Gas-phase CO Research Articles

Theoretical investigations of the interaction between diatomic molecules and coinage metal atoms

In this contribution, we investigate the nature of the electronic interaction between gas phase CO and NO with coinage metal atoms {Cu, Ag, Au} in different charge states. The electronic structure is first characterised by means of state-of-the-art coupled-cluster calculations for a wide range of configurations. An analytical Reactive Bond Order (REBO) force field is used to fit the data, revealing a strong corrugation of the potential energy landscape in some cases. The fundamental vibrational bands are variationally computed for the different system. It is found that the metal determines the binding interaction and the spectroscopic signature of the complexes, as well as their structure and geometry.

Influence of vegetation on occurrence and time distributions of regional new aerosol particle formation and growth

Abstract. The occurrence frequency of regional atmospheric new aerosol particle formation and consecutive growth events (fNPF) were studied with respect to vegetation activity, aerosol properties, air pollutants and meteorological data in Budapest over the time interval from 2008 to 2018. The data set evaluated contained results of in situ measurements on the land surface that were mostly performed at the Budapest platform for Aerosol Research and Training Laboratory, of satellite-based products recorded by MODIS on Terra and of modelled vegetation emission-related properties from an advanced regional biogeochemical model. The annual mean relative occurrence frequencies were considerable (with an overall mean of 21 %), remained at a constant level (with an overall SD of 5 %) and did not exhibit tendentious change over the years. The shape of the distributions of monthly mean fNPF exhibited large variability from year to year, while the overall average distribution already possessed a characteristic pattern. The structure of the new particle formation (NPF) occurrence distributions was compared to those of environmental variables including concentrations of gas-phase H2SO4, SO2, O3, NO, NO2, CO, PM10 mass and NH3; particle numbers in the size fractions of 6–1000, 6–100 and 100–1000 nm; condensation sink; air temperature (T); relative humidity (RH); wind speed (WS); atmospheric pressure (P); global solar radiation (GRad); gross primary production (GPP) of vegetation; leaf area index (LAI); and stomatal conductance (SCT). There were no evident systematic similarities between fNPF on the one hand and all of the variables studied on the other hand, except for H2SO4 and perhaps NH3. The spring maximum in the NPF occurrence frequency distribution often overlapped with the time intervals of positive T anomaly in vegetated territories. The link between the potential heat stress exerted on plants in sultry summer intervals and the summer fNPF minimum could not be proven. The relevance of environmental variables was assessed by their ratios on NPF event days and on non-event days. The gas-phase H2SO4 concentration showed the largest monthly ratios, followed by O3. The WS, biogenic precursor gases and SO2 can generally favour NPF events, although their influence seemed to be constrained. An association between the fNPF and vegetation growth dynamics was clearly identified.

Nitromethane Decomposition via Automated Reaction Discovery and an Ab Initio Corrected Kinetic Model.

We explore the systematic construction of kinetic models from in silico reaction data for the decomposition of nitromethane. Our models are constructed in a computationally affordable manner by using reactions discovered through accelerated molecular dynamics simulations using the ReaxFF reactive force field. The reaction paths are then optimized to determine reaction rate parameters. We introduce a reaction barrier correction scheme that combines accurate thermochemical data from density functional theory with ReaxFF minimal energy paths. We validate our models across different thermodynamic regimes, showing predictions of gas phase CO and NO concentrations and high-pressure induction times that are similar to experimental data. The kinetic models are analyzed to find fundamental decomposition reactions in different thermodynamic regimes.

How Does Gas-Phase CO2 Evolve in the Headspace of Champagne Glasses?

The chemical space perceived by a consumer of champagne or other sparkling wines is progressively modified all along tasting. Real-time monitoring of gas-phase CO2 concentration was performed, through a CO2-diode laser sensor, along a two-dimensional array of nine points in the headspace of three types of glasses poured with champagne. Two original glasses with distinct headspace volumes were compared with the standard INAO tasting glass. For each of the three glass types, a kind of temperature-dependent CO2 fingerprint was revealed and discussed as a function of the glass geometry and headspace volume. Moreover, a simple model was developed, which considers the rate of decrease of the concentration of gas-phase CO2 in the headspace of a glass after the pouring process as being mainly ruled by natural air convection in ambient air. The timescale which controls the rate of decrease of gas-phase CO2 was found to highly depend on the ratio of the headspace volume to the open aperture of the glass.

