Study Of Carbon Monoxide Adsorption Research Articles

Density functional theory study of carbon monoxide adsorption on transition metal doped armchair graphene nanoribbon

Density Functional Theory calculations are used to study adsorption of carbon monoxide gas on transition metal doped armchair graphene nanoribbon. Sensing behaviour of pristine armchair graphene nanoribbon (Pr-AGNR) and different geometries of osmium doped AGNR such as one-edge doped AGNR, center doped AGNR and both-edge doped AGNR have been investigated. Most stable adsorption geometry, adsorption energy, binding distance, band structure and density of states of different geometries using in our work have been discussed. Electronic properties of different sensing materials can be interpreted in terms of band structure and density of states. It was studied that a weak type of physical adsorption process took place when CO molecule interacts with pristine AGNR with a very small amount of adsorption energy of amount −0.22 eV. This suggests that pristine graphene is not a good adsorber for CO adsorption. In contrast, doping of graphene with osmium atom enhances the adsorption energy of Pr-AGNR to greater extent. Computational results concluded that osmium doping in graphene nanoribbon at one-edge and both-edge position increases the adsorption energies with values −6.77 eV and −9.53 eV respectively which is 30 times and 43 times greater than in comparison to Pr-AGNR. Energy gap calculations proves that large band gap variations are observed for both-edge doped graphene nanoribbon. Sharp and intense peaks at various energy levels from density of states analysis of both-edge doped geometry confirms adsorption of CO. Our results predicts that both-edge osmium doped sensing material can be considered as promising sensing material for CO adsorption.

Rethinking CO adsorption on transition-metal surfaces: Effect of density-driven self-interaction errors

Adsorption of the molecule CO on metallic surfaces is an important unsolved problem in Kohn-Sham density functional theory (KS-DFT). We present a detailed study of carbon monoxide adsorption on fcc (111) surfaces of 3d, 4d and 5d metals using nonempirical semilocal density functionals for the exchange-correlation energy: the local-density approximation (LDA), two generalized gradient approximations or GGAs (PBE and PBEsol), and a meta-GGA (SCAN). The typical error pattern (as found earlier for free molecules and for free transition metal surfaces), in which results improve from LDA to PBE or PBEsol to SCAN, due to the satisfaction of more exact constraints, is not found here. Instead, for CO adsorption on transition metal surfaces, we find that, while SCAN overbinds much less than LDA, it overbinds slightly more than PBE. Moreover, the tested functionals often predict the wrong adsorption site, as first pointed out for LDA and GGA in the ``CO/Pt (111) puzzle". This abnormal pattern leads us to suspect that the errors of PBE and SCAN for this problem are density-driven self-interaction errors associated with incorrect charge transfer between molecule and metal surface. We point out that, by the variational principle, overbinding by an approximate functional would be reduced if that functional were applied not to its selfconsistent density for the adsorbed system but to an exact or more correct density for that system. Finally, we show for CO on Pt(111) that the site preference is corrected and the adsorption energy is improved for the PBE functional by using not the selfconsistent PBE density but a PBE+U density. The resulting correction to the PBE total energy is much larger for the adsorbed system than for its desorbed components, showing that the error is in the density of the adsorbed system. This seems to solve the ``CO/Pt (111) puzzle", in principle if not fully in practice.

Combining IR Spectroscopy and Monte Carlo Simulations to Identify CO Adsorption Sites on Bimetallic Alloys

The atomic distribution on the surface of alloys dictates the nature of the ensembles available as possible active sites during catalytic reactions. In the present work, an infrared spectroscopic study of carbon monoxide adsorption on the surface of AuPd/Pd(111) alloys, combined with Monte Carlo simulations of the surface and bulk atomic distribution, identifies the correct distribution of available surface adsorption sites. For gold coverages >0.9 monolayers (ML), CO adsorbs weakly on top of Au atoms and with higher adsorption energy on top of Pd atoms (COtop), distributed mostly as monomers on the surface. For θAu = 0.8–0.4 ML, Pd–COtop is the predominant species, even though several other sites with multiple coordination are available. The simulations show no perfect ordering of the surface but a slight tendency to form lines of Pd atoms, thus favoring the appearance of bridge but not 3-fold hollow sites. Using 13CO:12CO isotopic mixtures, the frequency shifts due to chemical and intermolecular couplin...

