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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Self-Cleaning Boudouard Reactor for Full Oxygen Recovery from Carbon Dioxide

Oxygen recovery from respiratory carbon dioxide is an important aspect of human spaceflight. Methods exist to sequester the carbon dioxide, but production of oxygen needs further development. The current International Space Station Carbon Dioxide Reduction System (CRS) uses the Sabatier reaction to produce water (and ultimately breathing air). Oxygen recovery is limited to 50% because half of the hydrogen used in the Sabatier reactor is lost as methane which is vented overboard. The Bosch reaction, which converts carbon dioxide to oxygen and solid carbon, is capable of recovering all the oxygen from carbon dioxide, and it is a promising alternative to the Sabatier reaction. However, the last reaction in the cycle, the Boudouard reaction, produces solid carbon, and the resulting carbon buildup eventually fouls the catalyst, reducing reactor life and increasing consumables. To minimize this fouling and increase efficiency, a number of self-cleaning catalyst designs have been created. This paper will describe recent results evaluating one of the designs.

ECLSS↗
NASA NTRS2016

Self-Cleaning Boudouard Reactor for Full Oxygen Recovery from Carbon Dioxide

Oxygen recovery from respiratory carbon dioxide is an important aspect of human spaceflight. Methods exist to sequester the carbon dioxide, but production of oxygen needs further development. The current International Space Station Carbon Dioxide Reduction System (CRS) uses the Sabatier reaction to produce water (and ultimately breathing air). Oxygen recovery is limited to 50 because half of the hydrogen used in the Sabatier reactor is lost as methane, which is vented overboard. The Bosch reaction, which converts carbon dioxide to oxygen and solid carbon is capable of recovering all the oxygen from carbon dioxide, and is the only real alternative to the Sabatier reaction. However, the last reaction in the cycle, the Boudouard reaction, produces solid carbon and the resulting carbon buildup will eventually foul the nickel or iron catalyst, reducing reactor life and increasing consumables. To minimize this fouling and increase efficiency, a number of self-cleaning catalyst designs have been created. This paper will describe recent results evaluating one of the designs.

Oxygen Recovery↗
DOE OSTI2026

How to Minimize Faradaic Efficiency Error in Electrochemical CO 2 Reduction for Gas Products

Faradaic efficiency (FE) is an important metric for evaluating electrochemical processes, such as carbon dioxide reduction, that is often used for performance comparisons. Although the equation to calculate FE is well-known, details needed to yield accurate values are often overlooked, potentially leading to errors exceeding 100%. Avoiding any errors is crucial for drawing correct conclusions, especially during a catalysis optimization process. Factors with high potential for FE errors include incorrect mass flow rates and temperature values, imprecise gas chromatography calibrations, and uncorrected gas viscosities, while factors with less potential are also identified. In conclusion, this manuscript presents FE calculation guidelines intended for both newcomers and experts in the field of electrochemical fuel production.

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

Core–Shell Covalently Linked Graphitic Carbon Nitride–Melamine–Resorcinol–Formaldehyde Microsphere Polymers for Efficient Photocatalytic CO 2 Reduction to Methanol

Photocatalytic reduction of CO 2 with light and H 2 O to form CH 3 OH is a promising route to mitigate carbon emissions and climate changes. Although semiconducting metal oxides are potential photocatalysts for this reaction, low photon efficiency and leaching of environmental unfriendly, toxic metals limit their applicability. Here, we report a metal-free, core-shell photocatalysts consisting of graphitic carbon nitride (g-C 3 N 4 , CN) covalently linked to melamine-resorcinol-formaldehyde (MRF) microsphere polymers for this reaction. Cova-lent linkage enabled efficient separation of photo-generated carriers and photocatalysis. Using 100 mg of a photocatalyst containing 15 wt.% CN, a CH 3 OH yield of 0.99 μmol·h -1 was achieved at a reaction temperature of 80 °C and 0.5 MPa with external quantum efficiencies ranging from 5.5% at 380 nm to 1.7% at 550 nm. The yield was about 20 and 10 times higher than that of its components CN and MRF, respectively. Characterization with XPS, TEM, and bulk and surface elemental analyses supported a core-shell structure and charge transfer at C-N bond at the CN-MRF interface between the methoxy group in the 2,4-trishydroxylmethyl-1,3-diphenol part of MRF and the terminal amino groups in the CN. This enhanced ligand-to-ligand charge transfer resulted in 67% of photo-excited internal charge transferred from CN to hy-droxymethylamino group in MRF, whose amino group was the catalytic site for CO 2 photocatalytic reduction to CH 3 OH. Furthermore, this study provides a series of new metal-free photocatalyst designs and insights into the molecular-level structure-mediated photocatalytic response

