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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Metal-organic frameworks for the adsorption and catalytic transformations of carbon dioxide

Novel crystalline porous materials known as metal-organic frameworks (MOFs) and methods for their synthesis are provided herein. The MOFs include a M6(μ3-OH)8(OH)8(μ2,η2-(O2C)2cyclam)8 cluster, and a metal atom coordinated to the one or more cyclam of the cluster, wherein M is Zr or Hf, and the metal atom is any one of Cu, Ni, Cr, Ru, Co, and Gd. The MOFs can be used as an adsorbent, alone or in a medium with other components, of CO2. The MOFs can also be used as a catalyst for the transformation of CO2 and epoxides to cyclic carbonates. The MOFs can also be used in the electrochemical catalytic reduction of CO2. The MOFs can also be used for photocatalytic CO2 reduction for the production of carbon-based fossil fuels. The MOFs can also be used for light-induced nitric oxide (NO) release. The MOFs can also be used as magnetic resonance imaging (MRI) agents.

Morris, Amanda Jean↗
DOE OSTI2023

Cu-Doped Iron Oxide for the Efficient Electrocatalytic Nitrate Reduction Reaction

The electrochemical nitrate reduction reaction (NO 3 RR) is a promising alternative synthetic route for sustainable ammonia (NH 3 ) production, because it not only eliminates nitrate (NO 3 – ) from water but also produces NH 3 under mild operating conditions. However, owing to the complicated eight-electron reaction and the competition from the hydrogen evolution reaction, developing catalysts with high activities and Faradaic efficiencies (FEs) is highly imperative to improve the reaction performance. In this study, Cu-doped Fe 3 O 4 flakes are fabricated and demonstrated to be excellent catalysts for electrochemical conversion of NO 3 – to NH 3 , with a maximum FE of ~100% and an NH 3 yield of 179.55 ± 16.37 mg h –1 mg cat –1 at –0.6 V vs RHE. Here, theoretical calculations reveal that doping the catalyst surface with Cu results in a more thermodynamically facile reaction. These results highlight the feasibility of promoting the NO 3 RR activity using heteroatom doping strategies.

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

Chemically Controllable Porous Polymer–Nanocrystal Composites with Hierarchical Arrangement Show Substrate Transport Selectivity

Functional organic–inorganic hybrid materials with tunable properties are useful across many application areas, ranging from gas storage to electronics, flame retardants, separations, and catalysis. Combining polymers, with a suite of functional groups and conformational flexibility, and inorganic nanoparticles, with tunable surface chemistry and composition, yields hybrids with novel functional properties. Specifically, in catalysis, control of the electronic environment at a metal interface is paramount in determining the catalytic properties. In this contribution, we describe a modular process to prepare porous polymer–nanocrystal (NC) composites in a hierarchical, multilayered synthesis, in which multiple parameters can be accurately tuned: polymer functional groups and the corresponding pore structure, the polymer layer thickness, and the NC size, shape, and composition. This process provides for a variety of controlled materials with high surface area, tunable chemistry, and thermal and chemical stabilities. Furthermore, we demonstrate their utility for shape- and size-selective catalytic conversions both in oxidation and hydrogenation reactions, where they show increased selectivity by orders of magnitude compared to conventional polymer-supported metal catalysts. In light of the high degree of control in the composite structure, this method allows for the design and realization of catalysts for several reactions and reaction environments and for nanomaterials with other applications.

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

Sub‐5 nm Intermetallic Nanoparticles Confined in Mesoporous Silica Wells for Selective Hydrogenation of Acetylene to Ethylene

Abstract We report the synthesis and catalytic application of intermetallic PtSn nanoparticles confined in MSWs (Mesoporous Silica Wells) in the semi‐hydrogenation of acetylene. Platinum nanoparticles with a size of 2.9 nm supported on amine‐functionalized ∼180 nm silica spheres were enmeshed in a mesoporous silica shell. After the addition of tin via a polyol synthesis method, we obtained the final PtSn x @MSW (x=0.30, 0.50, 0.70, 1.0 and 2.0). Owing to the mesoporous encapsulation the sub‐5 nm bimetallic particles are shown to be monodisperse and well protected against aggregation on the silica sphere even under high‐temperature treatment conditions. In the gas phase semi‐hydrogenation of acetylene, the PtSn@MSW with Sn/Pt molar ratios equal to or greater than one displayed higher selectivity to ethylene. Meanwhile, increasing Sn content decreases acetylene conversion. The intermetallic PtSn@MSW catalysts also displayed long‐term stability and regenerability due to the confined environment provided by MSW.

