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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Origins of Lithium/Sodium Reverse Permeability Selectivity in 12-Crown-4-Functionalized Polymer Membranes

Direct lithium extraction via membrane separations has been fundamentally limited by lack of monovalent ion selectivity exhibited by conventional polymeric membranes, particularly between sodium and lithium ions. Recently, a 12- Crown-4-functionalized polynorbornene membrane was shown to have the largest lithium/sodium permeability selectivity observed in a fully aqueous system to date. Using atomistic molecular dynamics simulations, we reveal that this selectivity is due to strong interactions between sodium ions and 12-Crown-4 moieties, which reduce sodium ion diffusivity while leaving lithium ion mobility relatively unaffected. Furthermore, the ion diffusivities in the membrane, when scaled by their respective solution diffusivities and free ion fractions, can be collapsed to an almost universal relationship depending on solvent volume fraction.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Selective and Efficient Production of Biomass-Derived Vinylfurans

We describe a two-step catalytic process for the selective and rapid conversion of biomass-derived acetylfurans into vinylfurans. This is accomplished by nearly quantitatively reducing acetylfurans into furyl alcohols using a copper chromite catalyst and exploiting the promoter-like properties of ethanol, the solvent. Subsequently, furyl alcohol is dehydrated using solid-acid catalysts. Catalyst deactivation due to oligomeric species is a major issue, but the activity can be partially recovered by calcination. Optimization of reaction conditions showed that the selectivity could be increased by using nitrobenzene, a polar aprotic solvent. Here, the high-boiling point solvent allows the formation of vinylfurans with a selectivity of up to 85%; the product can be isolated in high purity by distillation.

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

Mechanistic Investigation of Enhanced Catalytic Selectivity toward Alcohol Oxidation with Ce Oxysulfate Clusters

Ceria-based materials have been highly desired in photocatalytic reactions due to their easily redox property and strong oxygen storage and transfer ability. Herein, we report the structures of one CeCe 70 oxysulfate cluster and four MCe 70 clusters (M = Cu, Ni, Co, Fe) with the same Ce 70 core. As noted, single crystal X-ray diffraction confirmed the structures of CeCe 70 and the MCe 70 series, while Raman spectroscopy indicated an increase in oxygen defects upon the introduction of Cu and Fe ions. The clusters catalyzed the oxidation of 4-methoxybenzyl alcohol under ultraviolet light. CuCe 70 and FeCe 70 exhibited enhanced reactivity compared to CeCe 70 and improved aldehyde selectivity compared to control experiments. In comparison with their homogeneous congeners, the CeCe 70 /MCe 70 clusters altered the location of radical generation from the bulk solution to the clusters’ surfaces. Mechanistic studies highlight the role of oxygen defects and specific transition metal introduction for efficient photocatalysis. Furthermore, the mechanistic pathway in this study provides insight on how to select or design a highly selective catalyst for photocatalysis.

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

Chirality-induced spin selectivity as a mechanism to control product selectivity during electrochemical CO 2 reduction

Electrocatalytic CO 2 reduction often suffers from competition with the hydrogen evolution reaction (HER), which lowers efficiency and limits product selectivity. Recent studies suggest that electron spin, when controlled at an electrode surface, can influence reaction pathways, but direct evidence linking spin effects to suppressed HER has been limited. Here, in this work, we show that helical chiral copper (Cu) electrodes reduce competing HER during CO 2 reduction, consistent with spin polarization induced via the chiral-induced spin selectivity effect. The helically structured Cu electrodes are fabricated by electrodeposition with a chiral templating reagent. Time-resolved Kerr ellipticity measurements, which track spin-polarized carriers generated by an ultrafast Seebeck current, confirm spin accumulation at the chiral Cu surface. This spin polarization disfavours H—H bond formation, thereby suppressing HER and enabling formate production alongside CO. These findings demonstrate that chirality-based spin control offers a strategy for steering selectivity in CO 2 reduction and other reactions where HER is an undesired competitor.

14 SOLAR ENERGY↗
DOE OSTI2026

Leveraging chiral induced spin selectivity to improve the efficiency and selectivity of electrocatalytic reduction

Energy production is a fundamental pillar of modern society, but it remains heavily reliant on fossil fuel combustion, which leads to environmental degradation and resource depletion. Electrocatalytic reduction reactions (ERRs) offer a cleaner alternative by functioning under mild conditions, eliminating the need for high temperatures or pressures. However, their widespread adoption is hindered by challenges such as low efficiency, inadequate selectivity, and sluggish kinetics. Here, the introduction of chiral-induced spin selectivity (CISS) offers a promising strategy to address these limitations by reducing energy barriers in reactions involving spin-sensitive intermediates or transition states. By leveraging CISS, ERR pathways can be manipulated to favor desired reactions, enhance product yield, and suppress unwanted byproducts, improving selectivity. Beyond reducing the impact of competing side reactions, CISS also enhances the kinetics of ERRs by accelerating reaction rates and lowering the energy barriers associated with multi-electron transfer steps. Thanks to its straightforward and versatile application, CISS shows significant potential in optimizing well-studied ERRs, such as the hydrogen evolution reaction (HER) and carbon dioxide reduction reaction (CO2RR), facilitating the future transition of these technologies from research laboratories to commercial energy plants worldwide.