Complex Organic Matter Synthesis on Siloxyl Radicals in the Presence of CO.

Heterogeneous phase astrochemistry plays an important role in the synthesis of complex organic matter (COM) as found on comets and rocky body surfaces like asteroids, planetoids, moons and planets. The proposed catalytic model is based on two assumptions: (a) siliceous rocks in both crystalline or amorphous states show surface-exposed defective centers such as siloxyl (Si-O•) radicals; (b) the second phase is represented by gas phase CO molecules, an abundant C1 building block found in space. By means of quantum chemistry; (DFT, PW6B95/def2-TZVPP); the surface of a siliceous rock in presence of CO is modeled by a simple POSS (polyhedral silsesquioxane) where a siloxyl (Si-O•) radical is present. Four CO molecules have been consecutively added to the Si-O• radical and to the nascent polymeric CO (pCO) chain. The first CO insertion shows no activation free energy with ΔG200K = −21.7 kcal/mol forming the SiO-CO• radical. The second and third CO insertions show Δ ≤ 10.5 kcal/mol. Ring closure of the SiO-CO-CO• (oxalic anhydride) moiety as well as of the SiO-CO-CO-CO• system (di-cheto form of oxetane) are thermodynamically disfavored. The last CO insertion shows no free energy of activation resulting in the stable five member pCO ring, precursor to 1,4-epoxy-1,2,3-butanone. Hydrogenation reactions of the pCO have been considered on the SiO oxygen or on the carbons and oxygens of the pCO chains. The formation of the reactive aldehyde SiO-CHO on the siliceous surface is possible. In principle, the complete hydrogenation of the (CO)1−4 series results in the formation of methanol and polyols. Furthermore, all the SiO-pCO intermediates and the lactone 1,4-epoxy-1,2,3-butanone product in its radical form can be important building blocks in further polymerization reactions and/or open ring reactions with H (aldehydes, polyols) or CN (chetonitriles), resulting in highly reactive multi-functional compounds contributing to COM synthesis.

Effects of CO2 gassy-supercritical phase transition on corrosion behaviors of carbon steels in saturated vapor environment

Corrosion behaviors of P110 and N80 tubular steels in CO2 gas phase and supercritical (S-CO2) phase in a saturated water vapor environment were explored in corrosion weight loss experiments by SEM, EDS, XRD, XPS and cross-section analysis techniques. With the increase in CO2 partial pressure, the average corrosion rate increased first and then decreased. The average corrosion rate reached the maximum value under the near-critical pressure. When CO2 partial pressure further increased to be above the critical pressure, the average corrosion rate gradually decreased and local aggregation of molecules was weakened.

Shape-tuned electrodeposition of bismuth-based nanosheets on flow-through hollow fiber gas diffusion electrode for high-efficiency CO2 reduction to formate

Gas-phase CO2 electrochemical reduction reaction (CO2RR) requires advanced gas diffusion electrodes (GDEs) for efficient mass transport. Meantime, engineering catalyst nanostructure and tuning surface wettability are decisive to enhance three-phase interfaces formation. Herein, Bi-based nanosheets are uniformly grown on flow-through Cu hollow fiber GDE (HFGDE) to benefit from the unique shape of HFGDEs, and abundant active surface area of nanosheets. Pulse electrodeposition is used to replenish Bi3+ ions in the vicinity of HFGDEs for uniform growth of Bi nanosheets. Further, thermal oxidation of nanosheets not only maximized the active sites and improved surface wettability but also induced Bi/Bi2O3 junctions in nanosheets, enhancing formate production via switching the rate-limiting step from the initial electron transfer to hydrogenation. Consequently, a current density of 141 mA cm−2 at -1 V vs. RHE with formate faradaic efficiency of 85 % and over six times greater catalyst mass activity compared to bulk particle shaped Bi, were achieved, outperforming other reported Bi-based GDEs used for formate production in bicarbonate electrolytes. This comes from less charge-transfer resistance, higher surface roughness, and improved wettability of Bi nanosheets after oxidation. This work represents a facile strategy to engineer efficient HFGDEs as advanced electrode materials for similar electrochemical reactions with low aqueous solubility gas-phase feeds.

