Vibrational spectroscopy of CO at Ni(110): Adsorption energy at adsorption sites

1987 ◽  
Vol 191 (3) ◽  
pp. 395-405 ◽  
Author(s):  
J. Bauhofer ◽  
M. Hock ◽  
J. Küppers
Keyword(s):  
Vibrational Spectroscopy ◽  
Adsorption Energy ◽  
Adsorption Sites

scholarly journals A theoretical and experimental study of the adsorptive removal of hexavalent chromium ions using graphene oxide as an adsorbent

2020 ◽  
Vol 18 (1) ◽  
pp. 936-942
Author(s):  
Ardhmeri Alija ◽  
Drinisa Gashi ◽  
Rilinda Plakaj ◽  
Admir Omaj ◽  
Veprim Thaçi ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Hexavalent Chromium ◽  
Adsorption Energy ◽  
Density Functional ◽  
Noncovalent Interactions ◽  
Theoretical Calculations ◽  
Chemical Oxidation ◽  
Chromium Ions ◽  
Adsorption Sites ◽  
Vis Spectroscopy

AbstractThis study is focused on the adsorption of hexavalent chromium ions Cr(vi) using graphene oxide (GO). The GO was prepared by chemical oxidation (Hummers method) of graphite particles. The synthesized GO adsorbent was characterized by Fourier transform infrared spectroscopy and UV-Vis spectroscopy. It was used for the adsorption of Cr(vi) ions. The theoretical calculations based on density functional theory and Monte Carlo calculations were used to explore the preferable adsorption site, interaction type, and adsorption energy of GO toward the Cr(vi) ions. Moreover, the most stable adsorption sites were used to calculate and plot noncovalent interactions. The obtained results are important as they give molecular insights regarding the nature of the interaction between GO surface and the adsorbent Cr(vi) ions. The found adsorption energy of −143.80 kcal/mol is indicative of the high adsorptive tendency of this material. The adsorption capacity value of GO toward these ions is q = 240.361 mg/g.

scholarly journals Water and Carbon Dioxide Adsorption on CaO(001) Studied via Single Crystal Adsorption Calorimetry

2021 ◽  
Author(s):  
J. Seifert ◽  
S. J. Carey ◽  
S. Schauermann ◽  
S. Shaikhutdinov ◽  
H.-J. Freund
Keyword(s):  
Adsorption Energy ◽  
Adsorbed Water ◽  
Spectroscopic Studies ◽  
Detector Response ◽  
Adsorption Calorimetry ◽  
Instrument Response Function ◽  
Line Shapes ◽  
Adsorption Sites ◽  
Saturation Coverage ◽  
Initial Adsorption

AbstractA new method to analyze microcalorimetry data was employed to study the adsorption energies and sticking probabilities of D2O and CO2 on CaO(001) at several temperatures. This method deconvolutes the line shapes of the heat detector response into an instrument response function and exponential decay functions, which correspond to the desorption of distinct surface species. This allows for a thorough analysis of the adsorption, dissociation, and desorption processes that occur during our microcalorimetry experiments. Our microcalorimetry results, show that D2O adsorbs initially with an adsorption energy of 85–90 kJ/mol at temperatures ranging from 120 to 300 K, consistent with prior spectroscopic studies that indicate dissociation. This adsorption energy decreases with increasing coverage until either D2O multilayers are formed at low temperatures (120 K) or the surface is saturated (> 150 K). Artificially producing defects on the surface by sputtering prior to dosing D2O sharply increases this adsorption energy, but these defects may be healed after annealing the surface to 1300 K. CO2 adsorbs on CaO(001) with an initial adsorption energy of ~ 125 kJ/mol, and decreases until the saturation coverage is reached, which is a function of surface temperature. The results showed that pre-adsorbed water blocks adsorption sites, lowers the saturation coverage, and lowers the measured adsorption energy of CO2. The calorimetry data further adds to our understanding of D2O and CO2 adsorption on oxide surfaces.

scholarly journals Towards Quaternary Alloy Au-Pd Catalysts For Direct Synthesis of Hydrogen Peroxide

