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

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.

Download Full-text

AGN evolution as seen in spectral lines: The case of narrow-line Seyfert 1s

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320002653 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 94-94

Author(s):

Marco Berton

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Spectroscopic Studies ◽

Spectral Lines ◽

Narrow Line ◽

Line Profiles ◽

Line Shapes ◽

Fundamental Information ◽

Line Region ◽

Gaussian Samples

AbstractLine profiles can provide fundamental information on the physics of active galactic nuclei (AGN). In the case of narrow-line Seyfert 1 galaxies (NLS1s) this is of particular importance since past studies revealed how their permitted line profiles are well reproduced by a Lorentzian function instead of a Gaussian. This has been explained with different properties of the broad-line region (BLR), which may present more pronounced turbulent motions in NLS1s with respect to other AGN. We investigated the line profiles in a recent large NLS1 sample classified using SDSS, and we divided the sources into two subsamples according to their line shapes, Gaussian or Lorentzian. The line profiles seem to separate all the properties of NLS1s. Black hole mass, Eddington ratio, [OIII] luminosity, and Fe II strength are all very different in the Lorentzian and Gaussian samples, as well as their position on the quasar main sequence. We interpret this in terms of evolution within the class of NLS1s. The Lorentzian sources may be the youngest objects, while Gaussian profiles may be typically associated to more evolved objects. Further detailed spectroscopic studies are needed to fully confirm our hypothesis.

Download Full-text

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

Open Chemistry ◽

10.1515/chem-2020-0148 ◽

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.

Download Full-text

Calorimetric and Spectroscopic Studies of Water Adsorption onto Alkaline Earth Fluorides

Adsorption Science & Technology ◽

10.1260/026361705774859910 ◽

2005 ◽

Vol 23 (6) ◽

pp. 425-436

Author(s):

Toshinori Mori ◽

Yasushige Kuroda ◽

Ryotaro Kumashiro ◽

Koji Hirata ◽

Hidehiro Toyota ◽

...

Keyword(s):

Alkaline Earth ◽

Water Adsorption ◽

Adsorbed Water ◽

Spectroscopic Studies ◽

Water Molecules ◽

Earth Fluoride ◽

Alkaline Earth Fluoride ◽

Pretreatment Temperature ◽

Argon Adsorption ◽

Ir Bands

Interactions between the surfaces of alkaline earth fluorides (CaF2, SrF2 and BaF2) and water molecules were investigated by calorimetric and spectroscopic methods. The exposed surfaces of the alkaline earth fluoride samples, with which the (100) crystalline plane is mainly associated, were found to be fully covered with strongly adsorbed water molecules, resulting in characteristic IR bands at 3684, 2561, 1947 and 1000 cm−1, respectively. This surface was homogeneous towards further water adsorption. The strongly adsorbed water molecules were almost completely desorbed from the surface on evacuating the sample up to 473 K. The heat of immersion in water also increased with increasing pretreatment temperature; this may be attributed to surface rehydration of the alkaline earth fluorides. The state of the surface changed drastically as the pretreatment temperature was increased and stabilized towards incoming water molecules. Thus, the surface formed after evacuation at temperatures greater than 473 K was resistant to hydration even after immersion in water at room temperature. This surface was relatively heterogeneous towards water adsorption, although it behaved homogeneously towards argon adsorption. These facts indicate that strongly adsorbed water molecules appear to be somewhat specific towards the adsorption of further incoming water molecules. The adsorption properties of the (100) plane of alkaline earth fluorides towards water and argon molecules depend strongly on both the electrostatic field strength and the extent of rehydration of the alkaline earth fluoride surface.

