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At least 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Fundamental Understanding of Methane-Carbon Dioxide-Water (CH 4 -CO 2 - H 2 O) Interactions in Shale Nanopores under Reservoir Conditions (Quarterly Report)

Shale is characterized by the predominant presence of nanometer-scale (1-100 nm) pores. The behavior of fluids in those pores directly controls shale gas storage and release in shale matrix and ultimately the wellbore production in unconventional reservoirs. Recently, it has been recognized that a fluid confined in nanopores can behave dramatically differently from the corresponding bulk phase due to nanopore confinement. CO 2 and H 2 O, either preexisting or introduced, are two major components that coexist with shale gas (predominately CH 4 ) during hydrofracturing and gas extraction. Note that liquid or supercritical CO 2 has been suggested as an alternative fluid for subsurface fracturing such that CO 2 enhanced gas recovery can also serve as a CO 2 sequestration process. Limited data indicate that CO 2 may preferentially adsorb in nanopores (particularly those in kerogen) and therefore displace CH 4 in shale. Similarly, the presence of water moisture seems able to displace or trap CH 4 in shale matrix. Therefore, fundamental understanding of CH 4 -CO 2 -H 2 O behavior and their interactions in shale nanopores is of great importance for gas production and the related CO 2 sequestration. This project focuses on the systematic study of CH 4 -CO 2 -H 2 O interactions in shale nanopores under high-pressure and high temperature reservoir conditions. The proposed work will help develop new stimulation strategies to enable efficient resource recovery from fewer and less environmentally impactful wells.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2020

Management of Risk and Uncertainty Through Optimized Co-Operation of Transmission Systems and Microgrids With Responsive Loads (Final Report)

The evolution of the power system to the reliable, efficient and sustainable system of the future will involve development of both demand- and supply-side technology and operations. Ambitious national and state-level goals around the decarbonization of electricity relies on the integration of very high levels of renewable resources, most of which are variable and intermittent. The use of demand response is an ideal approach to counterbalance the intermittency of renewable generation and brings the consumer into the spotlight. Though individual consumers are interconnected at the low-voltage distribution system, these resources are typically modeled as variables at the transmission network level. Demand-side participation cannot be leveraged effectively without explicitly including the distribution system dynamics in the optimization-based wholesale market operations. This project grew from a vision for co-optimized interaction of distribution systems, or microgrids, with the high-voltage transmission system. In this framework, microgrids encompass consumers, distributed renewables and storage. The energy management system of the lower voltage system (distribution or microgrid) can also sell (buy) excess (necessary) energy from the transmission system. Until recently, very little research had been conducted on the co-optimization of these two systems due to computational limitations. However, advances in computational capabilities, and the judicious use of decomposition methods and innovative approximation methods for high-dimension dynamic programming made this goal a viable objective for this project, leading to a fundamental shift in the ability to integrate and fully utilize demand-side resources. To this end, the modeling framework developed introduces a novel co-optimization framework, to include the operations of both the transmission and distribution systems (or microgrids) in operational decision making. This framework was used to analyze renewable and distributed generation along with responsive demand and to compare the capability of co-optimized systems to perform with higher levels of variable renewables. An ideal microgrid is defined as an electric entity capable of operating in both interconnected (with the high-voltage grid) and islanded mode. As such, the microgrid should incorporate generating units (traditional units and intermittent) and if needed, exchange power with the high-voltage grid. The interplay between the microgrid and high-voltage grid motivated the development of the co-optimization approach to ensure efficient performance of the interconnected network. Results show that the use of a bi-level optimization approach is an appropriate structure, capable of co-optimizing a transmission system with multiple distribution systems and microgrids. While increasing the number of connected systems provides increasing flexibility for renewables integration this can also the economic benefits to the low-voltage subsystems with each additional system connected. Comparison of a traditional single-level decision structure with the co-optimization approach illustrates a reduction in overall system cost under co-optimization, while specific cost allocations to transmission and distribution systems are changed.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

Carbonate Management to Enable Energy- and Carbon-Efficient CO 2 Electrolysis (Final Technical Report)

The rapid growth and plummeting cost of solar energy have created great interest in using CO 2 electrolysis to produce chemical feedstocks and fuels such as carbon monoxide, ethylene, ethanol, and propanol. While research in CO 2 electrolysis has yielded substantial progress in both fundamental understanding of the requisite electrocatalytic reactions and design of prototype devices, the energy efficiency (electrical energy to-product) and carbon efficiency (CO 2 -to-product) of CO 2 electrolysis remain far too low for large-scale deployment. A preponderance of evidence indicates that the principal reason for these low efficiencies is the rapid and thermodynamically favorable reaction of CO 2 with hydroxide (OH–) to form carbonate , which forces CO 2 electrolysis cells to operate under conditions that result in large voltage and CO 2 losses. This “CO 3 2 – problem” presents a fundamental scientific barrier to creating a viable electrochemical option for converting solar energy into chemicals and fuels.