Maligal‐Ganesh, Raghu V.↗
DOE OSTI2022

First-Principles Surface Characterization and Water Adsorption of Fe 3 P Schreibersite

We report the meteoritic mineral schreibersite, e.g., Fe 3 P, is a proposed abiotic source of phosphorus for phosphate ion (PO 4 – ) production, needed for nucleobases, phospholipids, and other life building materials. Schreibersite could have acted as both a source of elemental phosphorus and as a catalyst, and the hostile conditions on early Earth could have accelerated its degradation in different environments. Here, we present results from quantum calculations of bulk schreibersite and of its low Miller index surfaces. We also investigate water surface adsorption and identify possible dissociation pathways on the most stable facet. Our calculations provide useful chemical insights into schreibersite interactions in aqueous environments, paving the way for further detailed investigation on more reactive surfaces. Our results help provide a “bottom-up” understanding for phosphorylated organic synthesis on the primitive planet and its role in producing life building molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Intermetallic Single-Atom Alloy In–Pd Bimetallene for Neutral Electrosynthesis of Ammonia from Nitrate

Harvesting recyclable ammonia (NH 3 ) from the electrocatalytic reduction of nitrate (NO 3 RR) offers a sustainable strategy to close the ecological nitrogen cycle from nitration contamination in an energy-efficient and environmentally friendly manner. The emerging intermetallic single-atom alloys (ISAAs) are recognized to achieve the highest site density of single atoms by isolating contiguous metalatoms into single sites stabilized by another metal within the intermetallic structure, which holds promise to couple the catalytic benefits from intermetallic nanocrystals and single-atom catalysts for promoting NO 3 RR. Herein, ISAA In-Pd bimetallene, in which the Pd single atoms are isolated by surrounding In atoms, is reported to boost neutral NO 3 RR with a NH 3 Faradaic efficiency(FE) of 87.2%, a yield rate of 28.06 mg h -1 mg Pd -1 , and an exceptional electrocatalytic stability with increased activity/selectivity over 100 h and 20 cycles. The ISAA structure induces substantially diminished overlap of Pdd-orbitals and narrowed p-d hybridization of In-p and Pd-d states around the Fermi level, resulting in a stronger NO 3 - adsorption and a depressed energy barrier of the potential-determining step for NO 3 RR. Finally, further integrating the NO 3 RR catalyst into a Zn-NO 3 - flow battery as the cathode delivers a power density of 12.64 mW cm -2 and a FE of 93.4% for NH 3 production.

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

Optimizing hierarchical membrane/catalyst systems for oxidative coupling of methane using additive manufacturing

The advantage of a membrane/catalyst system in oxidative coupling of methane (OCM) compared to conventional reactive systems is that by introducing oxygen to the OCM catalytic sites through a membrane, parasitic gas phase reactions of O 2 (g), responsible for lowering product selectivity, can be avoided. The design and fabrication of membrane/catalyst systems has, however, been hampered by low volumetric chemical conversion rates, high capital cost, and difficulties in codesigning membrane and catalyst properties to optimize the performance. We solve these issues by developing a dual-layer additive manufacturing process, based on phase inversion, to design, fabricate and optimize a hollow fiber membrane/catalyst system for OCM. We demonstrate the approach though a case study using BaCe 0.8 Gd 0.2 O 3-δ (BCG) as the basis of both the catalyst and separation layers. We show that by using the manufacturing approach we can codesign the membrane thickness and catalyst surface area so that the flux of oxygen transport through the membrane and methane activation rates in the catalyst layer match each other. Here, we demonstrate that this “rate matching” is critical for maximizing the performance, with the membrane/catalyst system significantly overperforming conventional reactor designs under identical conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Molten Salt Synthesis of Increased (100)-Facet and Polycrystalline Nickel Oxide Nanoparticles for the Oxygen Evolution Reaction: Impact of Facet and Crystallinity on Electrocatalysis

