Adsorbate-surface Interaction Research Articles

CO Inversion on a NaCl(100) Surface: A Multireference Quantum Embedding Study.

We develop a multireference quantum embedding model to investigate a recent experimental observation of the isomerization of vibrationally excited CO molecules on a NaCl(100) surface [Science 2020, 367, 175-178]. To explore this mechanism, we built a reduced potential energy surface of CO interacting with NaCl(100) using a second-order multireference perturbation theory, modeling the adsorbate-surface interaction with our previously developed active space embedding theory (ASET). We considered an isolated CO molecule on NaCl(100) and a high-coverage CO monolayer (1/1), and for both we generated potential energy surfaces parametrized by the CO stretching, adsorption, and inversion coordinates. These surfaces are used to determine stationary points and adsorption energies and to perform a vibrational analysis of the states relevant to the inversion mechanism. We found that for near-equilibrium bond lengths, CO adsorbed in the C-down configuration is lower in energy than in the O-down configuration. Stretching of the C-O bond reverses the energetic order of these configurations, supporting the accepted isomerization mechanism. The vibrational constants obtained from these potential energy surfaces show a small (< 10 cm-1) blue- and red-shift for the C-down and O-down configurations, respectively, in agreement with experimental assignments and previous theoretical studies. Our vibrational analysis of the monolayer case suggests that the O-down configuration is energetically more stable than the C-down one beyond the 16th vibrational excited state of CO, a value slightly smaller than the one from quasi-classical trajectory simulations (22nd) and consistent with the experiment. Our analysis suggests that CO-CO interactions in the monolayer play an important role in stabilizing highly vibrationally excited states in the O-down configuration and reducing the barrier between the C-down and O-down geometries, therefore playing a crucial role in the inversion mechanism.

DFT insights into the adsorption mechanism of five-membered aromatic heterocycles containing N, O, or S on Fe(1 1 0) surface

Understanding the interaction of five-membered aromatic heterocycles with Fe(110) surface is crucial to the design of novel inhibitors against the corrosion of iron and steel. Herein, we report a detailed study of the adsorption properties and the bonding mechanism of pyrrole, furan, and thiophene on Fe(110) surface employing density functional theory (DFT) calculations. In the most stable adsorption geometries, the adsorbates lie flat at the hollow site and form covalent bonds with surface Fe atoms. The chemisorptions are demonstrated by large adsorption energies and charge transfers from Fe(110) to the adsorbates. Taking vdW corrections into account in the DFT calculations has a minimal effect on the adsorption geometries whereas it significantly increases the adsorption energies. The energetic and structural analysis demonstrates large molecular distortion induced by the adsorbate–surface interaction, and thiophene experiences the least molecular distortions, thereby having the largest adsorption energy among the adsorbates. The electronic structure analysis reveals that the electronic interactions of pyrrole, furan, and thiophene and Fe(110) are due to the overlaps of the frontier molecular orbitals with Fe-3dz2 and Fe-(3dxz + 3dyz) states. The charge transfer between the adsorbates and Fe(110) are elucidated by the charge density difference plot and Bader charge analysis.

Revealing the key role of bonding states in surface chemisorption

It has been widely accepted that the filling of the adsorbate-surface anti-bonding states dominates the variation of adsorption energies among transition metals. However, on the basis of chemical bonding analysis for adsorbate-surface interaction, we find an exception in the adsorption of O, OH, and OOH on nitrogen-coordinated transition metal-doped carbon material. In this material, a weaker (stronger) adsorption is mainly due to the decreasing (increasing) contribution of the filled adsorbate-surface bonding states. This work sheds light on the mechanism of the adsorbate-substrate interaction and suggests that care much be taken in interpreting the surface chemisorption.

