Adsorption Of Carbon Monoxide Research Articles

Functionalized graphene-based Quantum Dots: Promising adsorbents for CO, NO2, SO2, and NH3 Pollutant Gases

The development of more sensitive and accurate sensors is essential to monitor the levels of pollutant gases that are causing high damage to the biosphere. One of the most promising materials for such application is graphene, which, due to its extensive collection of properties, has shown itself capable of adsorbing gas molecules. Thus, the present work aims to investigate the adsorption of carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ammonia (NH3) on Graphene Quantum Dots (GQD) through electronic structure and molecular dynamics calculations. The data suggest doping GQDs with boron, nitrogen, or aluminum can greatly improve their adsorbing capabilities. For both CO and NH3, a functionalization with aluminum is the most effective, while the adsorption of SO2 was not much affected by any of the doping designs. Notably, quantum dots doped with all three heteroatoms are extremely promising with respect to the application in NO2 gas sensors. Thereby, the results indicate that accurate and resilient gas sensors based on doped GQDs may be a good substitute for the current sensors in the market.

Cu(I)-loaded boehmite microspheres prepared by the continuous flow-assisted spray-drying method for selective carbon monoxide separation

An efficient and low-cost adsorbent material is necessary for separating carbon monoxide (CO) from off-gases that also contain CO2 and N2. Boehmite (γ-AlOOH)-based materials have shown great potential for many applications. In this work, mesoporous γ-AlOOH microspheres were rapidly produced by combining the sol–gel and continuous flow-assisted spray-drying methods (SD-AlOOH). Then, Cu(I) chloride (CuCl) was thermally dispersed into the SD-AlOOH microspheres to obtain the CuCl@SD-AlOOH adsorbent. Gas adsorption experiments revealed that the CuCl@SD-AlOOH samples adsorbed CO over CO2 and N2 owing to the π-complexation reaction between CO and Cu(I). The adsorption properties were affected by the spray-drying conditions, CuCl load, and CuCl dispersion temperature. The optimal SD-AlOOH, which was loaded with 33 wt% CuCl, exhibited a CO adsorption capacity of ∼38.7 cm3 g−1 (25 °C and 100 kPa), which exceeds that of commercial CuCl-loaded AlOOH and many other Cu(I) π-complexation adsorbents. Furthermore, the prepared CuCl@SD-AlOOH showed high ideal adsorbed solution theory (IAST)-predicted CO/CO2 and CO/N2 selectivities of ∼87 and ∼730, respectively, at 100 kPa. Breakthrough tests showed that the CuCl-loaded SD-AlOOH microspheres effectively separated CO from a gas mixture with CO2 under dynamic flow conditions.

Preparation of Aluminum-Molybdenum Alloy Thin Film Oxide and Study of Molecular CO + NO Conversion on Its Surface.

Adsorption and interaction of carbon monoxide (CO) and nitric oxide (NO) molecules on the surface of bare Al-Mo(110) system and on that obtained by its in situ oxidation have been studied in ultra-high vacuum (base pressure: ca. 10−8 Pa) by means of Auger and X-ray photoelectron spectroscopy (AES, XPS), low energy electron diffraction (LEED), reflection–absorption infrared and thermal desorption spectroscopy (RAIRS, TDS), and by the work function measurements. In order to achieve the Al-Mo(110) alloy the thin aluminum film of a few monolayers thick was in situ deposited onto the Mo(110) crystal and then annealed at 800 K. As a result of Al atoms diffusion into the Mo(110) subsurface region and the chemical reaction, the surface alloy of a hexagonal atomic symmetry corresponding to Al2Mo alloy is formed. The feature of thus formed surface alloy regarding molecular adsorption is that, unlike the bare Mo(110) and Al(111) substrates, on which both CO and NO dissociate, adsorption on the alloy surface is non-dissociative. Moreover, adsorption of carbon monoxide dramatically changes the state of pre-adsorbed NO molecules, displacing them to higher-coordinated adsorption sites and simultaneously tilting their molecular axis closer to the surface plane. After annealing of this coadsorbed system up to 320 K the (CO + NO → CO2 + N) reaction takes place resulting in carbon dioxide desorption into the gas phase and nitriding of the substrate. Such an enhancement of catalytic activity of Mo(110) upon alloying with Al is attributed to surface reconstruction resulting in appearance of new adsorption/reaction centers at the Al/Mo interface (steric effect), as well as to the Mo d-band filling upon alloying (electronic effect). Catalytic activity mounts further when the Al-Mo(110) is in situ oxidized. The obtained Al-Mo(110)-O ternary system is a prototype of a metal/oxide model catalysts featuring the metal oxides and the metal/oxide perimeter interfaces as a the most active reaction sites. As such, this type of low-cost metal alloy oxide models precious metal containing catalysts and can be viewed as a potential substitute to them.