Nickel oxide nanocubes with increased (100) surface facet presence (NiO(100)) were synthesized through a molten salt synthesis procedure to probe their oxygen evolution reaction (OER) activity in order to investigate the relationship between the surface facet and OER performance. While altering the synthesis parameters to decrease NiO(100) particle sizes and agglomeration, a polycrystalline NiO nanoparticle system formed from using Li2O as a Lux-Flood base (labelled Li2O-MSS NiO, where MSS stands for molten salt synthesis). This novel synthesis was further elaborated and the obtained materials were also tested for OER activity. After thorough structural characterization to determine crystallinity, lattice spacings, and elemental distribution, their OER activity was compared versus high surface area NiO(111) nanosheets in a three-electrode rotating disk electrode (RDE) system. The activity trend of (111) > Li2O-MSS > (100) was observed. This decrease in activity of the nanocube and polycrystalline samples was explained by differences between theoretical and experimental conditions, differences in ink rheology and resulting catalyst layer properties, and significant agglomeration seen in the imaging of the sample. Methods for improving the OER activity of these samples are discussed in the conclusion of this study.

08 HYDROGEN↗
DOE OSTI2025

From Nonclassical to Classical: Crystallization Seeds Reshape Nucleation Mechanisms

Crystalline seeds are widely employed in crystallization to accelerate nucleation and control product polymorphs; yet, their impact on nucleation mechanisms remains poorly understood. While homogeneous nucleation of crystals from solution often proceeds through nonclassical pathways involving amorphous intermediates, it is unclear how seeds that promote heterogeneous nucleation reshape these mechanisms and govern polymorph selection. Here, in this study, we provide the first direct evidence that crystalline seeds can bypass the need for amorphous intermediates as nucleation sites, converting nonclassical nucleation mechanisms into classical, monomer-by-monomer crystallization pathways. Using molecular dynamics simulations of zeolite synthesis, we uncover a complex reaction network of competing nucleation processes mediated by intermediate interfacial polymorphs. The interplay between thermodynamic stability and kinetic favorability of these interfacial polymorphs dictates nucleation outcomes, creating a dynamic balance between the interfacial polymorph stability and crystallization rates. Furthermore, we show that the synthesis environment-whether monomers or aggregates serve as reactants-profoundly impacts these pathways. At moderate supersaturation, seeds eliminate amorphous intermediates and promote classical nucleation, whereas high supersaturation or aggregate-based reactants favor nonclassical pathways, even in the presence of seeds. These findings establish a general framework for understanding how seeds govern crystallization mechanisms, with broad implications for controlling nucleation kinetics, polymorph selection, and material properties. While focused on zeolites, this work reveals insights that may be applicable to biominerals, pharmaceuticals, functional materials, and catalysts, providing a basis for engineering crystallization pathways in diverse applications.

Chu-Jon, Carlos [Univ. of Utah, Salt Lake City, UT↗
DOE OSTI2021

Few‐Unit‐Cell MFI Zeolite Synthesized using a Simple Di‐quaternary Ammonium Structure‐Directing Agent

Abstract Synthesis of a pentasil‐type zeolite with ultra‐small few‐unit‐cell crystalline domains, which we call FDP (few‐unit‐cell crystalline domain pentasil), is reported. FDP is made using bis‐1,5(tributyl ammonium) pentamethylene cations as structure directing agent (SDA). This di‐quaternary ammonium SDA combines butyl ammonium, in place of the one commonly used for MFI synthesis, propyl ammonium, and a five‐carbon nitrogen‐connecting chain, in place of the six‐carbon connecting chain SDAs that are known to fit well within the MFI pores. X‐ray diffraction analysis and electron microscopy imaging of FDP indicate ca. 10 nm crystalline domains organized in hierarchical micro‐/meso‐porous aggregates exhibiting mesoscopic order with an aggregate particle size up to ca. 5 μm. Al and Sn can be incorporated into the FDP zeolite framework to produce active and selective methanol‐to‐hydrocarbon and glucose isomerization catalysts, respectively.

