Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “catalyst development”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Structure of maize BZR1-type β-amylase BAM8 provides new insights into its noncatalytic adaptation

Plant β-amylase (BAM) proteins play an essential role in growth, development, stress response, and hormone regulation. Despite their typical (β/α) 8 barrel structure as active catalysts in starch breakdown, catalytically inactive BAMs are implicated in diverse yet elusive functions in plants. Further, the noncatalytic BAM7/8 contain N-terminal BZR1 domains and were shown to be involved in the regulation of brassinosteroid signaling and possibly serve as sensors of yet an uncharacterized metabolic signal. While the structures of several catalytically active BAMs have been reported, structural characterization of the catalytically inactive BZR1-type BAMs remain unknown. Here, we determine the crystal structure of β-amylase domain of Zea mays BAM8/BES1/BZR1-5 and provide comprehensive insights into its noncatalytic adaptation. Using structural-guided comparison combined with biochemical analysis and molecular dynamics simulations, we revealed conformational changes in multiple distinct highly conserved regions resulting in rearrangement of the binding pocket. Altogether, this study adds a new layer of understanding to starch breakdown mechanism and elucidates the acquired adjustments of noncatalytic BZR1-type BAMs as putative regulatory domains and/or metabolic sensors in plants.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Site-Selective Probes of Mixed-Node Metal Organic Frameworks for Photocatalytic Hydrogen Generation

Metal organic frameworks (MOFs) have emerged as a novel platform offering new promise for photocatalytic applications. In this work, we report a mixed-node MOF (MOF-74) based on earth-abundant metals (i.e., Co and Fe) as highly active and robust photocatalysts for visible light-driven H 2 generation. Using in situ X-ray absorption spectroscopy which allows us to selectively probe the individual metal node in MOFs, we unambiguously identified the catalytic active sites and captured the key intermediate species under the standard catalytic conditions. We show that both Co and Fe centers in MOF-74 are the reversible active sites, and the accumulation of their reduced states is responsible for the observed induction period for H 2 generation. Moreover, we captured the key intermediate species formed when the reaction reaches equilibrium, which is featured by an elongated Co–O bond at the Co center and a more distorted octahedral geometry at the Fe center with respect to their original geometry. These results not only demonstrate the potential of MOF-74 as a single site catalyst for H 2 generation but also provide new insight into the catalytic mechanism for further development.

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

One-Step Facile Synthesis of High-Activity Nitrogen-Doped PtNiN Oxygen Reduction Catalyst

PtM alloy electrocatalysts (M = Fe, Co, Ni) have been the subject of many investigations aimed at increasing their attractive properties, in particular oxygen reduction reaction (ORR) activity, while reducing total platinum-group-metal content and improving durability. Despite some success, these catalysts still have relatively high Pt content and lack the necessary durability as M metals leach out from the alloys during potential cycling. Previously, we synthesized nitrogen (N)-doped PtMN/C catalysts consisting of thin Pt shells on M nitride cores by a two-step method, which showed higher ORR activity and stability than their PtM counterparts. In the present work, we developed a facile one-step synthesis method, which comprises a single thermal annealing process of the N-doped PtNiN/C alloy. The ORR performance of the one-step synthesized PtNiN/C catalyst is much higher than that of the two-step synthesized PtNiN/C, as revealed by rotating disk electrode measurements. Membrane electrode assembly fuel cell testing demonstrated superb durability and high activity. Formation of Pt monolayer shells on the nitrided (Pt x Ni 1-x ) 4 N cores was confirmed by in situ X-ray absorption spectroscopy. The origins of the enhanced activity and stability of the one-step synthesized PtNiN/C catalyst are elucidated based on density functional theory calculations together with the experimental results.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2025

Spatially Patterned Architectures to Modulate CO 2 Reduction Cascade Catalysis Kinetics