Forsterite Surfaces as Models of Interstellar Core Dust Grains: Computational Study of Carbon Monoxide Adsorption

Carbon monoxide (CO) is the second most abundant gas-phase molecule after molecular hydrogen (H2) of the interstellar medium (ISM). In molecular clouds, an important component of the ISM, it adsorbs at the surface of core grains, usually made of Mg/Fe silicates, and originates complex organic molecules through the catalytic power of active sites at the grain surfaces. To understand the atomistic, energetic, and spectroscopic details of the CO adsorption on core grains, we resorted to density functional theory based on the hybrid B3LYP-D* functional inclusive of dispersion contribution. We modeled the complexity of interstellar silicate grains by studying adsorption events on a large set of infinite extended surfaces cut out from the bulk Mg2SiO4 forsterite, the Mg end-member of olivines (Mg2xFe2–2xSiO4), also a very common mineral on the Earth’s crust. Energetic and structural features indicate that CO is exclusively physisorbed with binding energy values in the 23–68 kJ mol–1 range. Detailed analysis of data revealed that dispersive interactions are relevant together with the important electrostatic contribution due to the quadrupolar nature of the CO molecule. We performed a full thermodynamic treatment of the CO adsorption at the very low temperature typical of the ISM as well as a full spectroscopic characterization of the CO stretching frequency, which we prove to be extremely sensitive to the local nature of the surface-active site of adsorption. We also performed a detailed kinetic analysis of CO desorption from the surface models at different temperatures characterizing the colder regions of the ISM. Our computed data could be incorporated in the various astrochemical models of interstellar grains developed so far and thus contribute to improve the description of the complex chemical network occurring at their surfaces.

First-principles study of CO adsorption on 4H-SiC (001) surface

Using the first-principles method, the authors investigated the adsorption of carbon monoxide (CO) on a 4H-silicon carbide (SiC) (001) surface. The structure parameters and adsorption energy at different adsorption sites (top, bridge, hollow) of carbon monoxide on the 4H-silicon carbide (001) surface are calculated. By comparing the adsorption energies, it was deduced that the bridge site is the most favored site because its adsorption energy is larger than those at the top and hollow sites. The transfer trend of the charge in the progress of the adsorption is revealed by the density of states of the adsorbate, the orbital charge population change of the carbon monoxide molecule and the atomic orbital charge population change of the 4H-silicon carbide (001) surface. The conclusion shows that the main interaction in the process of adsorption comes from the 2p orbital of the carbon (C) atom and the 3s and 3p orbitals of the silicon (Si) atom. An interesting characteristic in electron transfer is that the π orbital of carbon takes a bridge role between silicon and oxygen (O).

Low-Temperature Adsorption of Carbon Monoxide on Gold Surfaces: IR Spectroscopy Uncovers Different Adsorption States on Pristine and Rough Au(111)

The morphology of gold surfaces plays a major role in many domains of contemporary research. Infrared (IR) spectroscopy in combination with carbon monoxide (CO) as a probe adsorbate is able to sensitively monitor differences in the morphology of gold surfaces on an atomic level if CO adsorption on the various surfaces is clarified. Our investigation comprises the first study of CO adsorption on Au(111) under well-defined ultrahigh vacuum conditions at 30 K. We find that CO adsorbs on Au(111) in atop geometry, as has been reported before for a variety of gold surfaces, but a significantly higher frequency of the internal CO stretching vibration is observed, confirming results from recent theoretical studies. Furthermore, the presence of a submonolayer amount of gold adatoms on the Au(111) surface results in the properties of gold surfaces toward CO adsorption at higher temperatures known from the literature. Step-wise annealing of these atomically rough surfaces leads to a gradual transition between the li...

