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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Low Power Radioisotope Conversion Technology and Performance Summary

This work presents a summary of low-power radioisotope-based power sources. This includes systems that use direct energy conversion from radioactive decay such as betavoltaics and systems that convert heat generated by the isotope decay. These types of power systems have terrestrial and space-based applications. Their main application is to provide low levels of power in remote environments where long life and reliability are the main objectives. This work looked at the potential performance of these types of systems and the range of output power they can achieve. Also considered was the amount of power that could be achieved from these different conversion technologies, while remaining under the critical limit acceptable for space flight without the need for special handling and controls. This is of interest for space missions where low power levels can be used for operating sensors or other devices, but the expense associated with the incorporation of radioactive material above this critical level would be cost prohibitive.

Colozza, Anthony J.↗
DOE OSTI2025

Direct Air Reactive Capture and Conversion for Utility-Scale Energy Storage (Final Report)

This final report for FEW0277 summarizes the work performed over the project performance period of October 2021 – March 2025. This project was funded under the “Reactive Capture and Conversion R&D” lab call released in FY2021. The goal of the project was to develop dual-function materials and process for capturing CO 2 from the atmosphere and converting it into CH 4 . The work was organized into four parallel tracks in 1) direct air capture materials synthesis and characterization, 2) catalysts for CO 2 conversion, 3) mechanistic investigations via ab initio simulations, and 4) process modeling, technoeconomic analysis, and lifecycle assessment. The project was split into two budget periods. The first budget period focused on development of amine-based materials, due to their known performance for CO 2 direct air capture and their potential to act synergistically with metal catalysts to enable a low-temperature methanation pathway. The second budget period focused on development of alkali-based materials and a simulated-moving-bed process for high conversion catalytic reduction of captured CO 2 to CH 4 . All project milestones were completed during the project performance period and are summarized in this report. Our work resulted in publication of eight peer-reviewed manuscripts, one patent application, and numerous presentations given at domestic and international conferences and invited academic department seminars.

03 NATURAL GAS↗
DOE OSTI2019

Transforming the carbon economy: challenges and opportunities in the convergence of low-cost electricity and reductive CO 2 utilization

The increasing availability of renewable electricity at costs competitive with, and even lower than, electricity from fossil sources along with growing interest and recent technological advancements in reducing carbon emissions through CO 2 capture is challenging the status quo in the way that we produce and consume energy and products. Renewable electricity can be leveraged to produce fuels and chemicals from CO 2 , offering sustainable routes to reduce the carbon intensity of our energy and products-driven economy. A number of approaches have been developed for the electron-driven reduction of CO 2 to products, including both direct and indirect (via an energy carrier such as H 2 ) pathways and spanning from electrochemical to biological to thermocatalytic conversion. While these approaches are at various stages of development, there are technical barriers related to each core conversion technology that need to be addressed in order to accelerate commercialization and drive the transition towards a circular carbon economy. In this perspective, we assess and characterize the top technical barriers for utilizing renewable electricity for CO 2 reduction across five different conversion approaches (direct electrochemical, direct bioelectrochemical, direct non-thermal plasma, indirect bioelectrochemical, and indirect thermochemical) under state-of-technology conditions, outline the R&D needs to overcome each barrier, and identify the most promising C 1 –C 3 hydrocarbons and oxygenates based on their relative ease of formation, economic viability, CO 2 utilization potential, and energy storage capacity. Our analysis suggests, based on current reported states of technology, that indirect pathways paired with the formation of C 1 products offer the most technically feasible approach for electron driven CO 2 reduction in the near term. However, as we strive for longer carbon chain molecules, and as technologies continue to advance, there are a multitude of advantages and limitations to be considered for all five approaches.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2020

Highly selective electrocatalytic CO 2 reduction to ethanol by metallic clusters dynamically formed from atomically dispersed copper

