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At least 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Formation of Nucleobases from the UV Photo-Irradiation of Pyrimidine in Astrophysical Ice Analogs

Astrochemistry laboratory simulations have shown that complex organic molecules including compounds of astrobiological interest can be formed under interstellarl/circumstellar conditions from the vacuum UV irradiation of astrophysical ice analogs containing H2O, CO, CO2, CH3OH, NH13, etc. Of all prebiotic compounds, the formation of amino acids under such experimental conditions has been the most extensively studied. Although the presence of amino acids in the interstellar medium (ISM) has yet to be confirmed, they have been detected in meteorites, indicating that biomolecules and/or their precursors can be formed under extraterrestrial, abiotic conditions. Nucleobases, the building blocks of DNA and RNA, as well as other 1V-heterocycles, have also been detected in meteorites, but like amino acids, they have yet to be observed in the ISM. In this work, we present an experimental study of the formation of pyrimidine-based compounds from the UV photo-irradiation of pyrimidine in ice mixtures containing H2O, NH3, and/or CH3OH at low temperature and pressure.

Milam, S. N.↗
NASA NTRS2020

Probing the Evolutionary History of Comets: an Investigation of the Hypervolatiles CO, CH4, and C2H6 in the Jupiter-Family Comet 21P/Giacobini–Zinner

Understanding the cosmogonic record encoded in the parent volatiles stored in cometary nuclei requires investigating whether evolution (thermal or otherwise) has modified the composition of short-period comets during successive perihelion passages. As the most volatile molecules systematically observed in comets, the abundances of CO, CH4, and C2H6 in short-period comets may serve to elucidate the interplay between natal conditions and post-formative evolution in setting present-day composition, yet secure measurements of CO and CH4 in Jupiter-family comets (JFCs) are especially sparse. The highly favorable 2018 apparition of JFC 21P/Giacobini–Zinner enabled a sensitive search for these "hypervolatiles" in a prototypical carbon-chain depleted comet. We observed 21P/Giacobini–Zinner with the iSHELL spectrograph at the NASA Infrared Telescope Facility on four pre-perihelion dates, two dates near-perihelion, and one post-perihelion date. We obtained detections of CO, CH4, and C2H6 simultaneously with H2O on multiple dates. We present rotational temperatures, production rates, and mixing ratios. Combined with previous work, our results may indicate that the hypervolatile coma composition of 21P/Giacobini–Zinner was variable across apparitions as well as within a particular perihelion passage, yet the spread in these measurements is a relatively small fraction of the variation in each molecule from comet to comet. We discuss the implications of our measured hypervolatile content of 21P/Giacobini–Zinner for the evolution of JFCs, and place our results in the context of findings from the Rosetta mission and ground-based studies of comets.

Roth, Nathan X.↗
DOE OSTI2026

A scalable, biopolymer-based microenvironment for electrochemical CO 2 conversion to multicarbon products with current densities over 2 A cm −2

The electrochemical CO 2 reduction reaction (CO 2 RR) relies heavily on the surrounding microenvironment to promote formation of desirable multicarbon (C 2+ ) products. However, microenvironment control to achieve high C 2+ yields at industrially relevant current densities remains a crucial challenge. We report that chitosan, cellulose and chitin biopolymer coatings on CO 2 RR electrocatalysts enhance the microenvironment by increasing local CO 2 /CO concentration, reducing local water activity and providing suitable ion conductivity and local pH. This facile approach achieves C 2+ Faradaic efficiencies of 90 ± 1.7% at 1.6 A cm −2 and C 2+ Faradaic efficiency = 83 ± 3.2% at 2.2 A cm −2 with a formation rate of 5,926 μmol h −1 cm −2 . Importantly, within the cathode, these ion-conductive hydrophilic biopolymers can fully substitute traditional hydrophobic ionomers/binders, such as Nafion, challenging previous assumptions about the non-viability of hydrophilic materials for selective CO 2 RR due to excess interfacial H 2 O. These findings unveil key insights into microenvironment design to enhance C–C coupling through a simple method.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2005

Robust Load-Sharing Control of Spacecraft Formations

This paper focuses on the design of autonomous and collaborative control strategies to govern the relative distances among multiple spacecraft in formation with no ground intervention. A coordinate load-sharing control structure for formation flying and a methodology to control their dynamic models with slow time-varying and uncertain parameters are the main objectives of this work. The method is applied to a deep space formation example, where the uncertainty in spacecraft fuel masses is also considered.

