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At least 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Carbon Fiber Reinforced Epoxy Vitrimer: Robust Mechanical Performance and Facile Hydrothermal Decomposition in Pure Water

Conventional carbon fiber reinforced thermosetting polymers (CFRPs) are neither recyclable nor repairable due to their crosslinked network. The rapid growing CFRP market raises a serious concern of the waste management. In this work, a viable method to develop a readily recyclable CFRP based on epoxy vitrimer is introduced. First, a self-catalytic epoxy prepolymer with built-in hydroxy and tertiary amine groups is designed, which upon reaction with an anhydride formed a catalyst-free epoxy vitrimer. The epoxy prepolymer is synthesized from a diamine and an excess of bisphenol A epoxy resin. The hydroxyls and tertiary amines of the epoxy prepolymer efficiently catalyze both curing and the dynamic transesterification of the crosslinked polymer without the need of a catalyst. Then, the epoxy vitrimer is used as the matrix resin to prepare CFRP. The resulting CFRP exhibited a tensile strength as high as 356 MPa. More interestingly, the matrix of the CFRP is efficiently degraded in pure water at above 160 °C. This is because the built-in tertiary amines catalyze the hydrolysis of the ester bonds of the crosslinked network. The simple method developed in this work provides a framework for the development of recyclable CFRP.

Liu, Tuan↗
DOE OSTI2018

Developing Novel Multifunctional Materials for High-Efficiency Electrical Energy Storage

This is the final report for the program “Developing Novel Multifunctional Materials for High-efficiency Electrical Energy Storage”, funded by The U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL), and performed by University of Tennessee, from September 01, 2013 to August 31, 2018. Securing a sustainable energy economy by developing affordable and clean energy from renewable energy is a central element to the mission of DOE/NETL. To further this mission, NETL funds research and development of novel multifunctional materials that can be used for high-efficiency electrical energy storage. The main objective of this research program is to conduct fundamental and applied research that lead to successful development and demonstration of novel multifunctional materials, which can improve the efficiency and reduce the cost of hydrogen production with water electrolysis. The specific objectives of this research program include: 1) Design, fabrication and demonstration of thin/well-tunable liquid/gas diffusion layer (TT-LGDLs) with different pore morphologies, including pore sizes and pore porosities. 2) Development of comprehensive computational models of proton exchange membrane water electrolyzer cell (PEMECs) for the investigation of influence of different operating conditions and physical design parameters on its performance. 3) Surface modification of TT-LGDLs for better catalyst access and product/reactant removal, and smaller interfacial contact resistance (ICR). To achieve the above challenging goals, a multidisciplinary research team was formed to work on fundamental and applied research on the following three major technical areas: 1) Design, fabrication and demonstration of thin/well-tunable LGDLs (TT-LGDLs) by using photolithography and wet etching of thin titanium (Ti) foils. During the project period, the team has successfully fabricated TT-LGDLs with different pore morphologies, including pore sizes and pore porosities. The manufacturing steps mainly include cleaning thin Ti foil, supporting the foils, applying photoresist, patterning the photoresist with designed mask, exposing and developing, etching, removing photoresist, and lift-off and cleaning. The manufactured TT-LGDLs were characterized with optical microscopies and scanning electron microscopies. Their pore morphologies, including pore size and porosity, were derived based on advanced image process. The feasibility for scale-up manufacturing has been demonstrated. The TT-LGDLs have been successfully investigated for water splitting in PEMECs, which showing better performance than their counterparts fabricated with the traditional fiber-based materials. 2) Comprehensive computational modeling of a PEMEC. A comprehensive computational model has been successfully developed, and the influence of different operating conditions and physical design parameters on its performance has been investigated, including operating temperature, pressure, exchange current density, electrode thickness, membrane thickness, and interfacial resistance. Results obtained from the present model provide a comprehensive understanding of design parameter effects and consequently improve the design/performance in a PEMEC. 3) Surface modification of TT-LGDLs. The proposed surface modifications of TT-LGDLs by sputter coating and/ electroplating have been successfully demonstrated. It has been found that the performance of PEMECs can be improved by both methods, and the thickness of the electroplated gold thin layer has limited effects on the performance. With the help of the surface modifications, the PEMECs achieved the best ever performance compared with the public literatures. In addition to completion of the proposed method, microporous layers (MPLs) with both irregular micro and sphere nano titanium particles on novel TT-LGDLs was developed for the first time. The MPLs were fabricated by a low-temperature air spraying method, which provide a better catalyst access and product/reactant removal. In summary, under the close collaborations among the research team, all the tasks have been completed and the proposed research objectives have been fulfilled. All the technical milestones have been achieved and the project has been completed successfully. The technical breakthroughs obtained under this project provide novel LGDLs with well-tunable pore morphologies that can significantly improve the performance of water splitting and energy storage. This development can be directly used in existing and next generation energy storage and fuel systems.