Direct electrochemical conversion of CO 2 to ethanol offers a promising strategy of lowering CO 2 emission while storing energy from renewable electricity. However, current electrocatalysts offer only limited selectivity toward ethanol. Here we report a copper catalyst synthesized by a unique Cu-Li amalgm method over a commercial carbon support that achieved Faradaic efficiency (FE) higher than 91% at -0.7 V (RHE) and the active potential as low as -0.4 V (RHE) during direct electrocatalytic CO 2 -to-ethanol conversion. The catalyst also demonstrated stability over an extended period of operation. A strong correlation between the catalytic selectivity and the initial Cu atoms dispersion was found and Operando X-ray absorption spectroscopy identified a dynamic and reversible transformation from atomically dispersed copper atoms to Cu n (n = 3 and 4) under the electrochemical reaction. Frist-principles calculations further elucidate the possible catalytic mechanism of CO 2 reduction over Cu n .

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

Microbial valorization of lignin to malic acid by Aspergillus niger

Lignin is the largest renewable source of aromatic carbon, yet its heterogeneity and recalcitrance limit its use in higher-value bioconversion processes. In this study, Aspergillus niger was engineered to enable the bioconversion of lignin-derived aromatics and base-catalyzed depolymerized (BCD) lignin streams into malic acid, a value-added C4 dicarboxylic acid with broad industrial relevance. Overexpression of the C4 dicarboxylate transporter C4T318 from Aspergillus oryzae enhanced malic acid secretion, while medium optimization under buffered conditions further improved the production. The engineered strain efficiently assimilated representative lignin-derived aromatics, including 4-hydroxybenzoic acid and p-coumaric acid, producing up to 3.9 g/L malic acid. Conversion of BCD lignin liquors from poplar and sorghum demonstrated effective utilization of heterogeneous aromatic mixtures, generating up to 0.82 g/L malic acid. This work demonstrates direct fungal conversion of real lignin streams into malic acid and establishes A. niger as a promising platform for sustainable lignin valorization.

Aromatic bioconversion↗
NASA NTRS1986

AMTEC: High efficiency static conversion for space power

Future manned and unmanned space missions will require reliable, high efficiency energy conversion systems. For a manned Mars mission, power levels in the range of 10 to 100 kWe will be needed. The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion technology with the potential to meet these needs. The AMTEC is a thermally regenerative electrochemical device that derives its operation from the sodium ion conducting properties of beta-alumina solid electrolyte (BASE). To date, an efficiency of 19%, area power density of 1 W/sq cm, and a lifetime of 10,000 hours at high temperature were demonstrated in laboratory devices. Systems studies show that projected AMTEC systems equal or surpass the performance of other static or dynamic systems in applications of 1 kWe-1 MWe. Thus, the laboratory experiments and applications studies conducted to date have shown that the AMTEC posseses great potential. In order to bring this technology to the stage where prototype units can be built and operated, several technical issues must be addressed. These include the need for long life, high power electrodes, minimization of radiative parasitic losses, and high temperature seals. In summary, the evidence shows that if AMTEC is developed, it can play a significant role in future space power applications.

Bankston, C. P.↗
DOE OSTI2026

Induction Melter Processing Alternatives for High Level Radioactive Wastes – 26198

This work investigates the potential to vitrify nuclear fuel directly, as well as the vitrification potential associated with experimental dissolver solutions. Greater understanding of the exothermicity is needed to quantify processing risk, especially with respect to potential phase changes and associated explosion hazards present in some systems. Thermal analysis was carried out on various simulants to elucidate the exothermic reaction potential from solid metal dissolution in glass and from the drying of alternative process dissolver solutions. Results from experimental testing of simulants to demonstrate vitrification potential and compatibility indicate that alternative dissolver flowsheets suppress the heat released during processing and that common silicate- and phosphate- based glass systems are potential candidates for direct vitrification. Direct vitrification (conversion) of fuel simulants was assessed using laboratory scale glass melts to obtain qualitative information on dissolution rates and waste loadings. Initial tests were successful to dissolve and incorporate metal directly into glass, although the kinetics and limits of dissolution and incorporation into glass are not fully understood.