Electrochemical CO 2 reduction using renewable sources of electrical energy holds promise for converting CO 2 into fuels and chemicals. The complex interactions among chemical/electrochemical reactions and mass transport make it difficult to analyze the effect of an individual process on electrode performance based only on experimental methods. Here, we developed a generalized steady-state simulation to describe an electrode surface in which sequential cascade catalysts are patterned in a periodic trench design. If appropriately constructed, this trench geometry is hypothesized to be able to yield a higher net current density for a CO 2 reduction (CO 2 R) cascade reaction. We have used realistic experimental reaction kinetics to investigate the role of trench geometry in mass transport, local microenvironments, and selectivity for a model CO 2 R cascade reaction. The model considers local concentration gradients of bicarbonate species at quasi-equilibrium and catalytic surface reactions based on concentration-dependent Butler–Volmer kinetics. Our results suggest that varying the spatial distribution of active sites plays a significant role in facilitating effective mass transport between active sites, modulating selectivity for the cascade reaction, and enhancing the yield of desirable cascade products. Moreover, we observe that this trench geometry significantly alters the cascade reaction rate by affecting the local pH, which can cause inadvertent depletion of available aqueous CO 2 to limit the CO 2 R cascade kinetics and modest suppression of the hydrogen evolution reaction (HER). The results highlight the trade-offs between mass transport, pH, and reaction kinetics that become apparent only when considering the coupled physics of all processes at the electrode surface. Here, this model can thus serve as a primary tool to build more selective and efficient patterned architectures for the CO 2 R cascade catalysis.

CO2 reduction↗
DOE OSTI2026

A Monolithic Artificial Leaf for Solar Methanol Production from CO 2 and H 2 O

Methanol, an important liquid fuel and chemical feedstock, has yet to be produced using solar energy, H 2 O, and CO 2 as sole inputs in a standalone device. Here, this study directly addresses this longstanding challenge through presenting the first demonstration of unbiased solar methanol production from CO 2 and H 2 O with a monolithic artificial leaf design, surpassing the previous best energy efficiency in solar alcohol production by at least 1 order of magnitude. We first develop a new generation of photocathodes based on Si micropillar arrays and a cobalt tetraaminophthalocyanine molecular catalyst. By integrating a C 60 interlayer that facilitates unidirectional electron transfer through the semiconductor/catalyst interface, we realize a photovoltage of 500 mV, one of the highest recorded for single-junction Si-based photoelectrodes in aqueous CO 2 reduction, as well as unprecedented methanol formation with a Faradaic efficiency of 30% and a partial current density of 6.3 mA cm –2 . We further integrate the photocathode with a multijunction perovskite photovoltaic minimodule to afford a standalone solar fuel system, which demonstrates a light-to-methanol conversion efficiency of 0.8%, 32 times higher than the present record in light-to-alcohol conversion with an artificial leaf.

alcohols↗
DOE OSTI2024

Correlating activities and defects in (photo)electrocatalysts using in-situ multi-modal microscopic imaging

Photo(electro)catalysts use sunlight to drive chemical reactions such as water splitting. A major factor limiting photocatalyst development is physicochemical heterogeneity which leads to spatially dependent reactivity. To link structure and function in such systems, simultaneous probing of the electrochemical environment at microscopic length scales and a broad range of timescales (ns to s) is required. Here, we address this challenge by developing and applying in- situ (optical) microscopies to map and correlate local electrochemical activity, with hole lifetimes, oxygen vacancy concentrations and photoelectrode crystal structure. Using this multi-modal approach, we study prototypical hematite (α-Fe 2 O 3 ) photoelectrodes. We demonstrate that regions of α-Fe 2 O 3 , adjacent to microstructural cracks have a better photoelectrochemical response and reduced back electron recombination due to an optimal oxygen vacancy concentration, with the film thickness and extended light exposure also influencing local activity. Our work highlights the importance of microscopic mapping to understand activity, in even seemingly homogeneous photoelectrodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Acid–base catalysis over perovskites: a review