Download Full-text

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

Surface Science ◽

10.1016/s0039-6028(87)81186-x ◽

1987 ◽

Vol 191 (3) ◽

pp. 395-405 ◽

Cited By ~ 49

Author(s):

J. Bauhofer ◽

M. Hock ◽

J. Küppers

Keyword(s):

Vibrational Spectroscopy ◽

Adsorption Energy ◽

Adsorption Sites

Download Full-text

A study of the adsorption sites of hydrogen on Ru(001) at saturation coverage by electron reflection

Surface Science ◽

10.1016/0039-6028(87)90046-x ◽

1987 ◽

Vol 180 (1) ◽

pp. 237-251 ◽

Cited By ~ 108

Author(s):

M. Lindroos ◽

H. Pfnür ◽

P. Feulner ◽

D. Menzel

Keyword(s):

Adsorption Sites ◽

Electron Reflection ◽

Saturation Coverage

Download Full-text

Protein Adsorption on Topographically Structured Surfaces: A Mesoscopic Computer Simulation for the Prediction of Prefered Adsorption Sites

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.542 ◽

2010 ◽

Vol 638-642 ◽

pp. 542-547 ◽

Cited By ~ 4

Author(s):

Patrick Elter ◽

Regina Lange ◽

R. Thull ◽

Ulrich Beck

Keyword(s):

Computer Simulation ◽

Brownian Dynamics ◽

Field Calculation ◽

Dispersion Interactions ◽

Structured Surfaces ◽

Adsorption Sites ◽

Egg White Lysozyme ◽

Initial Adsorption ◽

Solid Liquid Interface ◽

Solid Liquid

In this study the influence of edges and spikes of a topographical nanostructure on the adsorption behavior of proteins at a solid-liquid interface is examined by a computer simulation. An algorithm has been developed, which combines a Finite Differences field calculation with Brownian Dynamics. A (16 nm)3 nano-cube with sharp edges as well as flat faces was chosen as model system and the adsorption of Hen Egg White Lysozyme was investigated. An increased adsorption rate along the edges of a the model cube is reached in the initial adsorption phase under consideration of electrostatic and dispersion interactions. At later times also the surfaces of the cube are covered, if the salt concentration is sufficient to screen the repelling protein-protein electrostatic interaction.

Download Full-text

Adsorption of Co2+ by Oxides from Aqueous Solution

Canadian Journal of Chemistry ◽

10.1139/v72-263 ◽

1972 ◽

Vol 50 (11) ◽

pp. 1642-1648 ◽

Cited By ~ 121

Author(s):

P. H. Tewari ◽

A. B. Campbell ◽

Woon Lee

Keyword(s):

Solution Ph ◽

Langmuir Adsorption ◽

Adsorption Sites ◽

Wide Range ◽

Saturation Coverage ◽

Endothermic Process ◽

Adsorption Of Co ◽

Adsorption Of Co2 ◽

Hydrolysis Of ◽

Marked Dependence

The adsorption of Co(II) by Fe3O4, Al2O3, and MnO2 has been studied as a function of Co(II) concentration, solution-pH, and temperature. It is observed that the adsorption of cobalt increases markedly with the solution pH between pH 5 and 7.5. Above pH 8 adsorption becomes increasingly masked by precipitation of Co(OH)2 and no resolution of these two contributions to the loss of Co(II) from solution is possible. A log θ/(1–θ) vs. pH plot is found to be linear between pH 5 and 7.5, where θ is the fraction of occupied adsorption sites. The presence of 0.1 m Ba2+ and Mg2+ in the solution does not seem to affect the hydrogen ion dependence of the adsorption of Co(II) on alumina.The adsorption results have been analyzed by the Langmuir adsorption isotherm over a wide range of Co(II) concentration (10−6–10−3 m). The adsorption of Co(II) is found to be an endothermic process and increases markedly with temperature between 30 and 100 °C. The heat of adsorption decreases with increasing surface coverage of the oxides. At saturation coverage, the heats of adsorption for Co(II) on Al2O3, MnO2, and Fe3O4 are −14.9, −14.3, and −6.3 kcal/mol, respectively. Hydrolysis of Co(II) is suggested as a possible mechanism for the marked dependence of adsorption on pH and temperature.

Download Full-text

How to Extract Adsorption Energies, Adsorbateadsorbate Interaction Parameters, and Saturation Coverages from Temperature Programmed Desorption Experiments

10.26434/chemrxiv.14525496 ◽

2021 ◽

Author(s):

Sudarshan Vijay ◽

Henrik Høgh Kristoffersen ◽

Yu Katayama ◽

Yang Shao-Horn ◽

Ib Chorkendorff ◽

...

