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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 OSTI2023

Ni/CeO 2 Nanocatalysts with Optimized CeO 2 Support Morphologies for CH 4 Oxidation

Catalytic oxidation of CH 4 over nonprecious Ni/CeO 2 catalysts has attracted wide attention. Controlling the morphology of a CeO 2 support can enhance the CH 4 oxidation activity without changing the catalyst composition. Here, in this paper, a series of 2 wt % Ni/CeO 2 nanocatalysts with different CeO 2 support morphologies (nanoparticles (P), rods (R), cubes (C)) and synthetic procedures (precipitation, sol-gel (SG)) were evaluated for their CH 4 oxidation performance. The redox properties of CeO 2 supports and corresponding Ni loaded catalysts were characterized by H 2 -temperature-programmed reduction and oxygen storage capacity (OSC) measurements. The relationship among the CeO 2 morphologies, surface areas, redox properties, and CH4 oxidation activity for both CeO 2 supports and Ni/CeO 2 catalysts was established. The findings suggest that CeO 2 -R has a greater amount of surface oxygen vacancies as well as an improved OSC and CH4 oxidation activity compared to CeO 2 -P and CeO 2 -C supports. The same CH 4 oxidation activity pattern was observed for the Ni containing catalysts (Ni/CeO 2 -R > Ni/CeO 2 -P > Ni/CeO 2 -C). Increasing the CeO 2 surface area by using a sol-gel synthesis method (CeO 2 -SG) improved the amount of surface oxygen vacancies and CH 4 oxidation performance of CeO 2 -SG and Ni/CeO 2 -SG compared to CeO 2 -R and Ni/CeO 2 -R, respectively. Finally, all studied Ni/CeO 2 nanocatalysts showed improved hydrothermal stability compared to conventional Pd/Al 2 O 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Preparation of SBA-15-Supported Metals by Vapor-Phase Infiltration

A simple method is presented for incorporating various catalytic metals into the pores of SBA-15 using vapor-phase infiltration. The precursors used in Atomic Layer Deposition (ALD) for Pt, Pd, Rh, Ru, and Ni were exposed to an evacuated SBA-15, resulting in monolayer films of the adsorbed precursors inside the mesopores. The metal particles that formed after removal of the precursor ligands remained in the pores and had particle sizes ranging from 3.8 nm for Pt to 5.2 nm for Ni, as determined by Transmission Electron Microscopy (TEM), XRD, and CO chemisorption. Metal loadings for saturation exposures ranged from 5.1-wt% for Ni to 9.1-wt% for Pt; however, uniform deposition was demonstrated for lower loadings of Pd by decreasing the amount of precursor. To determine the effect of the surface composition of the mesopores, Pd particles were also added to SBA-15 that was coated with a 0.2-nm film of ZrO2.

Rh↗
DOE OSTI2024

Growth of Well-Defined Model Catalysts for Electrochemistry: From Surface Science Studies to Electrocatalytic CO2 Conversion

We combined ultrahigh vacuum (UHV) surface science techniques, electrochemical measurements, and computational modeling to investigate electrocatalytic systems that are crucial components of the carbon management effort, including oxygen evolution reactions (OER) and CO2 reduction reactions (CO2RR). Well-defined Model catalysts were grown on substrates in the UHV chamber and characterized with X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Selected model electrocatalysts were then tested in electrochemical cells to establish the structure-property relationships in OER and CO2RR. Our results showed that the edge sites of Fe2O3 grown on Au(111) were the most active toward OER and incorporation of Ni at the edge sites (NiFeOx) further boosted their OER activity. We also resolved the size-dependent electrocatalytic CO2-to-CO conversion of the Ag nanoparticle electrocatalysts with average particle diameter between 2 to 6 nm: smaller diameter (< 3 nm) particles favored H2 evolution reaction (HER) due to a high population of Ag edge sites, whereas larger diameter particles favored CO2RR as the population of Ag(100) surface sites grew. We further discovered that electronic interactions between small diameter Ag particles and highly defective carbon supports could break the size-dependent CO2RR selectivity, resulting in highly selective (CO Faradaic Efficiency > 90%) and active Ag nanoparticle electrocatalysts with sizes < 2 nm diameter.