We present that perovskite catalysts have been extensively studied for reduction–oxidation (redox) reactions; however, their acid–base catalytic properties are still under-explored. This review collects work aiming to study the acid–base catalytic properties of perovskites. Reports regarding combined acid–base/redox catalysis over perovskites lie beyond the scope of the present review. For the characterization of acid–base properties, researchers have studied the interaction of probe molecules with perovskite surfaces by means of multiple techniques that provide information about the density, strength and type of adsorption sites. The top-surface composition of perovskites, which relates to the abundance of the acid–base sites, has been studied by means of low energy ion scattering (LEIS), and, the less surface sensitive, conventional X-ray photoelectron spectroscopy (XPS). Probe reactions, with the conversion of 2-propanol as the common choice, have also been employed for characterizing the acid–base catalytic properties of perovskites. The complex nature of perovskite surfaces, which explains the still absent fundamental relations between the structure of the catalyst and reaction rates/selectivity, encounters a great challenge due to the surface reconstruction of these materials. In this review, we devote a special section to highlight recent publications that report the impact of surface reconstruction and particle shape on acid–base catalysis over perovskites. In addition, we review promising catalytic performances of perovskite catalysts for other reactions of interest. Challenges in acid–base catalysis over perovskites focus on the development of time-resolved monolayer-sensitive characterization of surfaces under operando conditions and the discernment of combined acid–base/redox reaction mechanisms. Finally, opportunities lay on tuning the acid–base characteristics of perovskites with computation-based catalytic descriptors to achieve desired selectivities and enhanced rates.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Development and Application of In Situ Nanocharacterization to Photocatalytic Materials for Solar Fuel Generation

Photocatalytic materials offer an attractive approach for converting solar energy into chemical energy but the performance of the current generation of materials is insufficient to make a technology viable. To address this deficiency, it is necessary to develop a fundamental atomic level understanding of the functioning of such materials so that strategies can be developed to improve performance. This project was undertaken to explore the fundamental structure and properties of photocatalytic materials using atomic resolution imaging and spectroscopy techniques available on advanced transmission electron microscopy. Specifically, there is a need to develop an understanding of how atomic structures/defects and nanoparticle configurations regulate electronic, optical, and catalytic properties to facilitate the design of next generation photocatalysts for solar fuel production. The work focused on fundamental materials information that can be gained from advanced transmission electron microscopy study on novel and existing photocatalytic systems with an emphasis on the hydrogen evolution reaction (HER). Throughout the project, new instrumentation and microscopy characterization tools were developed. Two focus areas were: developing in situ TEM methods and advanced electron energy-loss spectroscopic for nanoscale analysis of catalysts. The work spanned a period of 12 years and for convenience, the report is divided into four phases, approximately corresponding to the four funding periods of the program. Most of the significant results are reported in archival journal publications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Editorial: Deep-sea observation equipment and exploration technology

The increasing interest in deep-sea exploration is a crucial catalyst for driving advancements in deep-sea observation technology research. Numerous sophisticated sensors have been developed to facilitate comprehensive studies in deep-sea physics, chemistry, and geology. For example, cutting-edge small and compact seabed samplers are now employed on various platforms, such as Autonomous Underwater Vehicles (AUVs), Remotely Operated Vehicles (ROVs), and Human-Operated Vehicles (HOVs), enabling observation of the hadal zone. Additionally, Micro-electromechanical systems (MEMS) sensors are routinely utilized for ocean wave observation. This Research Topic aims to foster new insights into ocean exploration and observation technology, including ocean sensor technology, ocean observation platforms, and ocean observation reliability technology.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Oxygen Reduction Reaction Catalyzed by Carbon-Supported Platinum Few-Atom Clusters: Significant Enhancement by Doping of Atomic Cobalt

Oxygen reduction reaction (ORR) plays an important role in dictating the performance of various electrochemical energy technologies. As platinum nanoparticles have served as the catalysts of choice towards ORR, minimizing the cost of the catalysts by diminishing the platinum nanoparticle size has become a critical route to advancing the technological development. Herein, first-principle calculations show that carbon-supported Pt 9 clusters represent the threshold domain size, and the ORR activity can be significantly improved by doping of adjacent cobalt atoms. This is confirmed experimentally, where platinum and cobalt are dispersed in nitrogen-doped carbon nanowires in varied forms, single atoms, few-atom clusters, and nanoparticles, depending on the initial feeds. The sample consisting primarily of Pt 2~7 clusters doped with atomic Co species exhibits the best mass activity among the series, with a current density of 4.16 A mg Pt − 1 at +0.85 V vs. RHE that is almost 50 times higher than that of commercial Pt/C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

