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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Ultrasmall Cu Nanoparticles Supported on Crystalline, Mesoporous ZnO for Selective CO 2 Hydrogenation

Converting CO 2 to value-added chemicals, e. g., CH 3 OH, is highly desirable in terms of the carbon cycling while reducing CO 2 emission from fossil fuel combustion. Cu-based nanocatalysts are among the most efficient for selective CO 2 -to-CH 3 OH transformation; this conversion, however, suffers from low reactivity especially in the thermodynamically favored low temperature range. We herein report ultrasmall copper (Cu) nanocatalysts supported on crystalline, mesoporous zinc oxide nanoplate (Cu@mZnO) with notable activity and selectivity of CO 2 -to-CH 3 OH in the low temperature range of 200–250 °C. Cu@mZnO nanoplates are prepared based on the crystal-crystal transition of mixed Cu and Zn basic carbonates to mesoporous metal oxides and subsequent hydrogen reduction. Under the nanoconfinement of mesopores in crystalline ZnO frameworks, ultrasmall Cu nanoparticles with an average diameter of 2.5 nm are produced. Cu@mZnO catalysts have a peak CH 3 OH formation rate of 1.13 mol h −1 per 1 kg under ambient pressure at 246 °C, about 25 °C lower as compared to that of the benchmark catalyst of Cu−Zn−Al oxides. In conclusion, our new synthetic strategy sheds some valuable insights into the design of porous catalysts for the important conversion of CO 2 -to-CH 3 OH.

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

Changing Directions: Influence of Ligand Electronics on the Directionality and Kinetics of Photoinduced Charge Transfer in Cu(I)Diimine Complexes

A key challenge to the effective utilization of solar energy is to promote efficient photoinduced charge transfer, specifically avoiding unproductive, circuitous electron-transfer pathways and optimizing the kinetics of charge separation and recombination. We hypothesize that one way to address this challenge is to develop a fundamental understanding of how to initiate and control directional photoinduced charge transfer, particularly for earth-abundant first-row transition-metal coordination complexes, which typically suffer from relatively short excited-state lifetimes. Here, in this paper, we report a series of functionalized heteroleptic copper(I)bis(phenanthroline) complexes, which have allowed us to investigate the directionality of intramolecular photoinduced metal-to-ligand charge transfer (MLCT) as a function of the substituent Hammett parameter. Ultrafast transient absorption suggests a complicated interplay of MLCT localization and solvent interaction with the Cu(II) center of the MLCT state. This work provides a set of design principles for directional charge transfer in earth-abundant complexes and can be used to efficiently design pathways for connecting the molecular modules to catalysts or electrodes and integration into systems for light-driven catalysis.

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

Cu and Ni Co-sputtered heteroatomic thin film for enhanced nonenzymatic glucose detection

Abstract In this work, we report a wafer-scale and chemical-free fabrication of nickel (Ni) and copper (Cu) heteroatomic Cu–Ni thin films using RF magnetron sputtering technique for non-enzymatic glucose sensing application. The as-prepared wafer-scale Cu–Ni thin films exhibits excellent electrocatalytic activity toward glucose oxidation with a 1.86 μM detection limit in the range of 0.01 mM to 20 mM range. The Cu–Ni film shows 1.3- and 5.4-times higher glucose oxidation activity in comparison to the Cu and Ni electrodes, respectively. The improved electrocatalytic activity is attributed to the synergistic effect of the bimetallic catalyst and high density of grain boundaries. The Cu–Ni electrodes also possessed excellent anti-interference characteristics. These results indicate that Cu–Ni heteroatomic thin film can be a potential candidate for the development of non-enzymatic glucose biosensor because of its chemical free synthesis, excellent reproducibility, reusability, and long-term stability.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Nanostructured mixed metal oxides as catalysts and method of making thereof

A method of forming a metal oxide material having a rod shape or polyhedral nanostructure includes preparing a first reverse micro-emulsion system comprising an aqueous precipitating agent dispersion and a second reverse micro-emulsion system containing an aqueous metal salt dispersion; combining the micro-emulsions together to initiate a reaction; allowing the reaction to continue to form a product mixture comprising a metal oxide gel and aqueous media; separating the metal oxide gel from the aqueous media; collecting the metal oxide gel; and calcining the metal oxide gel to form the metal oxide material. The metal oxide material corresponds to the chemical formula of La2MxNi1-xO4, Pr2-yAyNiO4, or La2-zDzNiO4, wherein M is copper, cobalt, iron, manganese, chromium, aluminum, or platinum; A is lanthanum or neodymium; D is calcium, barium or strontium; x ranges from 0 to 1; y ranges from 0 to 2; and z ranges from 0 to 0.25.

