TY - JOUR
T1 - The Chemical Origins of Plasma Contraction and Thermalization in CO2 Microwave Discharges
AU - van de Steeg, A.W.
AU - Vialetto, L.
AU - da Silva, A.F.S.
AU - Viegas, P.
AU - Diomede, P.
AU - van de Sanden, M.C.M.
AU - van Rooij, G.J.
N1 - Funding Information:
This work received funding from The Netherlands Organization for Scientific Research (NWO) in the framework of the CO2-to-Products program with kind support from Shell and the ENW PPP Fund for the top sectors. This work is also part of the Shell-NWO/FOM initiative “Computational sciences for energy research” of Shell and Chemical Sciences, Earth and Life Sciences, Physical Sciences, FOM and STW. This work has also been supported by the project LM2018097 funded by Ministry of Education, Youth and Sports of the Czech Republic. We wish to express our gratitude for the fruitful discussions with our Shell project partners, Sander van Bavel and Joost Smits.
Publisher Copyright:
© 2022 American Chemical Society.
PY - 2022/2/10
Y1 - 2022/2/10
N2 - Thermalization of electron and gas temperature in CO2 microwave plasma is unveiled with the first Thomson scattering measurements. The results contradict the prevalent picture of an increasing electron temperature that causes discharge contraction. It is known that as pressure increases, the radial extension of the plasma reduces from similar to 7 mm diameter at 100 mbar to similar to 2 mm at 400 mbar. We find that, simultaneously, the initial nonequilibrium between similar to 2 eV electron and similar to 0.5 eV gas temperature reduces until thermalization occurs at 0.6 eV. 1D fluid modeling, with excellent agreement with measurements, demonstrates that associative ionization of radicals, a mechanism previously proposed for air plasma, causes the thermalization. In effect, heavy particle and heat transport and thermal chemistry govern electron dynamics, a conclusion that provides a basis for ab initio prediction of power concentration in plasma reactors.
AB - Thermalization of electron and gas temperature in CO2 microwave plasma is unveiled with the first Thomson scattering measurements. The results contradict the prevalent picture of an increasing electron temperature that causes discharge contraction. It is known that as pressure increases, the radial extension of the plasma reduces from similar to 7 mm diameter at 100 mbar to similar to 2 mm at 400 mbar. We find that, simultaneously, the initial nonequilibrium between similar to 2 eV electron and similar to 0.5 eV gas temperature reduces until thermalization occurs at 0.6 eV. 1D fluid modeling, with excellent agreement with measurements, demonstrates that associative ionization of radicals, a mechanism previously proposed for air plasma, causes the thermalization. In effect, heavy particle and heat transport and thermal chemistry govern electron dynamics, a conclusion that provides a basis for ab initio prediction of power concentration in plasma reactors.
U2 - 10.1021/acs.jpclett.1c03731
DO - 10.1021/acs.jpclett.1c03731
M3 - Article
C2 - 35089038
SN - 1948-7185
VL - 13
SP - 1203
EP - 1208
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 5
ER -