Adsorption Energies Of CO Molecules Research Articles

Enhanced CO sensor based on In2O3 nanocubes with decoration of Au under high humidity: Experimental combined with theoretical study

Au-modified In2O3 nanocubes with varying Au content (0.7, 1, 2, 3, 10 mol%) were prepared via a simple hydrothermal method and in-situ reduction. The morphology of Au-modified In2O3 was consistent with pure In2O3, both exhibiting cubic structures composed of ∼31 nm particles. Gas sensing tests revealed that compared to pure In2O3, 1 mol% Au-modified In2O3 nanocubes exhibited a 40 °C lower optimal operating temperature (OOT), and a higher response value of 4.88 to 100 ppm CO. Additionally, Au/In2O3 sensors showed significantly less influence from humidity (75 %, 85 %) than pure In2O3 sensors and maintained CO sensing ability under high humidity conditions. First-principles calculations of the adsorption energies of CO molecules on In2O3 and Au/In2O3 surfaces were further performed to investigate the gas sensing mechanism. The results indicated that the improved CO sensing performance of Au/In2O3 sensors can be attributed to the chemical sensitization effects of Au.

Theoretical Study of the Reactive Mechanisms of Li-Doped Ni-Based Oxygen Carrier during Chemical Looping Combustion.

Ni-based oxygen carriers (OCs) are considered promising materials in the chemical looping combustion (CLC) process. However, the reactivity of Ni-based OCs still offers the potential for further enhancement. In this work, the Li doping method has been employed for the modification of Ni-based OCs. The reactivity and microreaction mechanisms of different concentrations of Li-doped Ni-based OCs with CO in CLC are clarified using density functional theory (DFT) simulation. The structures, energy, and density of states are obtained through computational investigation of the reaction path in elementary reactions. The results show that (1) the adsorption energies of CO molecules on NiO surfaces with 4, 8, and 12% Li doping concentrations are -0.53, -0.48, and -0.54 eV, respectively, demonstrating an enhanced reactivity compared to that of pure NiO (-0.41 eV); (2) the calculation of the transition state indicates that the most favorable pathway for CO oxidation takes place on the surface of NiO with an 8% Li doping concentration, exhibiting the lowest energy barrier of 0.51 eV; and (3) the oxygen vacancy formation energies on the surface of NiO are 3.05, 2.30, and 2.10 eV for 4, 8, and 12% doping concentrations, respectively. Additionally, the decrease in oxygen vacancy formation energies exhibits a gradual decline with an increasing Li doping concentration. By comprehensive analysis, 8% is considered to be the optimal doping concentration of NiO for chemical looping combustion.

Adsorption of CO molecules on doped graphene: A first-principles study

As a typical kinds of toxic gases, CO plays an important role in environmental monitoring, control of chemical processes, space missions, agricultural and medical applications. Graphene is considered a potential candidate of gases sensor, so the adsorption of CO molecules on various graphene, including pristine graphene, Nitrogen-doped graphene (N-doped graphene) and Aluminum-doped graphene (Al-doped graphene), are studied by using first-principles calculations. The optimal configurations, adsorption energies, charge transfer, and electronic properties including band structures, density of states and differential charge density are obtained. The adsorption energies of CO molecules on pristine graphene and N-doped graphene are −0.01 eV, and −0.03 eV, respectively. In comparison, the adsorption energy of CO on Al-doped graphene is much larger, −2.69 eV. Our results also show that there occurs a large amount of charge transfer between CO molecules and graphene sheet after the adsorption, which suggests Al-doped graphene is more sensitive to the adsorption of CO than pristine graphene and N-doped graphene. Therefore, the sensitivity of gases on graphene can be drastically improved by introducing the suitable dopants.