Nikolla, Eranda↗
DOE OSTI2021

Gold-in-copper at low *CO coverage enables efficient electromethanation of CO 2

The renewable-electricity-powered CO 2 electroreduction reaction provides a promising means to store intermittent renewable energy in the form of valuable chemicals and dispatchable fuels. Renewable methane produced using CO 2 electroreduction attracts interest due to the established global distribution network; however, present-day efficiencies and activities remain below those required for practical application. Here we exploit the fact that the suppression of *CO dimerization and hydrogen evolution promotes methane selectivity: we reason that the introduction of Au in Cu favors *CO protonation vs. C-C coupling under low *CO coverage and weakens the *H adsorption energy of the surface, leading to a reduction in hydrogen evolution. We construct experimentally a suite of Au-Cu catalysts and control *CO availability by regulating CO 2 concentration and reaction rate. This strategy leads to a 1.6× improvement in the methane:H 2 selectivity ratio compared to the best prior reports operating above 100 mA cm -2 . We as a result achieve a CO 2 -to-methane Faradaic efficiency (FE) of (56 ± 2)% at a production rate of (112 ± 4) mA cm -2 .

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

Platinum on High-Entropy Aluminate Spinels as Thermally Stable CO Oxidation Catalysts

Thermal degradation is a leading cause of automotive catalyst deactivation. Because high-entropy oxides are uniquely stabilized at high temperatures via an increase in configurational entropy, these materials may offer new mechanisms for preventing the thermal deactivation of precious metal catalysts. In this work, we evaluated platinum loaded on simple and high-entropy aluminate spinels (MAl 2 O 4 , where M = Co, Cu, Mg, Ni, or mixtures thereof) in carbon monoxide oxidation before and after aging at 800 °C. Pt supported on all simple spinels showed significant deactivation after thermal aging compared to the fresh samples, with T 90 increasing by at least 60 °C. However, Pt on high-entropy spinels had nearly the same or better activity after aging, with T 90 increasing by only 6 °C at most. During aging and reduction, copper exsolved from the spinel supports and alloyed with platinum. This interaction promoted low temperature oxidation activity, presumably through weakened CO binding, but did not prevent deactivation. On the other hand, Co, Mg, and Ni constituents promoted stronger CO bonding, as evidenced by apparent negative order kinetics and poor activity at low temperatures. High-entropy spinels, containing a variety of active metals, displayed synergetic reactant adsorption capacity and cooperative effects with supported platinum particles, which collectively prevented thermal deactivation.

CO oxidation↗
DOE OSTI2020

The impact of nitrogen oxides on electrochemical carbon dioxide reduction

The electroreduction of carbon dioxide offers a promising avenue to produce valuable fuels and chemicals using greenhouse gas carbon dioxide as the carbon feedstock. Because industrial carbon dioxide point sources often contain numerous contaminants, such as nitrogen oxides, understanding the potential impact of contaminants on carbon dioxide electrolysis is crucial for practical applications. Herein, we investigate the impact of various nitrogen oxides, including nitric oxide, nitrogen dioxide, and nitrous oxide, on carbon dioxide electroreduction on three model electrocatalysts (i.e., copper, silver, and tin). We demonstrate that the presence of nitrogen oxides (up to 0.83%) in the carbon dioxide feed leads to a considerable Faradaic efficiency loss in carbon dioxide electroreduction, which is caused by the preferential electroreduction of nitrogen oxides over carbon dioxide. The primary products of nitrogen oxides electroreduction include nitrous oxide, nitrogen, hydroxylamine, and ammonia. Despite the loss in Faradaic efficiency, the electrocatalysts exhibit similar carbon dioxide reduction performances once a pure carbon dioxide feed is restored, indicating a negligible long-term impact of nitrogen oxides on the catalytic properties of the model catalysts.

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

Synthesis of core/shell nanocrystals with ordered intermetallic single-atom alloy layers for nitrate electroreduction to ammonia

Structurally ordered intermetallic nanocrystals (NCs) and single-atom catalysts (SACs) are two emerging catalytic motifs for sustainable chemical production and energy conversion. However, both have synthetic limitations which can lead to the aggregation of NCs or metal atoms. Single-atom alloys (SAAs), which contain isolated metal atoms in a host metal, can overcome the aggregation concern because of the thermodynamic stabilization of single atoms on host metal surfaces. We report a direct solution-phase synthesis of Cu/CuAu core/shell NCs with tunable SAA layers. This synthesis can be extended to other Cu/CuM (M = Pt, Pd) systems, in which M atoms are isolated in the copper host. Using this method, the density of SAAs on a copper surface can be controlled, resulting in both low and high densities of single atoms. Alloying gold into the copper matrix introduced ligand effects that optimized the chemisorption of *NO 3 and *N. As a result, the densely packed Cu/CuAu material demonstrated a high selectivity toward NH 3 from the electrocatalytic nitrate reduction reaction with an 85.5% Faradaic efficiency while maintaining a high yield rate of 8.47 mol h -1 g -1 . This work advances the design of atomically precise catalytic sites by creating core/shell NCs with SAA atomic layers, opening an avenue for broad catalytic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Electrocatalytic CO 2 Reduction to Fuels: Progress and Opportunities