Deng, Xingyi↗
DOE OSTI2024

Effective Modulation of Interlayer Excitons in WSe 2 /WS 2 Heterostructures by Plasmon–Exciton Interaction

Effective charge transfer and carrier separation at the interface are paramount for optimizing the performance of devices based on van der Waals heterostructures. In this investigation, surface plasmons generated by gold nanoparticles are employed to modulate the photocarrier dynamics in WSe 2 /WS 2 heterostructures. The results of pump-probe measurements reveal that the efficiency of carrier transfer across the WSe 2 /WS 2 heterostructure interface can be significantly enhanced via energy transfer mechanisms mediated by gold plasmons. Moreover, the electric field engendered by the plasmonic oscillations can modulate the dipole moment of the interlayer exciton. These well-aligned excitons avoid the annihilation and the extension of the lifetime of the excitons with increased pump power is realized by screening effect. The findings presented herein offer valuable insights for the active manipulation of charge transfer and extend our understanding of the integral role played by plasmon-exciton coupling in mediating charge separation in van der Waals heterostructures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

A General Strategy to Immobilize Single‐Atom Catalysts in Metal–Organic Frameworks for Enhanced Photocatalysis

Abstract Single‐atom catalysts (SACs) are witnessing rapid development due to their high activity and selectivity toward diverse reactions. However, it remains a grand challenge in the general synthesis of SACs, particularly featuring an identical chemical microenvironment and on the same support. Herein, a universal synthetic protocol is developed to immobilize SACs in metal–organic frameworks (MOFs). Significantly, by means of SnO 2 as a mediator or adaptor, not only different single‐atom metal sites, such as Pt, Cu, and Ni, etc., can be installed, but also the MOF supports can be changed (for example, UiO‐66‐NH 2 , PCN‐222, and DUT‐67) to afford M 1 /SnO 2 /MOF architecture. Taking UiO‐66‐NH 2 as a representative, the Pt 1 /SnO 2 /MOF exhibits approximately five times higher activity toward photocatalytic H 2 production than the corresponding Pt nanoparticles (≈2.5 nm) stabilized by SnO 2 /UiO‐66‐NH 2 . Remarkably, despite featuring identical parameters in the chemical microenvironment and support in M 1 /SnO 2 /UiO‐66‐NH 2 , the Pt 1 catalyst possesses a hydrogen evolution rate of 2167 µmol g –1 h –1 , superior to the Cu 1 and Ni 1 counterparts, which is attributed to the differentiated hydrogen binding free energies, as supported by density‐functional theory (DFT) calculations. This is thought to be the first report on a universal approach toward the stabilization of SACs with identical chemical microenvironment on an identical support.

Sui, Jianfei↗
DOE OSTI2021

Reduction and Agglomeration of Supported Metal Clusters Induced by High-Flux X-ray Absorption Spectroscopy Measurements

Supported metal clusters are widely used in catalysis for many important reactions. To understand the catalytic properties, in situ/operando characterization techniques, such as X-ray absorption spectroscopy (XAS), provide essential details of the size, shape, and chemical composition of the cluster and the nature of the active sites. New-generation synchrotrons combined with focusing beamlines provide high-flux-density X-rays for improved detection sensitivity as well as higher time and spatial resolution. Understanding the effects of a high-flux-density X-ray beam on the catalyst during the actual measurement, whether XAS or another synchrotron-based technique, is crucial. This is especially important for in situ and operando studies where both the high flux density and reaction conditions can affect the catalyst structure. In this work, we investigated the effect of the flux density on rhodium clusters supported on Al 2 O 3 at two different beamlines: National Synchrotron Light Source II beamline 08-ID and Stanford Synchrotron Radiation Light Source (SSRL) beamline 4-1. We show that the higher flux density at beamline 08-ID causes the reduction of the highly dispersed RhO x /Al 2 O 3 catalyst, even at room temperature. Additionally, exposure to the higher flux density X-rays at beamline 08-ID during in situ reduction results in significant agglomeration of the Rh clusters. The final size of the Rh nanoparticles reduced at 310 °C is equivalent to that of particles formed after the reduction at 600–650 °C in the absence of the beam. Significant beam-induced reduction and agglomeration is also shown for Ni supported on beta zeolite during in situ reduction at an intermediate-flux-density beamline 9-3 at SSRL, indicating that beam-induced changes in heterogeneous catalysts could be common at intermediate- and high-flux-density beamlines. We provide precautions and recommendations for detecting and minimizing beam damage during in situ/operando XAS measurements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

