CO₂ conversion by plasma technology: Insights from modeling the plasma chemistry and plasma reactor design

In recent years there has been growing interest in the use of plasma technology for CO₂ conversion. To improve this application, a good insight into the underlying mechanisms is of great importance. This can be obtained from modeling the detailed plasma chemistry in order to understand the chemical reaction pathways leading to CO₂ conversion (either in pure form or mixed with another gas). Moreover, in practice, several plasma reactor types are being investigated for CO₂ conversion, so in addition it is essential to be able to model these reactor geometries so that their design can be improved, and the most energy efficient CO₂ conversion can be achieved. Modeling the detailed plasma chemistry of CO₂ conversion in complex reactors is, however, very time-consuming. This problem can be overcome by using a combination of two different types of model: 0D chemical reaction kinetics models are very suitable for describing the detailed plasma chemistry, while the characteristic features of different reactor geometries can be studied by 2D or 3D fluid models. In the first instance the latter can be developed in argon or helium with a simple chemistry to limit the calculation time; however, the ultimate aim is to implement the more complex CO₂ chemistry in these models. In the present paper, examples will be given of both the 0D plasma chemistry models and the 2D and 3D fluid models for the most common plasma reactors used for CO₂ conversion in order to emphasize the complementarity of both approaches. Furthermore, based on the modeling insights, the paper discusses the possibilities and limitations of plasma-based CO₂ conversion in different types of plasma reactors, as well as what is needed to make further progress in this field.