2019 ◽  
Author(s):  
Conor T. Waldt ◽  
Sahithi Ananthaneni ◽  
Rees Rankin
Keyword(s):  
Hydrogen Peroxide ◽  
Transition Metal ◽  
Adsorption Energy ◽  
Large Scale ◽  
Direct Synthesis ◽  
Quaternary Alloy ◽  
Catalyst Design ◽  
Pd Catalysts ◽  
Transition Metal Alloy ◽  
Adsorption Sites

<div>The direct synthesis of hydrogen peroxide (H2O2) in situ to replace legacy large-scale commercial anthraquinone synthesis is a critical industrial technology required to advance applications in sustainable green chemistry and reduce energy consumption associated with transporting reagents and oxidants. Current state-of-the-art Au-Pd transition metal alloy catalysts show promise to selectively synthesize H2O2 however activity is not optimal and material costs and sustainability concerns hinder widespread use. In this manuscript, using values from previously derived Oxygen Reduction Reaction (ORR) Volcano Plots, we analyze and filter potential AuPdMN {M=metal 1, N=metal 2} quaternary alloys by their associated descriptor values, the adsorption energy of mono atomic oxygen and hydrogen. We report possible surface structures which have adsorption sites that optimize the adsorption energy of both descriptors and explain possibilities for using these results to leverage in future and ongoing work for truly optimal catalyst design for transition-metal alloys for direct synthesis of hydrogen peroxide. These results and recommendations should ultimately help increase the performance (activity and selectivity) of direct synthesis catalysts for hydrogen peroxide synthesis while simultaneously lowering the costs of materials in these catalysts and making them more sustainable.</div>

scholarly journals Theoretical Investigation on Rare Earth Elements of Y, Nd and La Atoms’ Adsorption on the Kaolinite (001) and (001¯) Surfaces

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 856
Author(s):  
Jian Zhao ◽  
Zheng Wang ◽  
Wei Gao ◽  
Yi-Fei Wang ◽  
Bo-Wen Huang
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Adsorption Energy ◽  
Density Functional ◽  
Adsorption Mechanism ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Surface Sites ◽  
Before And After ◽  
Adsorption Technology

With the growing demand of rare earth elements, the recovery of rare earth elements is a major issue for researchers in related fields. Adsorption technology is one of the most effective and popular recovery methods. Therefore, the adsorption mechanism of Yttrium (Y), Neodymium (Nd), and Lanthanum (La) atoms on the kaolinite (001) and (001¯) surfaces was examined by density functional theory (DFT). The most stable adsorption sites on the kaolinite (001) surface for Y atoms was the bridge site, and the hollow site was the most favorable adsorption site for Nd and La atoms with high adsorption energy. However, the adsorption energies of kaolinite (001¯) surface sites for Y, Nd, and La atoms were much lower than the (001) surface sites, indicating that the adsorption capability of the hydroxylated (001) surface is stronger. The effects of coverage on adsorption position, energy, and structures were entirely investigated on top, bridge, and hollow sites of the kaolinite (001) surface from 0.11 to 1.0 monolayers (ML). The adsorption energy of Y, Nd, and La atoms on three kinds of sites increased with increasing of the coverage implied the stronger capability of surface adsorption. The recovery capability of kaolinite for the rare earth atoms was in the order of La > Nd > Y. The changes in the atomic structure, charge density, and electron density of states for Y, Nd, and La/kaolinite (001) before and after adsorption were also analyzed in depth.

New Adsorption Models for Entirely Describing the Adsorption Isotherm and Heat of Methane in Heterogeneous Nanopore Structures of Coal

2021 ◽  
Vol 21 (1) ◽  
pp. 212-224
Author(s):  
Hai-Jian Li ◽  
Jian-Hong Kang ◽  
Zhe-Jun Pan ◽  
Fu-Bao Zhou ◽  
Jin-Chang Deng ◽  
...  
Keyword(s):  
Experimental Data ◽  
Adsorption Isotherm ◽  
Energy Distribution ◽  
Adsorption Isotherms ◽  
Adsorption Energy ◽  
Distribution Functions ◽  
Adsorption Heat ◽  
Adsorption Models ◽  
Adsorption Sites ◽  
New Models