Influence of Defects and Heteroatoms on the Chemical Properties of Supported Graphene Layers

A large and growing number of theoretical papers report the possible role of defects and heteroatoms on the chemical properties of single-layer graphene. Indeed, they are expected to modify the electronic structure of the graphene film, allow for chemisorption of different species, and enable more effective functionalisation. Therefore, from theoretical studies, we get the suggestion that single and double vacancies, Stone–Wales defects and heteroatoms are suitable candidates to turn nearly chemically inert graphene into an active player in chemistry, catalysis, and sensoristics. Despite these encouraging premises, experimental proofs of an enhanced reactivity of defected/doped graphene are limited because experimental studies addressing adsorption on well-defined defects and heteroatoms in graphene layers are much less abundant than theoretical ones. In this paper, we review the state of the art of experimental findings on adsorption on graphene defects and heteroatoms, covering different topics such as the role of vacancies on adsorption of oxygen and carbon monoxide, the effect of the presence of N heteroatoms on adsorption and intercalation underneath graphene monolayers, and the role of defects in covalent functionalisation and defect-induced gas adsorption on graphene transistors.

Comparative study on adsorption behaviour of the monolayer graphene, boron nitride and silicon carbide hetero-sheets towards carbon monoxide: Insights from first-principle studies

A comprehensive study on the sensitivity of graphene, boron nitride, silicon carbide and their in-plane hetero-sheets towards carbon monoxide (CO) was performed using first-principle density functional theory calculations. To rationalize the CO adsorption on pristine and hetero-sheets, molecular electrostatic potential contours, HOMO-LUMO distributions, the density of states plots, atomic charge distributions and quantum chemical descriptors were calculated. The optimized geometries showed that the CO molecule oriented itself at different angles with respect to sheets. A shift in the characteristic vibrational frequency of CO was observed through theoretically computed infra-red spectra. The maximum shift was observed for the GRA/SiC hetero-sheet. Charge analysis showed the partial charge transfer from the CO molecule to the adsorbent sheets. This was further confirmed by the HOMO-LUMO distributions of the interacting species. The reactivity descriptors calculated based on the HOMO-LUMO energies, molecular electrostatic potential contours and DOS plots showed that GRA/SiC hetero-structure exhibited better sensitivity towards CO than other sheets. The calculated adsorption energies, corrected for basis set superposition error, ranged from −3 to −10 kJ mol−1, confirming the physical nature of adsorption.

Unraveling the Interfacial Polarization Effect between Pd and Polymeric Carbon Nitride toward Efficient CO2 Electroreduction to CO.

The efficient electrochemical conversion of carbon dioxide (CO2) to carbon monoxide (CO) using renewable energy is an effective route to pursue carbon neutrality. Optimizing the binding energy of CO on palladium (Pd) metal-based materials used in this process is to make sure the timely desorption of CO from their active sites is critical. Tuning the electronic structure of the Pd center is an effective strategy to optimize its catalytic performance. Herein, we rationally design Pd nanoparticles (NPs)/polymeric carbon nitride (CN) (Pd/CN) composite, which alters the electronic structure of Pd by introducing the interfacial polarization effect to accelerate CO desorption and improve CO selectivity of Pd catalyst. The optimized Pd/CN exhibits a CO Faradaic efficiency of 92.7% at -0.9 V versus reversible hydrogen electrode in CO2-saturated 0.1 M KHCO3 solution. Experimental investigations and theoretical calculations jointly confirm that the enhanced CO selectivity and stability originate from the electron transfer at the Pd/CN interface, and the weakened *CO adsorption on the palladium hydride surface.