Amoroso, Jake [Savannah River National Laboratory ↗
DOE OSTI2020

Hierarchical Galloaluminosilicate MFI Catalysts for Ethane Nonoxidative Dehydroaromatization

This study presented an approach to overcome diffusion limitation and imbalance between Brønsted and Lewis acidities that affect conversion and aromatic yield in alkane nonoxidative dehydroaromatization (DHA) conversion. Three different Ga-promoted ZSM-5 catalysts were synthesized for the ethane DHA reaction. The hierarchical galloaluminosilicate Meso-GaZSM-5 was prepared by the solid-state crystallization technique wherein Ga was introduced through the in situ synthesis process. The microporous galloaluminosilicate Micro-GaZSM-5 was synthesized by the hydrothermal technique wherein Ga was introduced in situ during zeolite formation. The hierarchically structured Ga-Meso-ZSM-5 was synthesized by the solid-state crystallization method, but the Ga was introduced by the incipient wetness method. Additional Pt was incorporated by the incipient wetness technique for all three catalysts to enhance the DHA activity. The solid-state crystallization technique created the hierarchical structure without using a template. With the in situ technique, Ga species replaced the Al framework, reducing the strong Brønsted acidity. Meanwhile, they created the extraframework GaO + , introducing the strong Lewis acid sites into catalysts. Due to better synergistic interaction between the oxidation state of metals, acidic properties, and catalyst porosity, Pt-Meso-GaZSM-5 showed higher C 2 H 6 conversion and aromatic selectivity. The improvement on diffusivity not only reduces the effect of channel blockage but also improves the utilization of active sites. As a result, this work sheds light on the direct, nonoxidative conversion of shale gas without going through the syngas route.

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

A secondary diffraction effect and the generation of Scholte–Stoneley acoustic wave on periodically corrugated surface

When a wideband sound beam is incident onto a periodically corrugated surface, a series of diffraction related phenomena can occur. In this work, we report the observation of a secondary diffraction, which is different from those previously investigated. The search of the physical origin of this newly observed diffraction leads to the discovery of the possibility of generating Scholte–Stoneley waves, inspired by Guo, Margetan, and Thompson's work in sound backscattering from rough surfaces, through a nonconventional energy conversion mechanism: direct coupling of the incident energy with the periodic interface. This mechanism allows for the Scholte–Stoneley wave generation at any angle of incidence, which distinguishes it from the well-known energy conversion mechanism of the diffraction-related phenomena such as acoustic Wood anomaly and backward displacement in which wave generation is highly angle dependent. The findings of this work not only enrich the understanding of the interaction of sound with periodically corrugated structures but also provide a new surface wave generation method for the potential applications in nondestructive evaluation of materials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Oxidative coupling of methane (OCM) conversion into C 2 products through a CO 2 /O 2 co-transport membrane reactor

Oxidative coupling of methane (OCM), which transforms CH 4 into C 2 products (C 2 H 6 and C 2 H 4 ) with molecular O 2 as the oxidant, is one of the most studied direct methane conversions (DMCs). However, a major technical hurdle to the OCM process is to achieve high CH 4 conversion at high C 2 (C 2 H 6 and C 2 H 4 ) selectivity. One rudimentary cause for this “tradeoff” behavior is the high chemical reactivity of the products (C 2 H 6 or C 2 H 4 ), which can be re-oxidized by O 2 . To overcome this thermodynamic challenge, minimizing the oxidizing power of the oxidant and lowering the local oxygen partial pressure are keys. Here, In this work, we demonstrate a new membrane reactor that capture CO 2 /O 2 from a flue gas and uses it for OCM conversion. The results show that the co-captured CO 2 /O 2 mixture converts CH 4 into C 2 H 6 in the presence of a 2%Mn–5%Na 2 WO 4 /SiO 2 catalyst, followed by thermal cracking of C 2 H 6 into C 2 H 4 and H 2 . The presence of CO 2 decreases the local partial pressure of O 2 , thus reducing the propensity of C 2 -products re-oxidation and leading to a higher C 2 selectivity. We show that a small button-type membrane reactor can achieve 12% C 2 yield with ~57% C 2 -selectivity using a diluted CH 4 -Ar mixture as the feedstock. We expect higher C 2 yield with tubular plug-flow membrane reactors in the future. We also highlight the unique advantage of the membrane reactor in intensifying CO 2 capture from both flue gas and OCM purification process into one single step.

