CO Molecules Research Articles

Reaction mechanism of CO2 on the surface δ-Pu(1 0 0):a DFT study

This investigation elucidates the adsorptive and dissociative interactions of CO2 and CO molecules with the δ-Pu (100) surface, utilizing state-of-the-art first-principles calculations. The study unearths that the hollow site epitomizes the most favorable adsorption locus for both CO2 and CO. Within the paramount adsorption configuration, there prevails a propensity for both species to partake in dissociative adsorption, characterized by CO2 cleaving into an O atom and a concomitant CO moiety, whereas CO disintegrates into discrete C and O atoms. The dissociation energy barriers conducive to such configurations are computed to be 3.0568 eV for CO2 and 5.1667 eV for CO. A thorough analysis of electronic charges and density of states intimates a transfer of electrons from the Plutonium surface atoms to the carbonaceous adsorbates during dissociation. Post dissociation of the C-O bond, the 6d orbitals of Plutonium engage in electronic hybridization with the 2p orbitals of Carbon, culminating in the constitution of ionic bonding.

The PARSEC view of star formation in galaxy centres: from protoclusters to star clusters in an early-type spiral

ABSTRACT Understanding star formation in galaxies requires resolving the physical scale on which star formation often occurs: the scale of star clusters. We present a multiwavelength, eight-parsec resolution study of star formation in the circumnuclear star cluster and molecular gas rings of the early-type spiral NGC 1386. The cluster ring formed simultaneously ∼4 Myr ago. The clusters have similar properties in terms of mass and star formation rate, resembling those of H ii regions in the Milky Way disc. The molecular CO gas resolves into long filaments, which define a secondary ring detached from the cluster ring. Most clusters are in CO voids. Their separation with respect to the CO filaments is reminiscent of that seen in galaxy spiral arms. By analogy, we propose that a density wave through the disc of this galaxy may have produced this gap in the central kpc. The CO filaments fragment into strings of dense, unresolved clouds with no evidence of a stellar counterpart. These clouds may be the sites of a future population of clusters in the ring. The free-fall time of these clouds, ∼10 Myr, is close to the orbital time of the CO ring. This coincidence could lead to a synchronous bursting ring, as is the case for the current ring. The inward spiralling morphology of the CO filaments and co-spatiality with equivalent kpc-scale dust filaments are suggestive of their role as matter carriers from the galaxy outskirts to feed the molecular ring and a moderately active nucleus.

Silicate minerals enable the efficient photocatalytic RWGS reaction

Silicate minerals are the most abundant minerals on Earth’s crust and can originate from rock-forming minerals with the low risk to the environment. Herein, the chain pyroxene mineral NaFeSi2O6 nanosheets loaded with highly dispersed Cu nanoparticles have been used as an archetype platform for the efficient photocatalytic reverse water gas shift (RWGS) reaction. The resultant Cu/NaFeSi2O6 catalyst demonstrated high performance metrics in the gas-phase photocatalytic hydrogenation of CO2 to CO, with a yield as high as 13144 μmol gcat–1 h–1. It is shown that the coordinately unsaturated Fe atom in NaFeSi2O6 can serve as a robust Lewis acid site for adsorbing and activating CO2 molecules, while the metal/support interface facilitates the formation of intermediate species and the subsequent production of CO products through hydrogen spillover. The surface plasmon resonance (SPR) effect of Cu further promotes the injection of hot electrons into NaFeSi2O6 and the carrier separation and migration at the Schottky heterojunction. This low-cost and earth-abundant mineral-based catalyst exhibits 100 h of long-term photocatalytic stability, indicating its potential as a promising and feasible candidate for the future development of renewable synthetic fuels.

