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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Monitoring Offshore CO 2 Sequestration Using Marine CSEM Methods; Constraints Inferred from Field- and Laboratory-Based Gas Hydrate Studies

Offshore geological sequestration of CO 2 offers a viable approach for reducing greenhouse gas emissions into the atmosphere. Strategies include injection of CO 2 into the deep-ocean or ocean-floor sediments, whereby depending on pressure–temperature conditions, CO 2 can be trapped physically, gravitationally, or converted to CO 2 hydrate. Energy-driven research continues to also advance CO 2 -for-CH 4 replacement strategies in the gas hydrate stability zone (GHSZ), producing methane for natural gas needs while sequestering CO 2 . In all cases, safe storage of CO 2 requires reliable monitoring of the targeted CO 2 injection sites and the integrity of the repository over time, including possible leakage. Electromagnetic technologies used for oil and gas exploration, sensitive to electrical conductivity, have long been considered an optimal monitoring method, as CO 2 , similar to hydrocarbons, typically exhibits lower conductivity than the surrounding medium. We apply 3D controlled-source electromagnetic (CSEM) forward modeling code to simulate an evolving CO 2 reservoir in deep-ocean sediments, demonstrating sufficient sensitivity and resolution of CSEM data to detect reservoir changes even before sophisticated inversion of data. Laboratory measurements place further constraints on evaluating certain systems within the GHSZ; notably, CO 2 hydrate is measurably weaker than methane hydrate, and >1 order of magnitude more conductive, properties that may affect site selection, stability, and modeling considerations.

58 GEOSCIENCES↗
DOE OSTI2021

CO 2 -assisted ethane aromatization over zinc and phosphorous modified ZSM-5 catalysts

The tandem reactions of CO 2 -assisted oxidative dehydrogenation and aromatization (CO 2 -ODA) of ethane were investigated over ZSM-5 modified with zinc (Zn) and phosphorus (P) by experimental studies and DFT calculations. The nature of active Zn species and their interaction with P were elucidated for understanding Zn/P-ZSM-5 catalyzed CO 2 -ODA reaction of ethane. Compared to the direct dehydrogenation and aromatization (DDA) reaction, the Zn/P-ZSM-5 catalyst possessed higher ethane conversion, enhanced aromatics yield, and better stability in the CO 2 -ODA reaction. Here, the presence of CO 2 reduced the carbon deposition, stabilized the Zn species, and thereby facilitated the generation of more liquid aromatics in CO 2 -assisted ethane aromatization. In situ characterization and DFT calculations provided insight into the mechanisms of CO 2 -ODA over the Zn/P-ZSM-5 catalyst.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Copper-zirconia interfaces in UiO-66 enable selective catalytic hydrogenation of CO 2 to methanol

Molecular interactions with both oxides and metals are essential for heterogenous catalysis, leading to remarkable synergistic impacts on activity and selectivity. Here, we show that the direct link between the two phases (and not merely being together) is required to selectively hydrogenate CO 2 to methanol on catalysts containing Cu and ZrO 2 . Materials consisting of isolated Cu particles or atomically dispersed Cu–O–Zr sites only catalyze the reverse watergas shift reaction. In contrast, a metal organic framework structure (UiO-66) with Cu nanoparticles occupying missing-linker defects maximizes the fraction of metallic Cu interfaced to ZrO 2 nodes leading to a material with high adsorption capacity for CO 2 and high activity and selectivity for low-temperature methanol synthesis.

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

Morphology Dependent Reactivity of CsO $x$ Nanostructures on Au(111): Binding and Hydrogenation of CO 2 to HCOOH

