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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Structural and Chemical Evolution of an Inverse CeO x /Cu Catalyst under CO 2 Hydrogenation: Tunning Oxide Morphology to Improve Activity and Selectivity

Small nanoparticles of ceria deposited on a powder of CuO display a very high selectivity for the production of methanol via CO 2 hydrogenation. CeO 2 /CuO catalysts with ceria loadings of 5%, 20%, and 50% were investigated. Among these, the system with 5% CeO x showed the best catalytic performance at temperatures between 200 and 350 °C. The evolution of this system under reaction conditions was studied using a combination of environmental transmission electron microscopy (E-TEM), in situ X-ray absorption spectroscopy (XAS), and time-resolved X-ray diffraction (TR-XRD). For 5% CeO x /Cu, the in situ studies pointed to a full conversion of CuO into metallic copper, with a complete transformation of Ce 4+ into Ce 3+ . Images from E-TEM showed drastic changes in the morphology of the catalyst when it was exposed to H 2 , CO 2 , and CO 2 /H 2 mixtures. Under a CO 2 /H 2 feed, there was a redispersion of the ceria particles that was detected by E-TEM and in situ TR-XRD. Finally, these morphological changes were made possible by the inverse oxide/metal configuration and facilitate the binding and selective conversion of CO 2 to methanol.

03 NATURAL GAS↗
DOE OSTI2024

Controlling Bond Scission Pathways of Isopropanol on Fe- and Pt-Modified Mo 2 N Model Surfaces and Powder Catalysts

Biomass valorization can be used to produce value-added chemicals and fuels from renewable biomass resources by upgrading them via selective bond scission while retaining certain functional groups. Specifically, upgrading biomass through the dehydrogenation of alcohols to carbonyl compounds has gained interest as a method of utilizing biomass-derived alcohols while additionally producing H 2 . In this work, isopropanol was used as a probe molecule to control bond scission selectivity over Fe- and Pt-modified molybdenum nitride (Mo 2 N) model surfaces and powder catalysts. Trends in the selectivity toward dehydration and dehydrogenation were dependent on both the type and coverage of the metal overlayer on model surfaces. These results were then extended to the corresponding powder catalysts to demonstrate how model surface studies can inform the design of supported catalysts. Density functional theory calculations provided insights into controlling the dehydration and dehydrogenation pathways. In conclusion, this work shows that a fundamental understanding of the reactivity and intermediates on Mo 2 N-based model surfaces can be applied to understand the catalytic performance of metal-modified Mo 2 N powder catalysts, and also demonstrates that Mo 2 N-based catalysts are potentially promising materials for upgrading biomass-derived oxygenates.

09 BIOMASS FUELS↗
DOE OSTI2024

Design of Advanced Thin-Film Catalysts for Electrooxidation of Formic Acid

Successful development of catalysts for electrochemical formic acid oxidation (FAO) requires finding an optimal balance between catalytic performance (activity, stability, and selectivity) and catalyst cost. While platinum is one of the most active catalyst materials for FAO, it suffers from performance loss at low overpotentials due to poisoning with CO, which is one of the intermediates formed in the so-called indirect path of FAO. In this work, we explored the synergistic effects of the supporting material and annealing temperature on the performance of Pt thin films for FAO in acidic media. Compared to the as-prepared Pt films, the annealed films show up to 5-fold and 15-fold improvement for FAO on Pt@Ni and Pt@Cr, respectively. In conclusion, while the most active Pt@Ni thin film shows the lowest stability, the most active Pt@Cr thin film is also the most stable, challenging conventional trade-offs in electrocatalysis and providing a promising candidate for FAO nanocatalyst synthesis.