08 HYDROGEN↗
DOE OSTI2018

Developing titanium micro/nano porous layers on planar thin/tunable LGDLs for high-efficiency hydrogen production

Proton exchange membrane electrolyzer cells (PEMECs) have been considered one of the most promising devices for hydrogen generation and energy storage from water splitting, especially when coupled with sustainable energy resources. Microporous layers (MPLs), which have been widely used in fuel cells for better catalyst access and product/reactant removal, have limited investigations in PEMECs due to harsh environments and carbon corrosion. In this study, the MPLs with both irregular micro (~5 um) and spherical nano (30-50 nm) titanium particles are developed on novel thin/tunable liquid/gas diffusion layers (TT-LGDLs) and are investigated comprehensively both in-situ and ex-situ for the first time. The MPLs change the wettability of the TT-LGDLs and show super hydrophobic property. The results reveal that micro particle MPLs exhibit improved catalytic activity but increased ohmic resistances, and that nano particle MPLs do not impact catalytic activity meaningfully but exhibit even greater increases in ohmic resistance. The effects of the thickness of the MPLs are also investigated and the typical MPL is also studied by in-situ visualization in a transparent PEMEC with a high-speed and micro-scale visualization system (HMVS). The results indicate the strong feasibility of the TT-LGDLs with small pore size and large porosity for high-efficiency and low-cost PEMEC practical applications.

08 HYDROGEN↗
DOE OSTI2021

Reaction paths of methane activation and oxidation of surface intermediates over NiO on Ceria-Zirconia catalysts studied by In-situ FTIR spectroscopy

Methane activation over NiO/Ce 0.82 Zr 0.18 O 2 catalysts synthesized by combustion synthesis is studied by in-situ IR spectroscopy and correlated to the properties and oxygen speciation of the catalyst. Through XRD, H 2 -TPR, and pyridine adsorption followed by FTIR spectroscopy, the reducibility and Lewis acidity of the catalysts are assessed. In-situ FTIR spectroscopy is used to monitor the methane activation on catalyst surfaces. Complex IR features of methane-derived surface species are observed and are attributed to the formation of surface alkyl/alkoxy, aldehyde, formate/carbonate, and aromatic species. A data analysis algorithm is developed to evaluate the evolution of different surface species over time. The formation of formate and carbonate species is driven by adsorbed surface oxygen, while less reactive oxygen species associated with NiO allow for the production of aromatics and alkoxy intermediates. Finally, by tuning the reducibility and Lewis acidity of the catalyst, the selectivity to alkoxy intermediates can be improved.

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

System identity and transformation in petroleum jurisdictions: A multi-method approach for the North Slope Borough, Alaska

Capturing the multidimensionality of a bounded social-environmental system (SES) presents a range of challenges to interdisciplinary researchers due to the need to integrate divergent scientific paradigms, scalar data, and social theories. Contemporary Arctic circumpolar SESs studied under conditions of rapid and unprecedented climatic, ecological, economic, and sociopolitical change, defy any singular established methodological approach that aims to schematize and interpret the system for decision-making purposes. As a small interdisciplinary team working within a large Arctic SES modeling effort, we have found that developing systems models to support resilience in the Arctic requires an understanding of system dynamics that is attentive to holistic indicators of change, measured both quantitatively and qualitatively. Using the Alaska North Slope Borough as a case study, we apply three convergent frameworks to capture significant dimensions of the system for improved problem definition in confronting the challenges of Arctic climate change. We describe contemporary “oil and gas” social-ecological system components and dynamics, the historical processes and transformations that fundamentally altered the system, and the scientific projections for the most likely catalysts of future change. This analysis results in a typology for defining subnational Arctic hydrocarbon SESs. We conclude that the future of oil and gas development as a policy pathway in different locations experiencing rapid climate change can be evaluated when difficult-to-quantify variables are included.

