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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
DOE OSTI2024

Leveraging Triphenylphosphine-Containing Polymers to Explore Design Principles for Protein-Mimetic Catalysts

Complex interactions between noncoordinating residues are significant yet commonly overlooked components of macromolecular catalyst function. While these interactions have been demonstrated to impact binding affinities and catalytic rates in metalloenzymes, the roles of similar structural elements in synthetic polymeric catalysts remain underexplored. Using a model Suzuki–Miyuara cross-coupling reaction, we performed a series of systematic studies to probe the interconnected effects of metal–ligand cross-links, electrostatic interactions, and local rigidity in polymer catalysts. To achieve this, a novel bifunctional triphenylphosphine acrylamide (BisTPPAm) monomer was synthesized and evaluated alongside an analogous monofunctional triphenylphosphine acrylamide (TPPAm). In model copolymer catalysts, increased initial reaction rates were observed for copolymers untethered by Pd complexation (BisTPPAm-containing) compared to Pd-cross-linked catalysts (TPPAm-containing). Further, incorporating local rigidity through secondary structure-like and electrostatic interactions revealed nonmonotonic relationships between composition and the reaction rate, demonstrating the potential for tunable behavior through secondary-sphere interactions. Lastly, through rigorous cheminformatics featurization strategies and statistical modeling, we quantitated relationships between chemical descriptors of the substrate and reaction conditions on catalytic performance. Collectively, these results provide insights into relationships among the composition, structure, and function of protein-mimetic catalytic copolymers.

Catalysts↗
DOE OSTI2017

Exploring Oxygen Activity in the High Energy P2-Type Na 0.78 Ni 0.23 Mn 0.69 O 2 Cathode Material for Na-Ion Batteries

Large-scale electric energy storage is fundamental to the use of renewable energy. Recently, research and development efforts on room-temperature sodium-ion batteries (NIBs) have been revitalized, as NIBs are considered promising, low-cost alternatives to the current Li-ion battery technology for large-scale applications. Herein, we introduce a novel layered oxide cathode material, Na 0.78 Ni 0.23 Mn 0.69 O 2 . This new compound provides a high reversible capacity of 138 mAh g -1 and an average potential of 3.25 V vs Na + /Na with a single smooth voltage profile. Its remarkable rate and cycling performances are attributed to the elimination of the P2-O2 phase transition upon cycling to 4.5 V. The first charge process yields an abnormally excess capacity, which has yet to be observed in other P2 layered oxides. Metal K-edge XANES results show that the major charge compensation at the metal site during Na-ion deintercalation is achieved via the oxidation of nickel (Ni 2+ ) ions, whereas, to a large extent, manganese (Mn) ions remain in their Mn 4+ state. Interestingly, electron energy loss spectroscopy (EELS) and soft X-ray absorption spectroscopy (sXAS) results reveal differences in electronic structures in the bulk and at the surface of electrochemically cycled particles. At the surface, transition metal ions (TM ions) are in a lower valence state than in the bulk, and the O K-edge prepeak disappears. On the basis of previous reports on related Li-excess LIB cathodes, it is proposed that part of the charge compensation mechanism during the first cycle takes place at the lattice oxygen site, resulting in a surface to bulk transition metal gradient. We believe that by optimizing and controlling oxygen activity, Na layered oxide materials with higher capacities can be designed.

25 ENERGY STORAGE↗
DOE OSTI2018

Exploring the alternatives of biological nitrogen fixation

Most biological nitrogen fixation (BNF) results from the activity of the molybdenum nitrogenase (Mo-nitrogenase, Nif), an oxygen-sensitive metalloenzyme complex found in all known diazotrophs.

solar (fuels), biofuels (including algae and bioma↗
DOE OSTI2020

Recent experimental explorations of non-classical nucleation

Nucleation, the early stage of crystallization, is a key step in producing functional materials, but nucleation processes have yet to be understood in detail. Recent advanced characterization techniques, especially atomic force microscopy, liquid-cell transmission electron microscopy (TEM) and cryo-TEM, enable scientists to observe previously inaccessible nucleation details at the nanoscale. In this review, we summarize newly suggested non-classical nucleation models with respect to mechanistic understanding from experimental views, which highlight multi-step nucleation mechanisms. Different intermediated phases such as clusters at the pre-nucleation stage, liquid-like precursors, amorphous phases and even oligomers have been revealed, which play vital roles in nucleation and structure control. Moreover, these intermediated phases practically contribute in general to the structural variances of materials for nanoscience and nanotechnology. Overall, these studies ultimately enable us to control nucleation processes for materials synthesis.

Jin, Biao↗
DOE OSTI2013

Exploring high temperature phenomena related to post-detonation using an electric arc

We report a study of materials recovered from a uranium-containing plasma generated by an electric arc. The device used to generate the arc is capable of sustaining temperatures of an eV or higher for up to 100 μs. Samples took the form of a 4 μm-thick film deposited onto 8 pairs of 17 μm-thick Cu electrodes supported on a 25 μm-thick Kapton backing and sandwiched between glass plates. Materials recovered from the glass plates and around the electrode tips after passage of an arc were characterized using scanning and transmission electron microscopy. Recovered materials included a variety of crystalline compounds (e.g., UO{sub 2}, UC{sub 2}, UCu{sub 5},) as well as mixtures of uranium and amorphous glass. Most of the materials collected on the glass plates took the form of spherules having a wide range of diameters from tens of nanometers to tens of micrometers. The composition and size of the spherules depended on location, indicating different chemical and physical environments. A theoretical analysis we have carried out suggests that the submicron spherules presumably formed by deposition during the arc discharge, while at the same time the glass plates were strongly heated due to absorption of plasma radiation mainly by islands of deposited metals (Cu, U). The surface temperature of the glass plates is expected to have risen to ∼2300 K thus producing a liquefied glass layer, likely diffusions of the deposited metals on the hot glass surface and into this layer were accompanied by chemical reactions that gave rise to the observed materials. These results, together with the compact scale and relatively low cost, suggest that the experimental technique provides a practical approach to investigate the complex physical and chemical processes that occur when actinide-containing material interacts with the environment at high temperature, for example, during fallout formation following a nuclear detonation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