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

Lithium cuprate, a multifunctional material for NO selective catalytic reduction by CO with subsequent carbon oxide capture at moderate temperatures

Li 2 CuO 2 was evaluated as a possible catalyst for the NO selective catalytic reduction (NO SCR) by CO. The initial idea was supported by ab initio thermodynamic analysis. This analysis showed that NO SCR was favored by using Li 2 CuO 2 as a catalyst, based on the calculated heat of reaction and Gibbs free energy. The NO SCR reaction was evaluated under dynamic, isothermal and cyclic conditions using different NO : CO ratios (2 : 1, 1 : 1 and 1 : 2). The dynamic and isothermal experiments showed that Li 2 CuO 2 does reduce NO in the presence of CO to reach higher conversions (>90%) between 400 and 450 °C. However, it must be mentioned that the catalytic process was reduced once some of the produced CO 2 was captured on the ceramic. At that point, Li 2 CuO 2 acts as a bifunctional material, catalyzing the NO SCR reaction and capturing some of the produced CO 2 . Moreover, cyclic experiments evidenced high NO reduction. Finally, a different set of experiments showed that this catalytic reduction performed differently if NO and CO were previously fed. Finally, when lithium cuprate is previously carbonated (initial CO feed), the catalytic reaction does not complete. In contrast, when there was a previous nitrate formation (initial NO feed), the reaction reached 100% efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1976

Development of EPA aircraft piston engine emission standards

Piston engine light aircraft are significant sources of carbon monoxide in the vicinity of high activity general aviation airports. Substantial reductions in carbon monoxide were achieved by fuel mixture leaning using improved fuel management systems. The air quality impact of the hydrocarbon and oxides of nitrogen emissions from piston engine light aircraft were insufficient to justify the design constraints being confronted in present control system developments.

Houtman, W.↗
NASA NTRS1983

Advanced air revitalization system testing

A previously developed experimental air revitalization system was tested cyclically and parametrically. One-button startup without manual interventions; extension by 1350 hours of tests with the system; capability for varying process air carbon dioxide partial pressure and humidity and coolant source for simulation of realistic space vehicle interfaces; dynamic system performance response on the interaction of the electrochemical depolarized carbon dioxide concentrator, the Sabatier carbon dioxide reduction subsystem, and the static feed water electrolysis oxygen generation subsystem, the carbon dioxide concentrator module with unitized core technology for the liquid cooled cell; and a preliminary design for a regenerative air revitalization system for the space station are discussed.

Heppner, D. B.↗
NASA NTRS2015

Characterization of Carbon Particulates in the Exit Flow of a Plasma Pyrolysis Assembly (PPA) Reactor

The ISS presently recovers oxygen from crew respiration via a Carbon Dioxide Reduction Assembly (CRA) that utilizes the Sabatier chemical process to reduce captured carbon dioxide to methane (CH4) and water. In order to recover more of the hydrogen from the methane and increase oxygen recovery, NASA Marshall Space Flight Center (MSFC) is investigating a technology, plasma pyrolysis, to convert the methane to acetylene. The Plasma Pyrolysis Assembly (or PPA), achieves 90% or greater conversion efficiency, but a small amount of solid carbon particulates are generated as a side product and must be filtered before the acetylene is removed and the hydrogen-rich gas stream is recycled back to the CRA. In this work, we present the experimental results of an initial characterization of the carbon particulates in the PPA exit gas stream. We also present several potential options to remove these carbon particulates via carbon traps and filters to minimize resupply mass and required downtime for regeneration.