Lu, Peng↗
DOE OSTI2021

Few‐Unit‐Cell MFI Zeolite Synthesized using a Simple Di‐quaternary Ammonium Structure‐Directing Agent

Abstract Synthesis of a pentasil‐type zeolite with ultra‐small few‐unit‐cell crystalline domains, which we call FDP (few‐unit‐cell crystalline domain pentasil), is reported. FDP is made using bis‐1,5(tributyl ammonium) pentamethylene cations as structure directing agent (SDA). This di‐quaternary ammonium SDA combines butyl ammonium, in place of the one commonly used for MFI synthesis, propyl ammonium, and a five‐carbon nitrogen‐connecting chain, in place of the six‐carbon connecting chain SDAs that are known to fit well within the MFI pores. X‐ray diffraction analysis and electron microscopy imaging of FDP indicate ca. 10 nm crystalline domains organized in hierarchical micro‐/meso‐porous aggregates exhibiting mesoscopic order with an aggregate particle size up to ca. 5 μm. Al and Sn can be incorporated into the FDP zeolite framework to produce active and selective methanol‐to‐hydrocarbon and glucose isomerization catalysts, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2020

High-yield growth kinetics and spatial mapping of single-walled carbon nanotube forests at wafer scale

Emerging commercial applications of vertically aligned, single-walled carbon nanotube (SWCNT) “forests” require synthesis that minimizes nanotube diameter while maximizing number density across substrate areas exceeding centimeter scale. To address this need, we synthesized SWCNT forests on full silicon wafers with notable reproducibility and uniformity, and co-optimized growth for small diameters and high densities across large areas to access new territory in this 3D parameter space. We mapped the spatial uniformity of key structural features using Raman microscopy, synchrotron X-ray scattering, and Rutherford backscattering spectrometry. Low C 2 H 2 flux over sub-nm Fe/Mo catalysts produced small-diameter SWCNTs (2.1 nm) at high number densities (2.26 × 10 12 cm -2 ) on wafers up to 6 in. Although removing Mo resulted in larger SWCNT diameters and lower densities (<0.7 × 10 12 cm -2 ), mass conversion rates from C 2 H 2 to SWCNT product were high and remarkably invariant for catalyst compositions and densities (i.e., 47.7% or 1.30 × 10 6 % g-catalyst -1 on 4-in. wafers). These carbon conversion efficiencies far exceed typical benchtop reactors and are on par with the best reported literature values. Our detailed elucidation of correlations among structural characteristics within this resource-efficient process is expected to guide future scale-up efforts of SWCNT forest growth beyond wafer scale.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Stoichiometric metal nitration based novel green synthesis of mesoporous metal oxides and their enhanced heterogeneity

Here, in this work, a general and novel method for the green synthesis of mesoporous metal oxides via stoichiometric metal nitration has been demonstrated. Pluronic surfactants and their effect on synthesis procedures in terms of surface area have been experimentally studied in detail. Contrary to the traditional synthesis procedure, water has been utilized as the solvent and in several cases, such as tin oxide, manganese oxide, aluminum oxide, antimony oxide, zinc oxide, cobalt oxide, copper oxide, yttrium oxide, lanthanum oxide, and silver either the highest or comparable surface areas have been successfully synthesized. Through XRD, and TEM, all materials were observed to be crystalline except silver and magnesium oxide. SEM shows that with an increase in surfactant molar mass agglomeration decreases. Ammonia chemisorption on acidic materials gives quantitative amounts of ammonia chemical bonding with catalysts, whereas carbon dioxide chemisorption gives a quantitative value of CO 2 chemical binding with basic sites. As high as 1901.8 μmol/g and 994.6 μmol/g ammonia chemisorption values for oxides of vanadium and tin were achieved. Amphoteric materials give both acidic and basic enhanced adsorption. Finally, all synthesized materials are studied under organic catalytic transformations. Benzyl bromide is theoretically more active compared with benzylamine and benzyl alcohol which was also experimentally shown through the conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2026

From Serendipity to Exploration: Synthesis and Properties of PtSiSb

PtSiSb is a compound with covalent Si–Sb bonds, which are relatively rare instances in solid-state materials. The original report on PtSiSb indicates synthetic challenges for the isolation of single-phase samples, as well as potential discrepancies in the predicted electronic structure and experimental transport properties. In this work, we considered PtSiSb as a case study with the objective of demonstrating the importance of synthesis as a bridge between theoretical predictions and experimental properties. Using guidance from in situ powder X-ray diffraction, the synthesis of single-phase polycrystalline samples was developed, allowing further experimental characterization of transport and catalytic properties. Thermal conductivity and heat capacity demonstrated anomalous behavior, indicating an unconventional phonon scattering mechanism in PtSiSb. Charge transport measurements indicated semimetallic behavior. Hydrogen evolution reaction (HER) tests in acidic electrolyte revealed that the PtSiSb cathode needs an overpotential η 10 = 120 mV to achieve a current density j = −10 mA/cm 2 . This is lower activity than elemental Pt but comparable to known and active transition-metal phosphide HER catalysts, such as CoP, with η 10 = 93 mV when measured at identical conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Microscopic 3D Graphene for High-Performance Supercapacitors with Ultra-High Areal Capacitance