Cesium oxide (CsO $x$ ) nanostructures grown on Au(111) behave as active centers for CO 2 binding and hydrogenation reactions. The morphology and reactivity of these CsO $x$ systems were investigated as a function of alkali coverage using scanning tunnelling microscopy (STM), ambient pressure X-ray photoelectron spectroscopy (AP-XPS), and density functional theory (DFT) calculations. STM results show that initially (0.05 - 0.10 ML) cesium oxide clusters (Cs 2 O 2 ) grow at the elbow sites of the herringbone of Au(111), subsequently transforming into two-dimensional islands with increasing cesium coverage (> 0.15 ML). XPS measurements reveal the presence of suboxidic (Cs $y$ O; $y$ ≥ 2) species for the island structures. The higher coverages of cesium oxide nanostructures contain a lower O/Cs ratio resulting in a stronger binding of CO 2 . Moreover, the O atoms in the Cs $y$ O structure undergo a rearrangement upon the adsorption of CO 2 which is a reversible phenomenon. Under CO 2 hydrogenation conditions, the small Cs 2 O 2 clusters are hydroxylated, thereby preventing the adsorption of CO 2 . However, the hydroxylation of the higher coverages of Cs $y$ O did not prevent CO 2 adsorption, and the adsorbed CO 2 transformed to HCOO species that eventually yield HCOOH. DFT calculations further confirm that the dissociated H 2 attacks the C in the adsorbate to produce formate, which is both thermodynamically and kinetically favored during the CO 2 reaction with hydroxylated Cs $y$ O. These results demonstrate that cesium oxide by itself is an excellent catalyst for CO 2 hydrogenation that could produce formate, an important intermediate for the generation of value-added species. The role of the alkali oxide nanostructures as active centers, not merely as promoters, may have broad implications wherein the alkali oxides can be considered in the design of materials tuned for specific applications in heterogeneous catalysis.

03 NATURAL GAS↗
DOE OSTI2025

Effect of CO 2 Concentration on the Microbial Activity of Orenia metallireducens (Strain Z6) in Surface Inert Materials

Carbon dioxide (CO 2 ) sequestration has garnered widespread attention as a key strategy for mitigating CO 2 emissions and combating the greenhouse effect. However, the mechanisms underlying the interactions between CO 2 , widespread siliceous minerals and biological processes remain unclear. The present study explored the potential impacts of different CO 2 concentrations on microbial activity, environmental conditions and their feedback on the fate of CO 2 . A total of 20 experimental conditions was created, with the variables including different natural and synthetic siliceous minerals (e.g., quartz sand and a type of commercial glass beads), the presence or absence of the iron-reducing microorganism Orenia metallireducens (strain Z6) and varying CO 2 concentrations (0%, 20%, 50%, 100%) in the presence of ferrihydrite and pyruvate. Geochemical, microbial and mineralogical analyses revealed that elevated CO 2 concentrations significantly inhibited microbial Fe(III) reduction and pyruvate metabolism. Interestingly, compared to cultures without mineral amendments or those with glass beads alone, the addition of quartz sand enabled strain Z6 to better withstand the environmental stress caused by elevated CO 2 , promoting pyruvate fermentation and iron reduction. In addition to an increased pH, the formation of siderite, hematite and vivianite was also observed in the bioactive systems. Although both glass beads and quartz sand were primarily composed of silica, differences in the mineral structure, elemental composition and acid neutralization capacity rendered quartz sand more chemically active and unexpectedly led to greater CO 2 sequestration.

CO2 stress↗
DOE OSTI2022

Charting C–C coupling pathways in electrochemical CO 2 reduction on Cu(111) using embedded correlated wavefunction theory

The electrochemical CO 2 reduction reaction (CO 2 RR) powered by excess zero-carbon-emission electricity to produce especially multicarbon (C 2+ ) products could contribute to a carbon-neutral to carbon-negative economy. Foundational to the rational design of efficient, selective CO 2 RR electrocatalysts is mechanistic analysis of the best metal catalyst thus far identified, namely, copper (Cu), via quantum mechanical computations to complement experiments. Here, we apply embedded correlated wavefunction (ECW) theory, which regionally corrects the electron exchange-correlation error in density functional theory (DFT) approximations, to examine multiple C–C coupling steps involving adsorbed CO (*CO) and its hydrogenated derivatives on the most ubiquitous facet, Cu(111). We predict that two adsorbed hydrogenated CO species, either *COH or *CHO, are necessary precursors for C–C bond formation. The three kinetically feasible pathways involving these species yield all three possible products: *COH–CHO, *COH–*COH, and *OCH–*OCH. The most kinetically favorable path forms *COH–CHO. In contrast, standard DFT approximations arrive at qualitatively different conclusions, namely, that only *CO and *COH will prevail on the surface and their C–C coupling paths produce only *COH–*COH and *CO–*CO, with a preference for the first product. This work demonstrates the importance of applying qualitatively and quantitatively accurate quantum mechanical method to simulate electrochemistry in order ultimately to shed light on ways to enhance selectivity toward C 2+ product formation via CO 2 RR electrocatalysts.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2025