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

Comparison of Approaches for CO 2 Sequestration as Solid Carbon Products

The growing global climate crisis linked to the rising atmospheric CO 2 levels calls for urgent and innovative solutions. Fixing CO 2 as valuable solid carbon products, such as carbon nanofibers or nanotubes (CNFs or CNTs), offers a promising way to potentially achieve net-negative CO 2 emissions. However, direct CO 2 -to-solid carbon faces significant thermodynamic and kinetic constraints, especially under mild reaction conditions. This mini-review compares three emerging approaches for CO 2 conversion into solid carbon: 1) using molten salt at high temperatures to produce CNFs or CNTs, 2) converting CO 2 to amorphous carbon with pyrophoric liquid metals at near room temperature, and 3) employing an electrocatalytic-thermocatalytic tandem process to produce CNFs at relatively mild temperatures. We examine the underlying principles, thermodynamic driving forces, and recent advances of each approach, and discuss the challenges and opportunities in catalyst development, reactor design, and energy management. We aim to highlight CO 2 fixation, facilitate net-negative CO 2 emissions, and stimulate more innovations for both environmental and economic benefits.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2026

Methanol Steam Reforming on Ru/m-ZrO 2 : Sodium Promotion of the CO 2 -Forming Pathway

Sodium (Na) promotion of Ru/m-ZrO 2 was investigated to elucidate how an alkali modification tunes selectivity in methanol steam reforming (MSR). H 2 -TPR/XANES/EXAFS show that Na increases surface basicity and strengthens Ru–O interactions, shifting RuO x reduction and H 2 spillover to a higher temperature. DRIFTS reveals Na-induced red shifts of the formate ν(CH) band and changes in OCO vibrational splitting, consistent with weakening of the formate C–H bond and an altered binding geometry. CO 2 -TPD confirms a monotonic shift toward stronger basic sites with increasing Na concentrations. Under MSR conditions, Na selectively increases CO2 concentration at the expense of CO. At ~80% conversion and 325 °C, CO 2 selectivity increases from 12.0% (unpromoted) to 16.2, 21.0, and 26.5% for 0.5, 1.0, and 1.8% Na, respectively; at ~300 °C and ~66–69% conversion, CO 2 selectivity increases from 8.6% to 23.7% at 1.8% Na. Transient MSR experiments further show earlier and larger H 2 evolution upon Na addition, corroborating the promotion of the dehydrogenation/decarbonylation route to CO 2 + H 2 . We propose that Na increases basicity and modifies the Ru–support interface to favor formate dehydrogenation/decarboxylation, thereby increasing the H 2 yield and lowering CO formation. Ru’s higher-energy, less occupied d-band stabilizes CO and oxygenated intermediates more strongly in the reforming environment, making the CO-forming pathway more resistant to suppression than on Pt.

CO2 selectivity↗
DOE OSTI2020

Atomic Layer Deposition for Preparing Isolated Co Sites on SiO 2 for Ethane Dehydrogenation Catalysis

Unlike Co clusters, isolated Co atoms have been shown to be selective for catalytic dehydrogenation of ethane to ethylene; however, preparation of isolated Co sites requires special preparation procedures. Here, we demonstrate that Atomic Layer Deposition (ALD) of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt(III) (Co(TMHD) 3 ) on silica and other supports is effective in producing these isolated species. Silica-supported catalysts prepared with one ALD cycle showed ethylene selectivities greater than 96% at 923 K and were stable when CO 2 was co-fed with the ethane. Co catalysts prepared by impregnation formed clusters that were significantly less active, selective, and stable. Rates and selectivities also decreased for catalysts with multiple ALD cycles. Isolated Co catalysts prepared on Al 2 O 3 and MgAl 2 O 4 showed reasonable selectivity for ethane dehydrogenation but were not as effective as their silica counterpart.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Machine learning deciphers CO 2 sequestration and subsurface flowpaths from stream chemistry