Gas-phase CO2 electroreduction over Sn–Cu hollow fibers

SnO2 decorated Cu hollow fiber electrodes facilitate reaction kinetics for generating multicarbon oxygenate from gas-phase CO2 electroreduction.

Bismuth atom tailoring of indium oxide surface frustrated Lewis pairs boosts heterogeneous CO2 photocatalytic hydrogenation

The surface frustrated Lewis pairs (SFLPs) on defect-laden metal oxides provide catalytic sites to activate H2 and CO2 molecules and enable efficient gas-phase CO2 photocatalysis. Lattice engineering of metal oxides provides a useful strategy to tailor the reactivity of SFLPs. Herein, a one-step solvothermal synthesis is developed that enables isomorphic replacement of Lewis acidic site In3+ ions in In2O3 by single-site Bi3+ ions, thereby enhancing the propensity to activate CO2 molecules. The so-formed BixIn2-xO3 materials prove to be three orders of magnitude more photoactive for the reverse water gas shift reaction than In2O3 itself, while also exhibiting notable photoactivity towards methanol production. The increased solar absorption efficiency and efficient charge-separation and transfer of BixIn2-xO3 also contribute to the improved photocatalytic performance. These traits exemplify the opportunities that exist for atom-scale engineering in heterogeneous CO2 photocatalysis, another step towards the vision of the solar CO2 refinery.

Nondestructive production of exosomes loaded with ultrathin palladium nanosheets for targeted bio-orthogonal catalysis.

The use of exosomes as selective delivery vehicles of therapeutic agents, such as drugs or hyperthermia-capable nanoparticles, is being intensely investigated on account of their preferential tropism toward their parental cells. However, the methods used to introduce a therapeutic load inside exosomes often involve disruption of their membrane, which may jeopardize their targeting capabilities, attributed to their surface integrins. On the other hand, in recent years bio-orthogonal catalysis has emerged as a new tool with a myriad of potential applications in medicine. These bio-orthogonal processes, often based on Pd-catalyzed chemistry, would benefit from systems capable of delivering the catalyst to target cells. It is therefore highly attractive to combine the targeting capabilities of exosomes and the bio-orthogonal potential of Pd nanoparticles to create new therapeutic vectors. In this protocol, we provide detailed information on an efficient procedure to achieve a high load of catalytically active Pd nanosheets inside exosomes, without disrupting their membranes. The protocol involves a multistage process in which exosomes are first harvested, subjected to impregnation with a Pd salt precursor followed by a mild reduction process using gas-phase CO, which acts as both a reducing and growth-directing agent to produce the desired nanosheets. The technology is scalable, and the protocol can be conducted by any researcher having basic biology and chemistry skills in ~3 d.

(Keynote) Electrolyzer Development and Process Optimization: Paving the Road for Industrial Carbon-Dioxide Electroreduction

Electrochemical reduction of CO2 is a promising method for converting a greenhouse gas into value-added products, utilizing renewable energy. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance. In this talk, I am going to present a zero gap electrolyzer cell, which converts gas phase CO2 to products without the need for any liquid catholyte. I will show how to optimize the cell components, to simultaneously provide industrially relevant performance, such as high partial current density (up to 800 mA cm-2), low cell voltage (−2.8-3.2 V), high conversion efficiency (up to 45 %), and high selectivity for CO production (over 95%).I will also demonstrate our CO2 electrolyzer cell, where multiple layers are connected into an electrolyzer stack, thus scaling up the electrolysis process. The operation of the cell was validated using both silver nanoparticle and copper nanocube catalysts. Evenly distributing the CO2 gas among the layers (parallel connection), the operation of the cell stack was identical to the sum of multiple single-layer cells. When passing the CO2 gas through the layers one after the other (serial gas connection), the CO2 conversion efficiency was increased remarkably.Finally, I will show how the cell can operate with pure water feed on the anode side, therefore avoiding the use of alkaline anolyte. A carefully designed activation protocol will be presented, which allows the cell to operate at high current density, using pure water feed. The effect of temperature and flow rate on the operation will also be presented. Finally, the nature of ion-transport through the anion exchange membrane as a function of the operational conditions will be discussed.