Role of Polymer Architecture in CO 2 Capture from Air Using Supported Poly(alkylenimine)s: Linear vs Branched Polymers

Direct air capture (DAC) of CO 2 coupled with geologic storage is a promising climate change mitigation strategy, with some applications employing amines supported on porous solids as CO 2 sorbents. While branched poly(ethylenimine) (PEI) is the standard benchmark amine material, it suffers from limited oxidative stability. Poly(propylenimine) (PPI), as an alternative, has previously demonstrated improved resistance to degradation under harsh oxidative conditions. Linear and branched PEI are commercially available, though at different molecular weights, while PPI is not commercially available. For this reason, a comparative study of all four polymers (linear PEI, branched PEI, linear PPI, branched PPI) has not been reported for DAC. In this study, we synthesize and compare low-molecular-weight (∼800 g/mol) linear (L) and branched (B) PEI and PPI supported on a model support, SBA-15 silica. These materials are evaluated for CO 2 adsorption under dry, DAC-relevant conditions (400 ppm of CO 2 , 30 °C). LPPI exhibited the highest amine efficiency at all loadings, reaching a maximum of 0.14 mmol CO 2 /mmol N, outperforming BPEI, while LPEI consistently showed the lowest uptake capacity. Temperature-programmed desorption reveals that the structure of the amine polymer impacts the CO 2 binding strength, with branched polymers displaying higher desorption energies of 102−111 kJ/mol. In situ infrared spectroscopy experiments show that all sorbents preferentially capture CO 2 as ammonium carbamate. Isobaric CO 2 uptake studies further underscore the influence of polymer mobility and support pore crowding on performance, while demonstrating the sorbents’ performance at elevated temperatures and CO 2 concentrations. All materials demonstrated good stability over 25 adsorption−desorption cycles using thermal regeneration in an inert gas purge, with only BPPI displaying a 10−11% decrease in capacity/amine efficiency during cycling, possibly due to the loss of low molecular weight, oligomeric amines. This is the first side-by-side comparison of the CO 2 sorption properties of linear and branched PEI and PPI with similar molecular weights. These findings highlight the significant role of polymer architecture in CO 2 capture efficiency and inform future designs of durable, high-performance DAC sorbents.

adsorbents↗
DOE OSTI2025

Understanding CO 2 adsorption on the surfaces of SrO and its hydroxylated variants Sr(OH) 2 · n H 2 O ( n = 0, 1, 8)

Strontium oxide (SrO) is a promising material for CO 2 capture through a reversible cycle of carbonation and calcination, where SrO reacts with CO 2 to form SrCO 3 and can be regenerated by calcination. In the presence of moisture, SrO forms strontium hydroxide and its hydrates (Sr(OH) 2 ·nH 2 O). Here, this study, which employs density functional theory, investigates the CO 2 adsorption mechanism of these processes on various crystal surfaces, including SrO, Sr(OH) 2 , Sr(OH) 2 ·1H 2 O, and Sr(OH) 2 ·8H 2 O. A significant finding is that the interaction of CO 2 with these surfaces leads to carbonate/bicarbonate formation via electron transfer, with notable differences in CO 2 orientation and bond characteristics between SrO surfaces and its hydroxylated surfaces. To explore the effects of moisture on CO 2 adsorption, H 2 O adsorption on these stable surfaces was investigated. The results showed that H 2 O reacts with the SrO (100) surface to form hydroxyl (OH) groups while it bonds with the surfaces of Sr(OH) 2 ·nH 2 O (n = 0, 1, 8) with hydrogen bonding. A small amount of H 2 O can enhance CO2 adsorption while a large amount of H 2 O could decrease the capability of CO 2 adsorption.