Density Functional Theory Study of OH and CO Adsorption on the Pt2Ru3 Surface

In this work, we present results of periodic density functional theory study of the adsorption of carbon monoxide (CO) and hydroxyl (OH) on Pt2Ru3 alloy surface for different conformation of Pt and Ru. These results were compared with CO and OH adsorption on pure Pt and Ru surfaces. We find that the mixing of Pt by Ru leads to stronger bond of CO and OH to the Ru sites, whereas weaker bond notice of CO and OH to the Pt sites. We also analyze the effect of surface, sub surface and neighboring atoms effect on the adsorption of CO and OH on the Pt2Ru3 alloy surface. We notice that surface mixture with Pt and Ru atoms is more favourable adsorption sites for CO and OH than that of the homogeneous alloy surfaces.

A density functional theory study of carbon monoxide adsorption on platinum-doped gold clusters

An all-electron scalar relativistic (AER) calculation on Au n PtCO ( n = 1–12) clusters had been performed using density functional theory (DFT) with the generalized gradient approximation (GGA) at Perdew-Wang 91 (PW91) exchange-correlation functional level. The CO molecule prefers to be adsorbed on Pt in Au n Pt ( n = 1–12) clusters. The introduction of impurity Pt strengthens the adsorption toward CO molecule and then promotes the reactivity enhancement of CO molecule. The CO molecule is also more favorable to be adsorbed by the even-numbered Au n Pt clusters with closed-shell electronic structure.

A density functional study of carbon monoxide adsorption on small cationic, neutral, and anionic aluminum phosphide clusters

The chemisorption of CO on aluminum phosphide (AlP)n (n=1–12) clusters are studied with density functional theory. Among various possible CO adsorption sites, the on-top site is identified to be the most favorable chemisorption sit. The Al-top sites are the preferred one in the most cases for one CO adsorption in (AlP)n (n=3–12) clusters, irrespective of the charge state of the clusters. The Al–P bond lengths decrease generally as the size of the cluster increases. There is a slight increase in the mean Al–P bond lengths after CO adsorption on the lowest-energy sites of the most AlP clusters. In general, adsorption energies of CO are found to decrease with an increase in the cluster size for both neutral and ionic clusters. The adsorption energies of CO on the cationic (AlP)nCO+ (n=2–12) clusters are greater than those on the neutral and anionic complexes. The result shows that large adsorption energies of CO on neutral and ionic AlP clusters and large highest occupied and lowest unoccupied molecular-orbital gaps for (AlP)CO, (AlP)CO+ and (AlP)CO− make these species behaving like magic clusters. The CO vibrational frequencies νCO in all the cationic complexes are always larger than the corresponding quantities in the neutral and anionic clusters. All of them are smaller than those in the free CO molecule.

DFT study of carbon monoxide adsorption on α-Al 2O 3(0001)

The adsorption of CO on α-Al 2O 3(0001) was studied using the DFT-GGA computational method and on α-Al 2O 3 powder experimentally by Infra red spectroscopy. The core and valence level regions of α-Al 2O 3(0001) single crystal surface were also studied experimentally. Ar ions sputtering of the surface results in a slight but reproducible decrease in the XPS O2p lines in the valence band regions due to preferential removal of surface (and near surface) O atoms. Core level XPS O1s and Al2p further confirmed oxygen depletion with an associated surface stoichiometry close to Al 2O 2.9. The adsorption energy of CO was computed and found equal to 0.52 eV for θ = 0.25, it decreased to 0.42 eV at θ = 1. The IR frequency of νCO was also computed and in all cases it was blue shifted with respect to gas phase CO. The shift, Δν, decreased with increasing coverage where it was found equal to 56 cm − 1 for θ = 0.25 and decreased to 30 cm − 1 for θ = 1. Structural analyses indicated that the change in the adsorption energy and the associated frequency shift is due to surface relaxation upon adsorption. Experimentally the adsorption of CO gave rise to one main IR peak at 2154 cm − 1 at 0.3 Torr and above. Two far smaller peaks are also seen at lower pressures of 0.03–0.2 Torr at 2189 and 2178 cm − 1 . The isosteric heat of adsorption was computed for the IR band at 2154 cm − 1 and was found equal to 0.2 eV which did not change with coverage in the investigated range up to θ = 0.6.