A general strategy for preparing pyrrolic-N 4 type single-atom catalysts via pre-located isolated atoms

Single-atom catalysts (SACs) have been applied in many fields due to their superior catalytic performance. Because of the unique properties of the single-atom-site, using the single atoms as catalysts to synthesize SACs is promising. In this work, we have successfully achieved Co 1 SAC using Pt 1 atoms as catalysts. More importantly, this synthesis strategy can be extended to achieve Fe and Ni SACs as well. X-ray absorption spectroscopy (XAS) results demonstrate that the achieved Fe, Co, and Ni SACs are in a M1-pyrrolic N 4 (M= Fe, Co, and Ni) structure. Density functional theory (DFT) studies show that the Co(Cp) 2 dissociation is enhanced by Pt 1 atoms, thus leading to the formation of Co 1 atoms instead of nanoparticles. These SACs are also evaluated under hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the nature of active sites under HER are unveiled by the operando XAS studies. These new findings extend the application fields of SACs to catalytic fabrication methodology, which is promising for the rational design of advanced SACs.

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

Single-phase Ru 1- x-y Mn x Co y O 2 nanoparticles as highly effective oxygen reduction electrocatalysts in alkaline media with enhanced stability and fuel-tolerance

Here, a series of single-phase binary and ternary ruthenium and transition metal oxide nanoparticles supported on Vulcan - Ru 1-x MnxO2/C, Ru1-xCoxO 2 /C, Ru 1-x-y MnxCo y O 2 /C, Ru 1-x Fe x O 2 /C, Ru 1-x Ni x O 2 /C and Ru 1-x V x O 2 /C, as well as RuO 2 /C, MnO 2 /C, Co 3 O 4 /C and Mn 3-x Co x O 4 /C - were synthesized via a facile method and studied for their oxygen reduction reaction (ORR) activity in alkaline media. Single-phase Ru 1-x Mn x O 2 /C, Ru 1-x-y Mn x Co y O 2 /C and Ru 1-x Co x O 2 /C catalysts significantly boosted ORR kinetics in alkaline media. Moreover, they were H 2 and methanol tolerant, and exhibited long term stability due to their single-phase structure. Ru 0.85 Mn 0.15 O 2 /C stood out as the most active catalyst among them. A volcano relationship of the ORR activity of these binary and ternary metal oxide catalysts vs. the O adsorption energy was found, with the maximum activity observed for the Ru 1-x Mn x O 2 /C, Ru 1-x-y Mn x Co y O 2 /C and Ru 1-x Co x O 2 /C catalysts due to their optimal O binding energy. These materials have potential applications as highly active ORR catalysts in alkaline fuel cells and metal-air batteries.

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

Electrocatalytic Oxidative Coupling of Methane on NiFe Exsolved Perovskite Anode: Effect of Water

Oxidative coupling of methane (OCM) can be performed electrocatalytically by utilizing solid oxide cells, which provide a readily controlled oxygen supply through dense electrolytes. La 0.7 Sr 0.2 Ni 0.2 Fe 0.8 O 3 (LSNF) perovskite is an effective anode for OCM. Its surface characteristics and electrocatalytic activity can be improved by reduction and the resultant exsolution of bimetallic NiFe nanoparticles from its bulk. X-ray diffraction (XRD) and environmental transmission electron microscopy proved that the evolution of hetero-phases under reducing environment resulted in bimetallic NiFe nanoparticles being formed on the surface. Further, a 36 % improvement in C 2+ hydrocarbon production rate was achieved due to the reduction of LSNF with the exsolved NiFe nanoparticles. Co-feeding of H 2 O enhanced selective conversion of CH 4 resulting in the production rate of C 2+ hydrocarbons being increased by 56 %. Analysis of impedance spectra and in-situ DRIFTS under a CH 4 +H 2 O atmosphere provided an understanding for the enhancement on the electrocatalytic OCM.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Coupling Amorphization and Compositional Optimization of Ternary Metal Phosphides toward High-Performance Electrocatalytic Hydrogen Production