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

Discovering Ni/Cu Single-Atom Alloy as a Highly Active and Selective Catalyst for Direct Methane Conversion to Ethylene: A First-Principles Kinetic Study

Direct methane conversion to liquid fuels or value-added chemicals is a promising technology to utilize natural resources without resorting to further petroleum extraction. However, discovering efficient catalysts for this reaction is challenging due to either coke formation or unfavorable C-H bond activation. Herein, we design single-atom alloy (SAA) catalysts to simultaneously eliminate the above two bottlenecks based on mechanism-guided strategies: (1) the active single atom enables favorable C-H bond breaking and (2) the less reactive host metal facilitates C-C coupling and thus avoids strong binding of carbonaceous species. Employing electronic structure theory calculations, we screened the stability of multiple SAAs with 3d-5d transition metals atomically dispersed on a copper surface in terms of avoiding dopant aggregation and segregation. We then evaluated reactivities of the stable SAAs as catalysts for direct methane conversion to C2 products, including methane dehydrogenation and C-C coupling mechanisms. Combining selectivity analysis with kinetic modeling, we predicted that nickel dispersed on copper, i.e., Ni/Cu SAA, is a highly active and selective catalyst that can efficiently transform methane to ethylene. This work designs efficient SAA catalysts for direct methane activation and provides chemical insights into engineering compositions of SAAs to tune their catalytic performances.

Kothakonda, Manish↗
DOE OSTI2025

Restructuring of Benzimidazole-Based Copper Complexes during Electrochemical CO 2 Reduction

Copper-based molecular catalysts have been widely used for the electrochemical reduction of carbon dioxide (ERCO 2 ). However, establishing a correlation between structure and catalytic performance has been challenging due to the dynamic nature of these materials under ERCO 2 working conditions. Here, we report on the restructuring of the copper complexes [Cu(bzimpy)Cl 2 ] and [Cu(pyrben) 2 (NO 3 )]NO 3 during ERCO 2 in an acidic medium, evidencing its effects on the observed activity, selectivity, and stability. In situ X-ray absorption spectroscopy (XAS) suggested that, at sufficiently negative potentials, the Cu 2+ centers of both complexes are reduced to undercoordinated Cu 0 species. Pb underpotential deposition of post-ERCO 2 samples indicated that such Cu 0 species also present a dominant contribution of the (100) domain, which is in line with the high Faradaic efficiency toward C 2 products (∼45%) shown by both complexes at −1.24 V vs RHE. By combining online electrochemical mass spectrometry, in situ XAS, electron paramagnetic resonance (EPR), and quantitative product analysis, we found that [Cu(bzimpy)Cl 2 ] exhibits a partially reversible restructuring, regenerating the main complex moiety, [Cu(bzimpy)] 2+ , and its geometry.

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

Ternary Phosphides Ba M 2 P 2 : Tailoring Crystal and Electronic Structures Enables Highly Efficient HER Electrocatalysis

Binary transition metal phosphides and their solid solutions have emerged as promising hydrogen evolution reaction (HER) catalysts. Although many research endeavors have adopted strategies to vary compositions to optimize catalytic performance, they mainly focus on binary structures, which represent only a small fraction of the abundant phase space of structure types among transition metal phosphides. Here, the largely unexplored class of ternary and multinary ordered phosphides in catalysis comprises two or more metals with quite different chemical nature, concealing the structure–property relationships essential for advancing catalyst design. Here, we explored phosphides crystallizing in one of the most abundant ordered intermetallic structure types, —the ThCr 2 Si 2 type, —where square nets of 3d transition metal M and P atoms are separated by layers of electropositive Ba cations. Four ternary BaM 2 P 2 (M = Fe, Fe/Cu, Fe/Ni, Ni) catalysts were synthesized and characterized. BaNi 2 P 2 showed high HER activity in acidic electrolyte, which required an overpotential, η 10 , of only 62 mV to drive current density j = –10 mA/cm 2 and high stability with a potential drop rate of 0.25 mV/h. BaNi 2 P 2 outperformed other Ni-based catalysts, such as Ni 2 P and Ni 5 P 4 . Notably, at current densities above –170 mA/cm 2 , BaNi 2 P 2 outperformed the standard Pt electrode measured under identical conditions. Electronic structure analysis revealed a volcano-type activity trend among the four BaM 2 P 2 catalysts based on their d-band center positions, highlighting the role of electropositive Ba cations in shifting the Ni-3d orbitals into an optimal position.