14 SOLAR ENERGY↗
DOE OSTI2016

Engineering Gram Selectivity of Mixed‐Charge Gold Nanoparticles by Tuning the Balance of Surface Charges

Abstract Nanoparticles covered with ligand shells comprising both positively and negatively charged ligands exhibit Gram‐selective antibacterial action controlled by a single experimental parameter, namely the proportion of [+] and [−] ligands tethered onto these particles. Gram selectivity is attributed to the interplay between polyvalent electrostatic and non‐covalent interactions that work in unison to disrupt the bacterial cell wall. The [+/−] nanoparticles are effective in low doses, are non‐toxic to mammalian cells, and are tolerated well in mice. These results constitute the first example of rational engineering of Gram selectivity at the (macro)molecular level.

Pillai, Pramod P.↗
DOE OSTI2018

A Dynamically Stabilized Single‐Nickel Electrocatalyst for Selective Reduction of Oxygen to Hydrogen Peroxide

Abstract On‐location electrochemical generation of H 2 O 2 is of great current interest. Herein, selective two‐electron reduction of O 2 to H 2 O 2 by a single [Ni II (H 2 O) 6 ] 2+ cation that is dynamically associated with a negatively charged metal–organic layer (MOL) by hydrogen bonding and coulombic interactions is reported. In contrast, Ni II centers covalently immobilized on the MOL reduce O 2 to H 2 O in a four‐ electron process. Oxygen adsorption by [Ni II (H 2 O) 6 ] 2+ followed by two‐electron reduction generates neutral [Ni II (H 2 O) 4 (OH)(OOH)] 0 , which momentarily disconnects from the negatively charged MOL to avoid the injection of additional electrons. Release of H 2 O 2 from [Ni II (H 2 O) 4 (OH)(OOH)] 0 regenerates [Ni II (H 2 O) 6 ] 2+ , which regains affinity to the MOL. Such dynamically associated Ni II single‐metal electrocatalysts ensure high selectivity and represent a new strategy for generating selective catalysts for electrochemical production of important chemicals.

Wang, Tingting↗
DOE OSTI2018

Woody bioenergy crop selection can have large effects on water yield: A southeastern United States case study

Short-rotation woody crops in the southeastern United States will make a significant contribution to the growing renewable energy supply over the 21st century; however, there are few studies that investigate how species selection may affect water yield. Here we assessed the impact of species selection on annual and seasonal water budgets in unvegetated plots and late-rotation 14–15-year-old intensively managed loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) stands in South Carolina USA. We found that while annual aboveground net primary productivity and bioenergy produced was similar between species, sweetgum transpiration was 53% higher than loblolly pine annually and 92% greater during the growing season. Canopy interception was 10.5% of annual precipitation and was not significantly different between the two species. Soil evaporation was less than 1.3% of annual precipitation and did not differ between species, but was 26% of precipitation in unvegetated plots. Annual water yield was 69% lower for sweetgum than loblolly pine, with water yield to precipitation ratios of 0.13 and 0.39 for sweetgum and loblolly pine, respectively. If planted at a large scale, the high transpiration and low water yield in sweetgum could result in declines in downstream water availability relative to loblolly pine by the end of the growing season when storage in groundwater, streams, and water supply reservoirs are typically at their lowest. Our results suggest that species selection is of critical importance when establishing forest plantations for woody bioenergy production due to potential impacts on downstream water yield.

09 BIOMASS FUELS↗
DOE OSTI2021

Temperature Homogeneity under Selective and Localized Microwave Heating in Structured Flow Reactors

Selective heating of different phases of multiphase systems via microwaves can result in energy savings and suppression of side reactions. However, materials properties and operating conditions that maximize temperature gradients are poorly understood. Here we utilize computational fluid dynamics (CFD) computations and temperature measurements in structured flow reactors (monoliths) in a monomodal microwave cavity to assess the temperature difference between the walls and the fluid and develop a simple lumped model to estimate when temperature gradients exist. We also explore the material’s thermal and electrical properties of structured reactors for isothermal catalyst conditions. We propose that CFD simulations can be used as a nonintrusive, predictive tool of temperature homogeneity. Importantly, we demonstrate that localized heating in the bed under several conditions rather than selective heating is responsible for the selectivity enhancement. Furthermore, our results indicate that structured beds made of high thermal conductivity materials avoid arcing and enable temperature homogeneity and low electrical conductivity materials allow microwaves to penetrate the domain.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Highly Selective Colorimetric and Luminescence Response of a Square-Planar Platinum(II) Terpyridyl Complex to Aqueous TcO 4 –

Molecular recognition of an aqueous pertechnetate (TcO 4 – ) anion is fundamentally challenging partly due to the charge-diffuse nature of this anion, which hampers design of new technologies for its separation and detection. Here, to address this gap, simple salts of transition metal complexes that undergo a distinct spectroscopic change upon exposure to aqueous anions were explored. The Pt(II) complex [Pt(tpy)Br]SbF 6 (tpy = 2,2′;6′,2″-terpyridine) undergoes a dramatic color change and intense luminescence response upon TcO 4 – uptake due to concomitant enhancement of Pt···Pt interactions. The spectroscopic response was highly selective and quantitative for aqueous TcO 4 – among other competing anions. Complementary Raman spectroscopy and microscopy techniques, structural determination, and theoretical methods were employed to elucidate the mechanism of this response at the molecular level.

anions↗