Gas heating and plasma chemistry in low-pressure CO2 plasmas

Abstract

We develop a self-consistent kinetic model to simulate the evolution of species and energy transfers in low-pressure CO₂ plasmas. This model couples the electron, vibrational and chemical kinetics with the gas thermal balance equation, providing a comprehensive framework for understanding CO₂ plasmas. The kinetic model is thoroughly benchmarked and validated by comparison its predictions with reported simulation and experimental data on CO₂ DC glow discharges, operating at pressures 1–5 Torr, discharge currents of tenths of mA, and tube radius of 1 cm. The results show that the energy released from electronic and vibrational excitation of CO₂ dominates the gas heating at the early stage of the discharge. However, as the discharge progresses and reaches steady-state, following CO₂ dissociation, the de-excitation of electronically excited states of the products and the vibrational-translational exchanges of the CO vibrational state significantly contributes to the gas heating. Additionally, the quenching of excited states at the wall is both a major destruction pathway for these species and a contributor to the gas heating. This study provides a comprehensive perspective to the microscopic reactions and macroscopic parameters in CO₂ plasmas, which can inform optimization strategies for industrial applications.