First-principles DFT insights into the adsorption of hydrazine on bimetallic β1-NiZn catalyst: Implications for direct hydrazine fuel cells

We present a systematic first-principles density functional theory study with dispersion corrections (DFT-D3) of hydrazine adsorption on the experimentally observed (111), (110) and (100) surfaces of the binary β1-NiZn alloy. A direct comparison has been drawn between the bimetallic and monometallic Ni and Zn counterparts to understand the synergistic effect of alloy formation. The hydrazine adsorption mechanism has been characterised through adsorption energies, Bader charges, the d-band centre model, and the coordination number of the active site - which is found to dictate the strength of the adsorbate–surface interaction. The bimetallic β1-NiZn nanocatalyst is found to exhibit higher activity towards adsorption and activation of hydrazine compared to the monometallic Ni and Zn counterparts. The Ni-sites of the bimetallic NiZn surfaces are found to be generally more reactive than Zn sites, which is suggested to be due to the higher d-band centre of −0.13 eV (closer to the Fermi level), forming higher energy anti-bonding states through NiN interactions. The observed synergistic effects derived from surface composition and electronic structure modification from Ni and Zn alloying should provide new possibilities for the rational design and development of low-cost bimetallic Ni-Zn alloy catalysts for direct hydrazine fuel cell (DHFC) applications.

Predicting the Catalytic Activity of Surface Oxidation Reactions by Ionization Energies

Developing a descriptor to understand the reactivity of a catalyst is critical in achieving the rational design of heterogeneous catalysts. Ideally, the descriptor should be simple, predictive, as ...

Catalytic Chemistry Predicted by a Charge Polarization Descriptor: Synergistic O2 Activation and CO Oxidation by Au-Cu Bimetallic Clusters on TiO2(101).

The versatile properties of bimetallic nanoparticles greatly expand the range of catalyzed chemical reactions. We demonstrate that surface chemistry can be understood and predicted using a simple adsorbate-surface interaction descriptor that relates charge polarization to chemical reactivity. Our density functional theory studies of O2 activation and CO oxidation catalyzed by Au7-Cu1 bimetallic nanoparticles supported on the TiO2(101) surface demonstrate that the generated oxidized Cu atom (CuO x) can efficiently inhibit the aggregation of the active Cu sites. Moreover, because of the strong dipole-dipole interaction between the surface and the adsorbate on the oxidized Cu site, the adsorption of CO + O2/CO + O can be significantly enhanced, which can decrease the CO oxidation barriers and further improve catalytic performance. The product of the two electric dipole moments provides a parameter that allows us to predict the key catalytic properties for different adsorption sites and reaction pathways. The reported findings provide important insights into the mechanism of chemical reactivity of metallic clusters and generate a valuable principle for catalyst design.

Interpolating DFT Data for 15D Modeling of Methane Dissociation on an fcc Metal

ABSTRACTDetailed simulation of reactions occurring on and with the surfaces of crystalline materials usually require a continuous representation of the potential energy surface that describes the adsorbate–surface interaction. Only a few techniques are available to describe interactions with polyatomic adsorbates that respect all of the symmetries of the interactions. The modified Shepard interpolation has recently been reformulated to ensure symmetries are rigorously imposed. In this work, the modified Shepard interpolation is used to construct a 15D potential energy surface for the reaction of methane with the {100} surface of a face‐centered cubic metal, in the Born‐‐Oppenheimer static surface (BOSS) approximation. The energy of the system is calculated using density functional theory (DFT), and the geometries around which the potential is expanded are selected by quasi‐classical trajectory calculations. The energy of the resulting continuous potential energy surface exactly matched the DFT energy at these points; there is no fitting error. It is demonstrated that the classical reaction probability converges with a reasonable number of interpolation points for this 15D system.

Iron phthalocyanine on Cu(111): Coverage-dependent assembly and symmetry breaking, temperature-induced homocoupling, and modification of the adsorbate-surface interaction by annealing.

We have examined the geometric and electronic structures of iron phthalocyanine assemblies on a Cu(111) surface at different sub- to mono-layer coverages and the changes induced by thermal annealing at temperatures between 250 and 320 °C by scanning tunneling microscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. The symmetry breaking observed in scanning tunneling microscopy images is found to be coverage dependent and to persist upon annealing. Further, we find that annealing to temperatures between 300 and 320 °C leads to both desorption of iron phthalocyanine molecules from the surface and their agglomeration. We see clear evidence of temperature-induced homocoupling reactions of the iron phthalocyanine molecules following dehydrogenation of their isoindole rings, similar to what has been observed for related tetrapyrroles on transition metal surfaces. Finally, spectroscopy indicates a modified substrate-adsorbate interaction upon annealing with a shortened bond distance. This finding could potentially explain a changed reactivity of Cu-supported iron phthalocyanine in comparison to that of the pristine compound.