Carbon monoxide adsorption on carbon atom doped perfect and Stone–Wales defect single-walled boron nitride nanotubes: a DFT investigation

The CO adsorption on the perfect and defective boron nitride nanotubes (BNNTs) was investigated using the density functional theory at the B3LYP/LanL2DZ theoretical level. The 7-layered armchair (5,5) BNNT doping with C atom on B and N sites was selected for the doped BNNT models, in which the ends of the BNNTs were saturated by hydrogen atoms. The structural and electronic properties of BNNTs and their adsorption configurations with CO were obtained. The binding energies of carbon atom doping on BNNT and adsorption energies of CO molecules on BNNTs were also calculated. The adsorption strength of the CO on BNNT was significantly improved by defective and doped structural creation. The CO adsorption on carbon atom doping on the nitrogen site of Stone–Wales defect BNNT displayed the strongest adsorption with a binding energy of −2.46 kJ/mol.

Structural and Chemical Properties of Gold Rare Earth Disilicide Core−Shell Nanowires

Clear understanding of the relationship between electronic structure and chemical activity will aid in the rational design of nanocatalysts. Core-shell Au-coated dysprosium and yttrium disilicide nanowires provide a model atomic scale system to understand how charges that transfer across interfaces affect other electronic properties and in turn surface activities toward adsorbates. Scanning tunneling microscopy data demonstrate self-organized growth of Au-coated DySi₂ nanowires with a nanometer feature size on Si(001), and Kelvin probe force microscopy data measure a reduction of work function that is explained in terms of charge transfer. Density functional theory calculations predict the preferential adsorption site and segregation path of Au adatoms on Si(001) and YSi₂. The chemical properties of Au-YSi₂ nanowires are then discussed in light of charge density, density of states, and adsorption energy of CO molecules.

Density functional study of Pd nanoparticles with subsurface impurities of light element atoms

Atomic H, C, N and O at the surface and in the subsurface region of Pd nanoparticles were studied theoretically using an all-electron scalar relativistic density functional approach. We modelled nanosize metal clusters by the three-dimensional crystallites Pd79 and Pd116 chosen as octahedral fragments of bulk Pd; these clusters expose (111) and (001) facets. Adsorbed atoms were located at the three-fold hollow sites in the centre of (111) facets. Migration of the atoms from the surface of the cluster Pd79 to the octahedral subsurface (oss) site below was considered. Migration of C from the surface hollow site to the oss position was found to be almost isoenergetic; migration of H is somewhat endothermic (by 0.5 eV). For N and O, a lager endothermicity was calculated. Both H and C species exhibit moderate activation barriers for the diffusion to the oss site. C and O atoms in the tetrahedral subsurface (tss) position of the cluster Pd116 were also studied. For both species, this location is energetically disfavoured, although the endothermic effect of O atom migration to the tss position is ∼0.5 eV smaller than to the oss site. Subsurface C impurities were calculated to reduce the adsorption energy of CO molecules at Pd clusters.

Reply to Comment on “First principles determination of the bonding mechanism and adsorption energy for CO/MgO(001)”

Using the full potential linearized augmented plane wave (FLAPW) method, the bonding mode and adsorption energy of CO molecules on the MgO(001) clean surface are determined with both the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange-correlation effects. The calculated adsorption energies of a p(1×1) CO monolayer on MgO(001) are 0.28 eV/molecule (LDA) and 0.12 eV/molecule (GGA).

Quantum chemical consideration of CO adsorption over cation exchanged faujasite

CNDO/2 calculation for atomic charges, Wiberg bond orders and adsorption energies of CO molecules on the cluster model whose SitAI ratio varied were carried out. The data for the normal cluster and dealuminated cluster were compared. Decationization energies of the cations increased with the charge densities of cation and number o( aluminum involved. Adsorption process of CO on the monovalent cations such as H +, Li +, Na ~ and divalent cations, Be 2 +, Ca 2 +, and Mg 2+ was sup- posed to be occurring by tile donat on of non-bonded electrons from CO. The decationization energies c~f cations obviously decreased by the dealumination process. Adsorption energies of CO on the cations gener- ally decreased as the deaIumination look place except the case of H ' and Na ~ .