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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Geochemistry, volumetric water content, and active layer depths from rainfall simulations at the Kougarok Fire Site, Seward Peninsula, Alaska, 2022

Rainfall frequency and intensity is expected to increase in the Arctic, with potential implications for permafrost thaw and geochemical fluxes in soils. To conduct controlled rainfall experiments at remote field sites in the Arctic, the Next-Generation Ecosystem Experiments Arctic Rainfall Simulator (NARS) was developed at Los Alamos National Laboratory as part of the NGEE Arctic project. To better understand how rainfall may affect interflow biogeochemistry and permafrost thaw, rainfall simulations were performed on the Seward Peninsula of Alaska during late September and early October 2022 at the Kougarok Fire Site near mile marker 86 of the Nome-Taylor Highway. Water samples were collected before, during, and after rainfall simulations until interflow had ceased. Additional data collected included soil pore water samples from macrorhizons, active layer depths, and volumetric water content at each of the experimental plots. This dataset contains one *.csv file of water sample properties, one *.csv file of thaw depths, one *.csv file of soil moisture measurements, and one *.kml file of the locations where samples were collected.The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy’s Office of Biological and Environmental Research.The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska.Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy’s Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Covalency competition dominates the water oxidation structure–activity relationship on spinel oxides

Spinel oxides have attracted growing interest over the years for catalysing the oxygen evolution reaction (OER) due to their efficiency and cost-effectiveness, but fundamental understanding of their structure–property relationships remains elusive. Here we demonstrate that the OER activity on spinel oxides is intrinsically dominated by the covalency competition between tetrahedral and octahedral sites. The competition fabricates an asymmetric M$_T-O-M_O$ backbone where the bond with weaker metal–oxygen covalency determines the exposure of cation sites and therefore the activity. Driven by this finding, a dataset with more than 300 spinel oxides is computed and used to train a machine-learning model for screening the covalency competition in spinel oxides, with a mean absolute error of 0.05 eV. [Mn]$_T$[Al$_{0.5}$Mn$_{1.5}$]OO$_4$ is predicted to be a highly active OER catalyst and subsequent experimental results confirm its superior activity. This work sets mechanistic principles of spinel oxides for water oxidation, which may be extendable to other applications.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Redistribution of Ru in Fe 2 O 3 –Ru Nanocatalysts through an Oxidative Pretreatment Improves Reverse Water–Gas Shift Activity

We have synthesized Fe–Ru nanoparticles via a solvothermal method to create catalysts for the reverse water–gas shift reaction and demonstrated the impact of reductive and oxidative pretreatments on both catalytic performance and structure. Catalytic testing showed improved activity after exposure to O 2 at 600 °C. In contrast, the activity became lower if then exposed to H 2 at 600 °C. Environmental scanning transmission electron microscopy and scanning electron microscopy showed that exposure to O 2 at 600 °C changes the morphology and completely oxidizes Fe into Fe 2 O 3 . Exposure to H 2 at elevated temperature caused Ru coalescence at the surface of the nanoparticle, forming clusters which decreased the optimization of Ru. Reoxidation of the particles exposed to H 2 , however, caused a redistribution of Ru that appears beneficial in maximizing Ru exposure and synergy with Fe oxide, with no major changes in the morphology and oxide structure. Furthermore, our diagnostics demonstrate the complex and reversible rearrangements possible in these multicomponent particles and the benefits of oxidative pretreatment to enhance or regenerate Fe–Ru catalysts in other important catalytic reactions such as Fischer–Tropsch synthesis.

