Sorption Cryocooler Development for the Planck Surveyor Mission
We are developing metal-hydride based sorption cryocoolers for the Planck Surveyor mission.
sorption cryocooler metal hydride Joule-Thomson re↗
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Results for “Hydride”
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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Phase Composition and the Effect of Thermal Cycling for VH(sub x) V(sub 0.995) C(sub 0.005)H(sub x) and V(sub 0.975)Zr(sub 0.020)C(sub 0.005)H(sub x)
X-ray diffraction (XRD) studies were performed on hydride phases formed by vanadium and its carbon substituted alloys. It was previously found that thermal cycling of VHx across the B-y mixed phase region changed the reversible hydrogen storage capacity and other properties.
pressure-composition-temperature isotherms↗
NASA Glenn Research Center Experience with LENR Phenomenon
Since 1989 NASA Glenn Research Center (GRC) has performed some small-scale limited experiments that show evidence of effects claimed by some to be evidence of Low Energy Nuclear Reactions (LENR). The research at GRC has involved observations and work on measurement techniques for observing the temperature effects in reactions of isotopes of hydrogen with palladium hydrides. The various experiments performed involved loading Pd with gaseous H2 and D2, and exposing Pd thin films to multi-bubble sonoluminescence in regular and deuterated water. An overview of these experiments and their results will be presented.
hydrogen↗
Performance, reliability and life issues for components of the Planck Sorption Cooler
Continuous-duty hydrogen sorption cryocoolers are being developed for the European Space Agency (ESA) Planck mission. To achieve an acceptable level of performance and robust operation with these hydride refrigerators during flight, detailed investigations have been performed on the sorbent materials and on critical hardware components.
sorption↗
Accelerating CO 2 Electroreduction to CO Over Pd Single-Atom Catalyst
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99 GENERAL AND MISCELLANEOUS↗
Photocatalytic Semi‐Hydrogenation of Acetylene to Polymer‐Grade Ethylene with Molecular and Metal–Organic Framework Cobaloximes
Abstract The semi‐hydrogenation of acetylene in ethylene‐rich gas streams is a high‐priority industrial chemical reaction for producing polymer‐grade ethylene. Traditional thermocatalytic routes for acetylene reduction to ethylene, despite progress, still require high temperatures and high H 2 consumption, possess relatively low selectivity, and use a noble metal catalyst. Light‐powered strategies are starting to emerge, given that they have the potential to use directly the abundant and sustainable solar irradiation, but are ineffective. Here an efficient, >99.9% selective, visible‐light powered, catalytic conversion of acetylene to ethylene is reported. The catalyst is a homogeneous molecular cobaloxime that operates in tandem with a photosensitizer at room temperature and bypasses the use of non‐environmentally friendly and flammable H 2 gas feed. The reaction proceeds through a cobalt‐hydride intermediate with ≈100% conversion of acetylene under competitive (ethylene co‐feed) conditions after only 50 min, and with no evolution of H 2 or over‐hydrogenation to ethane. The cobaloxime is further incorporated as a linker in a metal–organic framework; the result is a heterogeneous catalyst for the conversion of acetylene under competitive (ethylene co‐feed) conditions that can be recycled up to six times and remains catalytically active for 48 h, before significant loss of performance is observed.
Stone, Aaron E. B. S.↗
Pressure Driven Alkane Dehydrogenation by Palladium Metal
Abstract Dehydrogenation of alkanes is of increasing importance in fulfilling global demand for olefins and offers a potential source of carbon‐neutral hydrogen as a co‐product. Currently commercial dehydrogenation processes occur at high‐temperatures (500–900 °C) which is energy intensive and results in side reactions and rapid coking of the catalysts. In addition, the hydrogen produced is often burned to maintain temperature and to inhibit the back reaction. Here, pressure is utilized as a parameter to enable novel chemical catalytic processes, and ambient‐temperature dehydrogenation of alkanes by palladium is observed at 50–100 MPa, with both hydrogen gas and olefins recovered on decompression. This reaction follows a fundamentally different path to current commercial high‐temperature low‐pressure dehydrogenation processes with the palladium catalyst reversibly forming a hydride intermediate.
