing a –CH 2 X pendant arm (X = Cl: epichlorohydrin; X = Br: epibromohydrin) to give the corresponding cyclic carbonates at T = 393 K and p CO 2 = 1 bar under green (solvent- and co-catalyst-free) conditions. A good conversion of 74% and a turnover frequency of 12.3 mmol (cyclic carbonate) per mmol Zr per h have been recorded with epibromohydrin as a substrate.

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

Surface immobilized copper(i) diimine photosensitizers as molecular probes for elucidating the effects of confinement at interfaces for solar energy conversion

Heteroleptic copper(I) bis(phenanthroline) complexes with surface anchoring carboxylate groups have been synthesized and immobilized on nanoporous metal oxide substrates. The species investigated are responsive to the external environment and this work provides a new strategy to control charge transfer processes for efficient solar energy conversion.

14 SOLAR ENERGY↗
DOE OSTI2020

Nanocluster and single-atom catalysts for thermocatalytic conversion of CO and CO 2

In this Minireview, we discuss recent advances in understanding nanocluster and single-atom catalysts for CO and CO 2 emissions control applications. Through analyzing thermocatalytic CO oxidation and CO 2 reduction, two fundamentally and industrially important reactions, we compare representative nanocluster and single-atom catalytic systems from perspectives of intrinsic chemistry and reaction engineering. Generally, nanoclusters and single atoms display different catalytic performances (i.e., activity, selectivity, and stability) for these reactions depending on the synthesis methods, support materials, and reaction conditions. Key observations of activity and selectivity tradeoffs between nanoclusters and single-atom catalysts are highlighted. Here, the dynamic structural responses of these catalytic species under CO oxidation or CO 2 reduction reaction conditions are also discussed. Synthetic control and detailed experimental and computational characterization of single-atom and nanocluster catalysts for CO and CO 2 conversion have led to exciting progress over the past decade. Still, more efforts are needed to understand and develop catalysts that meet the environmental, energy, and technical requirements to power a sustainable global economy.

03 NATURAL GAS↗
DOE OSTI2021

Conversion of cellulose to high-yield glucose in water over sulfonated mesoporous carbon fibers with optimized acidity

The hydrolysis of cellulose to high-yield glucose in water remains challenging owing to the limited acidity and substrate contact of sulfonated carbons. In this study, we report a unique sulfonated mesoporous carbon fiber with optimized acidity prepared by the pyrolysis of FeCl 3 -impregnated wipe fibers followed by acid treatment. The Bronsted acidity (especially for SO 3 H) was produced by sulfonation of the magnetic carbon fiber intermediate, while Lewis acidity originated from small Fe 3 O 4 nanoparticles and the remaining defects. The balanced Bronsted and Lewis acidity combined with hydrophilic functionalities was simultaneously tailored by varying the Fe/wipe fiber (WF) feed ratio and pyrolysis temperature to change the porous structure of the final catalysts. The elaborately fabricated MCF-SO 3 H-20-500 (20% Fe/WF feed ratio and pyrolysis at 500 degrees C) delivered 66.0% glucose yield as cellulose was completely converted. This is the highest glucose yield achieved by the hydrolysis of untreated cellulose in water over a sulfonated carbon catalyst. The optimized Bronsted and Lewis acidity was mainly responsible for the controlled conversion of cellulose to glucose, while the rich hydrophilic functionalities and superior mesoporous structure of the catalyst facilitated contact to cellulose and mass transfer. This investigation will open new avenues to design high-performance carbon sulfoacid catalysts toward cellulose hydrolysis.

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

Ion diffusion coefficients in poly(3-alkylthiophenes) for energy conversion and biosensing: role of side-chain length and microstructure

Conductive polymers are promising materials as active elements for energy storage and conversion devices due to mixed ion–electron conduction. The ion diffusion coefficient is a relative measure of the efficacy of ion transport, allowing for comparison between materials and electrochemical conditions. In this work, diffusion coefficients of hexafluorophosphate (PF6–) counterions in poly(3-alkylthiophene) (P3AT) materials are measured as a function of both side-chain length and microstructure using electrochemical impedance spectroscopy (EIS). For semi-crystalline films, the diffusion coefficient is found to be anomalous and nearly independent of applied electrochemical potential. Here, the anomalous behavior of diffusion indicates that spin casting yields compact films with an enthalpic barrier to ion transport, attributed to ionic trapping. Diffusion coefficient values ~10 –11 cm 2 s –1 were measured for all films, indicating interchain spacing, in the absence of strong intermolecular interactions with the electrolyte, is not a viable design strategy to control ion transport. For the prototypical system of poly(3-hexylthiophene), we observe almost no potential dependence in ion transport for regioregular and regiorandom films of comparable molecular weight, with both exhibiting anomalous diffusion. Alternatively, changing the microstructure of poly(3-hexylthiophene) to a mostly amorphous, ion-imprinted structure yields ~500× increase in the diffusion coefficient to ~2 × 10 –8 cm 2 s –1 at 0.8 V vs. Ag/Ag + with behavior closer to ordinary diffusion. Collectively, these results indicate new insight into ion transport in conductive polymers, where ionic trapping effects can be mitigated through electrodeposition protocols over post-synthesis processing (i.e. spin coating).

14 SOLAR ENERGY↗
DOE OSTI2021

Reversible electrochemical conversion from selenium to cuprous selenide

Using elemental selenium as an electrode, the redox-active Cu 2+ /Cu + ion is reversibly hosted via the sequential conversion reactions of Se → CuSe → Cu 3 Se 2 → Cu 2 Se. Here, the four-electron redox process from Se to Cu 2 Se produces a high initial specific capacity of 1233 mA h g –1 based on the mass of selenium alone or 472 mA h g –1 based on the mass of Cu 2 Se, the fully discharged product.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