HI-Light: A Glass-Waveguide-Based "Shell-and-Tube" Photothermal Reactor Platform for Converting CO2 to Fuels.

SummaryIn this work, we introduce HI-Light, a surface-engineered glass-waveguide-based “shell-and-tube” type photothermal reactor which is both scalable in diameter and length. We examine the effect of temperature, light irradiation, and residence time on its photo-thermocatalytic performance for CO2 hydrogenation to form CO, with a cubic phase defect-laden indium oxide, In2O3-x(OH)y, catalyst. We demonstrate the light enhancement effect under a variety of reaction conditions. Notably, the light-on performance for the cubic nanocrystal photocatalyst exhibits a CO evolution rate at 15.40 mmol gcat−1 hr−1 at 300°C and atmospheric pressure. This is 20 times higher conversion rate per unit catalyst mass per unit time beyond previously reported In2O3-x(OH)y catalyst in the cubic form under comparable operation conditions and more than 5 times higher than that of its rhombohedral polymorph. This result underscores that improvement in photo-thermocatalytic reactor design enables uniform light distribution and better reactant/catalyst mixing, thus significantly improving catalyst utilization.

Experimental Determination of H2 and CO Diffusion Coefficients in a Wax Mixture Confined in a Porous Titania Catalyst Support.

The ability to measure and predict molecular diffusion coefficients in multicomponent mixtures is not only of fundamental scientific interest but also of significant relevance in understanding how catalytic processes proceed. In the present work, the direct measurement of the molecular diffusion of H2 and CO gas-phase species diffusing in n-alkane mixtures using pulsed-field gradient (PFG) nuclear magnetic resonance (NMR) methods is reported. The work is of direct relevance to Fischer-Tropsch (FT) catalysis, with the measurements being made of the gas-wax system with the wax in both the bulk liquid state and when confined within a titania catalyst support, at temperatures and pressures typical of low-temperature FT synthesis. Molecular diffusion coefficients of H2 and CO within wax-saturated porous titania in the range (1.00-2.43) × 10-8 and (6.44-8.50) × 10-9 m2 s-1, respectively, were measured in the temperature range of 140-240 and 200-240 °C for H2 and CO, respectively, at a pressure of 40 bar. The wax mixture was typical of a wax produced during FT catalysis and had a molar average carbon number of 36. It is shown that the hydrogen diffusion coefficient within this wax mixture is consistent, to within experimental error, with the hydrogen diffusion coefficient measured in pure single-component n-hexatriacontane (n-C36) wax; this result held with the waxes in the bulk liquid state and when confined within the porous titania. The tortuosity of the porous titania was also measured using PFG NMR and found to be 1.77; this value is independent of temperature. The ability of existing correlations to predict these experimentally determined data was then critically evaluated. Although the Wilke-Chang correlation was found to underestimate the molecular diffusion coefficients of both H2 and CO diffusing in the wax in both the bulk state and when confined within the porous titania, parameterized correlations based on the rough hard sphere model, having accounted for the experimentally determined tortuosity factor, predicted the H2 and CO diffusion within bulk and confined wax to within 3%.

Integrated CO2 capture, nutrients removal and biodiesel production using Chlorella vulgaris

This study focused on the application of robust and promising Chlorella vulgaris for the simultaneous nutrient and CO2 removal, followed by examining biofuel production to overcome the existing drawbacks, including the burden of costs arising from current methodologies. The effects of operational parameters such as different CO2 concentrations (from 0.04 to 20% v/v) of the flue gas and wastewater C/N ratios (from 4 to 16) were examined on biomass production, culture pH, nutrients removal, CO2 capture, fatty acids content and biodiesel properties. The results showed that the C. vulgaris applicability depended directly on the microalgae growth rate and the highest growth was obtained at 5% (v/v) CO2 concentration with the C/N ratio of 4. C. vulgaris showed higher capability for ammonium removal(more than 99 %) compared to nitrate (81.05 %) and phosphate (87.95 %) removal, which was due to the fact that C. vulgaris prefered ammonium as a primary source of nitrogen. The gas-phase CO2 removal and CO2 fixation rate in the remaining biomass were found to be 76.92 % and 0.318 ± 0.009 (g L−1 d-1), respectively. Moreover, the biodiesel contained fatty acids with C16–C18 composition, which was determined as the main components of the applied microalgae and the results also revealed a beneficial approach to produce qualified biodiesel with high cetane number.