ChemInform Abstract: Ferroelectric‐Based Catalysis: Switchable Surface Chemistry

AbstractReview: 138 refs.

Ferroelectric-Based Catalysis: Switchable Surface Chemistry

The maximum efficiency of a fixed catalytic surface occurs when the adsorbate–surface interaction strength is optimal as per the Sabatier principle: strong enough to drive the reactions forward but weak enough to permit the products’ desorption. Such a compromise can fundamentally limit catalytic activity. One solution is to create a surface with switchable activity between strong binding (rapid dissociation) and weak binding (easy desorption). On the basis of first-principles theory, we describe a class of catalysts comprising an epitaxial monolayer of a transition metal oxide on an oxide ferroelectric substrate in which reversing the ferroelectric polarization state switches the surface activity between these two limits. As an example, a CrO2 monolayer on ferroelectric PbTiO3 permits direct NOx decomposition and CO oxidation while circumventing oxygen and sulfur poisoning. Our computed binding energy trends are explained by a generalization of the canonical d-band model for transition metals to metal ox...

Many-body dispersion effects in the binding of adsorbates on metal surfaces

A correct description of electronic exchange and correlation effects for molecules in contact with extended (metal) surfaces is a challenging task for first-principles modeling. In this work, we demonstrate the importance of collective van der Waals dispersion effects beyond the pairwise approximation for organic-inorganic systems on the example of atoms, molecules, and nanostructures adsorbed on metals. We use the recently developed many-body dispersion (MBD) approach in the context of density-functional theory [Tkatchenko et al., Phys. Rev. Lett. 108, 236402 (2012) and Ambrosetti et al., J. Chem. Phys. 140, 18A508 (2014)] and assess its ability to correctly describe the binding of adsorbates on metal surfaces. We briefly review the MBD method and highlight its similarities to quantum-chemical approaches to electron correlation in a quasiparticle picture. In particular, we study the binding properties of xenon, 3,4,9,10-perylene-tetracarboxylic acid, and a graphene sheet adsorbed on the Ag(111) surface. Accounting for MBD effects, we are able to describe changes in the anisotropic polarizability tensor, improve the description of adsorbate vibrations, and correctly capture the adsorbate-surface interaction screening. Comparison to other methods and experiment reveals that inclusion of MBD effects improves adsorption energies and geometries, by reducing the overbinding typically found in pairwise additive dispersion-correction approaches.

A DFT study on WO3 nanowires with different orientations for NO2 sensing application

The adsorption of NO2 molecule on the surface of WO3 nanowires with [001] and [010] orientations were investigated using density functional theory (DFT) calculations with aim to explore their potential sensing abilities theoretically. It is found that NO2 molecule can adsorb in multiple stable configurations for the WO3 nanowires with the two orientations, and the NO2 adsorption on the surface tunes the electronic structures of WO3 nanowires, giving rise to new impurity electronic states and then changing the band gap and the Fermi level position. The sensitive electronic structures as well as the multiple stable configurations to NO2 adsorption highlight the potential of WO3 nanowires as a sensor to detect NO2 gas. Further calculations about the atomic Mulliken charge population, planar averaged charge density differences, and electron localization functions (ELF) indicate that NO2 adsorption on [010]-oriented WO3 nanowire induces much stronger adsorbate-surface interaction and much more electrons extracted from the surface than on [001] nanowire, hinting a much higher sensitivity expectable for a NO2 gas sensor based on WO3 nanowire with [010] orientation.

High basicity adsorbents from solid residue of cellulose and synthetic polymer co-pyrolysis for phenol removal: Kinetics and mechanism

The activated carbons (ACs) produced from solid residue of cellulose and synthetic polymer co-pyrolysis (CACs) and commercial activated carbon from coconut shell (GC) were used for phenol removal. The adsorption kinetics and mechanism were investigated.All studied activated carbons are predominantly microporous and are characterized by basic surface characteristics. Surface area SBET varies between 1235 and 1499m2/g, whereas the pHPZC changes from 7.70 to 10.63. The bath adsorption of phenol (P) was carried out at ambient temperature. The equilibrium time and equilibrium sorption capacity were determined. It was found that the boundary layer effect is bigger in AC with high basic characteristics of the surface. The rate controlling step is the intraparticle diffusion in CACs only, whereas in ACs with higher amount of acidic functionalities the adsorbate–surface interaction influences the rate of kinetic as well. The equilibrium isotherms are L2 type for commercial AC and L4 for CACs. The CACs are characterized by very high adsorption capacity that vary between 312 and 417mg/g. The main mechanism of phenol adsorption is micropore filling within pores smaller than 1.4nm. In the absence of solvent effect further adsorption of phenol on CACs takes place. The enhanced adsorption is due to dispersive/repulsive interaction induced by oxygen functionalities.