On the nature of gallium species in gallium-modified mordenite and MFI zeolites. A comparative DRIFT study of carbon monoxide adsorption and hydrogen dissociation

The results of a DRIFT study of carbon monoxide molecular adsorption and hydrogen dissociative adsorption on gallium-modified mordenite and MFI (ZSM-5) zeolites are presented. It was found that in the reduced gallium-modified mordenite (Ga-MOR) both Ga(3+) and Ga(+) exchanged cations are present and can be detected by CO adsorption. Ga(3+) cations in Ga-MOR dissociatively adsorb molecular hydrogen at elevated temperatures, resulting in the formation of gallium hydride species and acidic hydroxyl groups. In the reduced Ga-MFI evacuated at 823 K under medium vacuum conditions only Ga(+) exchanged intrazeolite cations were detected. It was found, however, that Ga(3+) intrazeolite exchanged cations which form upon high-temperature disproportionation of Ga(+) cations in the reduced Ga-MFI and Ga-MOR can be stabilized by high-temperature oxidation of these zeolites.

Density functional theory study of carbon monoxide adsorption on the inside and outside of the armchair single-walled carbon nanotubes

Interaction of carbon monoxide with armchair single-walled carbon nanotubes (SWCNTs) of various diameters was investigated using the B3LYP density functional theory (DFT) level. For both the external and internal cases, the effect of molecular orientation on the adsorption process was studied. The adsorption energies, equilibrium distances, HOMO–LUMO energy gaps, partial charges, and natural atomic orbital occupancies of the interacting atoms were also studied. It was found that physisorption of molecular CO via the oxygen head was stronger than that via the carbon head, and that the most favorable adsorption angle between the molecular axis and x-axis of the tubes for all the armchair nanotubes was 135°. Furthermore, stability of the tube–molecule system for adsorption of a CO molecule on the outer wall of a nanotube decreases as the tube diameter increases, regardless of the adsorption angle. In contrast, CO penetration into a nanotube depends on the adsorption angle. The results show that molecular CO could be adsorbed on the inner walls of the armchair nanotubes provided that the molecular axis and the main axis of the nanotubes are parallel to each other.

Adsorption of carbon monoxide on Si x Ge4– x (x = 0–4) nano-clusters: a hybrid meta density functional study

Theoretical study of carbon monoxide adsorption on Si x Ge4 − x (x = 0–4) nano-clusters has been carried out using advanced hybrid meta density functional method of Truhlar (MPW1B95). MG3 semi-diffuse (MG3S) and correlation consistent valence basis sets with relativistic core potential were employed to improve the results. The agreement of the calculated ionization and dissociation energies with experimental values validates the reported structures of nano-clusters and justifies the use of hybrid meta density functional method. The geometry, adsorption energy, charge distribution, and vibrational frequency of CO adsorption on all possible structures were investigated. The maximum vibrational frequency changes occur in the bridge structures while the most stable structures occur when CO adsorbs on one silicon atom in a flat surface. The changes of spin densities arising through bridged structures with higher spin multiplicities were rationalized. Adsorption energies of CO on one Si atom are by far more negative than the corresponding value for on Ge atom, at the highest being nearly −77 and −35 kJ mol−1. Comparison was made of adsorbed CO bridging neighbouring and diagonal Si atoms and the former was more stable, having adsorption energy of nearly −77 kJ mol−1. Flat surfaces adsorb CO more favourably. Exhaustive vibrational frequency analyses were performed to confirm the local minima energy of all optimized structures.

A DFT study of carbon monoxide adsorption on a Si4 nano-cluster

Using the gradient-corrected hybrid density functional method of Predew, Burke, and Ernzerhof (PBEPBE) and the new hybrid meta-density functional method of Truhlar (MPW1B95), the geometry, adsorption energy, vibrational frequency, and charge distribution of carbon monoxide adsorption on a Si4 nano-cluster has been studied. Taking into account spin multicipility in the calculations, a new stable structure of CO absorbed on the Si4 cluster has been found, in addition to the previously reported structures. Exhaustive vibrational frequency analysis of optimized structures shows that some of the formerly reported structures have imaginary vibrational frequencies and are not proper stable structures. Thus, they do not represent real local energy minima. Also, CO vibrational frequency analysis shows that a significant change of vibrational frequency in the stable structures occurs.