To understand the adsorption mechanism of methane in heterogeneous nanopore structures of coal, integral adsorption models based on linear, exponential, hyperbolic and quadratic energy distribution functions are established. The adsorption energy domain of the new models is assumed to be a finite interval. These new adsorption models can describe both the adsorption isotherm and the adsorption heat. A volumetric method of adsorption with a microcalorimetry system is used to measure the adsorption isotherms and integral heat, and then the parameters of the new models are obtained by fitting the experimental data. Since the adsorption heat can be different for different adsorption models, it is necessary to fit the adsorption isotherms and heat simultaneously. The fitting results of the adsorption isotherms and heat show that the new models are able to describe the experimental data better than the Langmuir model. By comparing the fitting results and the effective range of adsorption energy of the different adsorption models, it is shown that the exponential energy distribution function is the most reasonable model for methane adsorption in coals, which can be used to evaluate the energetic heterogeneity of nanopores in coal samples. The decreasing exponential energy distributions of three coal samples indicate that a larger adsorption energy corresponds to fewer adsorption sites in the coal samples. The proportion of high adsorption energy is related to the micro-nanopore volume in the coal samples.

scholarly journals Density Functional Theory Study of Hydrogen Adsorption on Pt Pd/γ-Al2O3 Surface

2021 ◽  
Vol 2097 (1) ◽  
pp. 012020
Author(s):  
Liang Zhang ◽  
Jia Li ◽  
Yong Chen ◽  
Cheng Zeng ◽  
Wu Kang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Adsorption Energy ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Energy Gap ◽  
Solid Catalyst ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Lower Energy Level ◽  
Catalytic Hydrogen

Abstract At present passive hydrogen recombiners (PAR) are used to prevent hydrogen explosion. Hydrogen removal catalyst is the core component of PAR. The adsorption of hydrogen on the solid catalyst surface is the premise of catalytic hydrogen removal and is of great significance for deeper understanding of hydrogen removal mechanism. The adsorption behavior of H2-Pt Pd/γ-Al2O3 system has been studied by using density functional theory and periodic slab model. The results of different adsorption sites indicate the adsorption energy of top site is highest, which is -1.2584eV. Higher adsorption energy means stronger interaction between H2 and catalyst substrate, which elongates H-H bond and increases the negative charge on H2. With increasing doping content of Pd, the adsorption energy of substrate decreases gradually. The adsorption energy absolute value of Pt4/γ-Al2O3 is highest and its H-H bond is longest, arriving at 0.0967nm. After adsorbed on substrate, the energy gap of H2 decreases drastically with the lowest energy gap of H2-Pt4/γ-Al2O3 that is 0.5197eV, and the peaks of density of state pattern move to lower energy level. This is because that the d orbital of Pt/Pd atoms interacts with the τ* anti-bond orbital of H2 strongly, transferring electrons to the τ* anti-bond orbital of H2. Doping Pd increases the energy gap of molecule orbital.

A new way of assessing clay cation adsorption using normalized salt concentration

Clay Minerals ◽  
2003 ◽  
Vol 38 (2) ◽  
pp. 233-242 ◽  
Author(s):  
J . -L. Bersillon ◽  
F. Villiéras ◽  
L. Michot ◽  
J. -M. Cases
Keyword(s):  
Adsorption Energy ◽  
Gas Adsorption ◽  
Adsorption Sites ◽  
Adsorption Data ◽  
Alkaline Conditions ◽  
Site Category ◽  
Acidic Conditions ◽  
Cation Adsorption ◽  
Monolayer Coverage ◽  
Reference Phase

AbstractKaolinite cation adsorption data are processed using recent gas adsorption concepts such as the undersaturation ∆m = ln (C/Cs) and the monolayer coverage y. This process shows that using the proper reference phase through its solubility Cs, it is possible to characterize adsorption sites that have the same adsorption energy regardless of the nature of the cation. Under mildly acidic conditions, a single ‘Langmuirian’ site category fits cation adsorption data whereas another family of sites is revealed in mildly alkaline conditions. These results suggest that at mildly acidic pH, only silanol sites are available to ion exchange and adsorption whereas at higher pH, a wider range of sites is made available, some of them displaying the same average adsorption energy and the others constituting a different category of sites with a much lower adsorption energy. This latter category is attributed to the aluminol sites.

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