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

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.

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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.

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Hydrogen Pairing on Si(100)-(2×1): A Site-Blocking Study

MRS Proceedings ◽

10.1557/proc-334-69 ◽

1993 ◽

Vol 334 ◽

Cited By ~ 1

Author(s):

Wolf Widdra ◽

W. Henry Weinberg

Keyword(s):

Hydrogen Atoms ◽

Unusual Behavior ◽

First Order ◽

Adsorption Sites ◽

First Order Kinetics ◽

Adsorption Temperature ◽

Saturation Coverage ◽

Temperature Programmed ◽

A Site ◽

Site Blocking

AbstractThe thermal desorption of hydrogen from a Si(100)-(2×l) monohydride surface has been reported previously to follow first-order kinetics. Pairing of hydrogen atoms on a Si-Si dimer prior to desorption is most likely the cause of this unusual behavior. To examine the degree of hydrogen pairing at various surface temperatures, this study examines the blocking of adsorption sites by hydrogen for subsequent acetylene adsorption. Temperature programmed desorption and Auger electron spectroscopy were used to measure the absolute saturation coverage of acetylene for various coverages of preadsorbed atomic deuterium. The observed linear decrease in saturation coverage of acetylene with deuterium coverage, for atomic deuterium adsorption between 550 and 150 K, indicates that deuterium is paired on Si-Si dimers. The observation that pairing occurs even at 150 K suggests that the diffusion of chemisorbed hydrogen is not responsible for pairing.

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A Stationary Solution of High-Energy Electron Reflection (HEER) for An Arbitrary Surface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135472 ◽

1990 ◽

Vol 48 (2) ◽

pp. 374-375

Author(s):

YIQUN MA

Keyword(s):

Stationary Solution ◽

High Energy ◽

Bloch Wave ◽

Dynamical Theory ◽

High Energy Electron ◽

Bulk Materials ◽

Periodic Surface ◽

Electron Transmission ◽

Electron Reflection ◽

Long Time

For a long time, the development of dynamical theory for HEER has been stagnated for several reasons. Although the Bloch wave method is powerful for the understanding of physical insights of electron diffraction, particularly electron transmission diffraction, it is not readily available for the simulation of various surface imperfection in electron reflection diffraction since it is basically a method for bulk materials and perfect surface. When the multislice method due to Cowley & Moodie is used for electron reflection, the “edge effects” stand firmly in the way of reaching a stationary solution for HEER. The multislice method due to Maksym & Beeby is valid only for an 2-D periodic surface.Now, a method for solving stationary solution of HEER for an arbitrary surface is available, which is called the Edge Patching method in Multislice-Only mode (the EPMO method). The analytical basis for this method can be attributed to two important characters of HEER: 1) 2-D dependence of the wave fields and 2) the Picard iteractionlike character of multislice calculation due to Cowley and Moodie in the Bragg case.

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Tuning Transition Metal Carbides Activity by Surface Metal Alloying: Case Study on CO2 Capture and Activation

10.26434/chemrxiv.6377330.v1 ◽

2018 ◽

Author(s):

Marti Lopez ◽

Luke Broderick ◽

John J Carey ◽

Francesc Vines ◽

Michael Nolan ◽

...

Keyword(s):

Transition Metal ◽

Co2 Capture ◽

Density Functional ◽

Deep Understanding ◽

Metal Carbides ◽

Transition Metal Carbides ◽

Adsorption Sites ◽

Surface Metal ◽

A Minor

<div>CO2 is one of the main actors in the greenhouse effect and its removal from the atmosphere is becoming an urgent need. Thus, CO2 capture and storage (CCS) and CO2 capture and usage (CCU) technologies are intensively investigated as technologies to decrease the concentration</div><div>of atmospheric CO2. Both CCS and CCU require appropriate materials to adsorb/release and adsorb/activate CO2, respectively. Recently, it has been theoretically and experimentally shown that transition metal carbides (TMC) are able to capture, store, and activate CO2. To further improve the adsorption capacity of these materials, a deep understanding of the atomic level processes involved is essential. In the present work, we theoretically investigate the possible effects of surface metal doping of these TMCs by taking TiC as a textbook case and Cr, Hf, Mo, Nb, Ta, V, W, and Zr as dopants. Using periodic slab models with large</div><div>supercells and state-of-the-art density functional theory based calculations we show that CO2 adsorption is enhanced by doping with metals down a group but worsened along the d series. Adsorption sites, dispersion and coverage appear to play a minor, secondary constant effect. The dopant-induced adsorption enhancement is highly biased by the charge rearrangement at the surface. In all cases, CO2 activation is found but doping can shift the desorption temperature by up to 135 K.</div>

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Coverage and Stability of NHx Terminated Cobalt and Ruthenium Surfaces: a First Principles Investigation

10.26434/chemrxiv.8428217 ◽

2019 ◽

Author(s):

Ji Liu ◽

Michael Nolan

Keyword(s):