Despite graphene being considered as an ideal supercapacitor electrode material, its use in commercial devices is limited because few methods exist to produce high-quality graphene at large scale and low-cost. We report a simple method to synthesize 3D graphene by graphenization of coal tar pitch with a K2CO3 catalyst. This produces 3D graphenes with high specific surface areas up to 2113 m2 g-1 and exceptional crystallinity (Raman ID/IG as low as ~ 0.15). The material has an outstanding specific capacitance of 182.6 F g-1 at a current density of 1.0 A g-1. This occurs at mass loading of 30 mg cm-2 which is 3 times higher than commercial requirements, yielding an ultra-high areal capacitance of 5.48 F cm-2. Moreover, the K2CO3 is recycled and reused over 10 cycles. The synthesis method and resulting electrocapacitive performance properties create new opportunities for using 3D graphene more broadly in practical supercapacitor devices.

Pham, Viet Hung↗
DOE OSTI2023

Chemical Insights into the Formation of Colloidal Iridium Nanoparticles from In Situ X-ray Total Scattering: Influence of Precursors and Cations on the Reaction Pathway

Iridium nanoparticles are important catalysts for several chemical and energy conversion reactions. Studies of iridium nanoparticles have also been a key for the development of kinetic models of nanomaterial formation. However, compared to other metals such as gold or platinum, knowledge on the nature of prenucleation species and structural insights into the resultant nanoparticles are missing, especially for nanoparticles obtained from Ir$_x$Cl$_y$ precursors investigated here. We use in situ X-ray total scattering (TS) experiments with pair distribution function (PDF) analysis to study a simple, surfactant-free synthesis of colloidal iridium nanoparticles. The reaction is performed in methanol at 50 °C with only a base and an iridium salt as precursor. From different precursor salts–IrCl 3 , IrCl 4 , H 2 IrCl 6 , or Na 2 IrCl 6 –colloidal nanoparticles as small as Ir ~55 are obtained as the final product. The nanoparticles do not show the bulk iridium face-centered cubic ($fcc$) structure but show decahedral and icosahedral structures. The formation route is highly dependent on the precursor salt used. Using IrCl 3 or IrCl 4 , metallic iridium nanoparticles form rapidly from Ir$_x$Cl$_y$$^{n–}$ complexes, whereas using H 2 IrCl 6 or Na 2 IrCl 6 , the iridium nanoparticle formation follows a sudden growth after an induction period and the brief appearance of a crystalline phase. With H 2 IrCl 6 , the formation of different Ir$_n$ ($n$ = 55, 55, 85, and 116) nanoparticles depends on the nature of the cation in the base (LiOH, NaOH, KOH, or CsOH, respectively) and larger particles are obtained with larger cations. As the particles grow, the nanoparticle structure changes from partly icosahedral to decahedral. In conclusion, the results show that the synthesis of iridium nanoparticles from Ir$_x$Cl$_y$ is a valuable iridium nanoparticle model system, which can provide new compositional and structural insights into iridium nanoparticle formation and growth.

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

Synthesis of NiRu-Layered Double Hydroxide for Enhanced Oxygen Evolution Reaction

Nickel−ruthenium layered double hydroxide (NiRu-LDH) was synthesized by coprecipitation using formamide as both solvent and intercalant. The synthesis was performed at various temperatures to study the impact of temperature on electrochemical performance. Temperature plays a vital role in optimizing LDH synthesis to enhance oxygen evolution reaction (OER) efficiency. The optimal temperature yielded a well-defined morphology with balanced crystallinity, leading to more active sites and improved charge transfer. Electrochemical tests indicated that the NiRu-LDH sample prepared at 50 °C (NiRu-LDH-50) required only 280 mV overpotential versus the reversible hydrogen electrode to achieve 10 mA/cm 2 and exhibited a low Tafel slope of 52 mV/dec, demonstrating excellent catalytic kinetics. This study presents the synthesis of NiRu-LDH via coprecipitation and emphasizes how reaction temperature influences LDH structural properties and OER performance.

Catalysts↗