Adsorption capability and regenerability of carbon slit micropores for CO2 capture

To date, the exceptional performance of microporous carbon in CO2 capture has been widely acknowledged as a crucial step towards achieving global zero carbon emissions. In this molecular simulation study, we employ grand canonical Monte Carlo simulation (GCMC) to shed light on the significant influence of micropores on CO2 adsorption capability and regenerability, emphasizing the need for a rigorous selection of the swing adsorption process based on pore size. Our findings corroborate numerous experimental and numerical studies that the ultramicropore (pore size < 7 Å) is the appropriate range for CO2 capture, as it facilitates the formation of a horizontal monolayer of CO2 molecules. Furthermore, we highlight the importance of designing porous carbon materials with a large pore volume at the optimal ultramicropore sizes (approximately 5.8-6.4 Å depending on adsorption and desorption conditions) for obtaining high CO2 capture capacity and effective adsorbent regeneration. For the first time, taking into account the operational parameters of practical swing adsorption processes, our simulation study provides valuable guidance for selecting the most appropriate technology tailored to each specific range of micropore size in porous carbon. For porous carbon materials with an abundant volume of ultramicropores, pressure swing adsorption (PSA) and pressure-temperature swing adsorption (PTSA), as conventional and hybrid swing adsorption processes respectively, are the most effective practices, achieving high CO2 working capacity and regenerability exceeding 80%.

The impact of surface-impregnated versus support-dispersed Fe in Fe–Ni/γ-Al2O3 catalysts for partial oxidation of methane: Insights into the effect of Fe incorporation method on coking and on the reaction mechanism

Two sets of Fe-modified Ni/γ-Al2O3 catalysts were prepared and tested in partial oxidation of methane. In one set, Fe was co-impregnated on the surface (NiFe) and in the other set Fe was incorporated in the support bulk (Ni/Fe). The two types showed significantly different coking resistance and performance. While Fe well dispersed in the support bulk significantly enhanced coking resistance, Fe co-impregnated with Ni on the surface enhanced the rate of coke deposition on the catalysts’ surfaces. The impact of Fe in the Ni/Fe catalysts is referred to its partially reduced ions (Fe2+) in redox reactions, and to the Ni-support strong interaction retarding the coke formation pathways. On the contrary, carbon formation on the NiFe catalysts is referred to the formation of Ni–Fe alloy particles which may block Ni active sites and can promote cracking of methane as well as CO molecules resulting in higher rates of coking.

Tree-inspired semiconductor-on-ceramic 2D/1D heterostructure for efficient CO2 photoreduction

Two-dimension nanosheets are ideal photocatalysts for CO2 reduction due to their high exposure of active sites and short charge transfer pathway. However, 2D photocatalysts have a tendency to agglomeration, thus compromising the performance of photocatalytic CO2 reduction. Trees, one of the most important plants for photosynthesis, have a unique “leaf-on-branch” structure. This unique two-dimension/one-dimension (2D/1D) configuration maximizes the adsorption of CO2 molecules and light harvesting. Herein, a tree-inspired semiconductor-on-ceramic 2D/1D heterostructure for efficient photocatalytic CO2 reduction is reported. The cobalt silicate (CoSi) nanosheets (∼0.68 nm) are in situ grown on the surfaces of hydroxyapatite (HAP) nanowires, creating a well-defined 2D/1D hierarchical structure. The vertical alignment of ultrathin CoSi nanosheets on the HAP nanowires effectively suppresses their agglomeration, leading to a large BET surface area (106.45 m2/g) and excellent CO2 adsorption (8.00 cm3 g−1). The results of photoelectrochemical characterization demonstrate that the 2D/1D hierarchical structure is powerful to expedite charge transfer. As a result, the gas generation rate of CO is as high as 28780 μmol g−1 h−1 over the CoSi-on-HAP 2D/1D heterostructure. In addition, the electron transfer mechanism and reaction pathways of CO2 reduction are revealed by in situ irradiated XPS and in situ DRIFT spectra.

Chemical Orderings in CuCo Nanoparticles: Topological Modeling Using DFT Calculations.

The orderings of atoms in bimetallic 1.6-2.1 nm-large CuCo nanoparticles, important as catalytic and magnetic materials, were studied using a combination of DFT calculations with a topological approach. The structure and magnetism of Cu50Co151, Cu101Co100, Cu151Co50, and Cu303Co102 nanoparticles; their resistance to disintegrating into separate Cu and Co species; as well as the exposed surface sites, were quantified and analyzed, showing a clear preference for Cu atoms to occupy surface positions while the Co atoms tended to form a compact cluster in the interior of the nanoparticles. The surface segregation of Co atoms that are encapsulated by less-active Cu atoms, induced by the adsorption of CO molecules, was already enabled at a low coverage of adsorbed CO, providing the energy required to displace the entire compact Co species inside the Cu matrices due to a notable adsorption preference of CO for the Co sites over the Cu ones. The calculated adsorption energies and vibrational frequencies of adsorbed CO should be helpful indicators for experimentally monitoring the nature of the surface sites of CuCo nanoparticles, especially in the case of active Co surface sites emerging in the presence of CO.