42 ENGINEERING↗
DOE OSTI2026

Migration of Al within dealuminated beta extruded catalysts influences olefin distribution during ethanol upgrading

Zeolites serve as essential catalytic platforms for many industrial processes, including emerging ethanol-to-olefins (ETO) upgrading technologies. Although metal-loaded (Cu, Zn, Y) dealuminated beta (deAlBeta) zeolite powders are promising catalysts for direct ETO conversion with high selectivity to butene-rich C3+ olefins necessary for production of sustainable aviation fuels (SAF), development of these materials as shaped technical bodies through the incorporation of binders is required for scale-up and commercial viability. Here, we report the ethanol upgrading performance of Cu-Zn-Y/deAlBeta extruded catalysts formulated with either alumina or kaolin clay binders. Both extrudates exhibit high ethanol dehydration reactivity which competes with the initial ethanol dehydrogenation step in the direct ETO reaction network. Consequently, elevated selectivity to dehydration side products (ethylene, diethyl ether) at ∼100% ethanol conversion is observed on Cu-Zn-Y/deAlBeta extrudates compared to the powder catalyst, which inhibits production of desired C3+ olefins. Utilizing microscopy and spectroscopic characterizations, we attribute this to Al migration from binder to zeolite particles within the extrudates, thus re-aluminating the zeolite and generating Brønsted acid sites active for dehydration reactions. This work elucidates the effects of binder incorporation on ETO product distributions and emphasizes that binder selection must be carefully considered during design of extruded zeolite catalysts.

Jacobs, Hunter [ORNL] (ORCID:000000016190874X)↗
DOE OSTI2025

Cation Effects on CO 2 Delivery to Cu Electrode in Reactive Capture of CO 2

The direct electrochemical conversion of captured CO 2 , known as reactive capture of CO 2 (RCC), remains a formidable challenge in heterogeneous catalysis. Given that amines are one of the most widely used capture agents for CO 2 , it would be desirable to electrochemically reduce the resultant adducts, such as carbamate, directly in RCC. However, current understanding suggests that the primary species undergoing reduction in RCC with amines is the CO 2 dissociated from the sorbent. Herein, we employ ab initio molecular dynamics (AIMD) with DFT to analyze how the nature of alkali metal cations in the electrolyte affects carbamate at the Cu surface, thereby assessing the possibility of promoting RCC by cation effects. The simulations show that the carbamate’s orientation with respect to the electrode is governed by the optimal distance between the carbamate and the cation, specifically how this distance aligns with the cation’s hydration spheres. Moreover, the slow-growth AIMD results indicate that the CO 2 dissociation barrier correlates with the orientation of carbamate at the interface. When the carbamate resides beyond the cation’s first hydration sphere, it adopts a flat orientation with respect to the surface that promotes the release of CO 2 from the capture agent. In contrast, when the carbamate disrupts the first hydration sphere and exhibits a strong cation−π interaction, it adopts an upright orientation that is less conducive to CO 2 release. These findings reveal a nontrivial cation effect in RCC, suggesting that it should be possible to optimize RCC via the choice of the electrolyte.

ab initio molecular dynamics↗
DOE OSTI2026

Circumventing thermodynamic limitations in converting carbon dioxide into carbon nanotubes via tandem catalysis