Fe−Ru nanoparticles↗
DOE OSTI2023

A High-Entropy Oxide as High-Activity Electrocatalyst for Water Oxidation

High-entropy materials are an emerging pathway in the development of high-activity (electro)catalysts because of the inherent tunability and coexistence of multiple potential active sites, which may lead to earth-abundant catalyst materials for energy-efficient electrochemical energy storage. In this report, we identify how the multication composition in high-entropy perovskite oxides (HEO) contributes to high catalytic activity for the oxygen evolution reaction (OER), i.e., the key kinetically limiting half-reaction in several electrochemical energy conversion technologies, including green hydrogen generation. We compare the activity of the (001) facet of LaCr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 O 3-δ with the parent compounds (single B-site in the ABO 3 perovskite). While the single B-site perovskites roughly follow the expected volcano-type activity trends, the HEO clearly outperforms all of its parent compounds with 17 to 680 times higher currents at a fixed overpotential. As all samples were grown as an epitaxial layer, our results indicate an intrinsic composition–function relationship, avoiding the effects of complex geometries or unknown surface composition. In-depth X-ray photoemission studies reveal a synergistic effect of simultaneous oxidation and reduction of different transition metal cations during the adsorption of reaction intermediates. The surprisingly high OER activity demonstrates that HEOs are a highly attractive, earth-abundant material class for high-activity OER electrocatalysts, possibly allowing the activity to be fine-tuned beyond the scaling limits of mono- or bimetallic oxides.

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

Dynamic Evolution of Palladium Single Atoms on Anatase Titania Support Determines the Reverse Water–Gas Shift Activity

Research interest in single-atom catalysts (SACs) has been continuously rising. However, the lack of understanding of the dynamic behaviors of SACs during applications hinder catalyst development and mechanistic understanding. Herein, we report on the evolution of active sites over Pd/TiO 2 -anatase SAC (Pd 1 /TiO 2 ) in the reverse water-gas shift (rWGS) reaction. Combining kinetics, in-situ characterization, and theory, we show that at T ≥ 350 °C, the reduction of TiO 2 by H 2 alters the coordination environment of Pd, creating Pd sites with partially cleaved Pd-O interfacial bonds and a unique electronic structure that exhibit high intrinsic rWGS activity through the carboxyl pathway. The activation by H 2 is accompanied by the partial sintering of single Pd atoms (Pd 1 ) into disordered, flat, ~1 nm diameter clusters (Pd n ). The highly active Pd sites in the new coordination environment under H 2 are eliminated by oxidation, which, when performed at high temperature, also re-disperses Pd n and facilitates the reduction of TiO 2 . In contrast, Pd 1 sinters into crystalline, ~5 nm particles (Pd NP ) during CO treatment, deactivating Pd 1 /TiO 2 . During the rWGS reaction, the two Pd evolution pathways co-exist. The activation by H 2 dominates, leading to the increasing rate with time-on-stream, and steady-state Pd active sites similar with the ones formed under H 2 . Finally, this work demonstrates how the coordination environment and nuclearity of metal sites on a SAC evolve during catalysis and pre-treatments, and how their activity is modulated by these behaviors. These insights on SAC dynamics and structure-function relationship are valuable to mechanistic understanding and catalyst design.

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

CeO 2 Promoted CuO/MgO-Al 2 O 3 Catalyst with Enhanced Activity and Water-Resistance for CO Oxidation

Copper (Cu)-based catalysts have emerged as cost-effective and sustainable alternatives to noble metal systems (e.g., Pt, Pd) for catalytic CO oxidation. However, their practical application is hindered by insufficient low-temperature activity and rapid deactivation under wet conditions containing moisture. To address these challenges, this work introduces CeO 2 -modified CuO/MgO-Al 2 O 3 (Cu-Ce/MA) catalysts, strategically designed to enhance the catalytic performance and water resistance simultaneously. These catalytic materials were evaluated for CO oxidation under both dry and humid conditions, revealing that CeO 2 modification significantly improves the low-temperature activity. Specifically, the optimal catalyst, Cu-30Ce/MA, achieved a 50% CO conversion temperature (T 50 ) of 151 °C, a marked reduction from 218 °C on Cu/MA reference catalyst. Furthermore, the water resistance improves in a CeO 2 content-dependent manner, with higher CeO 2 loadings imparting greater stability in humid environments. Detailed characterizations demonstrate that CeO 2 promotes the dispersion of CuO and stabilizes Cu sites, while also enhancing the low-temperature reducibility and CO adsorption capacity. Crucially, CeO 2 modification suppresses the competitive H 2 O adsorption, mitigating water-induced deactivation. These synergistic effects collectively rationalize the superior activity and durability of Cu-Ce/MA catalysts. By elucidating the dual role of CeO 2 in optimizing Cu-based systems, this study advances the rational design of cost-effective catalysts for real-world CO emission control, particularly under water-rich industrial conditions.

