Adsorption Energy Of Molecules Research Articles

Assessing the reinforced molecular/mechanical behaviors of GOs@Mo-MOFs films deposited via electrophoresis onto microdevices: Experimental and theoretical perspectives.

One of the primary hurdles in microdevice fabrication lies in ascertaining the most impactful tactics for adapting metal surfaces. Through a one-pot tackle and distinct mechanochemical reactions evoked by 15minaqueous wet sand-milling (SM-15), we successfully grafted Mo-based metal-organic frameworks (Mo-MOFs) onto graphene oxides (GOs). Following this, a convenient and readily scalable methodology of electrophoretic deposition was implemented to create controllable thickness of SM-15 GOs@Mo-MOFs lubricating films, achieving considerable enhancements of 143% and 91% in hardness and Young's modulus, respectively, when compared to those of SM-15 Mo-MOFs. The successful synthesis of SM-15 GOs@Mo-MOFs was corroborated using strategies such as x-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. Analyses using the micro-tribotester indicated that the new film exhibited a lowest friction coefficient of roughly 0.5 when imposed with a load of 5 N and sliding speed of 8 mm/s. In addition, the optical profiler nano-indentation in situ scanning probe microscope revealed that SM-15 GOs@Mo-MOFs films had smaller and shallower scratches and grooves compared to SM-15 Mo-MOFs ones. The calculated results of key descriptors (EHOMO, ELUMO, ΔE, etc.) in density functional theory quantitatively disclosed the interaction mechanisms between GOs@Mo-MOFs molecules and microdevices. We first scrutinized the innate properties of molecule adsorption energy and frictional mechanical behaviors using synergetic cross-scale simulations, such as Monte Carlo and finite element methods. The expectation was that this process would motivate a valuable technique for shielding in the thriving micromanufacturing.

Construction of Monoatomic-Modified Defective Ti4+αTi3+1-αO2-δ Nanofibers for Photocatalytic Oxidation of HMF to Valuable Chemicals.

Efficiently upgrading 5-hydroxymethylfurfural (HMF) into high-value-added products, such as 2,5-diformylfuran (DFF) and 2,5-furan dicarboxylic acid (FDCA), through a photocatalytic process by using solar energy has been incessantly pursued worldwide. Herein, a series of transition-metal (TM = Ni, Fe, Co, Cu) single atoms were supported on Ti4+αTi3+1-αO2-δ nanofibers (NFs) with certain defects (Ov), denoted as TM SAC-Ti4+αTi3+1-αO2-δ NFs (TM = Ni, Fe, Co, Cu), aiming to enhance the photocatalytic conversion of HMF. A super HMF conversion rate of 57% and a total yield of 1718.66 μmol g-1 h-1 (DFF and FDCA) surpassing that of the Ti4+αTi3+1-αO2-δ NFs by 1.6 and 2.1 times, respectively, are realized when TM is Co (Co SAC-Ti4+αTi3+1-αO2-δ NFs). Experiments combined with density functional theory calculation (DFT) demonstrate that the TM single atoms occupy the Ti site of Ti4+αTi3+1-αO2-δ NFs, which plays a dominant role in the photo-oxidation of HMF. Raman, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) characterizations confirm the strong electron local exchange interaction in TM SAC-Ti4+αTi3+1-αO2-δ NFs and demonstrate the substitution of Ti by the TM SACs. The projected density of states and charge density difference reveal that the strong interaction between metal-3d and O-2p orbitals forms Ti-O-TM bonds. The bonds are identified as the adsorption site, where TM single atoms on the surface of Ti4+αTi3+1-αO2-δ NFs reduce HMF molecule adsorption energy (Eads). Furthermore, the TM single atom modulates the electronic structure of TM SAC-Ti4+αTi3+1-αO2-δ NFs through electron transfer, leading to narrow band gaps of the photocatalysts and enhancing their photocatalytic performance. This study has uncovered a newer strategy for enhancing the photocatalytic attributes of semiconducting materials.

Impact of Alloy Elements on the Adsorption and Dissociation of Gaseous Hydrogen on Surfaces of Ni–Cr–Mo Steel

In this study, the effect of alloying elements on the adsorption and dissociation behaviors of hydrogen molecules on the bcc-Fe (001) surface has been investigated using first-principles calculations. H2 molecules can easily dissociate on the hollow site, and the dissociated hydrogen atoms bond with the surrounding metal atoms. Doping Cr and Mo atoms on the surface would reduce the H2 molecule adsorption energy, which promotes the H2 molecule adsorption and dissociation. When only one or two Ni atoms doping on the surface, it improves the adsorption energies, which in turn can hinder the H2 molecule adsorption and dissociation. However, three or four Ni atoms doping on the surface is beneficial to the H2 molecule adsorption and dissociation. Thus, the nickel content in Ni–Cr–Mo steel should be reasonably controlled to improve the hydrogen embrittlement resistance of the steel.

