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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

High entropy powering green energy: hydrogen, batteries, electronics, and catalysis

A reformation in energy is underway to replace fossil fuels with renewable sources, driven by the development of new, robust, and multi-functional materials. High-entropy materials (HEMs) have emerged as promising candidates for various green energy applications, having unusual chemistries that give rise to remarkable functionalities. This review examines recent innovations in HEMs, focusing on hydrogen generation/storage, fuel cells, batteries, semiconductors/electronics, and catalysis—where HEMs have demonstrated the ability to outperform state-of-the-art materials. We present new master plots that illustrate the superior performance of HEMs compared to conventional systems for hydrogen generation/storage and heat-to-electricity conversion. We highlight the role of computational methods, such as density functional theory and machine learning, in accelerating the discovery and optimization of HEMs. The review also presents current challenges and proposes future directions for the field. We emphasize the need for continued integration of modeling, data, and experiments to investigate and leverage the underlying mechanisms of the HEMs that are powering progress in sustainable energy.

batteries↗
DOE OSTI2021

Site-selective tyrosine bioconjugation via photoredox catalysis for native-to-bioorthogonal protein transformation

The growing prevalence of synthetically modified proteins in pharmaceuticals and materials has exposed the need for efficient strategies to enable chemical modifications with high site-selectivity. While genetic engineering can incorporate non-natural amino acids into recombinant proteins, regioselective chemical modification of wild-type proteins remains a challenge. In this work, we use photoredox catalysis to develop a site-selective tyrosine bioconjugation pathway that incorporates bioorthogonal formyl groups, which subsequently allows for the synthesis of structurally defined fluorescent conjugates from native proteins. A water-soluble photocatalyst, lumiflavin, has been shown to induce oxidative coupling between a previously unreported phenoxazine dialdehyde tag and a single tyrosine site, even in the presence of multiple tyrosyl side chains, through the formation of a covalent C–N bond. A variety of native proteins, including those with multiple tyrosines, can successfully undergo both tyrosine-specific and single-site-selective labelling. This technology directly introduces aldehyde moieties onto native proteins, enabling rapid product diversification using an array of well-established bioorthogonal functionalization protocols including the alkyne–azide click reaction.

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

Enhanced active-site electric field accelerates enzyme catalysis

In this study, the design and improvement of enzymes based on physical principles remain challenging. Here we demonstrate that the principle of electrostatic catalysis can be leveraged to substantially improve a natural enzyme’s activity. We enhanced the active-site electric field in horse liver alcohol dehydrogenase by replacing the serine hydrogen-bond donor with threonine and replacing the catalytic Zn 2+ with Co 2+ . Based on the electric field enhancement, we make a quantitative prediction of rate acceleration—50-fold faster than the wild-type enzyme—which was in close agreement with experimental measurements. The effects of the hydrogen bonding and metal coordination, two distinct chemical forces, are described by a unified physical quantity—electric field, which is quantitative, and shown here to be additive and predictive. These results suggest a new design paradigm for both biological and non-biological catalysts.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Computational optimization of electric fields for better catalysis design

Although the ubiquitous role that long-ranged electric fields play in catalysis has been recognized, it is seldom used as a primary design parameter in the discovery of new catalytic materials. Here in this paper, we illustrate how electric fields have been used to computationally optimize biocatalytic performance of a synthetic enzyme, and how they could be used as a unifying descriptor for catalytic design across a range of homogeneous and heterogeneous catalysts. Although focusing on electrostatic environmental effects may open new routes toward the rational optimization of efficient catalysts, much more predictive capacity is required of theoretical methods to have a transformative impact in their computational design — and thus experimental relevance — when using electric field alignments in the reactive centres of complex catalytic systems.

