Gliding arc plasma for CO₂ conversion: Better insights by a combined experimental and modelling approach

A gliding arc plasma is a potential way to convert CO₂ into CO and O₂, due to its non-equilibrium character, but little is known about the underlying mechanisms. In this paper, a self-consistent two-dimensional (2D) gliding arc model is developed, with a detailed non-equilibrium CO₂ plasma chemistry, and validated with experiments. Our calculated values of the electron number density in the plasma, the CO₂ conversion and energy efficiency show reasonable agreement with the experiments, indicating that the model can provide a realistic picture of the plasma chemistry. Comparison of the results with classical thermal conversion, as well as other plasma-based technologies for CO₂ conversion reported in literature, demonstrates the non-equilibrium character of the gliding arc, and indicates that the gliding arc is a promising plasma reactor for CO₂ conversion. However, some process modifications should be exploited to further improve its performance. As the model provides a realistic picture of the plasma behaviour, we use it first to investigate the plasma characteristics in a whole gliding arc cycle, which is necessary to understand the underlying mechanisms. Subsequently, we perform a chemical kinetics analysis, to investigate the different pathways for CO₂ loss and formation. Based on the revealed discharge properties and the underlying CO₂ plasma chemistry, the model allows us to propose solutions on how to further improve the CO₂ conversion and energy efficiency by a gliding arc plasma.