Endmember mixing analysis (EMMA) is often used by hydrogeochemists to interpret the sources of stream solutes, but variations in stream concentrations and discharges remain difficult to explain. We discovered that machine learning can be used to highlight patterns in stream chemistry that reveal information about sources of solutes and subsurface groundwater flowpaths. The investigation has implications, in turn, for the balance of CO 2 in the atmosphere. For example, CO 2 -driven weathering of silicate minerals removes carbon from the atmosphere over ~106-year timescales. Weathering of another common mineral, pyrite, releases sulfuric acid that in turn causes dissolution of carbonates. In that process, however, CO 2 is released instead of sequestered from the atmosphere. Thus, understanding long-term global CO 2 sequestration by weathering requires quantification of CO 2 - versus H 2 SO 4 -driven reactions. Most researchers estimate such weathering fluxes from stream chemistry, but interpreting the reactant minerals and acids dissolved in streams has been fraught with difficulty. We apply a machine-learning technique to EMMA in three watersheds to determine the extent of mineral dissolution by each acid, without pre-defining the endmembers. The results show that the watersheds continuously or intermittently sequester CO 2 , but the extent of CO 2 drawdown is diminished in areas heavily affected by acid rain. Prior to applying the new algorithm, CO 2 drawdown was overestimated. The new technique, which elucidates the importance of different subsurface flowpaths and long-timescale changes in the watersheds, should have utility as a new EMMA for investigating water resources worldwide.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Optimizing Materials to Boost the Valorization of CO 2 : Tuning Cobalt–Cobalt Interactions on In 2 O 3 -Based Photothermal Catalysts

The valorization of CO 2 is an important challenge within the current panorama, since this molecule is probably the main contributor to climate change. In this study, the synthesis of materials based on a nanostructured batonnet-type indium oxide is carried out. In them, different amounts of Co are introduced, varying between 2 and 8% mol. It is verified that the most active sample in the transformation of carbon dioxide to carbon monoxide contains 6 mol %. of Co. This sample’s activity under dual excitation exceeds the thermal counterpart by more than 30%. After carrying out a complete physical and chemical characterization with the help of X-ray absorption spectroscopy and other techniques, it is shown that catalysts with amounts of cobalt equal to or below 4 mol % contain isolated single-atom species, while those with higher amounts of metal display a Co–Co interaction which triggers the evolution of the samples under reaction conditions. The optimum control of this Co–Co interaction and the nature of the final cobalt-containing species determine dual photothermal catalytic properties. In conclusion, this work establishes a structure–activity relationship to interpret the catalytic behavior of highly dispersed subnanometric cobalt species, and thus an avenue to optimize the photothermal valorization of carbon dioxide.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Oxophilicity Drives Oxygen Transfer at a Palladium–Silver Interface for Increased CO Oxidation Activity

A single-layer AgO x phase grown on Ag(111) efficiently transfers oxygen to Pd domains at room temperature, rendering the Pd-decorated surface highly reactive toward CO oxidation. Here, oxygen transfer from AgO x to Pd and the surface reactivity toward CO were investigated as a function of the Pd coverage using X-ray photoelectron spectroscopy, surface infrared spectroscopy of adsorbed CO, temperature-programmed reaction spectroscopy, and density functional theory (DFT) calculations. Our results show that all of the oxygen from the AgO x layer (~0.375 monolayer) migrates to the surface of Pd during formation of a nearly complete Pd bilayer at 300 K and that the oxygen coverages generated on Pd increase as the Pd cluster size decreases, reaching values that exceed the oxygen concentration in the AgO x layer by as much as a factor of 2. Experimental measurements and DFT calculations show that preferential binding of oxygen on the edges of the Pd clusters enhances the oxygen coverage on Pd clusters of decreasing size and produces a heterogeneous spatial distribution of oxygen. CO adsorbs in high coverages at 100 K by binding on both the terraces and O-rich edges of the Pd clusters. During subsequent heating, oxidation of the adsorbed CO consumes nearly all of the oxygen that transferred from AgO x to the Pd domains; in contrast, the pure AgO x layer exhibits limited reactivity toward CO adsorbed at 100 K. These results demonstrate that differences in oxophilicity drive facile oxygen transfer from Ag to the edges of Pd nanoclusters and thereby give rise to an efficient pathway for CO oxidation on bimetallic PdAg surfaces. The cooperation between the Pd and Ag domains results in near-interfacial chemistry that may be broadly important in catalysis by bimetallic alloys.