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

Structural and functional analyses explain Pea KAI2 receptor diversity and reveal stereoselective catalysis during signal perception

KAI2 proteins are plant α/β hydrolase receptors which perceive smoke-derived butenolide signals and endogenous, yet unidentified KAI2-ligands (KLs). The number of functional KAI2 receptors varies among species and KAI2 gene duplication and sub-functionalization likely plays an adaptative role by altering specificity towards different KLs. Legumes represent one of the largest families of flowering plants and contain many agronomic crops. Prior to their diversification, KAI2 underwent duplication resulting in KAI2A and KAI2B. Here we demonstrate that Pisum sativum KAI2A and KAI2B are active receptors and enzymes with divergent ligand stereoselectivity. KAI2B has a higher affinity for and hydrolyses a broader range of substrates including strigolactone-like stereoisomers. We determine the crystal structures of PsKAI2B in apo and butenolide-bound states. The biochemical, structural, and mass spectra analyses of KAI2s reveal a transient intermediate on the catalytic serine and a stable adduct on the catalytic histidine, confirming its role as a bona fide enzyme. Our work uncovers the stereoselectivity of ligand perception and catalysis by diverged KAI2 receptors and proposes adaptive sensitivity to KAR/KL and strigolactones by KAI2B.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol

We investigate surface plasmon assisted catalysis (SPAC) reactions of 4-aminothiophenol (4ATP) to and back from 4,4'-dimercaptoazobenzene (DMAB) by single particle surface enhanced Raman spectroscopy, using a self-designed gas flow cell to control the reductive/oxidative environment over the reactions. Conversion of 4ATP into DMAB is induced by energy transfer (plasmonic heating) from surface plasmon resonance to 4ATP, where O 2 (as an electron acceptor) is essential and H 2 O (as a base) can accelerate the reaction. In contrast, hot electron (from surface plasmon decay) induction drives the reverse reaction of DMAB to 4ATP, where H 2 O (or H 2 ) acts as the hydrogen source. More interestingly, the cyclic redox between 4ATP and DMAB by SPAC approach has been demonstrated. Finally, this SPAC methodology presents a unique platform for studying chemical reactions that are not possible under standard synthetic conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Boron–nitrogen–hydrogen (BNH) compounds: recent developments in hydrogen storage, applications in hydrogenation and catalysis, and new syntheses

The strong efforts devoted to the exploration of BNH compounds for hydrogen storage have led to impressive advances in the field of boron chemistry. This review summarizes progress in this field from three aspects. It starts with the most recent developments in using BNH compounds for hydrogen storage, covering NH 3 BH 3 , B 3 H 8 - containing compounds, and CBN compounds. The following section then highlights interesting applications of BNH compounds in hydrogenation and catalysis. The last part is focused on breakthroughs in the syntheses and discovery of new BNH organic analogues. Finally, the role of N–H δ+ ∙∙∙H δ- –B dihydrogen interactions in molecule packing, thermal hydrogen evolution, and syntheses is also discussed within the review.

BNH compounds↗
DOE OSTI2015

Recent advances in automotive catalysis for NOx emission control by small-pore microporous materials

The ever increasing demand to develop highly fuel efficient engines coincides with the need to minimize air pollution originating from the exhaust gases of internal combustion engines. Dramatically improved fuel efficiency can be achieved at air-to-fuel ratios much higher than stoichiometric. In the presence of oxygen in large excess, however, traditional three-way catalysts are unable to reduce NOx. Among the number of lean-NOx reduction technologies, selective catalytic reduction (SCR) of NOx by NH3 over Cu- and Fe-ion exchanged zeolite catalysts has been extensively studied over the past 30+ years. Despite the significant advances in developing a viable practical zeolite-based catalyst for lean NOx reduction, the insufficient hydrothermal stabilities of the zeolite structures considered cast doubts about their real-world applicability. During the past decade a renewed interest in zeolite-based lean NOx reduction was spurred by the discovery of the very high activity of Cu-SSZ-13 (and the isostructural Cu-SAPO-34) in the NH3 SCR of NOx. These new, small-pore zeolite-based catalysts not only exhibited very high NOx conversion and N2 selectivity, but also exhibited exceptional high hydrothermal stability at high temperatures. In this review we summarize the key discoveries of the past ~5 years that lead to the introduction of these catalysts into practical application. The review first briefly discusses the structure and preparation of the CHA structure-based zeolite catalysts, and then summarizes the key learnings of the rather extensive (but not complete) characterisation work. Then we summarize the key findings of reaction kinetics studies, and provide some mechanistic details emerging from these investigations. At the end of the review we highlight some of the issues that are still need to be addressed in automotive exhaust control catalysis. Funding A.M.B. and I.L.G. would like to thank EPSRC for funding. F.G., C.H.F.P. and J.Sz. gratefully acknowledge financial support from the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2016