Carbon nanotubes (CNTs) are important materials for electronics and structural composites, but their production still relies on hydrocarbon-based chemical vapor deposition, an energy-intensive and fossil-dependent process, limited by rapid catalyst deactivation. Using CO2 as a carbon feedstock offers a sustainable route for CNT synthesis, yet direct CO2 conversion to CNTs is thermodynamically unfavorable and existing CO2-to-carbon pathways mainly yield amorphous or weakly graphitized solids. Here, we demonstrate a tandem electrochemical–thermochemical (EC-TC) strategy that overcomes these limitations. CO2 is first electrochemically reduced to a tunable mixture of C2H4 and CO, which is directly fed into a thermochemical reactor and converted into CNTs with controllable morphology and high CNT-to-metal mass ratios (~200) over NiFe catalysts at 750 °C. In situ synchrotron-based characterization and density functional theory calculations reveal that CO dissociation and C2H4 decomposition on NiFe alloys cooperatively promote CNT nucleation and sustained growth. This EC-TC strategy establishes a modular route for converting CO2 into value-added carbon nanomaterials.

03 NATURAL GAS↗
DOE OSTI2024

Butene-Rich Alkene Formation from 2,3-Butanediol through Dioxolane Intermediates

The cost-effective production of sustainable aviation fuels (SAF) remains a major challenge within the energy sector. One approach to address this is the fermentation of biomass feedstocks into oxygenates followed by catalytic conversion to alkenes or other oligomerization precursors. 2,3-Butanediol (BDO) is a promising fermentation product due to its four-carbon nature, its decreased microorganism toxicity and associated higher maximum fermentation titers relative to other alcohols and oxygenates, and its capacity to be readily converted into butene isomers and longer chain alkenes. BDO conversion is currently constrained by separation challenges for BDO isolation due to its high boiling point and hydrophilicity. Here, this work expands upon previous BDO reactive separation via dioxolane formation over a solid acid catalyst by investigating the conversion of dioxolanes into alkene mixtures. Dioxolanes were formed from a range of aldehydes and subsequently converted over a Cu/ZSM-5 catalyst (448–523 K) via an ether cleavage, hydrogenation, and dehydration reaction network to form alkene-rich product mixtures (96% C 3+ alkene yield, 523 K). This selectivity is greater than that of direct BDO conversion to alkenes over an identical catalyst (89%, 523 K). C 3+ alkene selectivity is maximized between 498 and 523 K at complete dioxolane conversion without significant alkene hydrogenation to alkanes. The alkene product distributions can be tailored via both aldehyde selection during dioxolane formation and the dioxolane conversion reaction temperature. Alkene mixtures from dioxolane conversion predominantly reflect the carbon chain length and stereochemistry of BDO and the initial aldehyde at or below 498 K, yet higher reaction temperatures yield alkene mixtures of similar carbon chain distributions, regardless of initial aldehyde selection. Deactivation of the Cu/ZSM-5 catalyst is observed for multiple steps of the overall reaction network but can be minimized by facilitating the complete dioxolane-to-alkene reaction network at temperatures of at least 498 K.

2,3-butanediol↗
DOE OSTI2022

Experimental Validation and Continuous Testing of an On-Purpose High-Yield Pitch Synthesis Process for Producing Carbon Fiber from US Domestic Coal

This project aims to develop technology that converts domestic United States (US) raw coal to high quality, high value, and marketable carbon fiber. More specifically, the project aims to significantly improve the selectivity and yield of carbon fiber produced per ton of coal over conventional coal pitch-based production by using low-severity direct coal conversion technology to maximize the yield of pitch from coal, suitable for production of carbon fiber. To meet the stated objective of developing a technology platform, capable of producing high quality, high-value and marketable carbon fiber from domestic US coal, the proposed scope of work involves testing of a low-severity direct coal liquefaction (LS-DCL) process approach. The isotropic pitch produced from the LS-DCL process will be thermally treated using conventional processes to convert to a liquid crystal or “mesophase” pitch as a precursor for structural carbon fibers. This mesophase pitch will then be melt-spun into fiber, oxygen stabilized, and carbonized using conventional processes. The resulting carbon fiber will be evaluated for mechanical properties and suitability for structural applications such as automotive parts and spars for wind turbine blades. The overall process is expected to significantly lower the cost of fiber compared to state of the art fibers produced from polyacrylonitrile (PAN) precursors.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2026

Catalytic conversion of cellulose and its derived sugars to 5-Hydroxymethylfurfural, levulinate esters, and sorbitol: a comprehensive review