Clarifying trust of materials property predictions using neural networks with distribution-specific uncertainty quantification

It is critical that machine learning (ML) model predictions be trustworthy for high-throughput catalyst discovery approaches. Uncertainty quantification (UQ) methods allow estimation of the trustworthiness of an ML model, but these methods have not been well explored in the field of heterogeneous catalysis. Herein, we investigate different UQ methods applied to a crystal graph convolutional neural network to predict adsorption energies of molecules on alloys from the Open Catalyst 2020 dataset, the largest existing heterogeneous catalyst dataset. We apply three UQ methods to the adsorption energy predictions, namely k-fold ensembling, Monte Carlo dropout, and evidential regression. The effectiveness of each UQ method is assessed based on accuracy, sharpness, dispersion, calibration, and tightness. Evidential regression is demonstrated to be a powerful approach for rapidly obtaining tunable, competitively trustworthy UQ estimates for heterogeneous catalysis applications when using neural networks. Recalibration of model uncertainties is shown to be essential in practical screening applications of catalysts using uncertainties.

A graph neural network for predicting the adsorption energy of molecules on metal surfaces.

A graph neural network for predicting the adsorption energy of molecules on metal surfaces.

Dispersion corrected-DFT investigation on the adsorption and selective detection of organic solvent vapors by Cu2(HCOO)4 paddle wheel of metal organic framework

Porous metal organic frameworks (MOFs) has shown large surface area and high micropore volume making it a promising electrode material for sensing devices. Adsorption and electronic sensitivity of copper-based open metal sites paddlewheel (Cu2(HCOO)4) towards polar, moderately polar, and non-polar organic solvent vapors (OSVs) were was investigated using density functional theory, employing B3LYP. The most stable adsorption structures were those with the OSVs interacting with the metal node of PW. Based on calculations, the adsorption energy of molecules is in the range of −7.8 to −24.8 kcal/mol, −9.2 to −25.7 kcal/mol, and −6.6 to −10.9 kcal/mol for polar, moderately polar, and non-polar OSVs, respectively. Also sensing activities of PW were studied from three points of view band gap changing, sensing factor, and work function changes. From the standpoint of conductivity changing, Cu-PW has (i) low sensitivity to acetonitrile, acetone, dimethyl formamide, dimethyl ether, benzene, and ethanol; (ii) moderate sensitivity to toluene, and (iii) strong sensitivity to THF detection so that its HOMO/LUMO gap of the PW is significantly decreased from 1.63 to 0.97 eV which may increase the electrical conductivity, sensing factor is 1.4 * 1011, and work function changing is 0.45 eV after THF adsorption. Thus, we suggest that Cu-PW may be used as a highly sensitive/selective and multi-time reusable sensor material for THF detection.

Boosting urea-assisted water splitting by constructing sphere-flower-like NiSe2-NiMoO4 heterostructure

Urea-assisted water splitting is a promising hydrogen (H2) production technology, which can purify urea-rich wastewater, but the lack of cost-effective catalysts hampers its extensive application. In this work, the sphere-flower like NiSe2-NiMoO4 heterostructure catalyst self-supported on nickel foam (NiSe2-NiMoO4/NF) is successfully prepared through hydrothermal and selenization method. Only 1.32 V and −35.57 mV are required to obtain ±10 mA cm−2 for urea oxidation and hydrogen evolution reaction (UOR and HER), respectively. For a two-electrode electrolyzer, only a cell voltage of 1.37 V is required to drive 10 mA cm−2, and it shows robust durability with working continuously for 100 h at 150 mA cm−2 without obvious activity attenuation. The optimized H* and urea molecule adsorption energy on NiSe2-NiMoO4 heterostructure, novel morphology with mesoporous and self-supporting structure could be the reasons for this good performance. This work thus proposes a strategy for designing highly efficient bifunctional catalysts toward UOR and HER.