Methane pyrolysis↗
DOE OSTI2021

Low Carbon Technology Strategies: Midrise Apartment

This document includes steps that building owners and operators can implement to achieve smart, healthy, and low-carbon midrise apartment buildings within their existing building portfolios. Midrise apartments may use packaged rooftop units for heating, cooling, and ventilation or central plant systems for larger buildings.

analytics↗
DOE OSTI2021

Low Carbon Technology Strategies: Secondary School

This document includes steps that building owners and operators can implement to achieve smart, healthy, and low-carbon secondary schools within their existing building portfolios. Secondary schools often include complex heating and cooling systems or packaged rooftop units and can include specialty equipment for gymnasiums, pools, and buses.

analytics↗
DOE OSTI2021

Low Carbon Technology Strategies: Stand-Alone Retail and Strip Mall

This document includes steps that building owners and operators can implement to achieve smart, healthy, and low-carbon retail buildings within their existing building portfolios. Stand-alone retail and strip malls often use packaged rooftop units for heating, cooling, and ventilation.

analytics↗
DOE OSTI2024

Exploring the influence of interfacial solvation on electrochemical CO 2 reduction using plasmon‐enhanced vibrational sum frequency generation spectroscopy

Although interfacial solvation plays an important role in determining carbon dioxide reduction (CO 2 R) kinetics, present understanding of the potential dependent properties of the electrochemical double layer under conditions relevant for CO 2 R remains limited. This article summarizes the development and recent applications of plasmon-enhanced vibrational sum frequency generation (VSFG) spectroscopy to study the effects of cation hydration and interfacial solvation on CO 2 R using CO as a vibrational Stark reporter. Results show that electrolyte cations retain their entire solvation shell upon adsorption to inactive sites, while active sites retain only a single water layer between the gold surface and the cation. Measurements also show that the total interfacial electric field can be separated into two contributions: one from the electrochemical double layer (Stern field) and another from the polar solvation environment (Onsager field). Surprisingly, correlating VSFG spectra with reaction kinetics reveals that it is the solvation-mediated Onsager field that governs the chemical reactivity at the electrode/electrolyte interface. Measuring the interfacial water spectra during electrocatalysis also provides evidence for the proton source during H2 evolution, which competes with CO 2 R in aqueous electrolyte. These findings highlight the importance of directly probing cation hydration and interfacial solvation, which mediates reaction kinetics at electrochemical interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1988

Carbon dioxide electrolysis with solid oxide electrolyte cells for oxygen recovery in life support systems

The direct electrochemical reduction of carbon dioxide (CO2) is achieved without catalysts and at sufficiently high temperatures to avoid carbon formation. The tubular electrolysis cell consists of thin layers of anode, electrolyte, cathode and cell interconnection. The electrolyte is made from yttria-stabilized zirconia which is an oxygen ion conductor at elevated temperatures. Anode and cell interconnection materials are complex oxides and are electronic conductors. The cathode material is a composite metal-ceramic structure. Cell performance characteristics have been determined using varying feed gas compositions and degrees of electrochemical decomposition. Cell test data are used to project the performance of a three-person CO2-electrolysis breadboard system.

Isenberg, Arnold O.↗
DOE OSTI2025

Atomically Dispersed Ni‐N‐C Catalysts for Electrochemical CO 2 Reduction

Abstract The atomic dispersion of nickel in Ni‐N‐C catalysts is key for the selective generation of carbon monoxide through the electrochemical carbon dioxide reduction reaction (CO 2 RR). Herein, the study reports a highly selective, atomically dispersed Ni 1.0% ‐N‐C catalyst with reduced Ni loading compared to previous reports. Extensive materials characterization fails to detect Ni crystalline phases, reveals the highest concentration of atomically dispersed Ni metal, and confirms the presence of the proposed Ni‐N x active site at this reduced loading. The catalyst shows excellent activity and selectivity toward CO generation, with a faradaic efficiency for CO generation (FE CO ) of 97% and partial current density for CO (j co ) of ‐9.0 mA cm −2 at ‐0.9 V in an electrochemical H‐type cell. CO 2 RR activity and selectivity are also studied by rotating disk electrode (RDE) measurements where transport limitations can be suppressed. It is expected that the utility of these Ni‐N‐C catalysts will lie with tandem CO 2 RR reaction schemes to multi‐carbon (C 2+ ) products.

