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The radical amplifier as a method for measuring radical concentrations in the atmosphere has received renewed attention lately. In principle, it can measure the total concentration of HO(x) and RO(x) radicals by reacting ambient air with high concentrations of CO (3-10 percent) and NO (2-6 ppmv), and measuring the NO2 produced.
Light harvesting, separation of charge carriers, and surface reactions are three fundamental steps that are essential for an efficient photocatalyst. Here we show that these steps in the TiO 2 can be boosted simultaneously by disorder engineering. A solid-state reduction reaction between sodium and TiO 2 forms a core-shell c-TiO 2 @a-TiO 2-x (OH) y heterostructure, comprised of HO-Ti-[O]-Ti surface frustrated Lewis pairs (SFLPs) embedded in an amorphous shell surrounding a crystalline core, which enables a new genre of chemical reactivity. Specifically, these SFLPs heterolytically dissociate dihydrogen at room temperature to form charge-balancing protonated hydroxyl groups and hydrides at unsaturated titanium surface sites, which display high reactivity towards CO 2 reduction. This crystalline-amorphous heterostructure also boosts light absorption, charge carrier separation and transfer to SFLPs, while prolonged carrier lifetimes and photothermal heat generation further enhance reactivity. The collective results of this study motivate a general approach for catalytically generating sustainable chemicals and fuels through engineered disorder in heterogeneous CO 2 photocatalysts.
Ho(TiGa2)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a distorted square co-planar geometry to twelve Ga atoms. There are four shorter (2.89 Å) and eight longer (3.32 Å) Ho–Ga bond lengths. Ti is bonded in a 10-coordinate geometry to two equivalent Ti and eight Ga atoms. Both Ti–Ti bond lengths are 2.73 Å. All Ti–Ga bond lengths are 2.80 Å. There are eight inequivalent Ga sites. In the first Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, four equivalent Ti, and four Ga atoms. There are two shorter (2.67 Å) and two longer (2.91 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, four equivalent Ti, and four Ga atoms. There are two shorter (2.67 Å) and two longer (2.91 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, four equivalent Ti, and four Ga atoms. Both Ga–Ga bond lengths are 2.91 Å. In the fourth Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, four equivalent Ti, and four Ga atoms. Both Ga–Ga bond lengths are 2.91 Å. In the fifth Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, four equivalent Ti, and four Ga atoms. Both Ga–Ga bond lengths are 2.67 Å. In the sixth Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, four equivalent Ti, and four Ga atoms. Both Ga–Ga bond lengths are 2.67 Å. In the seventh Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, four equivalent Ti, and four Ga atoms. In the eighth Ga site, Ga is bonded in a 11-coordinate geometry to three equivalent Ho, four equivalent Ti, and four Ga atoms.
In addition to the semiconducting phase in AgNi 0.66 Co 0.33 O 2 , it is found that the coexistence of metallic phase when more than x = 0.33 of Co dopant is substituted in the single layer of NiO 2 in AgNi 0.66 Co 0.33 O 2 .
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A Pt/SnO2 catalyst has been developed at NASA Langley that is effective for the oxidation of CO at room temperature (1). A mechanism has been proposed to explain the effectiveness of this catalyst (2), but most of the species involved in this mechanism have not been observed under actual catalytic conditions. A number of these species are potentially detectable by Fourier Transform Infrared Spectroscopy (FTIR), e.g., HOSnO sub x, HO sub y PtO sub z, Pt-CO, and SnHCO3. Therefore a preliminary investigation was conducted to determine what might be learned about this particular catalyst by transmission FTIR. The main advantage of FTIR for this work is that the catalyst can be examined under conditions similar to the actual catalytic conditions. This can be of critical importance since some surface species may exist only when the reaction gases are present. Another advantage of the infrared approach is that since vibrations are probed, subtle chemical details may be obtained. The main disadvantage of this approach is that FTIR is not nearly as sensitive as the Ultra High Vacuum (UHV) surface analytical techniques such as Auger, Electron Spectroscopy for Chemical Analysis (ESCA), Electron Energy Loss Spectroscopy (EELS), etc. Another problem is that the assignment of the observed infrared bands may be difficult.