The electrochemical reduction of CO 2 continues to be an appealing option for storing renewable energy in a chemical form. In this review, we assess progress in designing catalysts that convert CO 2 to high energy density products. We explain how reaction data can be reported to reflect the intrinsic properties of the catalyst. This analysis shows that limited advances have been made in improving the performance of Cu. We suggest that opportunities remain using bimetallic catalysts that are resistant to dealloying. While aqueous systems are instrumental to developing our understanding of this chemistry, gas-fed systems that operate at high current densities must be developed. Although obstacles remain for practical application of CO 2 reduction, advances in fundamental understanding made over the years give reason for optimism.

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

Engineering a Cu‐Pd Paddle‐Wheel Metal–Organic Framework for Selective CO 2 Electroreduction

Optimizing the binding energy between the intermediate and the active site is a key factor for tuning catalytic product selectivity and activity in the electrochemical carbon dioxide reduction reaction. Copper active sites are known to reduce CO 2 to hydrocarbons and oxygenates, but suffer from poor product selectivity due to the moderate binding energies of several of the reaction intermediates. Here, we report an ion exchange strategy to construct Cu−Pd paddle wheel dimers within Cu-based metal–organic frameworks (MOFs), [Cu 3-x Pd x (BTC) 2 ] (BTC=benzentricarboxylate), without altering the overall MOF structural properties. Compared to the pristine Cu MOF ([Cu 3 (BTC) 2 ], HKUST-1), the Cu−Pd MOF shifts CO 2 electroreduction products from diverse chemical species to selective CO generation. In situ X-ray absorption fine structure analysis of the catalyst oxidation state and local geometry, combined with theoretical calculations, reveal that the incorporation of Pd within the Cu−Pd paddle wheel node structure of the MOF promotes adsorption of the key intermediate COOH* at the Cu site. This permits CO-selective catalytic mechanisms and thus advances our understanding of the interplay between structure and activity toward electrochemical CO 2 reduction using molecular catalysts.

CO2 electroreduction reaction↗
DOE OSTI2021

2D Copper Tetrahydroxyquinone Conductive Metal–Organic Framework for Selective CO 2 Electrocatalysis at Low Overpotentials

Abstract Metal–organic frameworks (MOFs) are promising materials for electrocatalysis; however, lack of electrical conductivity in the majority of existing MOFs limits their effective utilization in the field. Herein, an excellent catalytic activity of a 2D copper (Cu)‐based conductive MOF, copper tetrahydroxyquinone (CuTHQ), is reported for aqueous CO 2 reduction reaction (CO 2 RR) at low overpotentials. It is revealed that CuTHQ nanoflakes (NFs) with an average lateral size of 140 nm exhibit a negligible overpotential of 16 mV for the activation of this reaction, a high current density of ≈173 mA cm −2 at −0.45 V versus RHE, an average Faradaic efficiency (F.E.) of ≈91% toward CO production, and a remarkable turnover frequency as high as ≈20.82 s −1 . In the low overpotential range, the obtained CO formation current density is more than 35 and 25 times higher compared to state‐of‐the‐art MOF and MOF‐derived catalysts, respectively. The operando Cu K‐edge X‐ray absorption near edge spectroscopy and density functional theory calculations reveal the existence of reduced Cu (Cu + ) during CO 2 RR which reversibly returns to Cu 2+ after the reaction. The outstanding CO 2 catalytic functionality of conductive MOFs (c‐MOFs) can open a way toward high‐energy‐density electrochemical systems.