08 HYDROGEN↗
A Nanoscale Ternary Amide‐rGO Composite with Boosted Kinetics for Reversible H 2 Storage
Abstract Metal amides are attractive candidates for hydrogen storage due to their high volumetric and gravimetric hydrogen densities. However, the sluggish kinetics and competing side reactions during hydrogen uptake and release limit their practical use. Here, a novel nanoconfined Li 2 Mg(NH) 2 @reduced graphene oxide (rGO) composite is presented, which is fabricated using a melt‐infiltration method with a minimum weight penalty of only 2 wt.%. The presence of rGO ensures close contact between the active phases, effectively preventing aggregation during cycling process. As a result, the reversible capacity of Li 2 Mg(NH) 2 @rGO reaches 4.42 wt.%, with no capacity degradation observed after multiple cycling. Theoretical calculations show that rGO catalyzes the hydrogen bond cleavage at the Mg‐amide/Li hydride interface, leading to local dehydrogenation hotspots and significantly improves kinetics of dehydrogenation compared to the bulk counterpart. This study provides a promising strategy for designing metal imide‐based composites to overcome the kinetic limitations and improve their reversible hydrogen storage performance.
08 HYDROGEN↗
Partial-Single-Atom, Partial-Nanoparticle Composites Enhance Water Dissociation for Hydrogen Evolution
The development of an efficient electrocatalyst toward the hydrogen evolution reaction (HER) is of significant importance in transforming renewable electricity to pure and clean hydrogen by water splitting. However, the construction of an active electrocatalyst with multiple sites that can promote the dissociation of water molecules still remains a great challenge. Herein, a partial-single-atom, partial-nanoparticle composite consisting of nanosized ruthenium (Ru) nanoparticles (NPs) and individual Ru atoms as an energy-efficient HER catalyst in alkaline medium is reported. The formation of this unique composite mainly results from the dispersion of Ru NPs to small-size NPs and single atoms (SAs) on the Fe/N codoped carbon (Fe–N–C) substrate due to the thermodynamic stability. The optimal catalyst exhibits an outstanding HER activity with an ultralow overpotential (9 mV) at 10 mA cm -2 (η 10 ), a high turnover frequency (8.9 H 2 s -1 at 50 mV overpotential), and nearly 100% Faraday efficiency, outperforming the state-of-the-art commercial Pt/C and other reported HER electrocatalysts in alkaline condition. Both experimental and theoretical calculations reveal that the coexistence of Ru NPs and SAs can improve the hydride coupling and water dissociation kinetics, thus synergistically enhancing alkaline hydrogen evolution performance.
36 MATERIALS SCIENCE↗
Hydrocyclization/Defluorination of CF 3 ‐Substituted Acrylamides: Insights from Kinetics of Hydrogen Atom Transfer
Abstract The introduction of F‐containing groups into organic molecules can significantly alter their physical and chemical properties. Particularly, gem ‐difluoroalkenes serve as versatile precursors for a broad variety of organofluorine compounds, commonly used in agrochemicals, pharmaceuticals, and materials science. Based on the kinetics of H• transfer to acrylamide ( k H = 2.28 × 10 −4 M −1 s −1 at 300 K in toluene), the study describes a nickel‐hydride‐(or Li[BEt 3 H]) initiated hydrocyclization/defluorination of CF 3 ‐substituted acrylamides, offering alternative access to 4‐fluorovinyl‐substituted 2‐pyrrolidones (Seletracetam derivatives that are antiepileptic drug candidates). This process proceeds with high yields and remarkable chemo‐ and regioselectivity. The hydrocyclization/defluorination can be initiated by either H• or H – transfer, followed by a 5‐exo‐trig cyclization and subsequent fluorine elimination. The strategy has been applied in the late‐stage functionalization of drug molecules, providing a valuable tool in the synthesis of pharmaceutical compounds.