multi spacecraft↗
NASA NTRS2000

The Role of Electrolyte Upon the SEI Formation Characteristics and Low Temperature Performance of Lithium-Ion Cells With Graphite Anodes

Quarternary lithium-ion battery electrolyte solutions containing ester co-solvents in mixtures of carbonates have been demonstrated to have high conductivity at low temperatures (< -20C). However, in some cases the presence of such co-solvents does not directly translate into improved low temperature cell performance, presumably due to the formation of ionically resistive surface films on carbonaceous anodes. In order to understand this behavior, a number of lithium-graphite cells have been studied containing electrolytes with various ester co-solvents, including methyl acetate (MA), ethyl acetate (EA), ethyl propionate (EP), and ethyl butyrate (EB). The charge/discharge characterization of these cells indicates that the higher molecular weight esters result in electrolytes which possess superior low temperature performance in contrast to the lower molecular weight ester-containing solutions, even though these solutions display lower conductivity values.

Smart, M. C.↗
DOE OSTI2025

Promoting the oxidative coupling of methanol and dimethylamine using group 1 alkali metals on palladium-gold nanoparticles

PdAu/SiO 2 catalysts were synthesized by strong electrostatic adsorption (SEA) and characterized by TEM, DRIFTS, XRD, XAS, and O 2 -TPD. The use of group 1 alkali salt solutions to control pH during SEA syntheses led to uptake of alkali metals observed reductions in the densities of terminal silanol groups of the SiO 2 support. In the absence of alkali metals, PdAu/SiO 2 catalyzes oxidative C-N bond formation between methanol and dimethylamine (DMA), yielding dimethylformamide (DMF) with ∼95 % carbon selectivity (CO 2 ∼5 %) at temperatures below 413 K. When Na, K, and Cs were present on the catalyst, methyl formate (MF) and tetramethylurea (TMU) were observed as additional products (combined ∼30 % carbon selectivity) while only TMU was detected for the Li-promoted catalyst. Total coupling product rate increased for promoted samples in the order Li < Na < Cs < K, and the apparent kinetics over the Cs-promoted catalyst were distinct from those over the alkali-free catalyst as the apparent reaction order with respect to DMA decreased and the apparent activation energy increased. Finally, this work demonstrates the sensitivity of oxidative coupling reactions to alkali metal promoters and the opportunity to achieve alkali promotion of metal catalysts during SEA synthesis.

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

Spectral induced polarization monitoring of induced calcite precipitation in subsurface sediments

Co-precipitation of contaminants within the crystalline structure of calcite is a promising natural attenuation or remedial technology being considered at contaminated sites. We explore the sensitivity of the spectral induced polarization (SIP) method to induced calcite precipitation in natural sediments as a path forward to non-invasively monitor these sites. We performed time-lapse column experiments using phased (I-IV) injections over 40 days on natural sediments from the Hanford Site (Washington State, USA). In the phased injections, abiotic calcite precipitation was induced and confirmed to have occurred. Previous work in glass beads and homogeneous sand was limited to high frequency detection of calcite, however in this work we observed the development of two polarization mechanisms, one at high frequency (>100 Hz) and one at low frequency (< 100 Hz). Based on the characteristic frequencies from the SIP high and low frequency regimes, characteristic length scales (L) were computed where the adsorption mode of Na+ versus Ca2+ was compared by using diffusion coefficients corresponding to Na+ versus an arithmetically averaged value for Na+ and Ca2+. Using the diffusion coefficient of Na+, the high frequency L was found to correlate well with the size of the calcite crystals. The low frequency L correlated well with the individual natural sediment grain sizes within the columns. During late experimental times (day 36 and 40), the characteristic low frequency in two of the experimental columns shifted to lower frequencies (<0.001 Hz) which may signify SIP sensitivity of the formed calcite with the sediment grains. In field applications, the development of a low frequency polarization length scale to monitor calcite precipitation is promising for field monitoring applications, however further laboratory work needs to be performed to examine the SIP sensitivity of calcite formation in the presence of to natural sediments

calcium carbonate, calcite, precipitation, spectra↗
DOE OSTI2024

Modulating CO 2 Electrocatalytic Conversion to the Organics Pathway by the Catalytic Site Dimension

Electrochemical reduction of carbon dioxide to organic chemicals provides a value-added route for mitigating greenhouse gas emissions. Here, we report a family of carbon-supported Sn electrocatalysts with the tin size varying from single atom, ultrasmall clusters to nanocrystallites. High single-product Faradaic efficiency (FE) and low onset potential of CO 2 conversion to acetate (FE = 90% @ –0.6 V), ethanol (FE = 92% @ –0.4 V), and formate (FE = 91% @ –0.6 V) were achieved over the catalysts of different active site dimensions. The CO 2 conversion mechanism behind these highly selective, size-modulated p-block element catalysts was elucidated by structural characterization and computational modeling, together with kinetic isotope effect investigation.