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

Scanning electron microscopy, non-dispersive X-ray analysis and electron microprobe studies of lunar soil, rocks and microbreccia

Silicate glass of composition similar to brown lunar glass was reduced with carbon and hydrogen. The typical complex iron sulfide and metallic iron mound formed by reduction with carbon is zoned. Its interior is metallic iron or a mixture of iron sulfide and metallic iron. The outer layer is pure metallic iron which is generally discontinuous, but the surface of the mound next to the silicate host is iron sulfide. This type of mound commonly has a waist of metallic iron and a void beneath it. The silicate surface of the void is covered with droplets or stringers of iron sulfide. The complex iron sulfide and metallic iron mounds formed by reduction with hydrogen generally are zoned. The outer layer is iron sulfide or a mixture of iron sulfide and metallic iron but the interior is metallic iron and iron sulfide, and the mound material next to the silicate host is iron sulfide. On the surface of some complex mounds, globules of silicate material are present. In one example, the globules consist of particles of aluminum oxide surrounded by silicate material. In turn, the margin of the globules is surrounded by iron sulfide. Dimples are present and surface of the dimples is covered by dendritic sheaths of iron sulfide and isolated metallic iron globules.

Carter, J. L.↗
DOE OSTI2023

Hierarchically Porous Carbons with Highly Curved Surfaces for Hosting Single Metal FeN 4 Sites as Outstanding Oxygen Reduction Catalysts

Iron–nitrogen–carbon (Fe₋N₋C) materials have emerged as a promising alternative to platinum-group metals for catalyzing the oxygen reduction reaction (ORR) in proton-exchange-membrane fuel cells. However, their low intrinsic activity and stability are major impediments. Herein, an Fe₋N–C electrocatalyst with dense FeN 4 sites on hierarchically porous carbons with highly curved surfaces (denoted as FeN 4 - hc C) is reported. The FeN 4 - hc C catalyst displays exceptional ORR activity in acidic media, with a high half-wave potential of 0.85 V (versus reversible hydrogen electrode) in 0.5 m H 2 SO 4 . When integrated into a membrane electrode assembly, the corresponding cathode displays a high maximum peak power density of 0.592 W cm -2 and demonstrates operating durability over 30 000 cycles under harsh H 2 /air conditions, outperforming previously reported Fe–N₋C electrocatalysts. These experimental and theoretical studies suggest that the curved carbon support fine-tunes the local coordination environment, lowers the energies of the Fe d-band centers, and inhibits the adsorption of oxygenated species, which can enhance the ORR activity and stability. This work provides new insight into the carbon nanostructure–activity correlation for ORR catalysis. It also offers a new approach to designing advanced single-metal-site catalysts for energy-conversion applications.

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

Long-term impact of electrification and retrofits of the U.S residential building in diverse locations

The U.S. buildings sector contributes 30% of operational carbon emissions, with residential buildings accounting for 56%. Reducing residential carbon emissions is crucial for achieving net-zero carbon goal. While many studies examine energy efficiency retrofit (EER) and electrification, few explore their long-term impacts across diverse climates and dynamic grid clean energy penetrations, as well as their economic effects on households. Here, this study proposes a method to assess how EER and electrification affect long-term decarbonization and economics across different climates, focusing on carbon emissions, energy burden (the percentage of household income spent on energy), and payback period in four locations: Tampa, San Diego, Denver, and Great Falls. The study also introduces the concept of implicit energy burden by considering investment costs. Results show that while electrification can reduce long-term emissions with increased clean energy penetration, it may not always achieve decarbonization due to mismatches between clean energy availability and demand. In cooling-dominant locations, electrification lowers energy burden and peak demand, but in heating-dominant locations, it increases energy burden to 8.24%, raises peak demand by 632.78%, and shifts it from summer to winter. After integrating investment costs, the implicit energy burden can reach 8.35% in cold climates. For already highly electrified buildings in Denver and Great Falls, the payback period of EER measures can be shortened by up to 48.98%. The study highlights a tradeoff between decarbonization and energy burden alleviation, showing that while EER measures can reduce the energy burden, they only achieve one-quarter of the carbon emission reduction of electrification.

24 POWER TRANSMISSION AND DISTRIBUTION↗