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

Migration and aggregation of Pt atoms on metal oxide-supported ceria nanodomes control reverse water gas shift reaction activity

Abstract Single-atom catalysts (SACs) are particularly sensitive to external conditions, complicating the identification of catalytically active species and active sites under in situ or operando conditions. We developed a methodology for tracing the structural evolution of SACs to nanoparticles, identifying the active species and their link to the catalytic activity for the reverse water gas shift (RWGS) reaction. The new method is illustrated by studying structure-activity relationships in two materials containing Pt SACs on ceria nanodomes, supported on either ceria or titania. These materials exhibited distinctly different activities for CO production. Multimodal operando characterization attributed the enhanced activity of the titania-supported catalysts at temperatures below 320 ˚C to the formation of unique Pt sites at the ceria-titania interface capable of forming Pt nanoparticles, the active species for the RWGS reaction. Migration of Pt nanoparticles to titania support was found to be responsible for the deactivation of titania-supported catalysts at elevated temperatures. Tracking the migration of Pt atoms provides a new opportunity to investigate the activation and deactivation of Pt SACs for the RWGS reaction.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Large Aerosol Particles Favor Haze Conditions Through Limitations on Water Budget and Activation Kinetics

Experiments in the Pi Convection‐Cloud Chamber conducted by systematically changing the diameter of injected dry aerosol particles while holding the temperature difference constant demonstrate that dry diameter strongly influences the onset of haze‐dominated conditions. Two factors contribute: the system becomes water‐limited, resulting in reduction of supersaturation by growing aerosol particles to the activation diameter; and the activation process becomes kinetically limited. Dry aerosol diameter exerts a strong influence on activation time, with a power‐law exponent of 9/2. Kinetically limited activation occurs when the ratio of the activation and droplet residence times is greater than unity. The findings demonstrate that a haze‐dominated state, where cloud formation is suppressed, can be achieved not only with weak supersaturation forcing and high aerosol concentration but also with large, hygroscopic aerosol particles. These results have implications for cloud formation in polluted environments, fog development near the ocean, and hygroscopic cloud seeding.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

CsO x Nanostructures on Au(111): Morphology- and Size-dependent Activity for the Water–Gas Shift Reaction

Alkali oxides are typically used as promoters of heterogeneous catalysts for the water–gas shift (WGS; H 2 O + CO → H 2 + CO 2 ) reaction. On Au(111), CsO x exhibits diverse nanostructures at varying coverages, as revealed by scanning tunneling microscopy. Clusters of cesium oxide (Cs 2 O 2 ) nucleate at elbow sites of the Au(111) herringbone when θ Cs is less than 0.1 ML. Subsequently, these clusters transform into two-dimensional (2D) islands (Cs 2 O, Cs 2 O 2 , CsO 2 ) as the cesium coverage increases (θ Cs > 0.1 ML). Both types of CsO x nanostructures enable the WGS process on Au(111). The highest activity was seen for the cesium oxide clusters which facilitated the partial dissociation of water and binding of CO. The CO ads and OH ads groups were not strongly bound and probably reacted to yield a short-lived HOCO intermediate that led to gaseous H 2 and CO 2 . The 2D islands of CsO x also enabled the WGS but their efficiency was reduced due to the formation of cesium hydroxide compounds (limiting mobility of OH groups) and the generation of CO 3 and C species (blocking of active centers). The fact that the performance of the CsO x /Au(111) catalysts changed dramatically with variations in the chemical properties of the CsO x nanostructures indicates that the alkali oxide was an integral part of the active phase, playing a central role in the activation and conversion of the reactants. To attach the label of “promoter” to CsO x is a simplification that does not help in the design and optimization of catalysts for C1 chemistry. In conclusion, to achieve a rational design, one must consider the structural and chemical properties of the alkali oxide.