Space and time-resolved probing of heterogeneous catalysis reactions using lab-on-a-chip

Probing catalytic reactions on a catalyst surface in real time is a major challenge. In this paper, we demonstrate the utility of a continuous flow millifluidic chip reactor coated with a nanostructured gold catalyst as an effective platform for in situ investigation of the kinetics of catalytic reactions by taking 5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) conversion as a model reaction. The idea conceptualized in this paper can not only dramatically change the ability to probe the time-resolved kinetics of heterogeneous catalysis reactions but also used for investigating other chemical and biological catalytic processes, thereby making this a broad platform for probing reactions as they occur within continuous flow reactors.

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

Operando X-ray absorption and EPR evidence for a single electron redox process in copper catalysis

An unprecedented single electron redox process in copper catalysis is confirmed using operando X-ray absorption and EPR spectroscopies. The oxidation state of the copper species in the interaction between Cu(II) and a sulfinic acid at room temperature, and the accurate characterization of the formed Cu(I) are clearly shown using operando X-ray absorption and EPR evidence. Further investigation of anion effects on Cu(II) discloses that bromine ions can dramatically increase the rate of the redox process. Moreover, it is proven that the sulfinic acids are converted into sulfonyl radicals, which can be trapped by 2-arylacrylic acids and various valuable β-keto sulfones are synthesized with good to excellent yields under mild conditions.

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

Catalysis by framework zinc in silica-based molecular sieves

Microporous and mesoporous zincosilicates (e.g., CIT-6, VPI-8, Zn-MFI, and Zn-MCM-41) synthesized in the presence of alkali cations contain two broad types of Zn sites: one that is a dication analog of the monocation ion-exchangeable Al-site in aluminosilicates, while the other resembles isolated Zn sites on amorphous silica. The ratio of these sites varies, depending on the synthesis conditions of the zincosilicate. Post-synthetic strategies based on ion-exchange can alter the site distribution towards either population. Furthermore, post-synthetic introduction of isolated Zn sites of the latter type is possible for materials possessing silanol nests. Both types of sites behave as Lewis acid centers in probe-molecule IR spectroscopy, but have very different catalytic properties. Due to the unusually high adsorption energies of Lewis bases on such materials, Lewis acid catalysis is difficult at low temperatures and in solvents bearing Lewis basic functionality. However, at high temperatures, in hydrocarbon solvents, CIT-6 (Zn-beta) is able to selectively catalyze the Lewis-acid-catalyzed Diels–Alder cycloaddition–dehydration reactions of ethylene with methyl 5-(methoxymethyl)furan-2-carboxylate, a furan that can be derived quantitatively by partial oxidation of biomass-based 5-hydroxymethylfurfural. Additionally, zinc in silica-based molecular sieves is shown here to enable chemistries previously not accessible with framework Sn-, Ti- and Zr-based Lewis acid sites, e.g., the direct production of dimethyl terephthalate by Diels–Alder cycloaddition–dehydration reactions of ethylene and the dimethyl ester of furan-2,5-dicarboxilic acid.

09 BIOMASS FUELS↗
DOE OSTI2016

Membrane permeabilization by conjugated oligoelectrolytes accelerates whole-cell catalysis

Conjugated oligoelectrolytes (COEs) boost the electrical performance of a wide range of bioelectrochemical systems, yet their mechanism of action remains incompletely understood. One possible mode of action is that COEs permeabilize the cell envelope. We thus examined the effect of tetracationic COE, DSSN+, on the permeability of the inner and outer membrane of Escherichia coli by detecting extracellular activity of normally periplasmic and cytoplasmic enzymes. DSSN+ increases the release of the periplasmic enzyme alkaline phosphatase (ALP) up to 20-fold, but does not significantly change the release of the cytoplasmic enzyme β-galactosidase. Additionally, DSSN+ caused a 2-fold increase in the turnover of a cytoplasmic substrate. These studies present a more complete understanding of the mechanism of action in bioelectrochemical systems and pivot future applications of COEs towards a method for improving whole-cell catalysis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Addressing the characterisation challenge to understand catalysis in MOFs: the case of nanoscale Cu supported in NU-1000