European auxiliary propulsion, 1972

The chemical and electric auxiliary propulsion technology of the United Kingdom, France, and West Germany is discussed in detail, and the propulsion technology achievements of Italy, India, Japan, and Russia are reviewed. A comparison is presented of Shell 405 catalyst and a European spontaneous hydrazine catalyst called CNESRO I. Finally, conclusions are drawn regarding future trends in European auxiliary propulsion technology development.

Holcomb, L. B.↗
NASA NTRS1979

Fuel cell sesquicentennial

The development of fuel cell technology is summarized, and the potential for utility-type fuel cell installations is assessed on the occasion of the 150th anniversary of the construction of the first fuel cell by Sir William Grove. The only functional fuel-cell systems developed to date, the hydrogen-oxygen cells used by NASA, are indicated, and hydrazine and alcohol (methanol) cells are considered. Areas requiring development before the implementation of fuel cells as general purpose utility-type electric generators include catalysts for naturally occurring hydrocarbons or processes for low-cost methanol or hydrazine production, efficient means of scrubbing and enriching air, self-regulating systems, and 15- to 20-fold power density increases. It is argued that although ideas for eliminating certain of the above-mentioned problems have been proposed, fuel-cell systems can never be expected to equal the efficiency, reliability and low cost of conventional power plants, and thus developmental support should be discontinued.

Cohn, E. M.↗
NASA NTRS2011

Carbon Dioxide Reduction Technology Trade Study

For long-term human missions, a closed-loop atmosphere revitalization system (ARS) is essential to minimize consumables. A carbon dioxide (CO2) reduction technology is used to reclaim oxygen (O2) from metabolic CO2 and is vital to reduce the delivery mass of metabolic O2. A key step in closing the loop for ARS will include a proper CO2 reduction subsystem that is reliable and with low equivalent system mass (ESM). Sabatier and Bosch CO2 reduction are two traditional CO2 reduction subsystems (CRS). Although a Sabatier CRS has been delivered to International Space Station (ISS) and is an important step toward closing the ISS ARS loop, it recovers only 50% of the available O2 in CO2. A Bosch CRS is able to reclaim all O2 in CO2. However, due to continuous carbon deposition on the catalyst surface, the penalties of replacing spent catalysts and reactors and crew time in a Bosch CRS are significant. Recently, technologies have been developed for recovering hydrogen (H2) from Sabatier-product methane (CH4). These include methane pyrolysis using a microwave plasma, catalytic thermal pyrolysis of CH4 and thermal pyrolysis of CH4. Further, development in Sabatier reactor designs based on microchannel and microlith technology could open up opportunities in reducing system mass and enhancing system control. Improvements in Bosch CRS conversion have also been reported. In addition, co-electrolysis of steam and CO2 is a new technology that integrates oxygen generation and CO2 reduction functions in a single system. A co-electrolysis unit followed by either a Sabatier or a carbon formation reactor based on Bosch chemistry could improve the overall competitiveness of an integrated O2 generation and CO2 reduction subsystem. This study evaluates all these CO2 reduction technologies, conducts water mass balances for required external supply of water for 1-, 5- and 10-yr missions, evaluates mass, volume, power, cooling and resupply requirements of various technologies. A system analysis and comparison among the technologies was made based on ESM, technology readiness level and reliability. Those technologies with potential were recommended for development.

Jeng, Frank F.↗
NASA NTRS2016

Rocket Propulsion (RP) 21 Steering Committee Meeting - NASA Spacecraft Propulsion Update

Lander Tech is three separate but synergistic efforts: Lunar CATALYST (Lunar Cargo Transportation and Landing by Soft Touchdown) Support U.S. industry led robotic lunar lander development via three public-private efforts. Support U.S. industry led robotic lunar lander development via three public-private partnerships. Infuse or transfer landing technologies into these public private partnerships. Advanced Exploration Systems-Automated Propellant Loading (APL) -Integrated Ground Operations. Demonstrate LH2 zero loss storage, loading and transfer operations via testing on a large scale in a relevant launch vehicle servicing environment. (KSC, GRC). Game Changing Technology-20 Kelvin -20 Watt Cryocooler Development of a Reverse Turbo-Brayton Cryocooler operating at 20 Kelvin with 20 Watts of refrigeration lift.