Controlling Plasmonic Chemistry Pathways through Specific Ion Effects

AbstractPlasmon‐driven dehalogenation of brominated purines has been recently explored as a model system to understand fundamental aspects of plasmon‐assisted chemical reactions. Here, it is shown that divalent Ca2+ ions strongly bridge the adsorption of bromoadenine (Br‐Ade) to Ag surfaces. Such ion‐mediated binding increases the molecule's adsorption energy leading to an overlap of the metal energy states and the molecular states, enabling the chemical interface damping (CID) of the plasmon modes of the Ag nanostructures (i.e., direct electron transfer from the metal to Br‐Ade). Consequently, the conversion of Br‐Ade to adenine almost doubles following the addition of Ca2+. These experimental results, supported by theoretical calculations of the local density of states of the Ag/Br‐Ade complex, indicate a change of the charge transfer pathway driving the dehalogenation reaction, from Landau damping (in the lack of Ca2+ ions) to CID (after the addition of Ca2+). The results show that the surface dynamics of chemical species (including water molecules) play an essential role in charge transfer at plasmonic interfaces and cannot be ignored. It is envisioned that these results will help in designing more efficient nanoreactors, harnessing the full potential of plasmon‐assisted chemistry.

Hexagonal Single-Crystal CoS Nanosheets: Controllable Synthesis and Tunable Oxygen Evolution Performance.

Cobalt-based sulfides with variable valence states and unique physical and chemical properties have shown great potential as oxygen evolution reaction (OER) catalysts for electrochemical water-splitting reactions. However, poor morphological characteristics and a small specific surface area limit its further application. Here, hexagonal single-crystal two-dimensional (2D) CoS nanosheets with different thicknesses are successfully prepared by an atmospheric-pressure chemical vapor deposition method. Because of the advantages of the 2D structure, more exposed catalytic active sites, better reactant adsorption ability, accelerated electron transfer, and enhanced electrical conductivities can be achieved from the thinnest 5 nm CoS nanosheets (CoS-5), significantly improving OER performance. The electrochemical tests manifest that CoS-5 show an overpotential of 290 mV at 10 mA cm-2 and a Tafel slope of 65.6 mV dec-1 in the OER in an alkaline solution, superior to those for other thicknesses of CoS, bulk CoS, and RuO2. For the mechanistic investigation, the lowest charge transfer resistance (Rct) and the highest double-layer capacitance (Cdl) were obtained for CoS-5, demonstrating the faster OER kinetics and the larger active area. Density functional theory calculations further reveal the enhanced density of states around the Fermi level and higher H2O molecule adsorption energy for thinner CoS nanosheets, promoting its intrinsic catalytic activity. Moreover, the two-electrode system with CoS-5 as the anode and Pt/C as the cathode requires only 1.56 V to attain 10 mA cm-2 in the overall water-splitting reaction. We believe that this study will provide a fresh view for thickness-dependent catalytic performance and offers a new material for the study of electronic and energy devices.

Gas adsorption enhancement on transition-metal-decorated tin carbide monolayers

The interaction between diatomic gas molecules O2, N2 and NO with tin carbide monolayers (2DSnC) decorated with transition-metal (TM) atoms (Au, Ag and Cu) was investigated by using density functional calculations. The results indicate that the addition of TM atoms to 2DSnC considerably improves the molecule adsorption energy. The most stable molecule adsorption configurations and energies, together with the electronic properties of the molecule-TM-2DSnC complexes, were also obtained. The Cu adatom has the largest molecule adsorption-energy enhancement followed, in decreasing order, by Au and Ag. In general, NO is strongly bound to TM-2DSnC, followed by O2. Moreover, when O2 interacts with the Au adatom, it is spontaneously dissociated. N2 is, in comparison with the other studied molecules, less strongly adsorbed to TM-decorated 2DSnC. The results indicate that Cu- and Ag-2DSnC could be used as NO traps.

Accelerate stochastic calculation of random-phase approximation correlation energy difference with an atom-based correlated sampling

A kernel polynomial method is developed to calculate the random phase approximation (RPA) correlation energy. In the method, the RPA correlation energy is formulated in terms of the matrix that is the product of the Coulomb potential and the density linear response functions. The integration over the matrix’s eigenvalues is calculated by expanding the density of states of the matrix in terms of the Chebyshev polynomials. The coefficients in the expansion are obtained through stochastic sampling. Since it is often the energy difference between two systems that is of much interest in practice, another focus of this work is to develop a correlated sampling scheme to accelerate the convergence of the stochastic calculations of the RPA correlation energy difference between two similar systems. The scheme is termed the atom-based correlated sampling (ACS). The performance of ACS is examined by calculating the isomerization energy of acetone to 2-propenol and the energy of the water–gas shift reaction. Using ACS, the convergences of these two examples are accelerated by 3.6 and 4.5 times, respectively. The methods developed in this work are expected to be useful for calculating RPA-level reaction energies for the reactions that take place in local regions, such as calculating the adsorption energies of molecules on transition metal surfaces for modeling surface catalysis.

Local embedding of coupled cluster theory into the random phase approximation using plane waves.