Majidi, Leily↗
DOE OSTI2024

An Integrated Electrochemical Approach to the Precision Synthesis of Sustainable Catalyst Materials

There is a pressing need to replace critical materials such as platinum group elements (PGE) in applications related to energy. This work responds to the need for fundamental principles of materials design to replace these metals by addressing a gap in the understanding of how to precisely control the surface structure of nanoscale materials. Electrochemical nanomaterials synthesis, such as techniques developed in the PI’s research group, expands the toolbox of available synthetic handles to include both electrochemical and chemical parameters, providing access to control over synthetic conditions in ways that are not possible in purely chemical nanoparticle growth. However, electrochemical materials synthesis (electrodeposition) is inherently serial, limiting throughput and preventing widespread implementation. Initial efforts in the short period of this award resulted in an innovative, high throughput, parallel approach to synthetic discovery for the electrodeposition of shaped metal nanoparticles that overcomes this limitation. Looking ahead, this work establishes an important capability that will enable researchers to push boundaries in the shape control of nanoparticles composed of non-PGE such as copper, iron, nickel, or cobalt.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Dynamic Metal–Support Interaction Dictates Cu Nanoparticle Sintering on Al 2 O 3 Surfaces

Nanoparticle sintering remains a critical challenge in heterogeneous catalysis. In this work, we present a unified deep potential (DP) model based on the Perdew–Burke–Ernzerhof approximation of density functional theory for Cu nanoparticles on three Al 2 O 3 surfaces (γ-Al 2 O 3 (100), γ-Al 2 O 3 (110), and α-Al 2 O 3 (0001)). Using DP-accelerated simulations, we reveal that the nanoparticle size-mobility relationship strongly depends on the supporting surface. The diffusion of nanoparticles on the two γ-Al 2 O 3 surfaces is almost independent of the size of the nanoparticle, while the diffusion on α-Al 2 O 3 (0001) decreases rapidly with increasing size. Interestingly, nanoparticles with fewer than 55 atoms diffuse several times faster on α-Al 2 O 3 (0001) than on γ-Al 2 O 3 (100) at 800 K while expected to be more sluggish based on their larger binding energy at 0 K. The diffusion on α-Al 2 O 3 (0001) is facilitated by dynamic metal–support interaction (MSI), where Al atoms move out of the surface plane to optimize contact with the nanoparticle and relax back to the plane as the nanoparticle moves away. In contrast, the MSI on γ-Al 2 O 3 (100) and on γ-Al 2 O 3 (110) is dominated by more stable and directional Cu–O bonds, consistent with the limited diffusion observed on these surfaces. Our extended MD simulations provide insight into the sintering processes, showing that the dispersity of the nanoparticles strongly influences the coalescence driven by nanoparticle diffusion. We observed that the coalescence of Cu 13 nanoparticles on α-Al 2 O 3 (0001) can occur in a short time (10 ns) at 800 K even with an initial internanoparticle distance increased to 3 nm, while the coalescence on the two γ-Al 2 O 3 surfaces are inhibited significantly by increasing the initial internanoparticle distance. These findings demonstrate that the dynamics of the supporting surface is crucial to understanding the sintering mechanism and offer guidance for designing sinter-resistant catalysts by engineering the support morphology.

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

Synthesis of Sandwich-α-Diimine Ligands via Copper-Mediated Stille Coupling

While sandwich diimines have found use in transition metal catalysis, the general method for their preparation has been lacking. Here, this approach utilizes a copper-mediated Stille-type coupling between aryl stannanes and α-diimines bearing 8-bromonaphthylimino group in commercial-grade N,N-dimethylformamide solvent and employs CuI or thiophene-2-carboxylate to promote the reactions. No other additives or bases are required. Electron-poor, electron-rich, heterocyclic, and hindered aryl stannanes can be employed as coupling reagents. Ligand scaffolds derived from structurally diverse α-diketones can be used.

Catalysts↗
DOE OSTI2025

Chemical Functional Groups Regulate Ion Concentrations and pHs in Nanopores

Understanding ion behaviors in functionalized nanopores is essential to deciphering reactions in both natural and engineered systems, such as sediments, biological ion channels, and membranes. While many efforts have shown the modified ion behaviors in the functionalized nanopores, a direct measurement and analysis to show how chemical functional groups affect ion concentrations in nanopores are critically needed. In this work, we present a plasmonic nanosensor that can measure the local concentrations of protons, anions (phosphate, nitrate, sulfate, and arsenate), and cations (mercury, lead, and copper) in functionalized nanopores, and we compare their concentrations in nanopores with the corresponding bulk concentrations. Notably, chemical functional groups induced ion concentrations differently in nanopores. In pristine nanopores and methyl- and phenyl-functionalized nanopores, we discovered an unexpected concurrence of an enhanced anion concentration and a suppressed cation concentration. In addition, the nanopore pH is dependent on bulk solution compositions and can be lower by 2.5 units, even when the bulk solution is well-buffered. In contrast, for hydrophilic (amine, thiol, and carboxyl) nanopores, pH depended on the p K a of the functional groups, and the heavy metal concentrations depended on chemical interactions with the functional groups. Our findings provide a better understanding of water chemistry in nanopores and can help precisely control ions in nanopores to benefit the design of membrane-based desalination techniques, CO 2 storage, and porous catalysts.

54 ENVIRONMENTAL SCIENCES↗