10 SYNTHETIC FUELS↗
NASA NTRS2003

The Stable Isotope Fractionation of Abiotic Reactions: A Benchmark in the Detection of Life

One very important tool in the analysis of biogenic, and potentially biogenic, samples is the study of their stable isotope distributions. The isotope distribution of a sample depends on the process(es) that created it. One important application of the analysis of C & N stable isotope ratios has been in the determination of whether organic matter in a sample is of biological origin or was produced abiotically. For example, the delta C-13 of organic material found embedded in phosphate grains was cited as a critical part of the evidence for life in 3.8 billion year old samples. The importance of such analysis in establishing biogenicity was highlighted again by the role this issue played in the recent debate over the validity of what had been accepted as the Earth s earliest microfossils. These kinds of analysis imply a comparison with the fractionation that one would have seen if the organic material had been produced by alternative, abiotic, pathways. Could abiotic reactions account for the same level of fractionation? Additionally, since the fractionation can vary between different abiotic reactions, understanding their fractionations can be important in distinguishing what reactions may have been significant in the formation of different abiological samples (such as extraterrestrial samples). There is however, a scarcity of data on the fractionation of carbon and nitrogen by abiotic reactions. In order to interpret properly what the stable isotope ratios of samples tell us about their biotic or abiotic nature, more needs to be known about how abiotic reactions fractionate C and N. Carbon isotope fractionations have been studied for a few abiotic processes. These studies presumed the presence of a reducing atmosphere, focusing on reactions involving spark discharge, W photolysis of reducing gas mixtures, and cyanide polymerization in the presence of ammonia. They did find that the initial products showed a depletion in I3C with values in the range of a few per mil to as low as -60 % (potentially comparable to that which accompanies the biosynthesis of organic matter). We need to understand what kind of fractionations are observed with reactions under the non-reducing or mildly reducing conditions now thought to be present on the early Earth. While nitrogen is receiving increased attention as a tool for these kinds of analyses, almost nothing is known about the isotope fractionation that one would expect for abiotic sources of fixed/reduced nitrogen. This project will measure the fixation from a series of abiotic reactions that may have been present on the early Earth (and other terrestrial planets) and produced organic material that could have ended up in the rock record. The work will look at a number of reactions, under a non- reducing, or mildly reducing, atmosphere, covering sources of prebiotic organic C & N from shock heating, to photochemistry, to hydrothermal reactions. Some reactions that we plan to study are; Shock heating of a non-reducing atmosphere to produce CO and NO (in collaboration with Chris McKay), formation of formaldehyde (and related compounds) from COY the formation of ammonia from nitrogen oxides (ultimately from NO) by ferrous iron reduction, and the hydrothermal synthesis of compounds including the hydrocarboxylation/hydrocarbonylation reaction (in collaboration with George Cody), reactions of oxalate to form hydrocarbons and other oxygenated compounds and the formation of lipids from oxalic/formic acid (in collaboration with Tom McCollom), and reactions of carbon monoxide & carbon dioxide with N2, ammonia or nitritehitrate to form hydrogen cyanide, nitriles, ammonia/amines and nitrous

Summers, David P.↗
DOE OSTI2023

Paragenetic controls on CO 2 -fluid-rock interaction and weakening in a macroporous-dominated sandstone