CO2 capture↗
DOE OSTI2020

CO 2 chirped-probe-pulse femtosecond CARS thermometry

The application of CO 2 chirped-probe-pulse (CPP) fs coherent anti-Stokes Raman scattering (CARS) for flame thermometry is discussed. A phenomenological model for CO 2 /O 2 CPP fs CARS was developed, and the simulations showed the potential for CO 2 temperature measurements free of interferences from O 2 and with no contribution from the nonresonant background by using a long-time delay for the chirped probe pulse. The accuracy and precision for CO 2 CPP fs CARS thermometry is compared with N 2 CPP fs CARS thermometry for temperatures between 295 K and 1420 K. The measurement accuracy for the CO 2 measurements is comparable with that for the N 2 measurements, while the precision for the CO 2 temperature measurements is significantly better at lower temperatures. In conclusion, we also demonstrate that accurate flame thermometry using a single set of laser parameters can be achieved using the delayed CPP approach.

42 ENGINEERING↗
DOE OSTI2024

Synthesis and structural characterization of 2,2’-bipyridine zinc formate: Analysis of formate bonding and hydrosilylation of CO 2 and carbonyl compounds

The zinc formate compound (bipy)Zn(O 2 CH) 2 is obtained via the reaction of Zn(O 2 CH) 2 with 2,2’-bipyridine (bipy). In addition, (bipy)Zn(O 2 CH) 2 may be formed from zinc hydride via addition of bipy followed by addition of (i) HCO 2 H and (ii) CO 2 . The molecular structure of (bipy)Zn(O 2 CH) 2 has been determined by X-ray diffraction, thereby demonstrating that it exists as a monomeric species with a distorted tetrahedral zinc center and monodentate formate ligands. Analysis of the bonding within the formate ligand indicates that the zinc–formate moiety is not best represented by a Zn–O–C(=O)H resonance structure, but instead possesses a significant ionic component that reduces the C=O bond order and increases the C–O bond order. The formate compound (bipy)Zn(O 2 CH) 2 participates in hydrosilylation transformations involving CO 2 and carbonyl compounds.

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

CO 2 Chemisorption Behavior of Coordination-Derived Phenolate Sorbents

CO 2 chemisorption via C-O bond formation is an efficient methodology in carbon capture especially using phenolate-based ionic liquids (ILs) as the sorbents to afford carbonate products. However, most of the current IL systems involve alkylphosphonium cations, leading to side reactions via the ylide intermediate pathway. It is important to figure out the CO 2 chemisorption behavior of phenolate-derived sorbents using inactive and easily accessible cation counterparts without active protons. Herein, phenolate-based systems were constructed via coordination between alkali metal cations with crown ethers to avoid the participation of active protons in CO 2 chemisorption. Reaction pathway study revealed that CO 2 uptake could be achieved by O-C bond formation to afford carbonate. CO 2 uptake capacity and reaction enthalpy were significantly influenced by the coordination effect, alkali metal types, and alkyl groups on the benzene ring.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

A Six-Membered Concerted Mechanism for CO 2 Capture by Amines Studied under Charged Microdroplet Reaction Conditions

Carbon dioxide (CO 2 ) capture and storage represents an important technological challenge. A mechanistic understanding of interactions involved in the capture process is necessary not only for technological development but also for efficient conversion of captured CO 2 into value-added materials. Herein, we present a novel contained secondary electrospray ionization platform for studying the interactions of gaseous amines and CO 2 gas under microdroplet reaction conditions, which enables mass spectrometry (MS) characterization of CO 2 capture products and intermediates in real time. We detected [2 M + CO 2 + H] + species, which corresponds to a six-membered intermediate. DFT calculations confirmed the high stability of the protonated six-membered ring intermediate. This finding provides a plausible concerted mechanism in the microdroplet environment that excludes the involvement of thermodynamically disfavored ionic species. The carbamic acid counterpart of the final product/salt was readily characterized by tandem MS. The carbamic acid/amine salt was also isolated and characterized by Fourier transform infrared spectroscopy. By virtue of the fact that headspace vapors of amines are sampled, we were able to establish a high-throughput platform that enabled the CO 2 capture capacity of five different amines to be studied in under 2 min. The same device also enabled the absolute quantification of capture capacity.