36 MATERIALS SCIENCE↗
DOE OSTI2020

An Active–Site Sulfonate Group Creates a Fast Water Oxidation Electrocatalyst That Exhibits High Activity in Acid

The storage of solar energy in chemical bonds will depend on pH–universal catalysts that are not only impervious to acid, but actually thrive in it. Whereas other homogeneous water oxidation catalysts are less active in acid, we report a catalyst that maintained high electrocatalytic turnover frequency at pH values as low as 1.1 and 0.43 (k cat = 1501±608 s –1 and 831±254 s –1 , respectively). Moreover, current densities, related to catalytic reaction rates, ranged from 15 to 50 mA cm –2 mM –1 comparable to those reported for state–of–the–art heterogeneous catalysts and 30 to 100 times greater than those measured for two prominent literature homogeneous catalysts at pH 1.1 and 0.43. The catalyst also exhibited excellent durability when a chemical oxidant was used (Ce IV , 7400 turnovers, TOF 0.88 s –1 ). Here, preliminary computational studies suggest that the unusual active–site sulfonate group acts a proton relay even in strong acid, as intended.

14 SOLAR ENERGY↗
DOE OSTI2020

An Active‐Site Sulfonate Group Creates a Fast Water Oxidation Electrocatalyst That Exhibits High Activity in Acid

Abstract The storage of solar energy in chemical bonds will depend on pH‐universal catalysts that are not only impervious to acid, but actually thrive in it. Whereas other homogeneous water oxidation catalysts are less active in acid, we report a catalyst that maintained high electrocatalytic turnover frequency at pH values as low as 1.1 and 0.43 ( k cat =1501±608 s −1 and 831±254 s −1 , respectively). Moreover, current densities, related to catalytic reaction rates, ranged from 15 to 50 mA cm −2 mM −1 comparable to those reported for state‐of‐the‐art heterogeneous catalysts and 30 to 100 times greater than those measured for two prominent literature homogeneous catalysts at pH 1.1 and 0.43. The catalyst also exhibited excellent durability when a chemical oxidant was used (Ce IV , 7400 turnovers, TOF 0.88 s −1 ). Preliminary computational studies suggest that the unusual active‐site sulfonate group acts a proton relay even in strong acid, as intended.

Nash, Aaron G.↗
DOE OSTI2024

Sub-volt conversion of activated biochar and water for H 2 production near equilibrium via biochar-assisted water electrolysis

Sluggish water oxidation reactions limit water electrolysis for H 2 production, which can be alleviated by the use of carbon-based ma- terials like agricultural wastes as reducing agents. Biochar from such biomass can reduce equilibrium cell potentials at standard condi- tions from 1.23 V to 0.21 V by avoiding direct water splitting at the anode. However, some challenges hinder biochar oxidation, including poor biochar binding, electrode caking, and surface passivation. We find that enhanced C/O ratio, crystallinity, and negative zeta potential improve biochar oxidation kinetics at mod- erate temperatures. Smaller particle sizes and better mixing pre- vent electrode caking, enhancing biochar stability. Here, we report sub-volt biochar-coupled H 2 production, often referred to as a bio- char-assisted water electrolysis (BAWE), yielding 250 mA/g cat H 2 current at 100% Faradaic efficiency. Over 1 mA current was observed at a near-equilibrium cell potential of 0.2 V cell potential. Using a single-junction solar cell-powered BAWE, 15 mA H 2 is generated at 1 Sun, resulting in 4.8% solar-to-hydrogen efficiency, equivalent to 35% when the energy of H 2 relative to H 2 O (without biochar) is assumed.