DFT study of interaction of O, O2, and OH with unreconstructed Pt(hkl) (h, k, l = 0, 1) surfaces—similarities, differences, and universalities

Adsorption of O, O2, and OH on Pt(111), Pt(100), and Pt(110) surfaces was studied using periodic DFT calculations. It was found that generally adsorbate-surface interaction strengths increase with the decrease in surface packing density. On the Pt(111) surface the dissociation of O2 molecule was not predicted, but it was predicted on Pt(100) and Pt(110) surfaces. While the strength of the adsorbate-substrate interaction decreases with the rise in surface coverage by O atoms, in the case of OH adsorption adsorbate layer gets stabilized at higher surface coverage through the hydrogen bonding. In spite of all the mentioned differences, single parameter of surface electronic structure was identified, being useful for the explanation of the adsorption trends at different adsorption sites for O and OH adsorption on Pt surfaces of various crystallographic orientations and also provided a deeper understanding of atomic oxygen adsorption as a function of surface coverage.

Sensitive Layer Thickness Dependence on Microcantilever Sensor Sensitivity

A sensitive layer is a main component in detecting an analyte target in a microcantilever-based biosensor. The sensitive layer coated on the microcantilever surface can induce a surface stress change as consequence of adsorbate-surface interaction. Therefore, a presence of stress is necessary to be investigated because it determines a deflection which influences the sensor sensitivity. In this work, we study a dependence of the film stress and microcantilever deflection on the gold or 3-Aminopropyltriethoxysilane (aminosilane) layers thickness in static mode operation. It is found that the optimum thickness of the sensitive layer for both aminosilane and gold can be obtained by analyzing the maximum film stress and the maximum microcantilever deflection. We also investigated the effect of Youngs moduli on the maximum stress and the maximum deflection. It is obtained that the Youngs moduli is a function that determines the peaks on the maximum stress and the maximum deflection. Our results indicate that the material properties and the thickness of sensitive layer should be considered to obtain a high sensitivity of microcantilever biosensor.

Sensitive Layer Thickness Dependence on Microcantilever Sensor Sensitivity

A sensitive layer is a main component in detecting an analyte target in a microcantilever-based biosensor. The sensitive layer coated on the microcantilever surface can induce a surface stress change as consequence of adsorbate-surface interaction. Therefore, a presence of stress is necessary to be investigated because it determines a deflection which influences the sensor sensitivity. In this work, we study a dependence of the film stress and microcantilever deflection on the gold or 3-Aminopropyltriethoxysilane (aminosilane) layers thickness in static mode operation. It is found that the optimum thickness of the sensitive layer for both aminosilane and gold can be obtained by analyzing the maximum film stress and the maximum microcantilever deflection. We also investigated the effect of Youngs moduli on the maximum stress and the maximum deflection. It is obtained that the Youngs moduli is a function that determines the peaks on the maximum stress and the maximum deflection. Our results indicate that the material properties and the thickness of sensitive layer should be considered to obtain a high sensitivity of microcantilever biosensor.

Local surface structure effect on reactivity of molecules confined between metallic surfaces

Interactions between metallic surfaces separated by nanometer distances create an unusual reactivity environment. Here we evaluate the effect of the geometry given by differences in the structures of the interacting surfaces and by the presence of steps. Adsorption of an oxygen molecule and its dissociation is examined in gaps defined by interacting platinum surfaces that have separations between 5.36 and 4.70 Å, and by comparing the effect of the different gap geometries on the adsorption strength and barriers for dissociation. It is found that specific surface-surface configurations influence the electronic structure of the surface where the molecule is adsorbed, modifying the width of its d-orbital and therefore the adsorption strength due to changes in the overlap of the adsorbate molecular orbitals with the metal d-band. In addition, the degree of the molecule-metal interaction with the other surface may restrict the adsorbate mobility and its dissociation. The presence of defects may decrease the adsorbate-surface interaction strength, but the net result depends on the specific reaction and nature of the intermediates since in some cases weaker adsorptions may result in lower dissociation barriers.