The injection and storage of anthropogenic CO 2 in the subsurface is being deployed as a climate change mitigation tool; however, diagenetic-paragenetic heterogeneity in sandstone reservoirs often contributes to interval specific chemomechanical changes that affect injection and can increase leakage risk.In this paper we address reservoir heterogeneities’ impact on chemomechanical changes in a macroporous-dominated lithofacies of Morrow B sandstone, a formation containing several diagenetically-distinct hydraulic facies while undergoing enhanced oil recovery (EOR) and carbon dioxide (CO 2 ) sequestration. We performed three flow-through experiments using a CO 2 -charged or uncharged formation water combined with four indirect tensile strength tests per post-test sample. We then used the microstructure and paragenetic sequence to understand chemomechanical weakening with key observations as follows: dissolution of carbonates and feldspars changed porosity; increased permeability led to reclassifying each sample in a different hydraulic flow unit; decreased ultrasonic velocity; and did not lead to a loss of tensile strength. Tensile strength maintenance occurred due to the low abundance and minor dissolution of siderite, the stability of quartz, and the relative position of diagenetic ankerite within feldspar. This macroporous-dominated lithofacies is the primary reservoir for the Morrow B Sandstone, and is analogous to other porous sandstone reservoirs. It represents an end-member of a chemomechanically low-risk siliceous CO 2 sequestration and CO 2 -EOR reservoir.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1999

Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution

Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

Non-NASA Center↗
NASA NTRS2004

Workshop on Oxygen in the Terrestrial Planets

This volume contains abstracts that have been accepted for presentation at the Workshop on Oxygen in the Terrestrial Planets, July 20-23,2004, Santa Fe, New Mexico. The contents include: 1) Experimental Constraints on Oxygen and Other Light Element Partitioning During Planetary Core Formation; 2) In Situ Determination of Fe(3+)/SigmaFe of Spinels by Electron Microprobe: An Evaluation of the Flank Method; 3) The Effect of Oxygen Fugacity on Large-Strain Deformation and Recrystallization of Olivine; 4) Plagioclase-Liquid Trace Element Oxygen Barometry and Oxygen Behaviour in Closed and Open System Magmatic Processes; 5) Core Formation in the Earth: Constraints from Ni and Co; 6) Oxygen Isotopic Compositions of the Terrestrial Planets; 7) The Effect of Oxygen Fugacity on Electrical Conduction of Olivine and Implications for Earth s Mantle; 8) Redox Chemical Diffusion in Silicate Melts: The Impact of the Semiconductor Condition; 9) Ultra-High Temperature Effects in Earth s Magma Ocean: Pt and W Partitioning; 10) Terrestrial Oxygen and Hydrogen Isotope Variations: Primordial Values, Systematics, Subsolidus Effects, Planetary Comparisons, and the Role of Water; 11) Redox State of the Moon s Interior; 12) How did the Terrestrial Planets Acquire Their Water?; 13) Molecular Oxygen Mixing Ratio and Its Seasonal Variability in the Martian Atmosphere; 14) Exchange Between the Atmosphere and the Regolith of Mars: Discussion of Oxygen and Sulfur Isotope Evidence; 15) Oxygen and Hydrogen Isotope Systematics of Atmospheric Water Vapor and Meteoric Waters: Evidence from North Texas; 16) Implications of Isotopic and Redox Heterogeneities in Silicate Reservoirs on Mars; 17) Oxygen Isotopic Variation of the Terrestrial Planets; 18) Redox Exchanges in Hydrous Magma; 19) Hydrothermal Systems on Terrestrial Planets: Lessons from Earth; 20) Oxygen in Martian Meteorites: A Review of Results from Mineral Equilibria Oxybarometers; 21) Non-Linear Fractionation of Oxygen Isotopes Implanted in Lunar Metal Grains: Solar, Lunar or Terrestrial Origin? 22) Isotopic Zoning in the Inner Solar System; 23) Redox Conditions on Small Bodies; 24) Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update; 25) Mantle Redox Evolution and the Rise of Atmospheric O2; 26) Variation of Kd for Fe-Mg Exchange Between Olivine and Melt for Compositions Ranging from Alkaline Basalt to Rhyolite; 27) Determining the Partial Pressure of Oxygen (PO,) in Solutions on Mars; 28) The Influence of Oxygen Environment on Kinetic Properties of Silicate Rocks and Minerals; 29) Redox Evolution of Magmatic Systems; 30) The Constancy of Upper Mantlefo, Through Time Inferred from V/Sc Ratios in Basalts: Implications for the Rise in Atmospheric 0 2; 31) Nitrogen Solubility in Basaltic Melt. Effects of Oxygen Fugacity, Melt Composition and Gas Speciation; 32) Oxygen Isotope Anomalies in the Atmospheres of Earth and Mars; 33) The Effect of Oxygen Fugacity on Interdiffusion of Iron and Magnesium in Magnesiowiistite 34) The Calibration of the Pyroxene Eu-Oxybarometer for the Martian Meteorites; 35) The Europium Oxybarometer: Power and Pitfalls; 36) Oxygen Fugacity of the Martian Mantle from PigeoniteMelt Partitioning of Samarium, Europium and Gadolinium; 37) Oxidation-Reduction Processes on the Moon: Experimental Verification of Graphite Oxidation in the Apollo 17 Orange Glasses; 38) Oxygen and Core Formation in the Earth; 39) Geologic Record of the Atmospheric Sulfur Chemistry Before the Oxygenation of the Early Earth s Atmosphere; 40) Comparative Planetary Mineralogy: V/(CrCAl) Systematics in Chromite as an Indicator of Relative Oxygen Fugacity; 41) How Well do Sulfur Isotopes Constrain Oxygen Abundance in the Ancient Atmospheres? 42) Experimental Constraints on the Oxygen Isotope (O-18/ O-16) Fractionation in the Ice vapor and Adsorbant vapor Systems of CO2 at Conditions Relevant to the Surface of Mars; 43) Micro-XANES Measurements on Experimental Spinels andhe Oxidation State of Vanadium in Spinel-Melt Pairs; 44) Testing the Magma Ocean Hypothesis Using Metal-Silicate Partitioning of Te, Se and S; 45) Solubility of Oxygen in Liquid Iron at High Pressure and Consequences for the Early Differentiation of Earth and Mars Metallic Liquid Segregation in Planetesimals; 46) Oxygen Fugacity of Lunar Basalts and the Lunar Mantle. Range of fo2 and the Effectiveness of Oxybarometers; 47) Thermodynamic Study of Dissociation Processes of Molecular Oxygen in Vapor over Oxide Compounds; 48) Oxygen Profile of a Thermo-Haliophilic Community in the Badwater Salt Flat; 49) Oxygen Barometry Using Synchrotron MicroXANES of Vanadium; 50) Mass-Independent Isotopic Fractionation of Sulfur from Sulfides in the Huronian Supergroup, Canada; 51) Mass Independent Isotopes and Applications to Planetary Atmospheres; 52) Electrical Conductivity, Oxygen Fugacity, and Mantle Materials; 53) Crustal Evolution and Maturation on Earth: Oxygen Isotope Evidence; 54) The Oxygen Isotope Composition of the Moon: Implications for Planet Formation; 55) Oxygen Isotope Composition of Eucrites and Implications for the Formation of Crust on the HED Parent Body; and 56) The Role of Water in Determining the Oxygen Isotopic Composition of Planets.