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

Catalytic Mechanism of Interfacial Water in the Cycloaddition of Quadricyclane and Diethyl Azodicarboxylate

"On-water" catalysis, the unusual activity of water molecules at the organic solvent-water interface, has been demonstrated in many organic reactions. However, the catalytic mechanism has remained unclear, largely because of the irreproducibility of the organic-water interface under the common stirring condition. In this work, the interfacial area was controlled by employing adsorbed water on mesoporous silica nanoparticles as the catalyst. Reliable kinetics of the cycloaddition reaction of quadricyclane and diethyl azodicarboxylate (DEAD) at the toluene-water interface within the nanoparticle pores were measured. Data reveal an Eley-Rideal mechanism, wherein DEAD adsorbs at the toluene-water interface via hydrogen bonds formed with interfacial water, which lower the activation energy of the cycloaddition reaction. The mechanistic insights gained and preparation of surface water in silica pores described herein may facilitate the future design of improved "on-water" catalysts.

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

Tracking the dynamics of catalytic Pt/CeO2 active sites during water-gas-shift reaction

Abstract Understanding the atomistic structure of the active site during catalytic reactions is of paramount importance in both fundamental studies and practical applications, but such studies are challenging due to the complexity of heterogeneous systems. Here, we use Pt/CeO 2 as an example to study the dynamic nature of active sites during the water-gas-shift reaction (WGSR) by combining multiple in situ characterization tools. We show that the different concentrations of interfacial Pt δ+ – O – Ce 4+ moieties at Pt/CeO 2 interfaces are responsible for the rank of catalytic performance of Pt/CeO 2 catalysts: Pt/CeO 2 -rod > Pt/CeO 2 -cube > Pt/CeO 2 -oct. For all the catalysts, metallic Pt is formed during the WGSR, leading to the transformation of the active sites to Pt 0 – O v – Ce 3+ and interface reconstruction. These findings shed light on the nature of the active site for the WGSR on Pt/CeO 2 and highlight the importance of combining complementary in situ techniques for establishing structure-performance relationships.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Multi-hydrophilic functional network enables porous membranes excellent anti-fouling performance for highly efficient water remediation

Membrane technology is believed as a cost-effective approach for solving the water issues, where as it suffers from serious membrane fouling. Surface grafting and surface coating have been proved to be effective in abating the membrane fouling; however, these processes always need additional procedures and compromise the initial permeance of the membranes. Herein, we developed a kind of highly permeable polyacrylonitrile (PAN) membranes with excellent anti-fouling performance through one-step phase inversion of the PAN casting solution containing water-soluble active additives. During the process, the water-soluble active additives could segregate towards the membrane surface and pore walls; thereby finely tailoring the pore structures of the PAN-based membranes. Moreover, the active additives could react with each other to form crosslinked networks containing multi-hydrophilic functional groups including CH2-O-CH2, -OH or-Si-OH. Consequently, the PAN-based membranes exhibited surprising superhydrophilicity with water contact angle below 10. even after soaking in water for one week and the anti-fouling permeance of the membranes increased significantly with permeance recovery rate above 93%. Interestingly, the modified membranes also demonstrated both high permeances and high separation efficiency, thereby showing strong promise in water environmental remediation including wastewater treatment and oil/water emulsion separation.

Anti-fouling↗
DOE OSTI2024

Evaluation of Second Target Station Target Streaming for the Preliminary Design of the Target Assembly

This report documents the analysis of dose rate fields from a combination of two sources stemming from the target system of the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS) Second Target Station (STS). This analysis supports the target drive components’ lifetime estimates and conventional facilities’ preliminary design. The two sources detailed in this report are the radiation generated by the proton beam incident on the target and the activated cooling water in the pipes at the top of the target assembly. The analysis considers the STS target system in operational configuration, with all shielding in place. The dose rate fields are calculated in the target drive room and through the target drive room ceiling. This report calculates the thickness necessary for the target drive room’s high-density concrete ceiling to meet the 0.25 mrem/hr dose limit requirement in the high bay directly above the target drive room. In addition to sizing the target drive room ceiling, this report includes details of the dose field surrounding the target drive assembly to estimate the deposited dose in the target drive assembly components resulting from both streaming and decay of activated water. Prompt neutrons and gammas generated by the proton beam incident on the target primarily stream along the gaps between the target assembly and core vessel shielding. Because the models and analysis detailed in this report are based on the STS preliminary design, future analysis is needed to support the STS final design.

43 PARTICLE ACCELERATORS↗