Atomic Force Microscopy Imaging of Individual CO Molecules Adsorbed on a Cu(111) Surface

Atomic Force Microscopy Imaging of Individual CO Molecules Adsorbed on a Cu(111) Surface

Configuration rearrangement of squalane induced by carbon dioxide dissolution: A molecular simulation study

Squalane has emerged as a desirable absorbent material for carbon capture, utilization, and storage solutions due to its tunable sorption properties, microscopic structures, and cost-effectiveness in response to the increasing demand. Moreover, a thorough understanding of the fundamental characteristics of hydrocarbons and dissolved gases involved in the Fischer–Tropsch industrial synthesis processes is also essential for researching industrial purification and separation. However, these macromolecules may experience varying degrees of induced alterations in their structural rearrangement when absorbing absorbates, which impacts the performance indicators of squalane. This study examined the solubility characteristics of absorbents made from squalane and their interaction with gaseous CO2 molecules. The perturbed chain statistical associated fluid theory (PC–SAFT) was employed to comprehensively evaluate the macroscopic thermodynamic experimental density and solubility data. Simultaneously, the Monte Carlo (MC) simulation approach was utilized to investigate the rearrangement and swelling features of the squalane chain induced by the presence of CO2 gas in a broad spectrum of temperature and pressure conditions. This work indicated that elevated temperatures increased flexibility in the molecular structure of squalane, leading to a more pronounced spatial dispersion, while higher pressures may lead to spatial homogeneity and enhanced capacity for carrying additional CO2 molecules. The examples and methodologies presented demonstrate the effectiveness of molecular simulations in comprehending absorption–based phenomena at an atomistic and molecular level and offer essential guidance in forecasting the potential for separation, storage, or catalytic.

Efficient CO2 capture using a novel Zn-doped activated carbon developed from agricultural liquid biomass: Adsorption study, mechanism and transition state

A Zn-doped carbon was prepared and used as an effective CO2 adsorbent. This carbonaceous material was developed from olive mill wastewater (OMWW) by an innovative process using thermal shock flash pyrolysis followed by zinc chloride impregnation at ambient temperature. The developed Zn-doped carbon is highly porous (1406.56 m2.g−1), thermally stable and rich in active sites. The Temkin isotherm and the pseudo-second order kinetic model best describe the adsorption of CO2 on the developed material, and the storage capacity is of 370.41 mg g−1 (293 K). Thermodynamic parameters showed favorable, exothermic, and orderly adsorption. Two new isotherms, based on the number of layers formed at the surface, developed by advanced statistical modelling, were adapted and used to understand the mechanism in depth. The analysis of the results showed that CO2 adsorption occurs through the appearance of double layers on the adsorbent surface. Adapted models showed: only one molecule was adsorbed per surface active site, a very low degree of aggregation of CO2 molecules before adsorption and the molecules were adsorbed in a parallel orientation. The activation parameters showed a rapid and physical adsorption with a drop in entropy at the transition state. The mechanisms involved were governed by thermodynamic control with the possibility of easy desorption at high temperature. Zn-doped carbon is an ecological approach to reduce CO2 emissions on the globe.

Theoretical investigation of cobalt cluster size on adsorption kinetics in Fischer-Tropsch synthesis

In this study, the particles of cobalt with different sizes were simulated by Materials Studio software then the adsorption of H2, CO, and CH4 and its components (CH, CH2, CH3) as Fischer-Tropsch synthesis monomers were investigated using Density-functional theory. The results showed that the suitable sites for the adsorption of CO, H2 and monomers in Fischer-Tropsch synthesis are affected by the size of cobalt clusters. Increasing in the size of the cobalt cluster, the number of suitable sites for adsorption of the species decreases. In general, H2 adsorption energy decreases with increasing cobalt cluster size because larger clusters tend to have a less reactive surface due to increased coordination number and reduced surface charge density. On the other hand, CO adsorption energy tends to increase with cluster size because the larger clusters can accommodate the linear CO molecule more effectively due to their extended surface area. With considering the deformation of adsorbed species, Mulliken charge result, density of states and partial density of states, it could be stated that all species were chemically adsorbed on the surface of clusters, except CH4 that was adsorbed on Co-10 and Co-18 clusters is physically. Kinetic parameters for H2 and CO adsorption were calculated considering the change in cobalt cluster size.

