February 08, 2022
10:00
Louvain-La-Neuve
STUD 13
Accessing Gas Adsorption Micro- and Macroscopically by in situ Powder Diffraction
Gas adsorption is a spontaneous interaction that occurs on the interface between the gas and a condensed phase. In this project, we propose a new methodology based on in situ diffraction to obtain simultaneously micro- and macroscopic pictures of gas adsorption. As a porous material we use the first porous metal borohydride, γ-Mg(BH4)2. It contains a tubular-shaped microporous channel running through the volume diagonal of its cubic unit cell. The adsorption of a series of noble and fuel gasses is studied using in situ diffraction of X-rays and neutrons. The position and quantity of the guest molecules are followed using Rietveld refinement at constant pressure or temperature, producing experimental isobars and isotherms directly from diffraction data. These curves are fitted with relevant equations, allowing to extract the thermodynamic parameters of gas adsorption, such as isosteric heats of adsorption as a function of gas loading. We detect rearrangements of guests and correlate the changes with the adsorption properties and intermolecular interactions. Following the time evolution of the guest occupancies allows to access the energy barriers related to gas adsorption and thus to shed light on the diffusion mechanisms.
As a perspective, we identify the need to extend the class of porous hydridic materials to other members, beyond γ-Mg(BH4)2. Characterization of gas adsorption of such new members is required in order to understand which unusual properties found in this work are due to hydridic nature of the pores and which are due to the size and shape factors. We see a great potential to a wider use of diffraction to study equilibrium diagrams and thermodynamics of gas adsorption. The isobars/isotherms that we obtained are highly complementary to bulk measurements and can be coupled with the structural information readily available from the same experiment. Diffraction-based methodology to study kinetics of gas adsorption also looks very promising, despite it involves measurements and analysis of an immense amount of data.
Jury members :
- Prof. Yaroslav Filinchuk (UCLouvain), supervisor
- Prof. Eric Gaigneaux (UCLouvain), chairperson
- Prof. Tom Leyssens (UCLouvain), secretary
- Prof. Gian-Marco Rignanese (UCLouvain)
- Dr. Dmitry Chernyshov (European Synchrotron Radiation Facility, France)
- Prof. Haiwen Li (Hefei General Machinery Research Institute, China)
Pay attention :
The public defense of Xiao Li scheduled for Tuesday 08 February at 10:00 a.m will take place in the form of a video conference
You also can assist to the thesis defence in the auditorium STUD13 (Place de l'Agora 19, Louvain-La-Neuve)