BaNi2P2↗
DOE OSTI2026

Quantifying the Impact of Metal Population Distribution in MFI-Supported Mo Catalysts for Methane Dehydroaromatization

Precise evaluation of intrinsic kinetic behavior in Mo/MFI catalysts for methane dehydroaromatization (MDA) is confounded by variations in Mo dispersion and speciation, which are influenced by metal loading and zeolite acidity. This work advances the utility of H 2 -temperature programmed reduction (H 2 -TPR) for characterizing Mo/MFI catalysts by enabling quantitative comparison of MoO x populations distinguished by reduction behavior and linked to initial catalytic performance. A comprehensive H 2 reduction pathway is established through systematic H 2 - TPR studies varying catalyst composition (1–10 wt % Mo, Si/Al = 15, 40, ∞), supplemented by UV-Raman spectroscopy, X-ray powder diffraction, N 2 physisorption, NH 3 -TPD, and advanced spectroscopic analysis (in situ XAS with principal component analysis/multivariate curve resolution—alternating least squares). Two low-temperature H 2 -TPR regions capture distinct Mo populations undergoing initial Mo(VI)→Mo(IV) reduction: a lower-temperature population (Mo-RI) associated primarily with highly dispersed, anchored MoO x species expected to predominantly reside within MFI channels, and a higher-temperature population (Mo-RII) corresponding to a broader set of MoO x species that becomes increasingly bulk-like/extrazeolitic at higher Mo loading. Quantification of these populations provides practical, kinetically relevant descriptors for comparing initial MDA rates across catalysts with varying Mo loading, Si/Al ratio, and MoO x heterogeneity. Application of lower-temperature Mo-RI estimates to kinetic measurements reveals a minimum threshold of ∼0.12 × 10 –3 mol Mo-RI/g cat , above which initial forward benzene rates normalized to this population converge despite differences in metal loading and zeolite Brønsted acidity. This threshold coincides with a transition toward a common C 2 -mediated benzene-forming regime, as indicated by approach-to-equilibrium analysis of methane-to-ethane, ethane-to-ethylene, and ethylene-to-benzene reaction steps. Above this threshold, normalized initial benzene rates are nearly invariant with increasing Mo-RII/Mo-RI population ratio, indicating that excess Mo-RII populations, including bulk-like/extrazeolitic MoO x domains present at higher loading, do not measurably suppress benzene formation associated with anchored and mostly channel-confined Mo population under the initial-rate conditions examined.

Mo/MFI↗
DOE OSTI2026

Base-Free Catalytic Transfer Hydrogenation of Alkyl Formates and Organic Esters at Mild Temperature

The pincer-ligated ruthenium complex ( iPr PN H P)Ru(CO)H 2 ( iPr PN H P = ( i Pr 2 PC 2 H 4 ) 2 NH) is an active catalyst for the transfer hydrogenation of alkyl formates (HCO 2 R) and organic esters (RCO 2 R′) to the corresponding alcohols under base-free reaction conditions at mild temperatures. Specifically, a range of alkyl formate esters were reduced to MeOH and the corresponding alcohols in high yields using ( iPr PN H P)Ru(CO)H 2 as the catalyst and isopropanol ( i PrOH) as the hydrogen donor at 30 °C. The first step in the process is the metal-catalyzed transesterification of the alkyl formate with i PrOH to generate isopropyl formate, which is then reduced. The use of i PrOH as the hydrogen donor is crucial. ( iPr PN H P)Ru(CO)H 2 can also catalyze the transfer hydrogenation of a broad range of organic esters, including cyclic, acyclic, heteroatom-substituted, and long-chain bio-derived esters, to the corresponding alcohols in good yields using ethanol (EtOH) as the hydrogen donor at 55 °C. Computational studies were used to elucidate the proposed pathway for alkyl formate reduction and the underlying reasons why i PrOH is the most effective hydrogen donor for alkyl formate reduction, while EtOH is optimal for organic ester reduction. Overall, this work describes a highly active catalyst for alkyl formate and organic ester transfer hydrogenation and provides mechanistic insight into the factors responsible for the strong catalytic performance. Finally, these findings will be valuable for designing catalysts for both transfer hydrogenation and related reactions.