Amines↗
DOE OSTI2024

Molecular catalyst coordinatively bonded to organic semiconductors for selective light-driven CO 2 reduction in water

The selective photoreduction of CO 2 in aqueous media based on earth-abundant elements only, is today a challenging topic. Here we present the anchoring of discrete molecular catalysts on organic polymeric semiconductors via covalent bonding, generating molecular hybrid materials with well-defined active sites for CO 2 photoreduction, exclusively to CO in purely aqueous media. The molecular catalysts are based on aryl substituted Co phthalocyanines that can be coordinated by dangling pyridyl attached to a polymeric covalent triazine framework that acts as a light absorber. This generates a molecular hybrid material that efficiently and selectively achieves the photoreduction of CO 2 to CO in KHCO 3 aqueous buffer, giving high yields in the range of 22 mmol g -1 (458 μmol g -1 h -1 ) and turnover numbers above 550 in 48 h, with no deactivation and no detectable H 2 . The electron transfer mechanism for the activation of the catalyst is proposed based on the combined results from time-resolved fluorescence spectroscopy, in situ spectroscopies and quantum chemical calculations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Spin Polarization Enhanced Ethanol Selectivity in Electrocatalytic CO 2 Reduction on the Paramagnetic CuO Surface

We report an electrochemical CO 2 reduction reaction catalyzed by a paramagnetic and conductive CuO/Cu interface with spins polarized by a moderate external magnetic field (MF) of similar to 800 gauss, achieving a similar to 30% increase in CO 2 -to-C 2+ Faradaic efficiency (FE) compared to that in the absence of the MF in a flow cell electrolyzer. At a current density of 400 mA/cm 2 , the CO 2 -to-C 2+ FE reached 86.7 ± 2.7% with 47.9 ± 1.4% cathodic energy efficiency (EE) in contrast to the CO 2 -to-C 2+ FE of 67.6% with 36.4% of EE in the absence of MF. Notably, ethanol production exhibits a much higher response to the MF (similar to 55.6% increase in FE) than ethylene (similar to 6.4% increase in FE) at 400 mA/cm 2 . In situ surface-enhanced Raman spectroscopy (SERS) captured magnetic-field-enhanced *CO coverage and ethanol-forming C 2 intermediates on CuO/Cu, providing direct spectroscopic evidence of spin-modulated pathway selection. Here, computational study suggests that the enhancement of ethanol selectivity is due to the reduced reaction kinetic barrier under MF, while the ethylene selectivity is less affected, mainly due to the insensitivity of the kinetic barriers under MF.

10 SYNTHETIC FUELS↗
DOE OSTI2024

Nationwide cost and capacity estimates for sedimentary basin geothermal power and implications for geologic CO 2 storage

Sedimentary basins are naturally porous and permeable subsurface formations that underlie approximately half of the United States. In addition to being targets for geologic CO 2 storage, these resources could supply geothermal power: sedimentary basin geothermal heat can be extracted with water or CO 2 and used to generate electricity. The geothermal power potential of these basins and the accompanying implication for geologic CO 2 storage are, however, understudied. Here, we use the Sequestration of CO 2 Tool (SCO2T PRO ) and the generalizable GEOthermal techno-economic simulator (genGEO) to address this gap by a) estimating the cost and capacity of sedimentary basin geothermal power plants across the United States and b) comparing those results to nationwide CO 2 sequestration cost and storage potential estimates. We find that across the United States, using CO 2 as a geothermal heat extraction fluid reduces the cost of sedimentary basin power compared to using water, and some of the lowest cost capacity occurs in locations not typically considered for their geothermal resources (e.g., Louisiana, South Dakota). Additionally, using CO 2 effectively doubles the sedimentary basin geothermal resource base, equating to hundreds of gigawatts of new capacity, by enabling electricity generation in geologies that are otherwise (with water) too impermeable, too thin, too cold, or not deep enough. We find there is competition for the best sedimentary basin resources between water- and CO 2 -based power, but no overlap between the lowest-cost resources for CO 2 storage and CO 2 -based power. In this way, our results suggest that deploying CO 2 -based power may increase the cost of water based systems (by using the best resources) and the cost of CO 2 storage (by storing CO 2 in locations that otherwise may not be targeted). As such, our findings demonstrate that determining the best role for sedimentary basins within the energy transition may require balancing tradeoffs between competing priorities.

CPG↗