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

Materials Data on CoHRu3(CO)13 by Materials Project

RuRu2HCo(CO)4(CO)9 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of thirty-six formaldehyde molecules, four ruthenium molecules, four Co(CO)4 clusters, and four Ru2H clusters. In each Co(CO)4 cluster, Co2+ is bonded in a distorted trigonal pyramidal geometry to four C+0.92+ atoms. There are a spread of Co–C bond distances ranging from 1.75–1.89 Å. There are four inequivalent C+0.92+ sites. In the first C+0.92+ site, C+0.92+ is bonded in a distorted bent 150 degrees geometry to one Co2+ and one O2- atom. The C–O bond length is 1.18 Å. In the second C+0.92+ site, C+0.92+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.92+ site, C+0.92+ is bonded in a distorted single-bond geometry to one Co2+ and one O2- atom. The C–O bond length is 1.18 Å. In the fourth C+0.92+ site, C+0.92+ is bonded in a distorted single-bond geometry to one Co2+ and one O2- atom. The C–O bond length is 1.18 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In each Ru2H cluster, Ru+3.67+ is bonded in a 1-coordinate geometry to one H1+ atom. The Ru–H bond length is 1.80 Å. H1+ is bonded in a bent 120 degrees geometry to two equivalent Ru+3.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(NO5)2 by Materials Project

Co(NO5)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of one Co(NO5)2 cluster. Co is bonded in an octahedral geometry to six O atoms. There is four shorter (1.75 Å) and two longer (2.22 Å) Co–O bond length. N is bonded in a trigonal planar geometry to three O atoms. There are a spread of N–O bond distances ranging from 1.24–1.28 Å. There are five inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Co atom. In the second O site, O is bonded in a single-bond geometry to one Co atom. In the third O site, O is bonded in a bent 120 degrees geometry to one Co and one N atom. In the fourth O site, O is bonded in a single-bond geometry to one N atom. In the fifth O site, O is bonded in a single-bond geometry to one N atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(ClO3)2 by Materials Project

Co(O3Cl)2 crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two Co(O3Cl)2 ribbons oriented in the (0, 1, 0) direction. Co is bonded in an octahedral geometry to four equivalent O and two equivalent Cl atoms. All Co–O bond lengths are 1.94 Å. Both Co–Cl bond lengths are 2.24 Å. There are two inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two equivalent O atoms. Both O–O bond lengths are 1.36 Å. In the second O site, O is bonded in a distorted water-like geometry to one Co and one O atom. Cl is bonded in a single-bond geometry to one Co atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(CuO3)2 by Materials Project

Co(CuO3)2 crystallizes in the orthorhombic Fmmm space group. The structure is one-dimensional and consists of four Co(CuO3)2 ribbons oriented in the (0, 1, 0) direction. Co is bonded in a square co-planar geometry to four equivalent O atoms. All Co–O bond lengths are 1.77 Å. Cu is bonded in a square co-planar geometry to four O atoms. All Cu–O bond lengths are 1.82 Å. There are two inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two equivalent Cu atoms. In the second O site, O is bonded in a water-like geometry to one Co and one Cu atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(PO5)2 by Materials Project

Co(PO5)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Co(PO5)2 sheet oriented in the (-1, 0, 2) direction. Co is bonded to six O atoms to form CoO6 octahedra that share corners with four equivalent PO4 tetrahedra. There are a spread of Co–O bond distances ranging from 1.64–2.06 Å. P is bonded to four O atoms to form PO4 tetrahedra that share corners with two equivalent CoO6 octahedra. The corner-sharing octahedra tilt angles range from 44–52°. There is three shorter (1.55 Å) and one longer (1.56 Å) P–O bond length. There are five inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one P atom. In the second O site, O is bonded in a single-bond geometry to one P atom. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one Co and one P atom. In the fourth O site, O is bonded in a single-bond geometry to one Co atom. In the fifth O site, O is bonded in a bent 120 degrees geometry to one Co and one P atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(NO4)2 by Materials Project

Co(NO4)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Co(NO4)2 sheet oriented in the (1, 0, 0) direction. Co is bonded in an octahedral geometry to six O atoms. There are a spread of Co–O bond distances ranging from 1.73–2.05 Å. N is bonded in a trigonal planar geometry to three O atoms. There is one shorter (1.23 Å) and two longer (1.29 Å) N–O bond length. There are four inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to one Co and one N atom. In the second O site, O is bonded in a bent 120 degrees geometry to one Co and one N atom. In the third O site, O is bonded in a single-bond geometry to one N atom. In the fourth O site, O is bonded in a single-bond geometry to one Co atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(ClO)2 by Materials Project