Amorphous materials, with abundant active sites and unique electronic configurations, have the potential to outperform their crystalline counterparts in high-performance catalysis for clean energy. However, their synthesis and compositional optimization remain underexplored due to the strict conditions required for their formation. Here, in this study, we report the synthesis of ternary platinum-nickel-phosphorus (PtNiP) amorphous nanoparticles (ANPs) within milliseconds by flash Joule heating, which features ultrafast cooling that enables the vitrification of metal precursors. Through compositional optimization, the Gibbs free energy of hydrogen adsorption for Pt 4 Ni 4 P 1 ANPs is optimized at 0.02 eV, an almost ideal value, even surpassing that of the benchmark metallic platinum catalyst. As a result, the PtNiP ANPs exhibited superior activity in electrocatalytic hydrogen evolution in acid electrolyte (η 10 ∼ 14 mV, Tafel slope ∼ 18 mV dec –1 , and mass activity 5× higher than state-of-the-art Pt/C). Life-cycle assessment and technoeconomic analysis suggest that, compared to existing processes, our approach enables notable reductions in greenhouse gas emission, energy consumption, and production cost for practical electrolyzer catalyst manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Hierarchical low Pt-loading “core-shell” electrocatalysts for the oxygen reduction reaction in fuel cells

The sluggish kinetics of the oxygen reduction reaction (ORR) hinder cost-effective polymer electrolyte fuel cells (PEFCs), which rely on scarce, expensive platinum-based electrocatalysts (ECs). Here, we present a novel synthesis method for ORR ECs achieving exceptional platinum utilization. The design features a hierarchical “multi-carbon” support comprising carbon nanoparticles interacting with graphene nanoplatelets as the “core”, encapsulated by a porous carbon nitride (CN) “shell”. This configuration promotes strong core/shell interactions and a bimodal active site distribution, consisting of chemically dispersed Pt and Ni single-atom complexes and PtNix alloy nanoclusters embedded in the CN shell. These advantages enable high activity and durability, achieving an ORR activity of 1.6 A mgPt−1 at 0.9 V vs. RHE-an order of magnitude higher than Pt/C (0.17 A mgPt−1). A proof-of-concept PEFC demonstrates a specific power of 12.0 kW gPt−1 at 0.60 V. This approach offers a significant step toward more efficient and sustainable PEFC technologies.

Pagot, Gioele [University of Padova, Italy]↗
DOE OSTI2022

Anodic Shock-Triggered Exsolution of Metal Nanoparticles from Perovskite Oxide

Nanoparticles decorated electrodes (NDEs) are useful in fuel cells, electrolyzers, water treatment, and chemical synthesis. Here, in this study, we show that by rapidly bringing a mixed ionic-electronic conductor outside its electrochemical stability window, one can achieve uniform dispersion of metallic nanoparticles inside its bulk and at the surface and improve its electrocatalytic performance when back under normal functional conditions. Surprisingly, this can happen under anodic as well as cathodic current/voltage shocks in an ABO 3 perovskite oxide, La 0.4 Ca 0.4 Ti 0.88 Fe 0.06 Ni 0.06 O 3-δ (LCTFN), across a wide range of H 2 /O 2 gas environments at 800 °C. One possible mechanism for bulk Fe 0 /Ni 0 precipitation under anodic shock condition is the incomplete oxygen oxidation (O 2 – → O α– , 0 < α < 2), migration and escape of oxygen to interfaces, and “whiplash” transition-metal reduction due to low electronic conductivity. We show that both cathodic and anodic shocks can produce NDEs to enhance electrocatalytic performance, potentially improving the flexibility of this approach in practical devices.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Variable Effects of Dispersed Nanoparticles on Triboelectric Nanogenerators

Technology has recently seen a drastic physical downsizing. Wearable and small devices with lower power demands have become the norm and continue to be more prominent in daily life. With modern devices growing smaller and requiring less electricity, a power source will always be needed. Contemporary batteries are the most common means to power small electronics. However, reliance on conventional batteries may prove insufficient due to the non renewable resources (Li, Ni, Co) required to power the growing number of individual devices each person may own. Additionally, the infrastructure required to harvest and recycle the sheer number of batteries produced presents a further logistic issue to be addressed. A promising alternative to batteries is the usage of triboelectric nanogenerators (TENGs). TENGs are a class of energy harvesting devices that utilize triboelectric generation to convert mechanical/kinetic energy into electrical energy and have exhibited efficiencies up to 85 % at low frequencies. TENGs exhibit a high voltage but low current. Even with the high voltage, the low current output proves to be a significant factor preventing undoped TENGs from being commercially viable. This review will investigate factors that increase the total current produced by TENGs when nanoparticles are utilized in TENGs. Factors such as increasing porosity, surface area, surface charge density, charge storage, deep trap formation, and dielectric constant can be altered to affect the total current by impregnating nanoparticles into the polymer material will be explored.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Variable Effects of Dispersed Nanoparticles on Triboelectric Nanogenerators