Cellulose, an abundant, renewable, and sustainable non-edible carbon source from agriculture and forestry, has attracted great attention for producing diverse value-added chemicals and fuels. However, the rigid 3D structure of cellulose, maintained by an extensive hydrogen bonding network, hinders chemical conversion, requiring effective pretreatment to break down the crystalline structure. High-value cellulose-derived compounds such as 5-hydroxymethylfurfural (5-HMF), levulinate esters, and sorbitol, recognized as critical platform chemicals by the U.S. Department of Energy, are particularly attractive for versatile applications. This review provides a comprehensive overview of methodologies for the chemical synthesis of 5-HMF, levulinate esters, and sorbitol, focusing on direct catalytic conversion of cellulose. It delves into recent advancements in reaction systems and catalysts, highlighting catalytic pathways, selectivity, strategies for process optimization, and computational approaches, while discussing the challenges associated with the catalytic conversion of cellulose into these high-value products and offering potential strategies for enhancing future catalytic processes.

Huang, Kaixuan [Yancheng Teachers Univ. (China); N↗
DOE OSTI2025

Operando XAS and DFT Uncover Structure-Performance Relationships in Re/TiO 2 for Selective CO 2 Hydrogenation to Methanol

The conversion of CO 2 into value-added chemicals, such as methanol, offers a promising pathway toward a renewable energy future. However, a precise kinetic control and a highly selective catalyst are necessary to overcome the thermodynamic preference for CO 2 hydrogenation to methane. Rhenium-based catalysts, particularly Re/TiO 2 , demonstrate high activity and selectivity for methanol under high-pressure conditions. For example, at 100 bar and 200 °C, a methanol selectivity of 97−99% was obtained. Catalysts with 1 wt % Re and 5 wt % Re/ TiO 2 were used to study the effect of cluster sizes. At 250 °C, the 1 wt % catalyst achieves 97% selectivity at 23% conversion, whereas 5 wt % Re/TiO 2 achieves 74% selectivity at 40% conversion, corresponding to a drop in space-time yield from 65 to 16 g CH 3 OH ·g Re −1 ·h −1 , respectively. X-ray absorption spectroscopy provided insights into the structure of the active sites, while density functional theory calculations revealed the effects of cluster size on the energy barriers for H 2 activation, CH 3 OH dissociation, and CH 3 OH desorption, all of which directly influence conversion and selectivity. These results underscore the importance of balancing cluster size for optimal catalyst performance and provide insights into the design of efficient and selective catalysts for renewable methanol production.

XAS↗
DOE OSTI2019

Scalable One‐Step Gel Conversion Route to High‐Performance CHA Zeolite Hollow Fiber Membranes and Modules for CO 2 Separation

Efficient separation of CO 2 from other molecules such as CH 4 , N 2 , and hydrocarbons is a key problem in many energy production and greenhouse gas reduction schemes. Zeolite materials demonstrate attractive gas separation properties, but their industrial application as membranes in gas separation are elusive because of high cost and low reproducibility of conventional fabrication techniques. A facile method is demonstrated for the fabrication of high‐silica CHA zeolite membranes on low‐cost alumina hollow fiber substrates by a one‐step direct gel conversion method, along with a detailed characterization of the CHA hollow fiber membranes. To demonstrate the scalability of the method, 20 hollow fiber (710 μm OD and 390 μm ID) membranes are synthesized in the same batch and assembled into a module. Under dry conditions, the membranes show an excellent CO 2 permeance up to 3500 GPU (1 Gas Permeation Unit = 3.348 × 10 −10 mol m −2 s −1 Pa −1 ) and an excellent CO 2 separation performance (e.g., CO 2 /CH 4 separation factors up to 210 in the 1–7 bar feed pressure range). In addition, the membranes exhibit a considerable increase in CO 2 selectivity under humid (saturated water vapor) conditions with moderate permeance drops. This study opens a promising new path for accelerated development of low‐cost zeolitic membranes for gas separation technology.

Yang, Shaowei↗