In low-temperature flash photolysis of NH 3 /O 2 /N 2 mixtures, the NH 2 consumption rate and the product distribution is controlled by the reactions NH 2 + HO 2 → products (R1), NH 2 + H (+M) → NH 3 (+M) (R2), and NH 2 + NH 2 (+M) → N 2 H 4 (+M) (R3). In the present work, published flash photolysis experiments by, among others, Cheskis and co-workers, are re-interpreted using recent direct measurements of NH 2 + H (+N 2 ) and NH 2 + NH 2 (+N 2 ) from Altinay and Macdonald. To facilitate analysis of the FP data, relative third-body collision efficiencies compared to N 2 for R2 and R3 were calculated for O 2 and NH 3 as well as for other selected molecules. We report results were in good agreement with the limited experimental data. Based on reported NH 2 decay rates in flash photolysis of NH 3 /O 2 /N 2 , a rate constant for NH 2 + HO 2 → NH 3 + O 2 (R1a) of $k_{1\text{a}}$ = 1.5(±0.5) × 10 14 cm 3 mol –1 s –1 at 295 K was derived. This value is higher than earlier determinations based on the FP results but in good agreement with recent theoretical work. Kinetic modeling of reported N 2 O yields indicates that NH 2 + HO 2 → H 2 NO + O (R1c) is competing with R1a, but perturbation experiments with addition of CH4 indicate that it is not a dominating channel. Measured HNO profiles indicate that this component is formed directly by NH 2 + HO 2 → HNO + H 2 O (R1b), but theoretical work indicates that R1b is only a minor channel. Based on this analysis, we estimate $k_{1\text{c}}$ = 2.5 × 10 13 cm 3 mol –1 s –1 and $k_{1\text{b}}$ = 2.5 × 10 12 cm 3 mol –1 s –1 at 295 K, with significant uncertainty margins.
Membranes for post-combustion CO 2 capture are required to have a high CO 2 permeance due to the limited driving force. For facilitated transport membranes synthesized with polyvinylamine (PVAm), a defect-free selective layer of <200 nm is usually required to render sufficient permeance with high CO 2 /N 2 selectivity. In order to meet such a demand through the knife-coating process, the coating solution needs to have a high viscosity at a relatively low concentration to minimize its penetration into the substrate. The demand was met by synthesizing PVAm with an ultrahigh molecular weight (MW) via inverse emulsion polymerization (IEP) in this study. Compared to solution polymerization, IEP isolates the reaction in inverse micelles suspended in a continuous organic phase, which allows excellent dissipation of the heat generated by the reaction and reduces gel formation drastically. The polymerization parameters, including monomer concentration, initiator concentration, and reaction temperature, were investigated to obtain the optimal MW of PVAm for membrane performance. As compared to solution polymerization, IEP enhanced the MW of PVAm from 1.2 to 12.7 MDa, which minimized the penetration of the coating solution into the substrate and hence the extra mass transfer resistance. The effect of MW and degree of hydrolysis of PVAm on the membrane transport properties were studied. Furthermore, by employing PVAm with a MW of 12.7 MDa to strengthen the polymer matrix, the loading of piperazine glycinate in the membrane was increased up to 85 wt.%. In conclusion, the resultant membrane achieved a CO 2 permeance of 839 GPU and a CO 2 /N 2 selectivity of 161 at the typical flue gas temperature of 57°C.
Induced microwave absorption in carbon dioxide studied at frequency of 9260 mc/sec over temperature range from 270 to 500 degrees K and pressures as high as 95 atm
The objectives of this project are to develop a cost-effective design and fabrication process of a novel transformational membrane and its membrane modules that capture CO 2 from coal derived syngas. We have synthesized transformational membranes, scaled up the membrane to a prototype size of 14 inches wide by 20 feet in continuous roll-to-roll fabrication, fabricated at least 9 prototype membrane modules (each with about 2.5-inch diameter, 14-inch length, and 800 cm 2 membrane area) for testing with simulated syngas at OSU to achieve capture with at least 95% CO 2 purity. The membrane modules are in commercial spiral-wound (SW) configuration with a minimal pressure drop (<0.103 bar/meter (1.5 psi/meter)).
