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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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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Nano-Array Integrated Structured Catalysts: A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts?

The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing multi-fold challenges, including: (1) high Pt-group metals (PGM) material loading being required, driving the market prices; (2) less-than ideal distribution of washcoats in typically square-shaped channels associated with pressure drop sacrifice; and (3) far from clear correlations between macroscopic washcoat structures and their catalytic performance. To tackle these challenges, the well-defined nanostructure array (nano-array)-integrated structured catalysts which we invented and developed recently have been proven to be a promising class of cost-effective and efficient devices that may complement or substitute wash-coated catalysts. This new type of structured catalysts is composed of honeycomb-structured monoliths, whose channel surfaces are grown in situ with a nano-array forest made of traditional binary transition metal oxide support such as Al 2 O 3 , CeO 2 , Co 3 O 4 , MnO 2 , TiO 2 , and ZnO, or newer support materials including perovskite-type ABO3 structures, for example LaMnO 3 , LaCoO 3 , LaNiO, and LaFeO 3 . The integration strategy parts from the traditional washcoat technique. Instead, an in situ nanomaterial assembly method is utilized, such as a hydro (solva-) thermal synthesis approach, in order to create sound structure robustness, and increase ease and complex-shaped substrate adaptability. Specifically, the critical fabrication procedures for nano-array structured catalysts include deposition of seeding layer, in situ growth of nano-array, and loading of catalytic materials. The generic methodology utilization in both the magnetic stirring batch process and continuous flow reactor synthesis offers the nano-array catalysts with great potential to be scaled up readily and cost-effectively. The tunability of the structure and catalytic performance could be achieved through morphology and geometry adjustment and guest atoms and defect manipulation, as well as composite nano-array catalyst manufacture. Excellent stabilities under various conditions were also present compared to conventional wash-coated catalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Metal Oxide Nano-Array Catalysts for Low Temperature Diesel Oxidation. Final Report

In this project, a series of metal oxide nanostructure arrays (nano-arrays) with or without metal decoration, have been successful integrated onto monolithic honeycombs with well-defined size, shape, and chemical compositions, forming a new type of monolithic catalysts. These catalysts have displayed good durability and catalytic performance toward various gas phase catalytic reactions, while showing good potential of reducing the material usage. Specifically in situ grown onto monolithic honeycomb substrates, the metal oxide nanostructure arrays (nano-arrays) (e.g., CeO 2 , Co 3 O 4 , (Cu, Mn)O 2 , (La, Sr)MnO 3 , TiO 2 , etc.), with or without Pt-group metal (PGM) decoration, have displayed good durability and catalytic performance toward catalytic oxidation of hydrocarbons and CO, while showing good potential of reducing the material (noble metal and metal oxides) usage. As unique supports, the nano-array ‘forest-like’ structure configuration proves to improve the dispersion and immobilization of metal nanocatalysts under various aging and reactive conditions, besides the lower pressure drop and improved adherence to the monolith substrates over wash-coated catalysts. On the other hand, electronic interactions between metals and nano-array support are found to be adjustable toward favoring catalytic oxidation while improving the catalyst robustness. Furthermore, chemical leaching treatment in these metal oxide based catalysts could help tune their chemical and structural characteristics, boosting low temperature oxidation reactivity while maintaining robustness. Both CeO 2 and TiO 2 nano-array supported PGM catalysts have shown promising low temperature reactivity with 90% conversion at temperatures approaching 150oC toward CO, HC, and NO x oxidation under both probe and simulated exhaust conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Electrolyzer Integrated Modular Nano-Array Monolithic Catalytic Reactors

The project objective is to design and develop a new class of electrolyzer-integrated, modular, nanostructure array (nano-array) monolithic catalytic reactors for high-flux, robust and selective methanol synthesis. The modular reactor features metal oxide nano-array grown on an additively-manufactured channeled honeycomb monolith made of ceramic or metals; this low-pressure carbon dioxide hydrogenation reactor is fueled with hydrogen from a low-temperature water electrolyzer having reduced platinum group metal (PGM) content. Through these nanostructured monolithic reactors, methanol synthesis is enabled with cost-effective hydrogenation reactions under low-temperature (<200°C) and low-pressure (<10 atm) conditions, thus significantly reducing the energy demand of the entire process.

08 HYDROGEN↗
DOE OSTI2017

Balance on the charge generation, separation and transfer performance of different TiO{sub 2} nanostructures in quantum dot sensitized solar cells

Graphical abstract: QDSSCs with different structure: (a) J-V curves, (b) TRPL spectra. - Highlights: • Charge generation, separation and transfer performance have been balanced by different structures. • Excellent charge separation and transfer performance have been exhibited for nano-array structure. • Nanotube array structure relative better charge generation, excellent charge separation and transfer performance of QDSSCs. - Abstract: TiO{sub 2} nanoparticle and nano-array structures including nanorods, nanowires and nanotubes are prepared for the photo-electrodes of CuInS{sub 2} quantum dot sensitized solar cells, which are investigated the balance on charge generation, separation and transfer performance in solar cells. The optical absorption properties and PL spectra of different photo-electrodes are investigated, which indicates better charge generation property for nanoparticle structure and better charge separation property for nano-arrays structure. With the grain boundary of nanoparticle films and excellent charge transfer performance of nano-arrays films, higher short-circuit current density value has been performed for all the nano-array structure based solar cells. Due to the relative large surface area of three nano-arrays structure for charge generation, excellent charge separation and transfer performance, the TiO{sub 2} nanotube based CuInS{sub 2} quantum dot sensitized solar cells exhibits greater photovoltaic efficiency than other nanostructures, which can support the progress for further photovoltaic performance enhancement on quantum dot sensitized solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2017