Technology has recently seen a drastic physical downsizing. Wearable and small devices with lower power demands have become the norm and continue to be more prominent in daily life. With modern devices growing smaller and requiring less electricity, a power source will always be needed. Contemporary batteries are the most common means to power small electronics. However, reliance on conventional batteries may prove insufficient due to the non renewable resources (Li, Ni, Co) required to power the growing number of individual devices each person may own. Additionally, the infrastructure required to harvest and recycle the sheer number of batteries produced presents a further logistic issue to be addressed. A promising alternative to batteries is the usage of triboelectric nanogenerators (TENGs). TENGs are a class of energy harvesting devices that utilize triboelectric generation to convert mechanical/kinetic energy into electrical energy and have exhibited efficiencies up to 85 % at low frequencies. TENGs exhibit a high voltage but low current. Even with the high voltage, the low current output proves to be a significant factor preventing undoped TENGs from being commercially viable. This review will investigate factors that increase the total current produced by TENGs when nanoparticles are utilized in TENGs. Factors such as increasing porosity, surface area, surface charge density, charge storage, deep trap formation, and dielectric constant can be altered to affect the total current by impregnating nanoparticles into the polymer material will be explored.

42 ENGINEERING↗
DOE OSTI2021

Revealing High-Temperature Reduction Dynamics of High-Entropy Alloy Nanoparticles via In Situ Transmission Electron Microscopy

Understanding the behavior of high-entropy alloy (HEA) materials under hydrogen (H 2 ) environment is of utmost importance for their promising applications in structural materials, catalysis, and energy-related reactions. Herein, the reduction behavior of oxidized FeCoNiCuPt HEA nanoparticles (NPs) in atmospheric pressure H-2 environment was investigated by in situ gas-cell transmission electron microscopy (TEM). The reduction reaction front was maintained at the external surface of the oxide. During reduction, the oxide layer expanded and transformed into porous structures where oxidized Cu was fully reduced to Cu NPs while Fe, Co, and Ni remained in the oxidized form. In situ chemical analysis showed that the expansion of the oxide layer resulted from the outward diffusion flux of all transition metals (Fe, Co, Ni, Cu). Revealing the H-2 reduction behavior of HEA NPs facilitates the development of advanced multicomponent alloys for applications targeting H 2 formation and storage, catalytic hydrogenation, and corrosion removal.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Lanthanum-based double perovskite nanoscale motifs as support media for the methanol oxidation reaction

In this report we have not only analyzed the performance of perovskite oxides as support media for the methanol oxidation reaction (MOR) but also examined the impact and significance of various reaction parameters on their synthesis. Specifically, we have generated (a) La 2 NiMnO 6 , LaMnO 3 , and LaNiO 3 nanocubes with average sizes of ~200 nm, in addition to a series of La 2 NiMnO 6 (b) nanocubes possessing average sizes of ~70 and 400 nm and (c) anisotropic nanorods characterized by average diameters of 40-50 nm. All of these samples, when used as supports for Pt nanoparticles, exhibited activities which were at least twice that measured for Pt/C. We have investigated and correlated the effect of varying perovskite (i) composition, (ii) size, and (iii) morphology upon the measured MOR activity. (i) The Ni-containing perovskites yielded generally higher performance metrics than LaMnO 3 alone, suggesting that the presence of Ni is favorable for MOR, a finding supported by a shift in the Pt d-band in XPS. (ii) MOR activity is enhanced as the perovskite size increases in magnitude, suggesting that a growth in the perovskite particle size enables favorable, synergistic metal–support interactions. (iii) A comparison of the nanorods and nanocubes of a similar diameter implied that the one-dimensional morphology achieved a greater activity, a finding which can be attributed not only to the anisotropic structure but also to a desirable surface structure. Overall, these data yield key insights into the tuning of metal–support interactions via rational control over the composition, size, and morphology of the underlying catalyst support.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