Infrared reflection absorption study of carbon monoxide adsorption on Fe-deposited Pt(111) surface

Infrared reflection absorption spectroscopy (IRRAS) was used to investigate carbon monoxide (CO) adsorption on sub-monolayer (ML)-thick Fe deposited Pt(111). The CO exposure to a clean Pt(111) surface at room temperature yielded linear-bonded and bridge-bonded CO-Pt bands at 2090 and 1850 cm-1. The CO-Pt band intensities decreased steeply with increasing Fe thickness. For a 1-ML-thick-Fe/Pt surface, the bridge-bonded CO-Fe band at 1950 cm-1 dominated the spectra. Furthermore, the Fe depositions showed a new absorption band at around 2060 cm-1. The IRRAS spectrum for CO adsorption on the 3-Å-thick-Pt-covered a 1-ML-Fe/Pt(111) surface showed a single absorption at 2070 cm-1. Based on the IRRAS results, we discuss CO adsorption behavior on sub-ML-thick Fe/Pt(111) surfaces.

Infrared reflection absorption study of carbon monoxide adsorption on Cu(1 0 0)– c(2 × 2)–Pd surfaces formed by palladium vacuum-depositions at various temperatures

Using infrared reflection absorption spectroscopy (IRRAS) and temperature programmed desorption (TPD), we investigated carbon monoxide (CO) adsorption and desorption behaviors on atomic checkerboard structures of Cu and Pd formed by Pd vacuum deposition at various temperatures of Cu(1 0 0). The 0.15-nm-thick Pd deposition onto a clean Cu(1 0 0) surface at room temperature (RT) showed a clear c(2 × 2) low-energy electron diffraction (LEED) pattern, i.e. Cu(1 0 0)– c(2 × 2)–Pd. The RT-CO exposure to the c(2 × 2) surfaces resulted in IRRAS absorption caused by CO adsorbed on the on-top sites of Pd. The LEED patterns of the Pd-deposited Cu(1 0 0) at higher substrate temperatures revealed less-contrasted c(2 × 2) patterns. The IRRAS intensities of the linearly bonded CO bands on 373-K-, 473-K-, and 673-K-deposited c(2 × 2) surfaces are, respectively, 25%, 22%, and 10% less intense than those on the RT-deposited surface, indicating that Pd coverages at the outermost c(2 × 2) surfaces decrease with increasing deposition temperature. In the initial stage of the 90-K-CO exposure to the RT surface, the band attributable to CO bonded to the Pd emerged at 2067 cm −1 and shifted to higher frequencies with increasing CO exposure. At saturation coverage, the band was located at 2093 cm −1. In contrast, two distinct bands around 2090 cm −1 were apparent on the spectrum of the 473-K-deposited surface: the CO saturation spectrum was dominated by an apparent single absorption at 2090 cm −1 for the 673-K-deposited surface. The TPD spectra of the surfaces showed peaks at around 200 and 300 K, which were ascribable respectively to Cu–CO and Pd–CO. Taking into account the TPD and IRRAS results, we discuss the adsorption–desorption behaviors of CO on the ordered checkerboard structures.

Density functional study of carbon monoxide adsorption on small cationic, neutral, and anionic aluminum nitride clusters

AbstractCO adsorption on small cationic, neutral, and anionic (AlN)n (n = 1–6) clusters has been investigated using density functional theory in the generalized gradient approximation. Among various possible CO adsorption sites, an N on‐top (onefold coordinated) site is found to be the most favorable one, irrespective of the charge state of the clusters. The adsorption energies of CO on the anionic (AlN)nCO (n = 2–4) clusters are greater than those on the neutral and cationic complexes. The adsorption energies on the cationic and neutral complexes reflect the odd–even oscillations, and the adsorption energies of CO on the cationic (AlN)nCO (n = 5, 6) clusters are greater than those on the neutral and anionic complexes. The adsorption energies for the different charge states decrease with increasing cluster size. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