New Insights on a µm-Scale into the Transformation Process of CH4 Hydrates to CO2-Rich Mixed Hydrates

The global occurrences of natural gas hydrates lead to the conclusion that tremendous amounts of hydrocarbons are bonded in these hydrate-bearing sediments, serving as a potential energy resource. For the release of the hydrate-bonded CH4 from these reservoirs, different production methods have been developed during the last decades. Among them, the chemical stimulation via injection of CO2 is considered as carbon neutral on the basis of the assumption that the hydrate-bonded CH4 is replaced by CO2. For the investigation of the replacement process of hydrate-bonded CH4 with CO2 on a µm-scale, we performed time-resolved in situ Raman spectroscopic measurements combined with microscopic observations, exposing the CH4 hydrates to a CO2 gas phase at 3.2 MPa and 274 K. Single-point Raman measurements, line scans and Raman maps were taken from the hydrate phase. Measurements were performed continuously at defined depths from the surface into the core of several hydrate crystals. Additionally, the changes in composition in the gas phase were recorded. The results clearly indicated the incorporation of CO2 into the hydrate phase with a concentration gradient from the surface to the core of the hydrate particle, supporting the shrinking core model. Microscopic observations, however, indicated that all the crystals changed their surface morphology when exposed to the CO2 gas. Some crystals of the initial CH4 hydrate phase grew or were maintained while at the same time other crystals decreased in sizes and even disappeared over time. This observation suggested a reformation process similar to Ostwald ripening rather than an exchange of molecules in already existing hydrate structures. The experimental results from this work are presented and discussed in consideration of the existing models, providing new insights on a µm-scale into the transformation process of CH4 hydrates to CO2-rich mixed hydrates.

The coverage dependence of the infrared absorption of CO adsorbed to NaCl(100).

CO adsorbed to NaCl(100) exhibits perhaps the weakest possible coupling between the adsorbate and solid. It is, therefore, an ideal system to observe the influence of adsorbate-adsorbate interactions on infrared absorption. In this work, we report polarized FTIR absorption spectra of CO/NaCl(100) as a function of coverage (0.02 ≤ θ ≤ 1 ML), where the coverage has been quantitatively determined by temperature-programmed desorption and molecular beam dosing. We extend a previous semi-empirical model designed to describe the screening of the local electric field due to dipole-dipole interactions in a CO monolayer. The extended model applies to sub-monolayer coverages and describes properly the electric field of the absorbed radiation at the vacuum-substrate interface. Fitting this model to coverage-dependent IR absorption data allows us to derive the vibrational and electronic polarizabilities [χv = 0.0435(14) Å3, χe = 3.30(36) Å3] and the integrated absorption cross section of 2.51(8) × 10-17 cm/molecule for an isolated CO molecule adsorbed at the NaCl (100) surface. The determined integrated absorption cross section is substantially smaller than that of gas phase CO.

Assessing the influence of injection temperature on CO2 storage efficiency and capacity in the sloping formation with fault