Research on CO2 capture performance of DMEDA water-lean absorbents based on molecular dynamics

In recent years, a large number of studies have shown that amine based water-lean absorbents formed by amines and organic solvents exhibit high capture efficiency and low regeneration energy consumption in CO2 capture. However, there is a lack of research that combines molecular level structure with macroscopic properties. In order to optimize the performance of amine based homogeneous water-lean absorbents by utilizing the properties of organic solvents, and to explore the correlation between the macroscopic properties of the absorbents (CO2 capacity, removal efficiency, regeneration rate, regeneration efficiency, etc.) and the molecular structure of the absorbent components. We used experiments and molecular dynamics to study the linear terminal diamine DMEDA and non-proton polar solvent (DMF, DMPA, NMP, SFL, DMSO) system. It was found that the absorption and desorption performance of water-lean solvents was higher than that of aqueous solutions 30 wt% MEA and 30 wt% DMEDA, among which EFH with DMF as the solvent has better comprehensive performance. The molecular dynamics simulation was built to describe the solution structures of these absorbents. Through RDF calculations, the unique behavior of DMEDA in non-proton polar solvent was revealed on molecular level, it was found that organic solvents tend to aggregate with DMEDA molecules to form large molecular clusters, while CO2 molecules may diffuse through ordered pore structures, resulting in a significant improvement in the capture performance. And it was found that there is a quantitative relationship between the intensity of intermolecular interaction between DMEDA and CO2 and the removal efficiency change in DMEDA water-lean absorbents. A functional relationship was fitted, and a preliminary and rapid method for determining capture performance through molecular dynamics was proposed.

Preparation and characterization of Ni/Al2O3 catalyst for catalytic reduction of CO2 to formic acid in the presence of hydrazine hydrate as a hydrogen source

Abstract In this study, the catalytic reduction of CO2 into formic acid was investigated over a Ni/Al2O3 catalyst synthesized by wet-impregnation technique. The CO2 hydrogenation reaction was performed in a slurry reactor in the temperature range of 100–300 °C and at an autogenerated pressure. The Na2CO3 was used as a CO2 source, and hydrazine hydrate was used as a hydrogen source. The effect of reaction temperature, catalyst metal loading (5–15 wt%), and catalyst amount were optimized for the higher yield of formic acid. The catalyst was very selective to formic acid, and a very high formic acid selectivity of ∼99 % was achieved in the presence of 10 wt% Ni/Al2O3 catalyst at a much lower reaction temperature of 250 °C. The obtained formic acid yield was ∼53.5 %. The result demonstrated that the Ni/Al2O3 catalyst developed was very promising for the selective hydrogenation of CO2 molecules to formic acid via the in situ hydrogenation from hydrazine hydrate.

Structure and interactions of CO2 with reline (a 1:2 choline chloride – Urea mixture) according to quantum chemical calculations and molecular dynamics simulation

Quantum chemical DFT calculations [B3LYP+GD3/6-311++g(2d,2p)] of the structure and interactions in various complexes of CO2 molecule with a choline cation, a chloride anion, urea molecules, a choline chloride ion pair and a 1:2 choline chloride – urea complex were carried out. The contributions of Coulomb and van der Waals interactions were calculated. The QTAIM method was used to evaluate the strength of various bonds. A molecular dynamics simulation of CO2 molecules in reline in the NPT ensemble (1 atm, 298 K) was also carried out. The radial distribution functions of the particle centers of mass, local mole fraction functions, spatial distribution functions, and density profiles were calculated. Stronger interactions, compared to the other DES components, were observed in case of the chloride anion and the CO2 molecule according to the DFT calculations. However, in the system, stronger interactions were observed between the chloride anion and the system components, namely NHCl and OHCl hydrogen bonds. This made the chloride anion inaccessible and unable to interact with the CO2 molecule, according to the MD simulation results. Additionally, the presence of a fairly extensive surface layer containing DES and CO2 molecules was shown.