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

Methanol Synthesis from CO 2 Hydrogenation over a Potassium-Promoted Cu x O/Cu(111) ( x ≤ 2) Model Surface: Rationalizing the Potential of Potassium in Catalysis

Alkalis have been reported as a promotor in the heterogeneous catalysis, being able to enhance the activity and selectivity of catalysts. The effective utilization of alkalis in catalyst optimization requires the fundamental understanding of the underlying mechanism. In this work, we take a potassium (K)-modified Cu x O/Cu(111) (x ≤ 2) model surface as a case study to rationalize the nature of K during the carbon dioxide hydrogenation using combined density functional theory (DFT) calculation and the kinetic Monte Carlo (KMC) simulation. Our result demonstrates the significant tuning of selectivity from carbon monoxide to methanol on going from Cu(111) to K-modified Cu x O/Cu(111). The deposited K + stabilizes the Cu x O thin film under the reducing condition of carbon dioxide hydrogenation. More importantly, our study reveals that K + acts as an active center for selective tuning in the binding, an accelerator for charge transfer, and a mediator for the electron tunneling. As a result, the K-modified Cu x O/Cu(111) opens a methanediol [H 2 C(OH) 2 ]-mediated formate pathway to facilitate the selective conversion of carbon dioxide to methanol. Our study develops the intrinsic rules of design to tune the catalytic performance using alkali metals.

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

Revealing Structural Evolution of Single Atom Catalysts during Electrochemical CO 2 Reduction by in Situ X-ray Absorption Spectroscopy

Investigating the structural variation of single-atom catalysts (SACs) is crucial to reveal the reaction mechanism under working conditions. Different in situ techniques, especially X-ray absorption spectroscopy (XAS), have been reported to study the structural changes in active sites. However, a systematic study of the relationship between the coordination environment and the catalytic ability of different kinds of SACs is still lacking. Herein, we established isolated transition metal atoms (Fe, Co, Ni, Cu) on N-doped carbon (M-N-C) and employed them in electrocatalytic CO 2 reduction reaction (CO 2 RR). Significantly, Ni-N-C exhibits the highest selectivity (similar to 97.9%) toward CO at -0.8 V vs RHE. In situ XAS characterization discloses the coordination number dependent catalytic performance. Further, the decreased average coordination number of Ni in Ni-N-C at the voltage point with maximum Faradaic efficiency was observed. Density functional theory further provides the possible mechanism of CO 2 -to-CO over the undercoordinated Ni-N-C structure.

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

Metal–Organic Frameworks for Per- and Polyfluoroalkyl Substances Treatment in Contaminated Water

Per- and polyfluoroalkyl substances (PFAS) are synthetic pollutants known for their chemical stability, environmental persistence, and toxicological risks. Their widespread use has led to extensive contamination, particularly in aquatic systems. Conventional treatment methods often face challenges such as high energy consumption and the production of secondary pollutants. Metal− organic frameworks (MOFs), with their high surface areas and tunable structures, have emerged as promising materials for PFAS remediation. This review summarizes recent progress in MOF-based PFAS adsorption and degradation, highlighting key frameworks such as MIL, UiO, and ZIF. Mechanistic insights into adsorption behavior and regeneration capabilities are discussed, along with the catalytic performance of MOF composites and postmodified systems in degradation pathways. The review concludes with design strategies for next-generation MOF materials aimed at efficient, sustainable PFAS removal under realistic conditions.