Lovecraft, Amy Lauren↗
DOE OSTI2018

Overcoming ammonia synthesis scaling relations with plasma-enabled catalysis

Correlations between the energies of elementary steps limit the rates of thermally catalysed reactions at surfaces. Here, we show how these limitations can be circumvented in ammonia synthesis by coupling catalysts to a non-thermal plasma. We postulate that plasma-induced vibrational excitations in N 2 decrease dissociation barriers without influencing subsequent reaction steps. We develop a density-functional-theory-based microkinetic model to incorporate this effect, and parameterize the model using N 2 vibrational excitations observed in a dielectric-barrier-discharge plasma. We predict plasma enhancement to be particularly great on metals that bind nitrogen too weakly to be active thermally. Ammonia synthesis rates observed in a dielectric-barrier-discharge plasma reactor are consistent with predicted enhancements and predicted changes in the optimal metal catalyst. The results provide guidance for optimizing catalysts for application with plasmas.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Lean Miller Cycle System Development for Light-Duty Vehicles (Final Report)

This report summarizes activities conducted in support of the project “Lean Miller Cycle System Development for Light-Duty Vehicles” under Cooperative Agreement Number DE-EE0006853. In order to accomplish the government objective of achieving breakthrough thermal efficiencies while meeting U.S. EPA emission standards, this project focused on combining two enabling technologies in a gasoline engine: lean combustion and “Miller Cycle.” Lean combustion is thermodynamically more efficient than stoichiometric combustion but requires a more complex exhaust aftertreatment system compared to a traditional three-way catalyst system. The “Miller Cycle” concept increases expansion of combustion gases to extract additional work, reduces pumping losses, and increases efficiency. The objective of the project was to research, develop, and demonstrate the new Lean Miller Cycle (LMC) combustion concept to achieve a 35% improvement in fuel economy over a 2010 production baseline vehicle. The baseline vehicle chosen was a Chevrolet Impala equipped with a 3.5L V6 port-fuel injected naturally-aspirated engine, a four-speed automatic transmission with a peak-power and -torque of 157 kW and 290 N-m respectively. The enabling technologies were developed and demonstrated on a single cylinder engine and then integrated into a multicylinder engine and aftertreatment system. Along with achieving the efficiency targets, the downsized boosted LMC engine system was projected to achieve a peak-power and –torque of 172 kW at 354 Nm respectively exceeding the baseline engine performance. The multicylinder engine was optimized and calibrated over a set of steady-state operating points on an engine dynamometer. The target of the project was a 35% improvement in combined city/highway fuel economy at SULEV30 tailpipe emissions over the baseline vehicle. The project achieved a projected 42.4% from the vehicle drive cycle analysis assuming no penalty for management of the lean-aftertreatment system. This penalty was projected to fall within the fuel economy margin achieved and include control and calibration compromises for catalyst heating, NH3 formation for lean-NOx SCR and drive quality. A final vehicle demonstration was planned where emissions, drivability and performance were to be confirmed. Four decision gates were set up annually with deliverables to assess progress and determine whether status to deliverables warranted project continuation through the final vehicle demonstration. The project was closed in June 2019 at the end of budget period three after not passing the third decision gate due to projected system costs prohibiting economic feasibility in the light-duty vehicle industry landscape. However, the project’s efficiency targets were achieved by validation through steady-state dynamometer testing of the multicylinder engine.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2025

On-line Inductively Coupled Plasma Mass Spectrometry Reveals Material Degradation Dynamics of Au and Cu Catalysts during Electrochemical CO 2 Reduction

A significant challenge in commercializing electrochemical CO 2 reduction (CO 2 R) is achieving catalyst durability. Here, in this study, online inductively coupled mass spectrometry (ICP–MS) was used to investigate catalyst degradation via nanoparticle detachment and/or dissolution into metal ions under CO 2 R operating conditions in 0.1 M KHCO 3 . We developed an experimental framework with ex situ characterization to validate the online ICP–MS method for in situ evaluation of degradation from metal foils. By varying the applied potential and microenvironment (CO 2 vs N 2 -saturated electrolyte), we gained insights into the degradation of Au and Cu foils under CO 2 R and hydrogen evolution reaction (HER) conditions. While both Au and Cu foils were observed to be stable to dissolution in these regimes, degradation via nanoparticle detachment from the foil surface at the femtogram scale was observed as a function of reaction conditions, providing new insights into material degradation mechanisms. When applying potential steps at −0.1 and −1.0 V vs the reversible hydrogen electrode (RHE), Au was found to degrade via nanoparticle detachment under CO 2 R operating conditions more than under HER conditions, while Cu was found to degrade via nanoparticle detachment in similar amounts during both reactions. Au lost ∼1.8× more mass and ∼7.5× more nanoparticles than Cu under CO 2 R operating conditions. This study demonstrates the use of online ICP–MS to gain insight into the degradation of Au and Cu, the importance of studying unconventional degradation mechanisms such as nanoparticle detachment, and that online ICP–MS can be further utilized to gain fundamental understanding of catalyst durability for a variety of reaction systems.