Here, we explore the dynamic structure and reactivity of Cu species supported on NU-1000. By combining pair distribution function (PDF) analysis and difference envelope density (DED) analysis of in situ synchrotron-based X-ray scattering data, we simultaneously probe the local structure of supported Cu-species, their distribution within NU-1000 and distortions of the NU-1000 lattice under conditions relevant to catalysis and catalyst activation. Our analyses show that atomic layer deposition (ALD) of Cu in NU-1000 (Cu-AIM) leads to the formation of Cu-oxo clusters within the small pores that connect the triangular and hexagonal channels. Exposure of Cu-AIM to a reducing atmosphere at 200 °C produces metallic Cu 0 of two distinct particle sizes: ~4 nm nanoparticles and small sub-nanometer clusters. The size of these nanoparticles appears to be constrained by NU-1000 pore dimensions, with evidence of the sub-nanometer clusters being bound within the triangular channels flanked by pyrene rings. This supported Cu 0 –NU-1000 system is catalytically active for gas-phase ethylene hydrogenation. Exposure of the catalyst to oxidative atmosphere re-oxidises the Cu species to a Cu 2 O cuprite phase. The dynamic restructuring of the system in different chemical environments underscores the importance of probing these systems in situ .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Sequential catalysis controls selectivity in electrochemical CO 2 reduction on Cu

Electrochemical reduction of CO 2 in aqueous media is a strategy for sustainable production of fuels and commodity chemicals. Cu is the only catalyst which converts CO 2 to significant quantities of hydrocarbons and oxygenates. Here we demonstrate that oxygenate products can be favored over hydrocarbons by positioning a local source of CO generated by a CO producing catalyst (Au or Ag) in close proximity to a Cu catalyst. Use of a bimetallic device comprising interdigitated and independently controllable lines of Au and Cu allows the local CO concentration to be modulated. Notably, diffusional simulations show that the saturation concentration of CO can be exceeded locally. Actuating both the Au and Cu lines increases the oxygenate to ethylene ratio compared to actuating Cu only. Increasing the relative area of CO-producing Au relative to Cu also increases this ratio. These insights are translated into a second bimetallic system comprising Cu dots/lines patterned directly onto a Ag substrate, allowing for the distance between Cu and the CO generating metal to be precisely controlled. Controlling the relative areas of Ag and Cu allows for tuning of the oxygenate to ethylene ratio from 0.59 to 2.39 and an increase in oxygenate faradaic efficiency from 21.4% to 41.4%, while maintaining the selectivity to C 2 /C 3 products in the 50–65% range. We attribute this change in selectivity to be due to an increased *CO coverage on Cu. Finally, by utilizing diffusional transport of CO to the Cu, a sequential catalysis pathway is created which allows for the control of oxygenate selectivity in aqueous CO 2 reduction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Stabilization of noble metal nanostructures for catalysis and sensing

Noble metal nanocrystals have been widely used as active components in catalysis and chemical/bio-sensing. The sizes, structures, and shapes of noble metal nanocrystals are crucial to their electronic, optical, and catalytic properties. However, metal nanocrystals tend to lose their structural and morphological properties when they are subjected to thermal and chemical treatment. Therefore, stabilization of noble metal nanostructures remains a challenge. In this feature article, we present our recent efforts on the stabilization of noble metal nanocrystals, i.e., using inorganic and non-metal solids as supports and physical barriers, protecting the nanocrystal surface by a metal coating, and forming alloys with other metals. At the end of this review, we provide our perspectives on the future development of effective methods for nanocrystal stabilization.

77 NANOSCIENCE AND NANOTECHNOLOGY↗