Adsorption↗
DOE OSTI2024

Low-Temperature Activation and Coupling of Methane on MgO Nanostructures Embedded in Cu 2 O/Cu(111)

Here, the efficient conversion of methane into valuable hydrocarbons such as ethane and ethylene at relatively low temperatures without deactivation issues is crucial for advancing sustainable energy solutions. Herein, AP-XPS and STM studies show that MgO nanostructures (0.2-0.5 nm wide, 0.4-0.6 Å high) embedded in a Cu 2 O/Cu(111) substrate activate methane at room temperature, mainly dissociating it into CH x (x = 2 or 3) and H adatoms, with minimal conversion to C adatoms. These MgO nanostructures in contact with Cu 2 O/Cu(111) exhibit unique reactivity, enabling C-C coupling into ethane and ethylene at 500 K, a significantly lower temperature than that required for bulk MgO catalysts (>700 K), with negligible carbon deposition and no deactivation. DFT calculations corroborate these experimental findings. The CH 4,gas → *CH 3 +*H reaction is a downhill process on MgO/Cu 2 O/Cu(111) surfaces. The activation of methane is facilitated by an electron transfer from copper to MgO and the existence of Mg and O atoms with a low coordination number in the oxide nanostructures. The formation of O-CH 3 and O-H bonds overcomes the energy necessary for the cleavage of a C-H bond in methane. DFT studies reveal that smaller Mg 2 O 2 model clusters provide stronger binding and lower activation barriers for C-H dissociation in CH 4 , while larger Mg 3 O 3 clusters promote C-C coupling due to weaker *CH 3 binding. All these results emphasize the importance of size when optimizing the catalytic performance of MgO nanostructures in the selective conversion of methane.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Manipulating the Second Coordination Shell of Single-Atom Fe for Enhanced Fenton Reaction

While current methods use oxidizable metals as electron donors to effectively reduce Fe 3+ , they suffer from the irreversible oxidation of these metals, ultimately compromising the catalyst’s longevity. To address this challenge, we engineered the second coordination shell of a single-atom Fe center by doping boron (B) onto a graphene-based support (Fe 1 /B-graphene) and utilized H 2 O 2 as the electron source for efficient Fe 2+ regeneration. Experimental results, supported by theoretical calculations, revealed that the Fe–O–B motif functions like a micro galvanic cell, with intermediary O atoms facilitating electron transfer between electrodes. Specifically, electrons consumed during H 2 O 2 activation at Fe 1 sites (positive electrode) are replenished by electrons extracted from H 2 O 2 at B atoms (negative electrode), where the activation energy for H 2 O 2 oxidation is significantly lower than that at Fe 1 sites. This study offers inspirational insights into the design of Fenton catalysts through precise regulation of the second coordination shell, demonstrating the potential of tailoring the outer coordination environment of single-atom catalysts to enhance catalytic performance across various reactions.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Facile and Scalable Synthesis of Metal- and Nitrogen-Doped Carbon Nanotubes for Efficient Electrochemical CO 2 Reduction

Metal- and nitrogen-doped carbon (M–N–C) is a promising material to catalyze electrochemical CO 2 reduction reaction (CO 2 RR). However, most M–N–C catalysts in the literature require complicated synthesis procedures and produce small quantities per batch, limiting the commercialization potential. In this work, we developed a simple and scalable synthesis method to convert metal-impurity-containing commercial carbon nanotubes (CNTs) and nitrogen-containing organic precursors into M–N–C via one-step moderate-temperature (650 °C) pyrolysis without any other treatment nor the need to add metal precursors. Batches of catalysts in varied mass up to 10 g (150 mL in volume) per batch were synthesized, and repeatable catalytic performances were demonstrated. To the best of our knowledge, the 10 g batch is one of the largest batches of CO2RR catalysts synthesized in the literature while requiring minimal synthesis steps. The catalyst possessed single-atomic iron–nitrogen (Fe–N) sites, enabling a high performance of >95% CO product selectivity at a high current density of 400 mA/cm 2 and high stability for 45 h at 100 mA/cm 2 in a flow cell testing. The catalyst outperformed a benchmark noble-metal nanoparticle catalyst and achieved longer stability than many other reported M–N–C catalysts in the literature. The scalable and cost-effective synthesis developed in this work paves a pathway toward practical CO 2 RR applications. The direct utilization of metal impurities from raw CNTs for efficient catalyst synthesis with minimal treatment is a green and sustainable engineering approach.