Pore structure of ordered mesoporous Pt-CeO2 probed by CO via VT-DRIFTS

CeO2-supported Pt (1 wt%) catalysts have been synthesized using three ordered mesoporous silica templates, SBA-15, KIT-6, and COK-19, with the representative pore structures listed as 2D hexagonal, bicontinuous cubic and face-centered cubic structures. The effect of pore structure on surface and adsorption properties of those ordered mesoprous CeO2-supported Pt catalysts have been studied by in situ variable temperature diffuse reflectance infrared Fourier transform spectroscopy (VT-DRIFTS) using carbon monoxide (CO) as the probing molecule to study the Pt – COads and carbonate/formate surface species. VT-DRIFT spectra demonstrate that the mesoporous Pt-CeO2 catalyst synthesized from the SBA-15 template shows the largest amount of Pt – COads, indicating that mesoporous Pt-CeO2 synthesized from SBA-15 possesses the largest number of active metal sites, due to its larger pore volume and pore size, compared to the ones synthesized from KIT-6 and COK-19. The VT-DRIFT results of CO adsorption and desorption from ordered mesoporous CeO2-supported Pt catalysts will assist in understanding the surface chemistry of reactions with CO as a reactant, such as water–gas shift reaction; and help design effective mesoporous catalysts for CO reactions, under operando conditions.

Compressive Stress and Charge Redistribution during CO Adsorption onto Pt.

The change in surface stress associated with the adsorption and oxidative stripping of carbon monoxide (CO) on (111)-textured Pt is examined using the wafer curvature method in 0.1 mol/L KHCO3 electrolyte. The curvature of the Pt cantilever electrode was monitored as a function of potential in both CO-free and CO-saturated electrolytes. Although CO adsorbs as a neutral molecule, significant compressive stress, up to -1.3 N/m, is induced in the Pt. The magnitude of the stress change correlates directly with the CO coverage and, within the detection limits of the stress measurement, is elastically reversible. Density functional theory calculations of a CO-bound Pt surface indicate that charge redistribution from the first atomic layer of Pt to subsurface layers accounts for the observed compressive stress induced by the charge neutral adsorption of CO. A better understanding of adsorbate-induced surface stress is critical for the development of material platforms for sensing and catalysis.

Adsorption Characteristics of Carbon Monoxide on Ag- and Au-Doped HfS2 Monolayers Based on Density Functional Theory

A large amount of power equipment works in closed or semi-closed environments for a long time. Carbon monoxide (CO) is the most prevalent discharge gas following a fault in the components. Based on the density functional theory of first principles, the adsorption behavior of CO gas molecules on intrinsic, Ag-doped and Au-doped hafnium disulfide (HfS2) monolayers was systematically studied at the atomic scale. Firstly, the intrinsic HfS2 monolayer, Ag-doped HfS2 (Ag-HfS2) monolayer and Au-doped HfS2 (Au-HfS2) monolayer, with different doping sites, were created. The structural stability, dopant charge transfer, substrate conductivity and energy band structure of different doping sites of the Ag-HfS2 and Au-HfS2 monolayer structures were calculated. The most stable doping structure was selected with which to obtain the best performance on the subsequent gas adsorption test. Then, the CO adsorption models of intrinsic HfS2, Ag-HfS2 and Au-HfS2 were constructed and geometrically optimized. The results show that the adsorption energy of the Ag-HfS2 monolayer for CO gas is −0.815 eV, which has good detection sensitivity and adsorption performance. The adsorption energy of CO on the Au-HfS2 monolayer is 2.142 eV, the adsorption cannot react spontaneously, and the detection sensitivity is low. The research content of this paper provides a theoretical basis for the design and research of gas sensing materials based on HfS2, promoting the development and application of HfS2 in gas sensing and other fields.

First-principles study of CO gas adsorption on pristine and Fe-doped H[formula omitted]-graphyne

Due to the advantages of high surface volume ratio, stable structure and easy modification, two-dimensional carbon materials have received extensive attention in recent years. In order to find suitable materials for detecting or storing toxic carbon monoxide (CO) gas, first-principles calculations are used to systematically investigate the adsorption performance of pristine H4,4,4-graphyne (H4,4,4-G) and Fe-doped H4,4,4-graphyne (Fe-H4,4,4-G) for CO. The calculation results show that only weak physical adsorption occurs between CO and H4,4,4-G. On the contrary, in the Fe-H4,4,4-G system, the substrate interacts strongly with CO and chemical adsorption occurs. Fe-H4,4,4-G has excellent adsorption performance for CO and the charge transfer is more obvious. Its adsorption energy and charge transfer are -1.601 eV and -0.167 e, respectively. Therefore, Fe-H4,4,4-G can be used as a candidate material for storage or detection of CO. In addition, the applied electric field can effectively control the gas sensitivity of Fe-H4,4,4-G, and further enhance the adsorption performance of CO on the substrate. It is expected that CO can be captured or released by Fe-H4,4,4-G. The results of this research will help advance the study of the adsorption characteristics of H4,4,4-G, and the Fe-doped H4,4,4-G will provide a new idea for the application of gas sensors.