We present an embedding approach to treat local electron correlation effects in periodic environments. In a single consistent framework, our plane wave based scheme embeds a local high-level correlation calculation [here, Coupled Cluster (CC) theory], employing localized orbitals, into a low-level correlation calculation [here, the direct Random Phase Approximation (RPA)]. This choice allows for an accurate and efficient treatment of long-range dispersion effects. Accelerated convergence with respect to the local fragment size can be observed if the low-level and high-level long-range dispersions are quantitatively similar, as is the case for CC in RPA. To demonstrate the capabilities of the introduced embedding approach, we calculate adsorption energies of molecules on a surface and in a chabazite crystal cage, as well as the formation energy of a lattice impurity in a solid at the level of highly accurate many-electron perturbation theories. The absorption energy of a methane molecule in a zeolite chabazite is converged with an error well below 20 meV at the CC level. As our largest periodic benchmark system, we apply our scheme to the adsorption of a water molecule on titania in a supercell containing more than 1000 electrons.

Modeling and Comparing Gas Sensing Properties of CNT and CNT Decorated With Zinc Oxide

The use of hybrid nanostructures is of great interest to take advantage of their constructing components. However, the reason for the improved features of these structures has not yet been fully explained and there are some ambiguities. So we studied and compared sensing properties of carbon nanotube (CNT) and CNT decorated with zinc oxide (ZnO) nanoparticle (CNT/ZnO). Studied target gas molecules were CH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , CO, H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S and NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Different performance of CNT and CNT/ZnO structures were defined by calculating their density of sates before and after gas adsorption. The adsorption energy of molecules on both structures and charge transfer between molecules and their surfaces were also estimated using density functional theory (DFT) method. Compared to the pristine CNT, electrical properties of CNT/ZnO is influenced more notably according to the gas adsorption as the molecules have higher adsorption energy and larger charge transfer with the structure. Thus, the band gap of CNT/ZnO is also more affected by gas adsorption. The relation between band gap variations and the gas response of the structures was modeled and showed that the greater the band gap changes due to a gas adsorption, the better the structure gas sensing responses to it. Therefore, it can be concluded that the ZnO decorated CNT shows better gas sensing properties.

Black phosphorus hybridizing produces electron-deficient active sites on palladium nanoparticles for catalysis

The electronic structure of supported metal catalysts efficiently affects molecule adsorption energy and reaction energy barriers, which are crucial to the activity of a catalyst. By preparing nanohybrids palladium nanoparticle supported on few-layer black phosphorus (Pd P/FL-BP) as a catalyst, the electron-deficient structure of palladium nanoparticles induced by black phosphorus modification is demonstrated. The as-synthesized Pd P/FL-BP exhibits much enhanced catalytic activity for the hydrogenation of 4-nitrophenol to 4-aminophenol, even higher than the best performances reported to date. Density functional theory calculations indicate that the high activity correlates with the electron-deficient Pd atoms, which help to reduce the adsorption energy of reactants and promote desorption of products from the electron-deficient active sites.

Structural and electronic properties of the adsorption molecules on Co and Fe/N-doped graphene towards the application in direct liquid fuel cell

Co and Fe-nitrogen-doped graphene model (MN4) with an N/C ratio of 0.043 is tested for oxygen reduction reaction. The models and calculations were done using density functional theory (DFT). Four molecules, namely O2, OOH, OH, and H2O2, are adsorbed on the Co and Fe atom of MN4, and the changes in the adsorption energy are compared with the graphene model with MN4 model with the N/C ratio of 0.051. With the exception of the FeN4-OO complex, the adsorption energy for molecules in MN4 increases when the ratio is changed. Other molecules such as methanol, carbon monoxide, ethanol, formic acid, and glycerol also have been tested for adsorption on the Co and Fe atom to study its potential for the reaction using these catalyst models. The results show that these models display little positive activities for the oxidation reaction at anode direct liquid fuel cell (DLFC) as alternative energy. The competitive reaction may occur in DLFC if these catalysts are used as cathode catalyst in DLFC. Both models have a high potential to proceed with H2O production in the oxygen reduction reaction. Furthermore, these model catalysts may also suitable for polymer electrolyte membrane fuel cell (PEMFC) if pure hydrogen is used as fuel.