Yan, Katherine [Stanford Univ., CA (United States)↗
DOE OSTI2016

Insights into gold-catalyzed plasma-assisted CVD growth of silicon nanowires

Understanding and controlling effectively the behavior of metal catalyst droplets during the Vapor-Liquid-Solid growth of nanowires are crucial for their applications. In this work, silicon nanowires are produced by plasma-assisted Chemical Vapor Deposition using gold as a catalyst. The influence of hydrogen plasma on nanowire growth is investigated experimentally and theoretically. Interestingly, in contrast to conventional chemical vapor deposition, the growth rate of silicon nanowires shows a decrease as a function of their diameters, which is consistent with the incorporation of silicon via sidewall diffusion. We show that Ostwald ripening of catalyst droplets during nanowire growth is inhibited in the presence of a hydrogen plasma. However, when the plasma is off, the diffusion of Au atoms on the nanowire sidewall can take place. Based on this observation, we have developed a convenient method to grow silicon nanotrees.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Pushing Cu uphill of the volcano curve: Impact of a WC support on the catalytic activity of copper toward the hydrogen evolution reaction

Here, the adsorption of atomic H and H 2 on copper mono- and submonolayers supported on hexagonal WC(0001) surfaces has been investigated using density functional theory with the Perdew–Burke–Ernzerhof exchange correlation functional and D2 van der Waals corrections. Results evidence the impact of the termination of the carbide substrate on fundamental properties of Cu adatoms, and, hence, on the stability of molecular and atomic hydrogen, defining copper's catalytic activity for hydrogen evolution reaction. Using H adsorption energy as a descriptor, catalytic activity of Cu adlayers for hydrogen evolution reaction was estimated using traditional volcano curves and a curve, obtained at low hydrogen coverage. Obtained results evidence that copper adlayers supported on the WC may present a viable low-cost alternative to noble metal-based catalysts, with improved catalytic activity compared to that of copper. This, potentially, can be a useful basis for designing and developing novel functional materials with predetermined catalytic properties.

08 HYDROGEN↗
DOE OSTI2019

Correlated Multimodal Approach Reveals Key Details of Nerve-Agent Decomposition by Single-Site Zr-Based Polyoxometalates

Development of technologies for protection against chemical warfare agents (CWAs) is critically important. Recently, polyoxometalates have attracted attention as potential catalysts for nerve-agent decomposition. Improvement of their effectiveness in real operating conditions requires an atomic-level understanding of CWA decomposition at the gas–solid interface. We investigated decomposition of the nerve agent Sarin and its simulant, dimethyl chlorophosphate (DMCP), by zirconium polytungstate. Using a multimodal approach, we showed that upon DMCP and Sarin exposure the dimeric tungstate undergoes monomerization, making coordinatively unsaturated Zr(IV) centers available, which activate nucleophilic hydrolysis. Furthermore, DMCP is shown to be a good model system of reduced toxicity for studies of CWA deactivation at the gas–solid interface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Investigation of solvent effects on the hydrodeoxygenation of guaiacol over Ru catalysts

The effects of a liquid phase environment on the hydrodeoxygenation of guaiacol, a prototypical lignin derived compound, have been investigated over a Ru catalyst from first principles. A microkinetic reactor model with parameters obtained from density functional theory and implicit solvation schemes was developed to study the effects of condensed phases on the reaction mechanism and kinetic parameters. Phenol was found to be the major aromatic product across all reaction environments. Our model predicts that less protic solvents such as 1-butanol, diethyl ether, and n-hexane have a positive effect on the reaction kinetics for the production of phenolics relative to vapor and aqueous reaction environments. The dominant reaction mechanism for aromatics production remains unchanged across all reaction media. Next, we investigated the possibility of cycloalkane production through hydrogenation of phenol in vapor and liquid phase environments. Our calculations indicated that the reaction pathway for cycloalkane production from phenol will most likely follow an initial dehydrogenation of the hydroxyl group. Based on the vapor phase density functional theory calculations, we proposed a probable reaction pathway and calculated the condensed phase effects along this reaction route. We observed that an aqueous phase has a more favorable effect for cycloalkane production from phenol relative to vapor phase and other less protic solvent environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