Topological structures and adsorption properties of the [Fe4S4] clusters

The [Fe4S4] compositions are ubiquitous in biological systems as integral parts of the complex catalytic mechanisms as in hydrogenases and nitrogenases. The current reports about [Fe4S4] species are based on the cube-like structure framework. Here, the topological structures, stability and electronic properties of gas phase [Fe4S4]+, [Fe4S4]0 and [Fe4S4]− are analyzed. It is found that ground state structures of these three clusters have similar cubic cages but different symmetries and spin multiplicities. The molecular dynamics simulations demonstrate that the cubic cage remains thermodynamically stable at 700 K. The density of states show that the charge state is the key to affect electronic behaviors of them even under the same structural framework. The molecular orbitals show that the LUMO orbitals are distributed throughout whole structures, showing great delocalized characteristics, especially for the anionic [Fe4S4]−, while the HOMO orbits are mainly localized in Fe-S bonds, which are also confirmed by the electron localization function analyses. After one CO molecule is adsorbed on these clusters, it prefers to locate at the Fe atoms. Moreover, the C–O bond length and vibration frequency of the [Fe4S4]−-CO undergone a significant red shift. Our work shows that the [Fe4S4]− may act as a potential catalyst for activating the C–O bond.

Facile one-step solvothermal synthesis of Co3O4/CuO nanoflowers as an excellent catalyst for CO oxidation in coal mines

In the present study, Cobalt oxide (Co3O4)/Copper oxide (CuO) nanoflower catalysts were synthesized through a one-step solvothermal method, and the impact of various factors, including reaction time, on the catalytic activity of the catalysts towards carbon monoxide (CO) was investigated. The results showed that the catalysts synthesized at 140 °C and a reaction time of 4 h provided the best catalytic performance for carbon monoxide, and the regular nanoflower-like morphology provided a larger specific surface area as well as a greater number of active sites, allowing the instantaneous 100 % elimination of CO at 200 °C. Additionally, a plausible reaction mechanism was elucidated, wherein CO initially adsorbed onto the sample's surface, subsequently reacting with lattice oxygen to form intermediate carbonate species. This process ultimately led to the production of carbon dioxide (CO2), followed by the desorption of CO2 molecules from the sample's surface. The results demonstrate that these composite catalysts effectively mitigate CO levels during CO over limit in coal mines, thereby enhancing the safety of production personnel.

Investigating the effect of ZIF-8@PEI filler and its comparison with ZIF-8 in mixed matrix membranes for CO2/CH4 separation with the help of DFT study

In this study, Zeolitic Imidazolate Framework-8 (ZIF-8) and modified ZIF-8 (ZIF-8@PEI)with polyethyleneimine (PEI) were used as dispersed particles inside the polysulfone (PSF) matrix to separate CO2 and CH4. The distributions of dispersed particles in mixed matrix membranes (MMMs) were analysed with the help of Fourier transfer infrared radiation, Thermal gravimetric analysis, Scanning electronic microscope and X-ray diffraction. The mixed matrix membranes investigated the permeability and selectivity of pure gas (CO2) and mixed gas (CO2/CH4). It was highest at 5 wt% ZIF-8@PEI blended into the PSF matrix. In case of pure gas studies, we investigated the CO2 permeability (18.10 Barrer) and CO2/CH4 selectivity (23.91) as compared to ZIF-8/PSF MMM (10.36 Barrer, 5.81); and in case of mixed gas studies, the CO2 permeability (17.11 Barrer) and CO2/CH4selectivity (21.28) as compared to ZIF-8/PSF MMM (7.86 Barrer, 4.21).Using DFT studies, the interaction energies of the ZIF-8@PEI material with CO2 and CH4 gas molecules werefound to be -74.39 kJ/mol and -23.25 kJ/mol, respectively. It was more toward the ZIF-8@PEI-CO2geometry complex.From the observation, the experimentalgas permeation results and DFT studiesinvestigated that ZIF-8@PEI filler can be a good candidate for applying CO2 capture.