Thermodynamics of Carbon Monoxide Adsorption on Cu/SBA-15 Catalysts: Under Vacuum versus under Atmospheric Pressures

Thermodynamics of Carbon Monoxide Adsorption on Cu/SBA-15 Catalysts: Under Vacuum versus under Atmospheric Pressures

Adsorption of carbon monoxide on novel and Merck activated carbon treated by dielectric barrier discharge

Adsorption of carbon monoxide on novel and Merck activated carbon treated by dielectric barrier discharge

The Impact of Water Concentration on the Electro-Oxidation of Formic Acid on Platinum

Water plays a pivotal role in several electrocatalytic reactions. In the electrooxidation of small organic molecules, water can for instance assist the oxidation of adsorbed species or inhibit the reaction through the oxidation of surface sites. This paper is the third in a series of studies aiming at evaluating the impact of water concentration on the electro-oxidation of small organic molecules on polycrystalline platinum. The study was performed in phosphoric acid electrolyte, and the water concentration was varied from 14 to 50 mol l−1. Voltammetric profiles and potential oscillations were studied at distinct [H2O]/[H3PO4] ratios and constant concentration of formic acid. There is a diminution in the catalytic activity accompanying the decrease in the water concentration. The removal of carbon monoxide demands oxygenated species and can proceed in the absence of water for ethanol and methanol, but not for formic acid. Under oscillatory regime, the impact of water concentration, it is seen that higher water concentration implies higher oscillation frequencies, shorter and less stable time-series, and sharper transitions from low to high potential, where the adsorbed carbon monoxide is oxidized by adsorbed oxygenated species. Results are discussed in connection with the voltammetric study and also compared with other parent systems.

Theoretical Study on Carbon Monoxide Adsorption on Unsupported and γ-Al2O3-Supported Silver Nanoparticles: Size, Shape, and Support Effects.

Nanoparticles (NPs) supported on metal oxides exhibit high catalytic activities for various reactions. The shape and oxidation state of such NPs, which are related to the catalytic activity, are often determined by the support. Herein, we conducted a density functional theory study on isolated silver (Ag) NPs and two types of Ag-NPs supported on gamma-aluminum oxide (γ-Al2O3). First, carbon monoxide (CO) adsorption on the isolated Ag NPs was investigated for decahedra (D5h), icosahedra (Ih), and cuboctahedra (Oh) of various sizes. Ih and Oh NPs showed moderate size dependence, whereas D5h NPs showed high size dependence when the height was below 1.4 nm. The enhancement of CO adsorption on D5h NPs was attributed to the presence of superatomic states. Next, we performed geometrical optimization of Ag54/γ-Al2O3(110) with a decahedral shape. Two types of structures were obtained: amorphous Ag54(A) and locally fivefold symmetrical Ag54(B) structures. Both NPs on γ-Al2O3(110) were found to be positively charged, but electron transfer to the support occurred only from the Ag atoms at the two bottom layers, and the upper part of NPs was relatively neutral. The enhancement of CO adsorption on Ag54(B) disappeared due to loss of the high symmetry. In turn, the moderate size dependence of neutral isolated NPs can be applied.

Vibrational Fine Structure in C 1s High-Resolution Core-Level Spectra of CO Chemisorbed on Ir(111)

The vibrational features of carbon monoxide (CO) adsorbed on Ir(111) were studied by means of high-resolution core-level spectroscopy. By monitoring the Ir 4f7/2 core level as a function of exposure, we proved that the CO adsorbs on the surface always in on-top sites, in agreement with the results of vibrational spectroscopy techniques and density functional theory studies. The C 1s vibrational splittings measured for the p(√3 × √3)R30° (233.4 ± 0.5 meV) and c(4 × 2√3)rect (231.4 ± 0.4 meV) structures were in good agreement with the Z + 1 model. Despite the very small error bar of the measurements, it was not possibile to reveal any anharmonic contribution to the spectral lineshape. We speculate that the contribution of the unresolved vibrational mode of the frustrated translation or the effect of phonon-mediated interaction with the substrate can account for the observation of this outcome.

