Mechanistic study on nonthermal plasma conversion of CO₂

Dimas Adrianto, Zunrong Sheng, Tomohiro Nozaki^*

^* The author to whom correspondence should be addressed.

Department of Mechanical Engineering, Tokyo Institute of Technology, Tokyo, Japan

Abstract

Dielectric barrier discharge (DBD) was generated in a wide range of electric field from 60 to 700 Td by adjusting the operating pressure and the gas gap for the parametric study of electron impact reaction on CO₂ dissociation. Moreover, the effect of specific energy input (SEI) was clarified in terms of CO₂ conversion as well as energy efficiency. The results show that CO₂ conversion efficiency increased at higher pressure, while low-pressure operation showed a negligible effect, indicating that generation of vibrational species followed by vibration-to-vibration (V–V) energy transfer, known as ladder-climbing dissociation mechanism, provides a more efficient pathway than electron impact direct CO₂ dissociation reaction. CO₂ conversion increases linearly with SEI because energy input per molecule increases. However, energy conversion efficiency decreases by SEI, showing a clear trade-off between CO₂ conversion and energy efficiency: such a trade-off relationship is correlated with ladder-climbing dissociation mechanism. Electron impact reaction process was further studied by BOLSIG+, electron Boltzmann equation solver, to gain deep insight into the electronic activation CO₂ in DBD type nonthermal plasma.

Keywords - CO₂ activation, nonthermal plasma, dielectric barrier discharge, vibrational excitation, ladder-climbing dissociation.

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