Propellant↗
DOE OSTI2020

Single Atom Catalysis: An Analogy between Heterogeneous and Homogeneous Catalysts

In recent years, enormous efforts have been invested to improve the atom-efficiency of metal catalysts by decrease the size of metal particles to the limit of isolated atoms in heterogenous catalysis, termed single atom catalysts (SACs). In addition to being atom-efficient, these SACs are increasingly gaining attention due to the unique reactivity and selectivity they have exhibited in industrially relevant reactions, including both oxidation and hydrogenation reactions. Clear parallels can be drawn between heterogeneous SACs and their analogous homogeneous catalysts. In this chapter, we highlight SACs that demonstrate this relationship and report on relevant, recent developments in the field of single atom catalysis.

Yuk, Simuck F.↗
DOE OSTI2022

Reaction mechanism and kinetics for N 2 reduction to ammonia on the Fe–Ru based dual-atom catalyst

Environmental and energy considerations demand that the Haber-Bosch process for reducing N 2 to NH 3 be replaced with electrochemical ammonia synthesis where the H atoms come from water instead of from H 2 . But a practical realization of electrochemical N 2 reduction reaction (NRR) requires the development of new generation electrocatalysts with low overpotential and high Faraday efficiency (FE). A major problem here is that the hydrogen evolution reaction (HER) competes with NRR. Herein, we consider new generation dual-site catalysts involving two different metals incorporated into a novel two-dimensional C 3 N–C 2 N heterostructure that provides a high concentration of well-defined but isolated active sites that bind two distinct metal atoms in a framework that facilitates electron transfer. We report here the mechanism and predicted kinetics as a function of applied potential for both NRR and HER for the (Fe–Ru)/C 3 N–C 2 N dual atom catalyst. These calculations employ the grand canonical potential kinetics (GCP-K) methodology to predict reaction free energies and reaction barriers as a function of applied potential. The rates are then used in a microkinetic model to predict the turn-over-frequencies (TOF) as a function of applied potential. At U = 0 V, the FE for NRR is 93%, but the current is only 2.0 mA cm –2 . The onset potential (at 10 mA cm –2 ) for ammonia on Fe–Ru/C 3 N–C 2 N is –0.22 V RHE . This leads to a calculated TOF of 434 h –1 per Fe–Ru site. In conclusion, we expect that the mechanisms for NRR and HER developed here will help lead to new generations of NRR with high TOF and FE.

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

Self‐Stabilized Heterometallic Pair Sites for Selective Ethanol Dehydrogenation on Pt–Cr–Ag Alloy Catalysts

Self‐stabilized, heterometallic pair‐sites can enable fine‐tuning of catalytic functionality while also mitigating dynamic structural changes that degrade catalytic performance. This study demonstrates the development and characterization of trimetallic Pt x Cr x Ag 1‐2x ( x ≤ 0.1) alloys with active Pt–Cr pair‐ensembles for non‐oxidative ethanol dehydrogenation, leveraging predictions that favorable bonding stabilizes Pt–Cr pairs diluted in Ag. Operando X‐ray absorption spectroscopy confirms the preferential formation and stability of Pt–Cr pairings dispersed throughout the Ag matrix, and ambient‐pressure X‐ray photoelectron spectroscopy shows that Pt–Cr sites have significant activity for ethanol dehydrogenation, while suppressing reaction processes that deactivate binary Pt–Ag and Cr–Ag alloys. This work demonstrates that stabilizing heterometallic pair sites within trimetallic alloys provides a new avenue for designing catalysts with discrete active sites that are durable and highly selective.

36 MATERIALS SCIENCE↗