Topographic signatures and manipulations of Fe atoms, CO molecules and NaCl islands on superconducting Pb(111).

Topological superconductivity emerging in one- or two-dimensional hybrid materials is predicted as a key ingredient for quantum computing. However, not only the design of complex heterostructures is primordial for future applications but also the characterization of their electronic and structural properties at the atomic scale using the most advanced scanning probe microscopy techniques with functionalized tips. We report on the topographic signatures observed by scanning tunneling microscopy (STM) of carbon monoxide (CO) molecules, iron (Fe) atoms and sodium chloride (NaCl) islands deposited on superconducting Pb(111). For the CO adsorption a comparison with the Pb(110) substrate is demonstrated. We show a general propensity of these adsorbates to diffuse at low temperature under gentle scanning conditions. Our findings provide new insights into high-resolution probe microscopy imaging with terminated tips, decoupling atoms and molecules by NaCl islands or tip-induced lateral manipulation of iron atoms on top of the prototypical Pb(111) superconducting surface.

Причины низкого значения работы выхода гексаборида лантана как эффективного электронного эмиттера

To establish the mechanism of high emission efficiency of lanthanum hexaboride as one of the most widely used electron emitters, a comparative study of the state of La and B atoms in the La–B double film, on one hand, and in the separate La and B films – on the other, was done via probing the state of such films via carbon monoxide adsorption. It is shown that the formation of the La–B dipole layer on the surface is the main reason for the high emission effectiveness of lanthanum hexaboride. As such, the subnanometer La–B film systems may be promising as electron emitter of a high degree of spatial locality.

Preparation and Application Prospect of Activated Carbon Fiber Catalysts from Smart City Condition

Activated carbon fiber, also known as the third generation of activated carbon material, is a new type of activated carbon material after powder and granules, made of the organic fiber. Activated carbon fiber has a strong adsorption capacity due to its large specific surface area, and can adsorb and remove organic matter in water, including some carcinogenic or toxic macro-aromatic substances. Physical adsorption is caused by electrostatic interaction between the surface molecules of the adsorbent and the adsorbate molecules, which is characterized by adsorption without selectivity. Chemical adsorption is due to the chemical bonding between the two molecules, forming a strong chemical bond and also the surface complex. Chemical adsorption has the certain selectivity, generally monolayer adsorption. With the large increase in vehicle usage and the exhaust emissions from equipment such as oil-fired boilers, the pollution of nitrogen oxides and carbon monoxide gas has become an important issue in environmental management. Adsorption or catalytic conversion of nitrogen oxides and carbon monoxide is an important means of treatment. This paper integrates the smart city scenario to construct the novel scenario for the analysis and research. The simulation results prove the effectiveness.

Термические свойства наноструктур СО-Yb-подложка

Influence of adsorbed carbon monoxide molecules on the thermal properties of rare-earth metal ytterbium films of nanoscale thickness has been studied. The films are produced at room temperature by metal deposition on single-crystal silicon substrates with the Si(111) surface orientation or textured tungsten ribbons with the predominant (100) face. It is shown that the adsorbed molecules hinder evaporation of ytterbium. The strength of such hindering is dependent on the chemical nature of substrate material. It is established that the substrates affect the state of adsorbed molecules through the nanofilms. This in turn influences on the evaporation rate of nanolayer material.

Thermal properties of CO-Yb-substrate nanostructures

Influence of adsorbed carbon monoxide molecules on the thermal properties of rare-earth metal ytterbium films of nanoscale thickness has been studied. The films are produced at room temperature by metal deposition on single-crystal silicon substrates with the Si(111) surface orientation or textured tungsten ribbons with the predominant (100) face. It is shown that the adsorbed molecules hinder evaporation of ytterbium. The strength of such hindering is dependent on the chemical nature of substrate material. It is established that the substrates affect the state of adsorbed molecules through the nanofilms. This in turn influences on the evaporation rate of nanolayer material. Keywords: thermal stability of nanofilms, surface, adsorbed molecules, carbon monoxide, ytterbium, silicon, tungsten, Auger electron spectroscopy, mass spectrometry.