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

Epitaxial and Strong Support Interactions between Pt and LaFeO 3 Films Stabilize Pt Dispersion

The ability to stabilize very small Pt crystallites in supported-metal catalysts following harsh treatments is an important industrial problem. Herein, we demonstrate that Pt particles can be maintained in the 1- to 2-nm range following multiple oxidation and reduction cycles at 1073 K when the particles are supported on 0.5-nm LaFeO 3 films that have been deposited onto MgAl 2 O 4 using atomic layer deposition (ALD). Characterization by Scanning Transmission Electron Microscopy (STEM) suggest that, when the catalyst is oxidized at 1073 K, the Pt crystallites are oriented with respect to the underlying LaFeO 3 . X-Ray Absorption Spectroscopy (XAS) also shows evidence for changes in the Pt environment. CO-oxidation rates for the reduced catalyst remain unchanged after five redox cycles at 1073 K. Epitaxial growth of Pt clusters and the consequent strong metal-support interaction between Pt and LaFeO 3 are indicated to be prime reasons for the enhanced catalytic performances.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Heterogeneous Supramolecular Catalysis through Immobilization of Anionic M 4 L 6 Assemblies on Cationic Polymers

Although most of the currently developed supramolecular catalysts that emulate enzymatic reactivity with unique selectivity and activity through specific host-guest interactions work under homogeneous conditions, enzymes in nature can operate under heterogeneous conditions as membrane-bound enzymes. In order to develop such a heterogeneous system, an immobilized chiral supramolecular cluster Ga 4 1 6 ( 2 ) was introduced into cross-linked polymers with cationic functionalities. These heterogeneous supramolecular catalysts were used in aza-Prins and aza-Cope reactions and successfully applied to continuous-flow reactions. Additionally, they showed high durability and maintained high turnovers for long periods of time. In sharp contrast to the majority of examples of heterogenized homogeneous catalysts, the newly developed catalysts showed enhanced activity and robustness compared to those exhibited by the corresponding soluble cluster catalyst. An enantioenriched cluster was also immobilized to enable asymmetric catalysis, and activity and enantioselectivity of the supported chiral catalyst were maintained during recovery and reuse experiments and under a continuous-flow process. Significantly, the structure of the ammonium cations in the polymers affected stability, reactivity, and enantioselectivity, which is consistent with the hypothesis that the cationic moieties in the polymer support interact with cluster as an exohedral protecting shell, thereby influencing their catalytic performance.

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

Optically Pure C 1 -Symmetric Cyclic(alkyl)(amino)carbene Ruthenium Complexes for Asymmetric Olefin Metathesis

An expedient access to the first optically pure ruthenium complexes containing C 1 -symmetric cyclic (alkyl)(amino)carbene (CAAC) ligands is reported. Furthermore, they demonstrate excellent catalytic performances in asymmetric olefin metathesis with high enantioselectivities (up to 92% ee). Preliminary mechanistic insights provided by DFT models highlight the origin of the enantioselectivity.

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

Mechanism of Methanol Decomposition over Single-Site Pt 1 /CeO 2 Catalyst: A DRIFTS Study

Single-site catalysts have drawn broad attention in catalysis because of their maximum atomic utilization and unique catalytic performance. Early work in our group has shown a 40-fold higher activity of methanol decomposition over single-site Pt 1 /CeO 2 catalyst than CeO 2 supported 2.5 nm Pt nanoparticles, while a molecular-level understanding of such enhancement is lacking. Herein, the reaction mechanism of methanol decomposition over Pt 1 /CeO 2 was carefully investigated using in situ DRIFTS, and a reaction pathway was proposed. Methanol molecules were dissociatively adsorbed on nanoceria support first, followed by the diffusion of as-formed methoxy species onto Pt single sites where the dehydrogenation occurs and results in the weakly bonded CO. The ease of methanol dissociative adsorption on nanoceria support and the tailored electronic property of Pt 1 via the metal-support interaction are believed to be strongly correlated with the high activity of Pt 1 /CeO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