Revealing the nontrivial topological surface states of catalysts for effective photochemical carbon dioxide conversion

Topological semimetals with protected surface states mark a new paradigm of research beyond the early landmarks of band-structure engineering, allowing fabrication of efficient catalyst to harness the rich metallic surface states to activate specific chemical processes. Herein, we demonstrate a facile solid-phase method for in-situ doping of Ir at the Os sites in the Os3Sn7, an alloy with topological states, which significantly improves the photocatalytic performance for the reduction of CO2 to CO and CH4. Experimental evidence combined with theoretical calculations reveal that the nontrivial topological surface states greatly accelerate charge-separation/electron-enrichment and adsorption/activation of CO2 molecules, rendering highly efficient reaction channels to stimulate the formation of *COOH and *CO, as well CHO*. This work shows the promise of achieving high photocatalytic performances with synthesizing topological catalysts and provides hints on the design of novel topological catalysts with superior photoactivity towards the CO2 reduction reaction.

Bottom-up fabrication of DABCO-based bicationic ionic liquid-grafted MIL-101(Cr): Facilitating simultaneous activation of CO2 and epoxides for cyclic carbonate synthesis

Efficient activation of substrates as an orthogonal pathway for facilitating CO2 fixation into cyclic carbonates, poses ongoing challenges for the ingenious design and development of heterogeneous cooperative catalysts. Herein, a bottom-up strategy was employed to stepwise graft chloromethyl, triethylenediamine (DABCO), and chloroethylamine onto the organic linkers, forming bicationic ionic liquid tethered to MIL-101(Cr). The introduced –NH2 and quaternary ammonium groups dangling within the micro-mesopores ensured the fast enrichment and polarization of CO2 molecules, while the inherent unsaturated Cr3+ sites bonded with the epoxides to promote the simultaneous activation. The ample Cl- counter-anions further nucleophilically attacked to proceed the ring opening process, triggering an upgradation in catalytic performance for cycloaddition. After optimized by the response surface methodology (RSM), a chloropropene carbonate (CPC) yield of 97.8 % with a selectivity of 99.3 % were attained over the developed Cl[TNH2]Cl@MIL-101(Cr) at mild conditions (104.5 °C, 1.07 MPa, 3.75 wt% of catalyst, 1.91 h) in the absence of any solvent or co-catalyst. Furthermore, Cl[TNH2]Cl@MIL-101(Cr) displayed good durability, universality, and recyclability. The synergy of multiple sites was testified by the in-situ DRIFTS spectra and DFT calculations, and thus the potential catalytic mechanism was deduced. The implement of this work could shed some lights on the rational assembling of robust IL@MOFs nanocomposites and offered novel avenues for the fabrication of high-efficiency catalysts for practical CO2 conversion.

Highly efficient separation of CO2/N2 and CO2/CH4 via metal-ion regulation in ultra-microporous metal-organic frameworks

Efficient separation of CO2 from CH4 and N2 is crucial for industrial processes. This study presents a novel approach to enhance CO2/N2 and CO2/CH4 separation using metal-ion regulation in ultra-microporous metal–organic frameworks (MOFs). Specifically, we synthesized ZSTU-8-M (M=Cd, Zn) by coordinating norfloxacin ligands with different metal ions, achieving precise modulation of the pore structure. Ideal adsorption solution theory (IAST) calculations demonstrated that ZSTU-8-Cd exhibited superior selectivity for CO2/N2 (952) and CO2/CH4 (369) mixtures compared to ZSTU-8-Zn. Grand canonical Monte Carlo (GCMC) simulations and in situ single-crystal X-ray diffraction (SCXRD) confirmed the presence of specific CO2 binding sites within the pore channels. The CO2 molecule shows a unique strong adsorption mechanism of hydrogen bonding sites in this structure, and thus achieves high adsorption capacity at low pressure. Dynamic breakthrough experiments further validated the practical separation efficiency of ZSTU-8-Cd, with high retention times and saturated adsorption capacities for CO2. These findings highlight the ability of metal-ion modulation to achieve simultaneous improvement in adsorption capacity and selectivity, demonstrating the potential of MOFs for advanced gas separation applications.