One Step Hydrogen Generation Through Sorption Enhanced Reforming

One-step hydrogen generation, using Sorption Enhanced Reforming (SER) technology, is an innovative means of providing critical energy and environmental improvements to US manufacturing processes. The Gas Technology Institute (GTI) is developing a Compact Hydrogen Generator (CHG) process, based on SER technology, which successfully integrates previously independent process steps, achieves superior energy efficiency by lowering reaction temperatures, and provides pathways to doubling energy productivity with less environmental pollution. GTI’s prior CHG process development efforts have culminated in an operational pilot plant. During the initial pilot testing, GTI identified two operating risks- 1) catalyst coating with calcium aluminate compounds, 2) limited solids handling of the sorbent. Under this contract GTI evaluated alternative materials (one catalyst and two sorbents) to mitigate both risks. The alternate catalyst met performance targets and did not experience coating with calcium aluminate compounds of any kind. The alternate sorbent materials demonstrated viable operation, with one material enabling a three-fold increase in sorbent flow. The testing also demonstrated operation at 90% of its rated capacity. Lastly, a carbon dioxide co-production study was performed to assess the advantage of the solid phase separation of carbon dioxide- inherent in the CHG process. Approximately 70% lower capital cost is achievable compared to SMR-based hydrogen production with CO2 capture, as well as improved operating costs.

08 HYDROGEN↗
DOE OSTI2024

Next-Generation Materials Design: Quantum Mechanics and Data-Driven Modeling

The future of materials design is rapidly advancing through the combination of quantum mechanics and data-driven modeling. These approaches integrate quantum principles with advanced data analysis, enabling precise insights into material behavior. This talk will highlight recent progress in using these methods for computational design, particularly in high-entropy alloy catalysts, emphasizing the role of hierarchical machine-learning architectures for accurate predictions. Additionally, I will discuss our work on developing machine learning interatomic potentials (MLPs) for single-element metals, metal oxides, and alloys under extreme conditions, focusing on melting behavior and phase properties at high temperatures and pressures. We have also refined our MLP models to capture dynamic surface interactions, such as CO2 and CO adsorption on MgO, using both static and molecular dynamics simulations. These models maintain high accuracy while significantly reducing computational costs compared to first-principles calculations. By enabling efficient and accurate simulations, this work supports broader community adoption, optimizes datasets for materials discovery, and extends the accessible time, size, and environmental conditions beyond the limits of experiments and traditional simulations.

machine learning↗
NASA NTRS2000

The Sugar Model: Catalytic Flow Reactor Dynamics of Pyruvaldehyde Synthesis from Triose Catalyzed by Poly-L-Lysine Contained in a Dialyzer

The formation of pyruvaldehyde from triose sugars was catalyzed by poly-L-lysine contained in a small dialyzer (100 MWCO) suspended in a much larger triose substrate reservoir. The polylysine confined in the dialyzer functioned as a catalytic flow reactor that constantly brought in triose from the substrate reservoir by diffusion to offset the drop in triose concentration within the reactor caused by its conversion to pyruvaldehyde. A 400 mM solution of poly-L-lysine contained in a 0.35 ml dialyzer placed in a 120 ml solution of triose substrate (pH 5.5, 40 C) generated pyruvaldehyde 11 -times faster than an a control reaction without the catalytic dialyzer. However, since the catalytic dialyzer's volume was 343-times smaller than the control reaction, the synthetic intensity (rate/volume) of pyruvaldehyde synthesis within the catalytic dialyzer was 3400-times greater than that of the control reaction and substrate solution. A similar result was obtained using a dialyzer with a 500 MWCO value. Acting as a catalytic flow reactor the polylysine catalytic dialyzer synthesized about 3.5 molecules of pyruvaldehyde per lysine residue in 7 days -- an amount of triose equal to twice the weight of the catalyst. At 7 days the catalytic activity of polylysine was 16% of its initial value, a result indicating catalyst-poisoning caused by reaction of pyruvaldehyde with the e-amino groups of polylysine. The dialyzer method of catalyst containment was selected it provides a simple, flexible, and easily manipulated experimental system for studying the dynamics and evolutionary development of confined autocatalytic processes related to the origin of life under anaerobic conditions.

Weber, Arthur L.↗