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Chemisorption
About: Chemisorption is a research topic. Over the lifetime, 16298 publications have been published within this topic receiving 554989 citations.
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TL;DR: In this article, the chemisorption of H2 on Cu(100) is treated using a many-electron embedding theory in which the copper lattice is modeled as a 38-atom cluster.
Abstract: The chemisorption of H2 on Cu(100) is treated using a many‐electron embedding theory in which the copper lattice is modeled as a 38‐atom cluster. Ab initio valence (4s) CI calculations carried out on a local electronic subspace permit an accurate description of bonding at the surface. Dissociated hydrogen is found to bind exotherimically to the (100) surface at several stable adsorption sites in fourfold, bridge, and atop atom H positions. Calculated H2 binding energies are in the range 13–22 kcal/mol. However, high energy barriers to dissociation of 35–40 kcal/mol exist due to the repulsion of molecular H2 by the surface and the difficulty of stretching H2 significantly above the surface. A characteristic of stretched or dissociated H2 is the occurrence of H levels well up into the Cu 4s band from 5.5 to 7.8 eV below EF.
124 citations
TL;DR: In this paper, electron energy loss spectroscopy (EELS) and molecular beam techniques were used to examine the translational energy adsorption of oxygen on the (111) surface of platinum and found that the activation barrier for dissociation from the peroxolike precursor to be approximately 0.29 eV.
Abstract: High translational energy adsorption of oxygen on the (111) surface of platinum was examined with electron energy loss spectroscopy (EELS) and molecular beam techniques. EEL spectra indicate that over an incident energy range of 0.2–1.37 eV and on a Pt(111) surface held at 77 K, oxygen adsorbs in an associative chemisorbed state—yielding to the dissociated state only after sufficient substrate heating. Simple direct dissociation appears negligible for all incident kinetic energies studied. At near-zero surface coverages, exclusive population of the peroxolike molecular precursor is observed for adsorption at these high translational energies, while both superoxolike and peroxolike forms are detected for low energy adsorption (0.055 eV). This peculiarity represents evidence that translational energy is effective in differentially populating reaction intermediates and provides better quantification of potential energy barriers to dissociation. We estimate the activation barrier for dissociation from the peroxolike precursor to be approximately 0.29 eV. Initial adsorption probability measurements over a wide range of surface temperatures and high incident kinetic energies corroborate a molecular chemisorption mediated mechanism.
124 citations
TL;DR: In this article, the effects of preoxidation on catalytic rates and selectivity were found to be sensitive to the structure of the platinum surface, kink sites playing a particularly active role in the enhancement of dehydrogenation and hydrogenation activity by strongly bound oxygen.
124 citations
TL;DR: In this article, a method for increasing the lateral chain density in self-assembled monolayers (SAMs) of alkanethiols on polycrystalline gold was presented.
Abstract: We present a method for increasing the lateral chain density in self-assembled monolayers (SAMs) of alkanethiols on polycrystalline gold. This method relies on exposure of the alkanethiolate monolayers to mercury vapor and subsequent reimmersion into the thiol solution. Mercury adsorption on the gold surface induces a structural rearrangement in the alkanethiolate monolayers, as indicated by changes in dichroism in the Fourier transform infrared (FTIR) spectra, in line shape in the sum frequency generation (SFG) spectra, and in the macroscopic wetting behavior of the monolayers. X-ray photoelectron spectroscopy (XPS) data show that saturation of the thiolate samples with mercury occurs after 20−30 min of exposure to air saturated with mercury vapor. For 100 nm evaporated gold films a mercury bulk concentration of 14−16 atom % was determined by energy-dispersive X-ray analysis (EDX). Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) data indicate that after mercury adsorption the monolayers consist...
124 citations
TL;DR: Using a pair bond type model for the interatomic interactions, the authors determined surface segregation on clean, H, O and CO covered surfaces of various alloys and studied surface segregation caused by bulk hydrogen absorption.
124 citations