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Lecture

Adsorption at Gas/Solid Interface

In course

CH-341: Physical chemistry of interfaces

Acquire an understanding of interfacial phenomena, micro-heterogeneous colloidal solution systems and dynamic electrochemistry. ...

Description

This lecture covers the concepts of adsorption at the gas/solid interface, including physisorption and chemisorption, Langmuir and BET isotherms, and examples like methane chemisorption. It also discusses the manipulation of Xenon atoms on surfaces using STM.

Instructor

Rainer Beck

Professor titulaire EPFL, 2006 Privat Docent EPFL, 1997 Habilitation and venia legendi, Universität Karlsruhe, 1996 Ph.D. in Physical Chemistry, Oregon State University, 1990 Degree in Physics, Universität Stuttgart, 1985

Official source

Ontological neighbourhood

Chemistry

Physical chemistry: Surface science

Related concepts (32)

Adsorption

Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid (the absorbate) is dissolved by or permeates a liquid or solid (the absorbent). Adsorption is a surface phenomenon and the adsorbate does not penetrate through the surface and into the bulk of the adsorbent, while absorption involves transfer of the absorbate into the volume of the material, although adsorption does often precede absorption.

Surface tension

Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to float on a water surface without becoming even partly submerged. At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion). There are two primary mechanisms in play.

Surface science

Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces. It includes the fields of surface chemistry and surface physics. Some related practical applications are classed as surface engineering. The science encompasses concepts such as heterogeneous catalysis, semiconductor device fabrication, fuel cells, self-assembled monolayers, and adhesives.

Langmuir adsorption model

The Langmuir adsorption model explains adsorption by assuming an adsorbate behaves as an ideal gas at isothermal conditions. According to the model, adsorption and desorption are reversible processes. This model even explains the effect of pressure i.e. at these conditions the adsorbate's partial pressure, , is related to the volume of it, V, adsorbed onto a solid adsorbent. The adsorbent, as indicated in the figure, is assumed to be an ideal solid surface composed of a series of distinct sites capable of binding the adsorbate.

Surface energy

In surface science, surface free energy (also interfacial free energy or surface energy) quantifies the disruption of intermolecular bonds that occurs when a surface is created. In solid-state physics, surfaces must be intrinsically less energetically favorable than the bulk of the material (the atoms on the surface have more energy compared with the atoms in the bulk), otherwise there would be a driving force for surfaces to be created, removing the bulk of the material (see sublimation).

Related lectures (32)

Adsorption and Chemisorption

Explores chemisorption, catalysis, and adsorption on solid surfaces, including energy differences and bond formation.

Adsorption at the Gas/Solid Interface

Covers Langmuir, Fowler-Guggenheim, and BET adsorption isotherms, capillary condensation, and chemisorption concepts.

Thermodynamics of Interfaces: Gibbs Model and Micelles

Explores the Gibbs model of interfaces and micelle formation in surfactant solutions.

Basic Introduction into Catalysis II

Introduces the basics of catalysis, covering chemical bond breaking, molecular orbital theory, metal bonding, adsorption, and reaction kinetics.