The effect of H2O on the vibrational populations of CO2 in a CO2/H2O microwave plasma: a kinetic modelling investigation

Abstract Plasma has been studied for several years to convert CO 2 into value-added products. If CO 2 could be converted in the presence of H 2 O as a cheap H-source for making syngas and oxygenates, it would mimic natural photosynthesis. However, CO 2 /H 2 O plasmas have not yet been extensively studied, not by experiments, and certainly not computationally. Therefore, we present here a kinetic modelling study to obtain a greater understanding of the vibrational kinetics of a CO 2 /H 2 O microwave plasma. For this purpose, we first created an electron impact cross section set for H 2 O, using a swarm-derived method. We added the new cross section set and CO 2 /H 2 O-related chemistry to a pure CO 2 model. While it was expected that H 2 O addition mainly causes quenching of the CO 2 asymmetric mode vibrational levels due to the additional CO 2 /H 2 O vibrational-translational relaxation, our model shows that the modifications in the vibrational kinetics are mainly induced by the strong electron dissociative attachment to H 2 O molecules, causing a reduction in electron density, and the corresponding changes in the input of energy into the CO 2 vibrational levels by electron impact processes.