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Accueil > A propos du LPP > Communication > Actualités archivées > 2020 > Fundamental data for CO2 dissociation determined experimentally at LPP

Fundamental data for CO2 dissociation determined experimentally at LPP

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Décharge plasma luminescente en CO2 pur à quelques mbarNon Thermal CO2 Plasmas are currently attracting considerable interest, as they are one of the most promising CO2 recycling technologies. Indeed, they present several advantages relevant for environmental purposes : they can be powered by renewable energy sources and therefore serve to store these energies, they can be turned On or Off immediately (an advantage considering the variability and intermittency of wind or solar energy for instance), they limit the energy cost of CO2 conversion by minimizing the heating of the gas and therefore could achieve better energy efficiency than thermodynamical equilibrium limit. Pure CO2 and CO2-containing plasmas are also studied in other fields, such as atmospheric re-entry of space vehicles (Mars and Venus in particular), plasma-assisted combustion or for the synthesis of carbonaceous deposits on surfaces (e.g. carbon nanotubes). Illustration de la variabilité des sections efficaces de dissociation du CO2 par impact électronique publiées dans la littératureFor all these applications, understanding the CO2 dissociation mechanisms is essential to control the induced chemistry. Therefore, one of the critical parameters is the dissociation efficiency of the CO2 molecule by collision with an electron. Surprisingly, although CO2 plasmas were already studied for the development of CO2 lasers in the 60s and 70s, the probability of CO2 dissociation as a function of the energy of the colliding electron (i.e. the effective dissociation cross section by electron impact) was poorly known. Values several orders of magnitude different could be found in the literature. Without this fundamental data, no accurate description or correct numerical model can be developed, hindering the development of efficient plasma processes for CO2 recycling.

To remedy this, an original experiment was developed in the framework of the thesis of Ana Sofia Morillo-Candas funded by the ANR project JCJC SYCAMORE. The experiment, carried out in a low-pressure DC glow discharge in a closed reactor (without gas flow), allowed to measure unambiguously the dissociation rate coefficient by electron impact for a large range reduced electric fields (E/N). By comparing the experimental rate coefficients with the values calculated from the various effective cross sections available in the literature, it was possible to highlight which effective cross section is the most correct to describe the dissociation of CO2. A comparison with the results of a 0D model developed in collaboration with the group of V. Guerra from IST Lisbon provides an alternative validation and reinforces the experimental conclusions. It is often difficult to isolate a particular process within a plasma environment, but the originality of the measurements carried out at LPP was to find a regime in which CO2 dissociation is largely dominated by this process, and to succeed in proving it. These results, useful to anyone seeking to describe plasmas containing CO2, have been recently published as a letter in Plasma Sources Science and Technology and can be found here.

Voir en ligne : https://iopscience.iop.org/article/...

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