Chemistry and temperature-assisted dehydrogenation of C60H30 molecules on TiO2(110) surfaces

The thermal induced on-surface chemistry of large polycyclic aromatic hydrocarbons (PAHs) deposited on dielectric substrates is very rich and complex. We evidence temperature-assisted (cyclo)dehydrogenation reactions for C60H30 molecules and the subsequent bottom-up formation of assembled nanostructures, such as nanodomes, on the TiO2(110) surface. To this aim we have deposited, under ultra-high vacuum, a submonolayer coverage of C60H30 and studied, by a combination of experimental techniques (STM, XPS and NEXAFS) and theoretical methods, the different chemical on-surface interaction stages induced by the increasing temperature. We show that room temperature adsorbed molecules exhibit a weak interaction and freely diffuse on the surface, as previously reported for other aromatics. Nevertheless, a slight annealing induces a transition from this (meta)stable configuration into chemisorbed molecules. This adsorbate-surface interaction deforms the C60H30 molecular structure and quenches surface diffusion. Higher annealing temperatures lead to partial dehydrogenation, in which the molecule loses some of the hydrogen atoms and LUMO levels spread in the gap inducing a net total energy gain. Further annealing, up to around 750 K, leads to complete dehydrogenation. At these temperatures the fully dehydrogenated molecules link between them in a bottom-up coupling, forming nanodomes or fullerene-like monodisperse species readily on the dielectric surface. This work opens the door to the use of on-surface chemistry to generate new bottom-up tailored structures directly on high-K dielectric surfaces.

Analysis of the origin of lateral interactions in the adsorption of small organic molecules on oxide surfaces

A decomposition scheme is proposed to analyze the physical contributions to the decrease in the binding energy of chemisorbed species with increasing coverage. This scheme is applied to the acetaldehyde–TiO2 (110) rutile system as a model for other small organic molecule—oxide surface systems. Different density functional theory (DFT) functionals have been employed at both low-medium and high coverages to understand how the different theoretical descriptions of the various terms influence the adsorbate–surface interaction. At low coverages, it is found that the localized adsorbate to surface electron donation is the fundamental physical process that influences the adsorbate–surface interaction. This results shows that while it is usually assumed that only pairwise adsorbate–adsorbate interactions influence the adsorption energy, the progressive modification of the surface properties (surface reduction in this case) may also play a significative role. The DFT+U functional results, in this case, in the best agreement with the experimental binding energy, and the inclusion of the dispersive forces results in largely overestimated adsorption energies. At higher coverages, the pure GGA and GGA+U functionals overestimate the repulsive terms and the computed binding energy is well below the experimental data. The inclusion of the dispersive forces is required to correctly reproduce the experimental results. The contributions of the different physical terms are also analyzed.

Methodologies to analyze surface bonding properties using parametric and density functional methods

AbstractThis work presents two general methodologies to calculate bond adsorption energy (BAE) between surface and adsorbate using parametric quantum (PQM) and density functional (DFM) methods. The first one corresponds to the bond partition energy technique that is directly applied to PQMs by using energy partition approach and considering diatomic and monoatomic energy changes. The second methodology to evaluate BAE, as well as for PQMs and DFMs, is by means of the following equation: where Eads is the adsorption energy and ΔEs and ΔEa correspond to energy changes in the surface and substrate due to adsorption, respectively. Applications to radical adsorption: H°, CH2°, and CH3° is performed on a grafitic grain model, using a polyaromatic hydrocarbon (PAH), such as coronene. The methods employed are a PQM (CATIVIC program) and DFMs (GAUSSIAN and DMol software packages). Results show that Eads is completely different of BAE, because of distortion of surface and adsorbate. There is a strong destabilization in the region adjacent to the adsorption site and stabilization in the rest of the surface. Two terms for BAE are reported: one that corresponds to direct bonding interaction (BAEb) and other to long range ones, due to electrostatic interaction (BAEe). Owing to the important effects of bond strength adsorbate–surface interaction, results suggest that BAE is fundamental for understanding bond activation in adsorbate and surface, cooperative effects, diffusion, reaction, and desorption process. In general, similar results were found for both CATIVIC and DFMs, by using the second methodology. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010