Ba2Ho2Co4O11 crystallizes in the orthorhombic Pmma space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with four equivalent BaO12 cuboctahedra, faces with four equivalent BaO12 cuboctahedra, faces with four CoO6 octahedra, and faces with four CoO5 square pyramids. There are a spread of Ba–O bond distances ranging from 2.73–3.08 Å. Ho3+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ho–O bond distances ranging from 2.45–2.67 Å. There are four inequivalent Co3+ sites. In the first Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four equivalent CoO6 octahedra, corners with two equivalent CoO5 square pyramids, and faces with four equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Co–O bond distances ranging from 1.84–2.11 Å. In the second Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four equivalent CoO6 octahedra, corners with two equivalent CoO5 square pyramids, and faces with four equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Co–O bond distances ranging from 1.91–2.19 Å. In the third Co3+ site, Co3+ is bonded to five O2- atoms to form CoO5 square pyramids that share corners with two equivalent CoO6 octahedra, corners with three equivalent CoO5 square pyramids, and faces with four equivalent BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 17°. There are a spread of Co–O bond distances ranging from 1.89–2.14 Å. In the fourth Co3+ site, Co3+ is bonded to five O2- atoms to form distorted CoO5 square pyramids that share corners with two equivalent CoO6 octahedra, corners with three equivalent CoO5 square pyramids, and faces with four equivalent BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 22°. There are a spread of Co–O bond distances ranging from 1.84–2.04 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Ba2+ and two Co3+ atoms to form a mixture of distorted corner and edge-sharing OBa4Co2 octahedra. The corner-sharing octahedral tilt angles are 4°. In the second O2- site, O2- is bonded to four equivalent Ba2+ and two Co3+ atoms to form a mixture of distorted corner and edge-sharing OBa4Co2 octahedra. The corner-sharing octahedral tilt angles are 4°. In the third O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ho3+ and two Co3+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+, two equivalent Ho3+, and two Co3+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+, two equivalent Ho3+, and two Co3+ atoms. In the sixth O2- site, O2- is bonded in a 6-coordinate geometry to two equivalent Ba2+, two equivalent Ho3+, and two Co3+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two equivalent Ho3+, and two Co3+ atoms.
Gas intercalation into clay interlayers may result in hydrogen loss in the geological storage of hydrogen; a phenomenon that has not been fully understood and quantified. Here we use metadynamics molecular simulations to calculate the free energy landscape of H 2 intercalation into montmorillonite interlayers and the H 2 solubility in the confined water; in comparison with results obtained for CO 2 . Furthermore, the results indicate that H 2 intercalation into hydrated interlayers is thermodynamically unfavorable while CO 2 intercalation can be favorable. H 2 solubility in hydrated clay interlayers is in the same order of magnitude as that in bulk water and therefore no over-solubility effect due to nanoconfinement is observed – in striking contrast with CO 2 . These results indicate that H 2 loss and leakage through hydrated interlayers due to intercalation in a subsurface storage system, if any, is limited.
Over the past decade, CO 2 separation and capture have become the new bandwagon for polymer science and membrane research. This review presents the fundamentals of CO 2 /gas separation in polymeric membranes and discusses how these principles underpin opportunities and challenges for post-combustion carbon capture (CO 2 /N 2 ), hydrogen purification (CO 2 /H 2 ), and natural gas and biogas sweetening (CO 2 /CH 4 ). Emerging polymeric membrane materials are discussed, including a few polymers containing a high content of polar functional groups (i.e., ether oxygen-rich polymers and polymeric ionic liquids), shape-persisting glassy polymers (i.e., perfluoropolymers, thermally rearranged polymers, iptycene-containing polymers), and reactive polymers featuring facilitated transport. Moreover, the promising candidates for each CO 2 separation application are highlighted. Lastly, the permeability-selectivity data reviewed were plotted against their 2008 and 2019 upper bounds.
Low concentrations of NOx accumulated in air in semi-enclosed spaces is a severe health hazard, but its efficient removal at low cost is a grand challenge. A simple method in preparing CoOOH for low-concentration NO removal at room temperature is described here. The samples are synthesized by oxidizing Co(OH)2 to CoOOH with different oxidants (Na2S2O8, O2 and H2O2). Among them, CoOOH prepared by Na2S2O8 (Co-NS) shows remarkable performance for NO abatement, while the samples synthesized by and H2O2 (Co-HO) and O2 (Co-OG) have no apparent NO removal capacity. It is found that the Co-NS material contains a higher concentration of residual Na, which contributes to the decreased crystallinity and increased concentrations of surface active species (Co2+, active oxygen) for NO storage. Following NO storage, the material can be readily regenerated by water washing. The authors from East China University of Science and Technology acknowledge support from National Basic Research Program of China (2013CB933200), National Natural Science Foundation of China (21577035, 21577034), Commission of Science and Technology of Shanghai Municipality (15DZ1205305) and 111 Project (B08021). Aiyong Wang acknowledges the China Scholarship Council for the Joint-Training Scholarship Program with the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the US DOE under contract DE-AC05-76RL01830. FG is supported by the U.S. DOE/Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office.