Source record↗
DOE OSTI2023

Pulsed-Potential Electrolysis Enhances Electrochemical C–N Coupling by Reorienting Interfacial Ions

The electrochemical processing of anthropogenic CO 2 is an emerging technology aimed at utilizing renewable energies to synthesize valuable chemicals. Recently, developments in broadening the scope of the CO 2 reduction reaction (CO 2 RR) by enabling heteroatom coupling have surged with a focus on C–N bond formation. Herein, we investigate the factors that govern the selectivity and activity in synthesizing urea from environmentally malignant chemical feedstocks (CO 2 and NO 3 – ). Through a combination of electrolyte optimization and pulsed potential electrolysis, electrochemical urea production was optimized to a Faradaic efficiency of 60.4% with current densities reaching as high as 310 μA cm –2 . This work was further supported by in situ surface enhanced infrared absorbance spectroscopy that reveals the formation of C–N-related species at low overpotentials. Density functional theory calculations revealed that the reaction progresses between early reduction intermediates for the CO 2 RR and NO 3 RR and offered insights into the impacts of pulsed-potential on substrate transport.

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

Real-time Atomic-scale Visualization of Reversible Copper Surface Activation during the CO Oxidation Reaction

Dynamic structural and chemical information of catalyst surface during a catalytic reaction is critical for deciphering the mechanisms governing the properties of catalysts. Transition-metal based catalysts have emerged as an important alternative to noble metal catalysts, but their catalytic mechanism remains largely elusive, complicated by dynamic structure and valence evolution. Herein, by using in situ aberration-corrected environmental transmission electron microscopy, we capture, for the first time at atomic level, the dynamic evolution of Cu surface during CO oxidation reaction. We discovered that, under reaction condition, the Cu surface is activated, typically involving 2-3 atomic layers with the formation of a reversible meta-stable phase that only exists during catalytic reactions. Further, we reveal the distinctive role of CO and O2 in the surface activation, featuring CO exposure to lead to surface roughening and consequently formation of low-coordinated Cu atoms, while O2 exposure to induce quasi-crystalline CuOx phase. Corrugated by DFT calculations, we rationalize crystalline CuOx reversibly transforms into the amorphous phase, acting as an active species to facilitate the interaction of gas reactants and catalyzing CO oxidation.