Metal Surfaces ◽

High Vacuum ◽

Atomic Layer ◽

Nitrogen Plasma ◽

Operating Conditions ◽

Ultra High Vacuum ◽

Bridge Site ◽

Stable Surface ◽

Saturation Coverage ◽

The Stability

<div>In the atomic layer deposition (ALD) of Cobalt (Co) and Ruthenium (Ru) metal using nitrogen plasma, the structure and composition of the post N-plasma NHx terminated (x = 1 or 2) metal surfaces are not well known but are important in the subsequent metal containing pulse. In this paper, we use the low-index (001) and (100) surfaces of Co and Ru as models of the metal polycrystalline thin films. The (001) surface with a hexagonal surface structure is the most stable surface and the (100) surface with a zigzag structure is the least stable surface but has high reactivity. We investigate the stability of NH and NH2 terminations on these surfaces to determine the saturation coverage of NHx on Co and Ru. NH is most stable in the hollow hcp site on (001) surface and the bridge site on the (100) surface, while NH2 prefers the bridge site on both (001) and (100) surfaces. The differential energy is calculated to find the saturation coverage of NH and NH2. We also present results on mixed NH/NH2-terminations. The results are analyzed by thermodynamics using Gibbs free energies (ΔG) to reveal temperature effects on the stability of NH and NH2 terminations. Ultra-high vacuum (UHV) and standard ALD</div><div>operating conditions are considered. Under typical ALD operating conditions we find that the most stable NHx terminated metal surfaces are 1 ML NH on Ru (001) surface (350K-550K), 5/9 ML NH on Co (001) surface (400K-650K) and a mixture of NH and NH2 on both Ru (100) and Co (100) surfaces.</div>

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Adsorption and advanced oxidation of diverse pharmaceuticals and personal care products (PPCPs) from water using highly efficient rGO–nZVI nanohybrids

Environmental Science Water Research & Technology ◽

10.1039/d0ew00140f ◽

2020 ◽

Vol 6 (8) ◽

pp. 2223-2238 ◽

Cited By ~ 2

Author(s):

Arvid Masud ◽

Nita G. Chavez Soria ◽

Diana S. Aga ◽

Nirupam Aich

Keyword(s):

Graphene Oxide ◽

Reduced Graphene Oxide ◽

Personal Care Products ◽

Advanced Oxidation ◽

Zero Valent Iron ◽

Redox Activity ◽

Personal Care ◽

Adsorption Sites ◽

Reduced Graphene ◽

Nanoscale Zero Valent Iron

Reduced graphene oxide-nanoscale zero valent iron (rGO–nZVI) nanohybrid, with tunable adsorption sites of rGO and unique catalytic redox activity of nZVI, perform enhanced removal of diverse PPCPs from water.

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Molecular simulation of gases competitive adsorption in lignite and analysis of original CO desorption

Scientific Reports ◽

10.1038/s41598-021-91197-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jing Zhang ◽

Jiren Wang ◽

Chunhua Zhang ◽

Zongxiang Li ◽

Jinchao Zhu ◽

...

Keyword(s):

Adsorption Capacity ◽

Molecular Simulation ◽

Competitive Adsorption ◽

Air Leakage ◽

Adsorption Characteristics ◽

Adsorption Sites ◽

Simulation Based ◽

Lignite Coal ◽

Model C ◽

Grand Canonical

AbstractTo study the adsorption characteristics of CO, CO2, N2, O2, and their binary-components in lignite coal, reveal the influence of CO2 or N2 injection and air leakage on the desorption of CO in goafs, a lignite model (C206H206N2O44) was established, and the supercell structure was optimized under temperatures of 288.15–318.15 K for molecular simulation. Based on molecular dynamics, the Grand Canonical Monte Carlo method was used to simulate the adsorption characteristics and the Langmuir equation was used to fit the adsorption isotherms of gases. The results show that for single-components, the order of adsorption capacity is CO2 > CO > O2 > N2. For binary-components, the competitive adsorption capacities of CO2 and CO are approximate. In the low-pressure zone, the competitive adsorption capacity of CO2 is stronger than that of CO, and the CO is stronger than N2 or O2. From the simulation, it can be seen that CO2, N2 or O2 will occupy adsorption sites, causing CO desorption. Therefore, to prevent the desorption of the original CO in the goaf, it is not suitable to use CO2 or N2 injection for fire prevention, and the air leakage at the working faces need to be controlled.

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Adsorption process and mechanism of heavy metal ions by different components of cells, using yeast (Pichia pastoris) and Cu2+ as biosorption models

RSC Advances ◽

10.1039/d0ra09744f ◽

2021 ◽

Vol 11 (28) ◽

pp. 17080-17091

Author(s):

Xinggang Chen ◽

Zhuang Tian ◽

Haina Cheng ◽

Gang Xu ◽

Hongbo Zhou

Keyword(s):

Heavy Metal ◽

Pichia Pastoris ◽

Metal Ions ◽

Cell Walls ◽

Heavy Metal Ions ◽

Adsorption Process ◽

Yeast Pichia Pastoris ◽

Adsorption Sites

The Cu2+ first bound to the outer mannan and finally entered the cytoplasm. During the whole adsorption process, the number of adsorption sites in the outer and middle cell walls was the largest, and then gradually decreased.

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