Keyword(s):

Adsorption Energy ◽

Density Functional ◽

Configurational Entropy ◽

Density Functional Theory Calculations ◽

Temperature Programmed Desorption ◽

Functional Theory ◽

Interaction Terms ◽

Saturation Coverage ◽

Adsorption Energies ◽

Temperature Programmed

We present a simple scheme to extract the adsorption energy, adsorbate interaction parameter and the saturation coverage from temperature programmed desorption (TPD) experiments. We propose that the coverage dependent adsorption energy can be fit using a functional form including the configurational entropy and linear adsorbate-adsorbate interaction terms. As one example of this scheme, we analyze TPD spectra of desorption on Au(211) and Au(310) surfaces. We determine that under atmospheric pressure, the steps of both facets adsorb between 0.4-0.9 ML coverage of CO*. We show this result to be consistent with density functional theory calculations of adsorption energies with the BEEF-vdW functional.

Download Full-text

Insights into the Adsorption of Water and Oxygen on the Cubic CsPbBr3 Surfaces: A First-Principle Study

Chinese Physics B ◽

10.1088/1674-1056/ac3987 ◽

2021 ◽

Author(s):

Xin Zhang ◽

Ruge Quhe ◽

Ming Lei

Keyword(s):

Adsorption Energy ◽

Density Functional ◽

Degradation Mechanism ◽

Perovskite Solar Cells ◽

Density Functional Theory Calculations ◽

Adsorbed Water ◽

Energy Difference ◽

Device Fabrication ◽

Water Molecules ◽

Inorganic Perovskite

Abstract The degradation mechanism of the all-inorganic perovskite solar cells in the ambient environment remains unclear. In this paper, water and oxygen molecule adsorptions on the all-inorganic perovskite (CsPbBr3) surface are studied by density-functional theory calculations. In terms of the adsorption energy, the water molecules are more susceptible than the oxygen molecules to be adsorbed on the CsPbBr3 surface. The water molecules can be adsorbed on both the CsBr- and PbBr-terminated surfaces, but the oxygen molecules tend to be selectively adsorbed on the CsBr-terminated surface instead of the PbBr-terminated one due to the significant adsorption energy difference. While the adsorbed water molecules only contribute deep states, the oxygen molecules introduce interfacial states inside the bandgap of the perovskite, which would significantly impact the chemical and transport properties of the perovskite. Therefore, special attention should be paid to reduce the oxygen concentration in the environment during the device fabrication process so as to improve the stability and performance of the CsPbBr3 based devices.

Download Full-text

Synthesis, structure and water sorption in Zr metal-organic frameworks

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314087592 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1240-C1240

Author(s):

Felipe Gándara ◽

Hiroyasu Furukawa ◽

Zhang Yue-Biao ◽

Juncong Jiang ◽

Wendy Queen ◽

...

Keyword(s):

Water Adsorption ◽

Metal Organic Frameworks ◽

Adsorbed Water ◽

Neutron Diffraction Study ◽

Water Molecules ◽

Remote Areas ◽

Adsorption Sites ◽

Thermal Batteries ◽

Secondary Building Units ◽

Metal Organic

Metal-organic frameworks (MOFs) based on zirconium secondary building units (SBUs) have proven to have great thermal and chemical stability,[1,2] which make them ideal for their use in different applications. We have prepared a series of six new MOFs made from the Zr6O4(OH)4(-CO2)nsecondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl organic linkers to make extended porous frameworks, with the aim of studying their performance as water adsorbents. Thus, we have evaluated the water adsorption properties of these new MOFs and other reported porous materials to identify the compounds with the most promising materials for use in applications such as thermal batteries or delivery of drinking water in remote areas. An X-ray single-crystal and a powder neutron diffraction study reveal the position of the water adsorption sites in one of the best performing materials, and highlight the importance of the intermolecular interactions between adsorbed water molecules within the pores.

Download Full-text