High performance diesel oxidation catalysts using ultra-low Pt loading on titania nanowire array integrated cordierite honeycombs

High performance of an ultra-low Pt loading diesel oxidation catalyst can be achieved by using a combination of novel nano-array structured support, precise control of ultrafine active Pt particles, and an addition of H 2 as a promoter into the exhausts. Highly stable mesoporous rutile TiO 2 nano-array was uniformly grown on three-dimensional (3-D) cordierite honeycomb monoliths using a solvothermal synthesis. Atomic layer deposition was employed for precise dispersion of ultrafine Pt particles (0.95 ± 0.24 nm) on TiO 2 nano-array with a Pt loading of 1.1 g/ft 3 . Despite low Pt loading, the Pt/TiO 2 nano-array catalyst shows impressive low-temperature oxidation reactivity, with the conversion of CO and total hydrocarbon (THC) reaching 50% at 224 and 285 °C, respectively, in the clean diesel combustion (CDC) simulated exhaust conditions. The excellent activity is attributed to the unique nano-array structure that promotes gas-solid interaction and ultra-small Pt particle dispersion that increase surface Pt atoms. We also demonstrate that addition of more H 2 into the exhaust can lower light-off temperature for CO and THC by up to ~60 °C and ~30 °C, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Ceria-based nanoflake arrays integrated on 3D cordierite honeycombs for efficient low-temperature diesel oxidation catalyst

A new, surfactant-free hydrothermal method has been developed for the growth of CeO 2 -based nanoflake arrays onto three-dimensional-channeled cordierite honeycomb substrates. Herein, a leaching-crystallization mechanism was proposed where the hydrothermal reaction, only involving cerium nitrate and water, leached the cordierite surface slightly and induced the formation of CeO 2 nanoparticles subsequently. Further continued reaction reincorporated Al and Si atoms leached from cordierite into CeO 2 , finally recrystallizing Ce-Al-Si composite nanoflake structures. Here, by using atomic layer deposition process, well-dispersed, size-controlled Pt nanoparticles were uniformly decorated on the CeO 2 -based nanoflakes to form the Pt/ CeO 2 nano-array-based monolithic catalyst. Despite 5-50 times reduction in the active material usage compared with the traditional wash-coated catalyst, the Pt/CeO 2 nano-array monolithic catalyst exhibited good catalytic oxidation activities over various individual gases, such as propylene, propane, CO, and NO oxidation, with 90% conversion efficiencies at temperatures below 200 °C. Under the simulated exhaust condition of low-temperature diesel combustion (LTC-D) developed by US DRIVE, the monolithic catalyst with low Pt loading (˜1 g/l) exhibits 90% conversion of catalytic oxidation over CO and hydrocarbonsat temperatures as low as ˜180 °C, much superior to the performance of traditional washcoated catalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Surface-Enhanced Raman Scattering (SERS) Studies of Disc-on-Pillar (DOP) Arrays: Contrasting Enhancement Factor with Analytical Performance

The use of nanomachining methods capable of reproducible construction of nano-arrayed devices have revolutionized the field of plasmonic sensing by the introduction of a diversity of rationally engineered designs. Significant strides have been made to fabricate plasmonic platforms with tailored interparticle gaps to improve their performance for surface-enhanced Raman scattering (SERS) applications. Over time, a dichotomy has emerged in the implementation of SERS for analytical applications, the construction of substrates, optimization of interparticle spacing as a means to optimize electromagnetic field enhancement at the localized surface plasmon level, and the substrate sensitivity over extended areas to achieve quantitative performance. Here, we assessed the enhancement factor of plasmonic Ag/SiO 2 /Si disc-on-pillar (DOP) arrays of variable pitch with its analytical performance for quantitative applications. Experimental data were compared with those from finite-difference time-domain (FDTD) simulations used in the optimization of the array dimensions. A self-assembled monolayer (SAM) of benzenethiol rendered highly reproducible signals (RSD ~4–10%) and SERS substrate enhancement factor (SSEF) values in the orders of 10 6 –10 8 for all pitches. Furthermore, spectra corresponding to rhodamine 6G (R6G) and 4-aminobenzoic acid demonstrated the advantages of using the more densely packed DOP arrays with a 160 nm pitch (gap= 40 nm) for quantitation in spite of the strongest SSEF was attained for a pitch of 520 nm corresponding to a 400 nm gap.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Rooting binder-free tin nanoarrays into copper substrate via tin-copper alloying for robust energy storage

The need for high-energy batteries has driven the development of binder-free electrode architectures. However, the weak bonding between the electrode particles and the current collector cannot withstand the severe volume change of active materials upon battery cycling, which largely limit the large-scale application of such electrodes. Using tin nanoarrays electrochemically deposited on copper substrate as an example, here we demonstrate a strategy of strengthening the connection between electrode and current collector by thermally alloying tin and copper at their interface. The locally formed tin-copper alloys are electron-conductive and meanwhile electrochemically inactive, working as an ideal "glue" robustly bridging tin and copper to survive harsh cycling conditions in sodium ion batteries. The working mechanism of the alloy "glue" is further characterized through a combination of electrochemical impedance spectroscopy, atomic structural analysis and in situ X-ray diffraction, presenting itself as a promising strategy for engineering binder-free electrode with endurable performance. The authors here report a binder-free electrode based on tin nanoarrays deposited on copper substrate. It is found that the locally formed electrochemically inactive tin-copper alloys work as a glue that bridges tin and copper to survive harsh cycling conditions in sodium ion batteries.

25 ENERGY STORAGE↗