Hydrogen is a clean alternative to fossil fuels, emitting only water vapor during combustion. In a future hydrogen economy, large-scale storage will be an important component of the supply chain. Due to its low volumetric density, conventional surface storage methods are inadequate. Underground hydrogen storage (UHS) offers a viable solution, enabling the storage of millions of cubic meters. Among potential geological sites, including salt caverns, aquifers, and depleted gas reservoirs, depleted oil reservoirs show promise. Studying hydrogen interactions with residual oil and reservoir minerals is vital for understanding the properties of hydrogen and the reservoir post-injection. In this work, we employed molecular dynamics simulations to gain molecular-level insights into these interactions. We investigated hydrogen dissolution in oil, adsorption at kaolinite/oil interfaces, the role of CO 2 as a cushion gas, and the influence of kaolinite’s hydrophobicity on H 2 behavior. The main findings include: (1) hydrogen dissolves more in oil than in water, (2) the introduction of CO 2 suppresses hydrogen dissolution in oil and reduces the interfacial tension (IFT) between oil and gas, (3) CO 2 decreases H 2 partitioning near kaolinite surfaces due to its strong affinity for the hydrophilic gibbsite surface of kaolinite, and (4) CO 2 is more effective than H 2 in reducing IFT between kaolinite and the oil–gas mixture. These findings emphasize the effectiveness of CO 2 as a cushion gas and the important role of clay hydrophobicity in UHS, providing insights that are challenging to obtain experimentally.
Due to the excellent catalytic properties of Ce-based materials, the development of thermally stable metal-organic frameworks (MOFs) based on Ce-oxo clusters has attracted significant attention but remains challenging. In this work, we report the synthesis of an unreported Ce 4 Ti 2 -TMA (Ce IV 4 Ti IV 2 O 4 (OH) 4 (C(CH 3 ) 3 COO) 12 ·3H 2 O·3MeCN) cluster, which serves as an ideal source for the assembly of robust Ce/Ti-MOFs. Using this cluster, we constructed two isostructural MOFs, denoted as NU-3000 and NU-3001. Single-crystal X-ray diffraction analysis confirms these MOFs as mesoporous structures with 12-coordinated Ce 3 Ti 3 nodes. Furthermore, structural analysis reveals a plane triangular node structure that likely contributes to the excellent thermal stability of these MOFs. Finally, both MOFs show catalytic activity toward high-temperature (250°C) CO oxidation and maintain significant porosity, emphasizing the thermal stability of these materials under practical catalytic conditions. Furthermore, the straightforward synthesis of thermally robust Ce/Ti-MOFs from the Ce 4 Ti 2 -TMA cluster will pave the way for future Ce/Ti-MOF-based catalyst development.
Ni(HO)4(HSO4)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two sulfur trioxide monohydrate molecules and one Ni(HO)4 cluster. In the Ni(HO)4 cluster, Ni is bonded in a square co-planar geometry to four O atoms. There is two shorter (1.73 Å) and two longer (2.16 Å) Ni–O bond length. There are two inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the second H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to one Ni and one H atom. In the second O site, O is bonded in a bent 150 degrees geometry to one Ni and one H atom.
Ho(CuO2)2 crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight equivalent O2- atoms. There are four shorter (2.37 Å) and four longer (2.38 Å) Ho–O bond lengths. Cu+2.50+ is bonded in a square co-planar geometry to four equivalent O2- atoms. There is two shorter (1.90 Å) and two longer (1.92 Å) Cu–O bond length. O2- is bonded to two equivalent Ho3+ and two equivalent Cu+2.50+ atoms to form a mixture of distorted corner and edge-sharing OHo2Cu2 tetrahedra.