A density functional study of carbon monoxide adsorption on (1 0 0) surface of γ-uranium

Adsorption of carbon monoxide on γ-U(1 0 0) surface has been studied at both non-spin-polarized and spin-polarized levels using the generalized gradient approximation of density functional theory (GGA-DFT) with Perdew and Wang (PW) functionals. For CO adsorption, the bridge position of (1 0 0) surface with Vert2 approach is found to be the most favorable site with a chemisorption energy of 2.9315 eV for the non-spin-polarized case, and 3.1875 eV for the spin-polarized case. The distances of the lower carbon atom from the uranium surface are found to be 1.589 Å and 1.716 Å for non-spin-polarized and spin-polarized cases, respectively. The distances between the carbon and oxygen atoms for this most favorable position are found to be 1.134 Å and 1.208 Å for the non-spin-polarized and spin-polarized cases, respectively. The magnetic moment for the most favorable site is found to be 0.042 μ B per atom. A significant charge transfer from the first layer of the uranium surface to the carbon and oxygen atoms is found to occur, implying that the bonding is partly ionic. CO 2p orbitals are found to hybridize with U 5f bands resulting in more localization of the U 5f electrons. Spin polarization does increase the chemisorption energies by a small factor but does not play a significant role in the overall chemisorption process. Overall pattern of the density of states does not change significantly after the adsorption of CO on uranium layers. Also, in none of the cases studied, dissociation of CO molecule was possible for any of the approaches in any of the sites at the non-spin-polarized and spin-polarized levels of theory. This appears to contradict experimental results where CO adsorbed dissociatively on U surface. However, experimental data is for polycrystalline α-U at finite temperatures, whereas our present ab initio study refers to γ-U at 0 K.

Infrared reflection absorption study of carbon monoxide adsorption on Pd/Cu(1 1 1)

Pd–Cu bimetallic surfaces formed through a vacuum-deposition of Pd on Cu(1 1 1) have been discussed on the basis of carbon monoxide (CO) adsorption: CO is used as a surface probe and infrared reflection absorption (IRRAS) spectra are recorded for the CO-adsorbed surfaces. Low energy electron diffraction (LEED) patterns for the bimetallic surfaces reveal six-fold symmetry even after the deposition of 0.6 nm. The lattice spacings estimated by the separations of reflection high-energy electron diffraction (RHEED) streaks increase with increasing Pd thickness. Room-temperature CO exposures to the bimetallic surfaces formed by the Pd depositions less than 0.3 nm thickness generate the IRRAS bands due to the three-fold-hollow-, bridge- and linear-bonded CO to Pd atoms. In particular, on the 0.1 nm-thick Pd surface, the linear-bonded CO band becomes apparent at an earlier stage of the exposure. In contrast, the bridge-bonded CO band dominates the IRRAS spectra for CO adsorption on the 0.6 nm-thick Pd surface, at which the lattice spacing corresponds to that of Pd(1 1 1). A 90 K-CO exposure to the 0.1 nm-thick Pd surface leads to the IRRAS bands caused not only by CO–Pd but also by CO–Cu, while the Cu-related band is almost absent from the spectra for the 0.3 nm-thick Pd surface. The results clearly reveal that local atomic structures of the outermost bimetallic surface can be discussed by the IRRAS spectra for the probe molecule.

Electrolyte electroreflectance study of carbon monoxide adsorption on polycrystalline silver and gold electrodes

We have carried out an electrolyte electroreflectance (EER) study of the adsorption of CO on polycrystalline Ag and Au electrodes. EER proved to be a very sensitive tool for detecting the presence of chemisorbed CO on the surface of the Ag electrode, clearly distinguishing between strong adsorption (chemisorption) and weak adsorption (physisorption). In the case of Au, onto which CO chemisorbs in both alkaline and acid media, EER also detects the presence of this chemisorbed CO. However, while in alkaline medium CO adsorption provokes major changes in the EER spectrum of Au, in acid medium only minor changes are observed, since the CO coverage is 10 times lower than that in the former case. An analysis of the EER spectra of CO-covered Au provided valuable information regarding the surface electronic levels involved in the formation of the chemisorption bond.