Wan, Yanjun [College of Pharmaceutical Sciences Zh↗
Iron Single‐Atom Catalyzed N‐Alkylation of Amines with Alcohols via Solvent‐Free Borrowing Hydrogen Strategy
Abstract Industrial hydrogenation is a pivotal process in chemical synthesis. However, it has significant drawbacks, including high cost, safety risks associated with the use of molecular hydrogen gas, and substantial energy demands due to the need for elevated temperatures and pressures to achieve satisfactory yields. The borrowing hydrogen synthesis, which enables the transfer of hydrogen between molecules, offers a promising approach for green, one‐pot synthesis of industrially important chemicals and intermediates. Despite its potential, the broad application remains limited due to the reliance on toxic solvents, expensive noble metal catalysts, and the still restricted efficiency and substrate scope. In this study, the first solvent‐free strategy for theN‐alkylation of amines with alcohols is presented, employing an N‐doped graphene‐supported Fe single‐atom catalyst (Fe SA @N‐G; 1.06 wt.%). This approach achieves superior conversion and selectivity (up to 99%) along with record values for turnover number (TON, 1032.7) and turnover frequency (TOF, 413.1 h -1 ) for the coupling reaction of aniline with benzyl alcohol, surpassing all previously reported catalysts. DFT calculations, combined with experimental data, elucidated the reaction mechanism and identified the Fe 1 (III)‐N 4 active site participating in Fe‐H hydride transfer and containing two pyrrolic and two pyridinic nitrogens bound to the Fe center. The developed technology is further supported by the catalyst's excellent scalability, reusability, and performance under continuous‐flow conditions. Additionally, the exceptional efficiency of the single‐atom catalyst is demonstrated across more than 50 substrates, including reactions involving both aliphatic and aromatic amines with aliphatic and aromatic alcohols. The industrial applicability of this technology is validated through the synthesis of pharmaceutically relevant compounds, including stimulant drugs, antihistamines, and pharmaceutical intermediates.
Chemistry↗
Co‐Electrolysis of CO 2 and H 2 O to Syngas on Bimetallic Pd x Cu 1‐ x Catalysts for Tandem Thermochemical Conversion to Carbon Nanofibers
Electrification of chemical production using renewable energy and abundant feedstocks offers a promising pathway for decarbonizing the chemical industry. Current efforts on CO 2 valorization largely focus on making chemicals and fuels. Here, to help achieve net-negative emissions through long-term carbon storage, this study aims to develop efficient electrocatalysts for a tandem electrochemical-thermochemical process to convert CO 2 into carbon nanofibers (CNFs). CO 2 and water are first electrochemically reduced in a membrane electrode assembly (MEA) electrolyzer to produce syngas (CO + H 2 ), which is subsequently fed into a thermochemical packed bed reactor to facilitate CNF growth. This work systematically evaluated Pd x Cu 1-x bimetallic electrocatalysts to assess the effect of Pd–Cu alloying on enhancing syngas production while reducing Pd loading. Transmission electron microscopy and Raman spectroscopy confirmed the formation of high-purity, crystalline CNFs, regardless of the syngas composition from the MEA. In situ X-ray absorption spectroscopy and X-ray diffraction measurements revealed that increasing Cu content in the Pd x Cu 1-x alloy progressively inhibited palladium hydride formation, consistent with DFT calculations on the stability of Pd x Cu 1-x under reducing electrochemical potentials.
58 GEOSCIENCES↗
Mechanistic Studies on the Insertion of Carbonyl Substrates into Cu‐H: Different Rate‐Limiting Steps as a Function of Electrophilicity
Abstract We report mechanistic studies on the insertion reactions of [(NHC)Cu(μ‐H)] 2 complexes with carbonyl substrates by UV‐vis and 1 H NMR spectroscopic kinetic studies, H/D isotopic labelling, and X‐ray crystallography. The results of these comprehensive studies show that the insertion of Cu‐H with an aldehyde, ketone, activated ester/amide, and unactivated amide consist of two different rate limiting steps: the formation of Cu‐H monomer from Cu‐H dimer for more electrophilic substrates, and hydride transfer from a transient Cu‐H monomer for less electrophilic substrates. We also report spectroscopic and crystallographic characterization of rare Cu‐hemiacetalate and Cu‐hemiaminalate moieties from the insertion of an ester or amide into the Cu−H bond.