Co(OCl)2 crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two Co(OCl)2 ribbons oriented in the (0, 0, 1) direction. Co is bonded in a distorted linear geometry to two equivalent O and four equivalent Cl atoms. Both Co–O bond lengths are 1.63 Å. There are two shorter (2.38 Å) and two longer (2.45 Å) Co–Cl bond lengths. O is bonded in a single-bond geometry to one Co atom. Cl is bonded in an L-shaped geometry to two equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Quantification of regional net CO 2 flux errors in the Orbiting Carbon Observatory-2 (OCO-2) v10 model intercomparison project (MIP) ensemble using airborne measurements

Inverse model intercomparison projects (MIPs) provide a chance to assess the uncertainties in inversion estimates arising from various sources. However, accurately quantifying ensemble CO 2 flux errors remains challenging and often relies on the ensemble spread. This study proposes a method for quantifying the errors in regional net surface–atmosphere CO 2 flux estimates from models taken from the Orbiting Carbon Observatory-2 (OCO-2) v10 MIP by using independent airborne CO 2 measurements for the period 2015–2017. We first calculate the root mean square error (RMSE) between the ensemble mean of posterior CO 2 concentrations and airborne observations and then isolate the CO 2 concentration errors caused solely by the ensemble mean of posterior net fluxes by subtracting the observation, representation, and transport errors from seven regions. Our analysis reveals that the flux errors projected onto CO 2 space account for 55 %–85 % of the regional average RMSE over the 3 years, ranging from 0.88 to 1.91 ppm. In five regions, the error estimates based on observations exceed those computed from the ensemble spread of posterior fluxes by a factor of 1.33–1.93, implying an underestimation of the actual flux errors, while their magnitudes are comparable in two regions. The adjoint sensitivity analysis identifies that the underestimation of flux errors is prominent where the magnitudes of fossil fuel emissions exceed those of terrestrial-biosphere fluxes by a factor of 3–31 over the 3 years. This suggests the presence of systematic biases in the inversion estimates associated with errors in the prescribed fossil fuel emissions common to all models. Our study emphasizes the value of airborne measurements for quantifying regional errors in ensemble net CO 2 flux estimates.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Mechanistic and kinetic relevance of hydrogen and water in CO 2 hydrogenation on Cu-based catalysts

Here, we ally steady-state kinetics, kinetic isotope effects, and density functional theory (DFT) calculations to illustrate that Cu-based catalysts remain saturated by H-adatoms (H*) and molecular formic acid (HCOOH**) during CO 2 hydrogenation. High H* coverage under methanol synthesis conditions is evidenced by reverse water-gas shift (RWGS) rates that exhibit positive H 2 reaction orders only at P H2 ≲ 0.5 bar, above which methanol synthesis and RWGS rates exhibit first and zeroth order dependence on P H2 , respectively. HCOOH** also accumulates on the surface with increasing P CO2 as informed by the Langmuir-type dependence on P CO2 (0.25-23 bar) for both methanol synthesis and RWGS. As both HCOOH** and H* have one H-atom per site occupied, the two species share the same P H2 dependence and give rise to CO 2 reaction orders that are independent of P H2 . Surface coverages determined based on kinetic analyses are further corroborated with DFT-derived adsorption energies that show favorable HCOOH** adsorbate-adsorbate interactions as well as repulsive interactions for bidentate formate (HCOO**) on H*-saturated surfaces. Methanol selectivity remains invariant with P CO2 and P CO despite CO inhibiting reaction rates, thereby demonstrating methanol synthesis and RWGS occur on the same active site. In contrast, water preferentially inhibits methanol synthesis rates, increases methanol synthesis H 2 reaction order from 1.0 to 1.5, and alters the methanol synthesis H 2 /D 2 kinetic isotope effect; the inhibitory effect of H 2 O thus cannot be attributed to competitive adsorption alone and instead reflects a change in the rate-determining step for methanol synthesis. The disparate kinetics of methanol synthesis and RWGS evince a branching pathway where methanol is formed from formates and CO is formed from carboxylates. The presented work thus identifies the relevant surface species, underscores the distinct catalytic role of water in branching methanol synthesis and RWGS pathways, and, in doing so, details a mechanistic picture that yields predictable rates and reaction orders for both methanol synthesis and RWGS on Cu-based CO 2 hydrogenation catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