Adsorption Kinetics Model of Hydrogen on Graphite
Jean-Marc Simon1, Guilherme Carneiro Queiroz da Silva1
1Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR-6303 CNRS-Université Bourgogne Europe (UBE), 9 Av. A. Savary, 21000 Dijon, France.
Entropy (Basel, Switzerland)
|March 28, 2025
Summary
A novel kinetic equation for hydrogen adsorption on graphite was developed using molecular dynamics, offering a new way to interpret experimental data and simulate adsorption processes under various conditions.
Area of Science:
- Physical Chemistry
- Surface Science
- Chemical Engineering
Background:
- Understanding gas adsorption kinetics on solid surfaces is crucial for many industrial processes.
- Existing models like Langmuir kinetics do not fully capture the complex adsorption-desorption dynamics observed in some systems.
- Molecular dynamics simulations offer a powerful tool to investigate these dynamics at a fundamental level.
Purpose of the Study:
- To derive a new kinetic equation for hydrogen (H2) adsorption and desorption on graphite.
- To validate the new equation against experimental data and simulate adsorption under diverse thermodynamic conditions.
- To explore the relationship between adsorption kinetics and mass flow within non-equilibrium thermodynamics.
Main Methods:
- Molecular dynamics simulations were employed to determine adsorption and desorption equilibrium rates.
- A new kinetic equation was derived based on these rates, which are proportional to phase activities.
- The derived equation was used to simulate isothermal and non-isothermal adsorption kinetics.
Main Results:
- The new kinetic equation accurately describes H2 adsorption/desorption on graphite, deviating from Langmuir kinetics.
- Simulations using the new equation showed good agreement with characteristic adsorption/desorption times from literature.
- Expressions for transport coefficients related to mass transfer and coupled mass-heat fluxes were proposed.
Conclusions:
- The developed kinetic equation provides a more accurate framework for understanding hydrogen adsorption on graphite.
- The study bridges molecular-level insights with macroscopic thermodynamic descriptions of heterogeneous systems.
- The findings contribute to the development of advanced models for gas-surface interactions and transport phenomena.
More Related Videos
07:23Experimental Study of the Relationship Between Particle Size and Methane Sorption Capacity in Shale
Published on: August 2, 2018
8.1K
08:40Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production
Published on: December 6, 2021
4.4K
Related Concept Videos
02:34Arrhenius Plots
50.1K
The Arrhenius equation relates the activation energy and the rate constant, k, for chemical reactions. In the Arrhenius equation, k = Ae−Ea/RT, R is the ideal gas constant, which has a value of 8.314 J/mol·K, T is the temperature on the kelvin scale, Ea is the activation energy in J/mole, e is the constant 2.7183, and A is a constant called the frequency factor, which is related to the frequency of collisions and the orientation of the reacting molecules.
The Arrhenius equation can be used...
The Arrhenius equation can be used...
50.1K
02:50Catalysis
32.5K
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
32.5K
01:28Adsorption of Gases on Solids
229
Adsorption is a process where molecules, known as the adsorbates, accumulate on a surface, which is referred to as the adsorbent or substrate. Occurring at the solid-gas interface, this phenomenon is crucial in various scientific and industrial contexts. The reverse of adsorption is desorption.Two types of adsorptions exist: physical (physisorption) and chemical (chemisorption). Physisorption involves gas molecules held to the solid's surface by relatively weak intermolecular van der Waals...
229
01:29Adsorption Isotherms I
181
Adsorption isotherms are mathematical models that describe how molecules in a gas or liquid phase interact with surfaces. Two of the most common isotherm models are the Langmuir and Freundlich isotherms, which relate to Type I monolayer chemisorption. The Langmuir model is based on four key assumptions:• Adsorption cannot exceed monolayer coverage.• All surface sites are equivalent.• Molecules adsorb only at vacant sites.• There are no interactions between adsorbed...
181
01:25Adsorption Isotherms II
118
Brunauer, Emmett, and Teller (BET) introduced a theory in 1938 that modified Langmuir's assumptions to explain multilayer physical adsorption. This theory is applicable to Type II isotherms and provides a more realistic picture of adsorption processes. The BET theory assumes a uniform solid surface with localized adsorption sites, where adsorption at one site doesn't affect adsorption at neighboring sites. This theory also allows for the possibility of additional molecules being adsorbed on top...
118
01:22Heterogeneous Catalysis
123
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
123