Complex factors can affect carbon dioxide (CO2) geological storage efficiency and capacity. In this paper, a three-dimensional (3D) conceptual model of the Shiqianfeng formation in the Ordos basin was established (a total of 16 sets of schemes) to study the influence of injection temperature on CO2 storage efficiency and migration safety in the sloping formation with a fault. In addition, storage capacity is investigated for CO2 storage site selection. The results show that injection temperature and formation slope have a significant effect on CO2 storage efficiency. Faulting provides a possible channel for CO2 leakage. High injection temperature is more likely to cause CO2 leakage in the sloping formation. When the injection temperatures are 11, 31.5, 51 and 71 °C in the 15° slope formation, the time points of CO2 leakage are 200, 170, 150 and 140 years, respectively. The lower injection temperature results in a higher CO2 concentration near the injection well and a closer migration distance of dissolved CO2. The larger the formation slope is, the farther the dissolved CO2 migration distance will be. The higher injection temperature results in a greater gas phase, dissolved phase, and total CO2 storage amount in the whole formation. The larger the formation slope is, the smaller the CO2 storage capacity will be for CO2 injected over 20 years. However, the larger formation slope resulted in a smaller gas phase and larger storage amount of the dissolved phase CO2 for CO2 migration after 140 years. The influence of the formation slope on the dissolved CO2 migration safety is more obvious than that of injection temperature. However, the influence of the injection temperature on CO2 storage capacity is more obvious than that of the formation slope.

DFT calculations and in situ DRIFTS study of CO oxidation on CeO2/Co3O4 catalyst

The surface structures, CO adsorption, and oxidation-reaction properties of CeO2/Co3O4(110) have been investigated by using density functional theory including on-site Coulomb corrections (DFT+U) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). Results indicate that CO can be chemisorbed on the Co sites of the terrace and interface of CeO2/Co3O4(110). At the interface, adsorbed and gas-phase CO reacting with lattice oxygen are investigated, respectively. It has been found that the lattice oxygen at the interface is more likely to be attacked by gas-phase CO directly to form adsorbed CO2. For desorption of the CO2, very high energy barriers are required. Furthermore, the infrared spectra reveal that the intermediate species at interface still exist even at 300 °C.

Selective reduction of iron and phosphorus from oolitic ore

Possibility of selective solid-phase reduction of iron from oolitic ore has been experimentally confirmed. Solid phase reduction was carried out at temperatures of 850 and 1000 °C in CO atmosphere and in the mixture with solid carbon. Distribution of iron and phosphorus was investigated with scanning electron microscope. It was found that at temperature of 1000 °C minimum amount of phosphorus (up to 0.3 %) is transformed into the metallic phase at reduction by carbon monoxide. Upon reduction in mixture of ore with carbon, phosphorus content in metal phase reaches 1.0 – 1.3 % evenat temperature of 850 °C. Thermodynamic modeling of the processes occurring during reductive roasting of oolitic ore was carried out depending on temperature (1000 – 1400 K) and amount of carbon in the system. It is shown that reduction temperature and degree of phosphorus reduction vary depending on ratio of CO and CO2 in the gas phase. At temperatures below 892 °C, phosphorus is not reduced and all iron is in metal phase. With an increase in amount of carbon in the system, phosphorus appears in metal phase. With an excess of carbon in the system, all phosphorus is in metal phase at temperature of 892 °С. Thus, with a certain amount of carbon in the system and, correspondingly, with a certain ratio of CO and CO2 in gas phase, selective reduction of iron is possible without phosphorus reduction even at temperature of 1100 °С. Comparison of experimental results with results of thermodynamic calculation confirms possibility of se selective reduction of iron without phosphorus reduction only by carbon monoxide.

Dehydrogenation of pure methanol in an alkaline solution using copper electrodes

Herein, we focused on electrolysis to produce hydrogen-based energy to reduce pollution and cost of energy generation by replacing platinum (Pt) and ruthenium (Ru) anodes with copper (Cu) anodes, while demonstrating that H2 and CO can be obtained by dehydrogenating pure methanol in a non-compartment cell. Also this is a new study that is completely different from DMFC. Redox products of methanol and electrochemical efficiency were determined using various techniques. 1 V (vs Ag/AgCl [KCl sat’]) was applied to quantitatively evaluate H2 generation; on average, 801.17 mmol g−1 L−1 h−1 of H2 was generated. The Cu electrode was electrochemically stable under the stirring at 150 rpm, indicating reduced toxicity by CO adsorption. Gas-phase CO and H2, along with liquid-phase formate, carbonate, and paraformaldehyde, were obtained; the main product was H2. However, details of the dehydrogenation mechanism remain unclear, and merit further investigations.