Tran, Ba L.↗
Photoenzymatic Hydrogenation of Heteroaromatic Olefins Using ‘Ene’‐Reductases with Photoredox Catalysts
Abstract Flavin‐dependent ‘ene’‐reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using the native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in the presence of a photoredox catalyst. Experimental evidence suggests the reaction proceeds via a radical mechanism where the vinyl pyridine is reduced to the corresponding neutral benzylic radical in solution. DFT calculations reveal this radical to be “dynamically stable”, suggesting it is sufficiently long‐lived to diffuse into the enzyme active site for stereoselective hydrogen atom transfer. This reduction mechanism is distinct from the native one, highlighting the opportunity to expand the synthetic capabilities of existing enzyme platforms by exploiting new mechanistic models.
Nakano, Yuji↗
Economizing on Precious Metals in Three‐Way Catalysts: Thermally Stable and Highly Active Single‐Atom Rhodium on Ceria for NO Abatement under Dry and Industrially Relevant Conditions**
Abstract We show for the first time that atomically dispersed Rh cations on ceria, prepared by a high‐temperature atom‐trapping synthesis, are the active species for the (CO+NO) reaction. This provides a direct link with the organometallic homogeneous Rh I complexes capable of catalyzing the dry (CO+NO) reaction. The thermally stable Rh cations in 0.1 wt % Rh 1 /CeO 2 achieve full NO conversion with a turn‐over‐frequency (TOF) of around 330 h −1 per Rh atom at 120 °C. Under dry conditions, the main product above 100 °C is N 2 with N 2 O being the minor product. The presence of water promotes low‐temperature activity of 0.1 wt % Rh 1 /CeO 2 . In the wet stream, ammonia and nitrogen are the main products above 120 °C. The uniformity of Rh ions on the support, allows us to detect the intermediates of (CO+NO) reaction via IR measurements on Rh cations on zeolite and ceria. We also show that NH 3 formation correlates with the water gas shift (WGS) activity of the material and detect the formation of Rh hydride species spectroscopically.
Khivantsev, Konstantin↗
Reactivity and Mechanisms of Photoactivated Heterometallic [Ru II Ni II ] and [Ru II Ni II Ru II ] Catalysts for Dihydrogen Generation from Water
Abstract Two heterometallic photocatalysts were designed and probed for water reduction. Both [(bpy) 2 Ru II Ni II (L 1 )](ClO 4 ) 2 ( 1 ) and [(bpy) 2 Ru II Ni II (L 2 ) 2 Ru II (bpy) 2 ](ClO 4 ) 2 ( 2 ) can generate the low‐valent precursor involved in hydride formation prior to dihydrogen generation. However, while the bimetallic [Ru II Ni II ] ( 1 ) requires the presence of an external photosensitizer to trigger catalytic activity, the trimetallic [Ru II Ni II Ru II ] ( 2 ) displays significant coupling between the catalytic and light‐harvesting units to promote intramolecular multielectron transfer and perform photocatalysis at the Ni center. A concerted experimental and theoretical effort proposes mechanisms to explain why 1 is unable to achieve self‐supported catalysis, while 2 is fully photocatalytic.
El Harakeh, Nour↗
Interdependence of Support Wettability ‐ Electrodeposition Rate‐ Sodium Metal Anode and SEI Microstructure
Abstract This study examines how current collector support chemistry (sodiophilic intermetallic Na 2 Te vs. sodiophobic baseline Cu) and electrodeposition rate affect microstructure of sodium metal and its solid electrolyte interphase (SEI). Capacity and current (6 mAh cm −2 , 0.5–3 mA cm −2 ) representative of commercially relevant mass loading in anode‐free sodium metal battery (AF‐SMBs) are analyzed. Synchrotron X‐ray nanotomography and grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) are combined with cryogenic ion beam (cryo‐FIB) microscopy. Highlighted are major differences in film morphology, internal porosity, and crystallographic preferred orientation e.g. (110) vs. (100) and (211) with support and deposition rate. Within the SEI, sodium fluoride (NaF) is more prevalent with Te−Cu versus sodium hydride (NaH) and sodium hydroxide (NaOH) with baseline Cu. Due to competitive grain growth the preferred orientation of sodium crystallites depends on film thickness. Mesoscale modeling delineates the role of SEI (ionic conductivity, morphology) on electrodeposit growth and onset of electrochemical instability.
Lo, Chang‐An↗
Photoenzymatic Hydrogenation of Heteroaromatic Olefins Using 'Ene'-Reductases with Photoredox Catalysts
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99 GENERAL AND MISCELLANEOUS↗