Luo, Langli↗
NASA NTRS1988

Transmission electron microscopy study of the formation of epitaxial CoSi2/Si (111) by a room-temperature codeposition technique

Co and Si have been codeposited on Si (111) substrates near room temperature in a stoichiometric 1:2 ratio in a molecular beam epitaxy system. Annealing of these deposits yields high-quality single-crystal CoSi2 layers. Transmission electron microscopy has been used to examine as-deposited layers and layers annealed at 300, 500, and 600 C. Single-crystal epitaxial grains of CoSi2 embedded in a matrix of amorphous Co/Si are observed in as-deposited samples, while the layer is predominantly single-crystal, inhomogeneously strained CoSi2 at 300 C. At 600 C, a homogeneously strained single-crystal layer with a high density of pinholes is observed. In contrast to other solid phase epitaxy techniques used to grow CoSi2 on Si (111), no intermediate silicide phases are observed prior to the formation of CoSi2.

D'Anterroches, Cecile↗
DOE OSTI2025

External perturbation-driven Sabatier breakthrough

The Sabatier reaction (CO 2 + 4H 2 → CH 4 + 2H 2 O) is gaining renewed interest due to its potential to reduce energy carrier storage costs, serve as a feedstock for various organic chemicals, and supply in-situ propellant and life-support resources for long-duration Mars missions. This study demonstrates that combining a modest 2 mA electric field with H 2 feed modulation markedly elevates the CO 2 hydrogenation activity of 2 wt% Ru/CeO 2 catalyst. CO 2 conversion reaches 88 % and 93 % with a CH 4 yield of 83 % and 89 % at 350 °C and 450 °C, respectively. A simple lumped kinetic model reveals that the combined external perturbations not only shift the reaction mechanism but also redistribute key surface-adsorbed intermediates such as hydrogen adatoms and hydrogen-activated CO 2 among the Ru clusters, Ru/CeO 2 interface, and ceria surface. The electric field accelerates the conversion of adsorbed CO 2 to the hydrogenated CO 2 species on Ru and boosts CH 4 formation rate constant, while simultaneously suppresses the formation of undesired, non-reactive surface intermediates. Degree-of-rate-control analysis pinpoints proton migration across the metal-support interface as the decisive lever under these coupled perturbations. In conclusion, these findings establish that rational pairing of metal-support design with well-tuned electric fields and feed oscillations can unlock unprecedented Sabatier rates, guiding the development of next-generation reactors for efficient CO 2 to CH 4 conversion.

10 - SYNTHETIC FUELS↗
DOE OSTI2022

Structure/Interface Coupling Effect for High-Voltage LiCoO 2 Cathodes

LiCoO 2 (LCO) is widely applied in today's rechargeable battery markets for consumer electronic devices. However, LCO operations at high voltage are hindered by accelerated structure degradation and electrode/electrolyte interface decomposition. To overcome these challenges, co-modified LCO (defined as CB-Mg-LCO) that couples pillar structures with interface shielding are successfully synthesized for achieving high-energy-density and structurally stable cathode material. Benefitting from the "Mg-pillar" effect, irreversible phase transitions are significantly suppressed and highly reversible Li + shuttling is enabled. Interestingly, bonding effects between the interfacial lattice oxygen of CB-Mg-LCO and amorphous Co x B y coating layer are found to elevate the formation energy of oxygen vacancies, thereby considerably mitigating lattice oxygen loss and inhibiting irreversible phase transformation. Meanwhile, interface shielding effects are also beneficial for mitigating parasitic electrode/electrolyte reactions, subsequent Co dissolution, and ultimately enable a robust electrode/electrolyte interface. As a result, the as-designed CB-Mg-LCO cathode achieves a high capacity and excellent cycle stability with 94.6% capacity retention at an extremely high cut-off voltage of 4.6 V. We report these findings provide new insights for cathode material modification methods, which serves to guide future cathode material design.

25 ENERGY STORAGE↗