A study on the hydrogen storage performance of graphene–Pd(T)–graphene structure

The 1–6 H2 molecule adsorption energy and electronic properties of sandwich graphene–Pd(T)–Graphene (G–Pd(T)–G) structure were studied by the first-principle analysis. The binding energies, adsorption energies, and adsorption distances of Pd atoms-modified single-layer graphene and bilayer graphene with H2 molecules at B, H, T adsorption sites were calculated. In bilayer graphene, the adsorption properties at T sites were found to be more stable than those at B and H sites. The binding energy of Pd atoms (4.16 eV) on bilayer graphene was higher than the experimental cohesion energy of Pd atoms (3.89 eV), and this phenomenon eliminated the impact of metal clusters on adsorption properties. It was found that three H2 molecules were stably adsorbed on the G–Pd(T)–G structure with an average adsorption energy of 0.22 eV. Therefore, it can be speculated that G–Pd(T)–G is an excellent hydrogen storage material.

Amorphous transitional metal borides as substitutes for Pt cocatalysts for photocatalytic water splitting

Cocatalysts for H2 production are often made from noble metals, which are expensive and rare. Cocatalysts made from cheap and abundant elements are therefore highly desirable for economically viable H2 production. Here, we demonstrate that amorphous transitional metal borides (TMBs)—made from abundant materials and costing less than 0.1% of the price of Pt cocatalysts—are effective substitutes for Pt-based cocatalysts and result in superior H2 production via water-splitting under visible light irradiation. Under visible-light driven photocatalytic water-splitting, using TMBs as cocatalysts for nanostructured NiCoB/CdS composites achieved an extraordinary H2 production of 144.8mmolh−1g−1, up to 36 times greater than that observed when using CdS alone. The apparent quantum efficiency was measured as 97.42% at 500nm, which is the highest value reported for CdS photocatalysts. The hydrogen atom adsorption energy (ΔE(H)) and hydrogen molecule adsorption energy (ΔE(H2)) of NiB, NiCoB and Pt have been calculated for the first time. Compared with Pt cocatalyst, amorphous TMBs cocatalysts more readily adsorb hydrogen protons and desorb molecular hydrogen during the photocatalytic process. Superior performance of TMBs as cocatalyst, much better than Pt, can be attributed to its powerful trapping electrons ability and highly adsorption of protons. These findings provide a straightforward and effective route to produce cheap and efficient cocatalysts for large-scale water splitting.

Experimental and Theoretical Comparison of Gas Desorption Energies on Metallic and Semiconducting Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) exhibit high surface areas and precisely defined pores, making them potentially useful materials for gas adsorption and purification. A thorough understanding of the interactions between adsorbates and SWNTs is therefore critical to predicting adsorption isotherms and selectivities. Metallic (M-) and semiconducting (S-) SWNTs have extremely different polarizabilities that might be expected to significantly affect the adsorption energies of molecules. We experimentally and theoretically show that this expectation is contradicted, for both a long chain molecule (n-heptane) and atoms (Ar, Kr, and Xe). Temperature-programmed desorption experiments are combined with van der Waals corrected density functional theory, examining adsorption on interior and exterior sites of the SWNTs. Our calculations show a clear dependence of the adsorption energy on nanotube diameter but not on whether the tubes are conducting or insulating. We find no significant experimental or theoretical difference in adsorption energies for molecules adsorbed on M- and S-SWNTs having the same diameter. Hence, we conclude that the differences in polarizabilities between M- and S-SWNTs have a negligible influence on gas adsorption for spherical molecules as well as for highly anisotropic molecules such as n-heptane. We expect this conclusion to apply to all types of adsorbed molecules where van der Waals interactions govern the molecular interaction with the SWNT.

High energy resolution fluorescence detection XANES – an in situ method to study the interaction of adsorbed molecules with metal catalysts in the liquid phase

The change in the Pt electronic structure following the adsorption of an α,β-unsaturated aldehyde and ketone was followed by in situ HERFD-XANES in the liquid phase. The resulting shift in the Pt Fermi energy is in good agreement with the molecule adsorption energy trends calculated by DFT and provides insight into the reaction selectivity.

A MODEL FOR SOLVENT MEDIATED INTERACTIONS BETWEEN MOLECULES AND SURFACES

This work introduces a novel coarse-grained model representing the dynamics of polar molecules that adsorb on a substrate in the presence of a solvent. The motivation of the model is to avoid the explicit representation of the solvent. Instead, the solvent-mediated interaction is indirectly represented using a fluctuating energy landscape. The dynamics, on which this model is based, are similar to the dynamics in game theory. In particular, the strategy of an agent in a game is similar to the modification of the free energy barrier between the molecule and the substrate induced by other companion molecules. The aim of this method is to show how the interplay between solvents and companion molecules can imply a modification in the adsorption energy of molecules, and how this modification can buffer the adsorption of specific molecules on surfaces. The results, and their implications in the molecular recognition of surfaces, are discussed.