Tuning of conversion and optical emission by electron temperature in inductively coupled CO2 plasma

This paper focuses on how the electron temperature and other plasma properties affect optical emission and CO2 conversion in CO2 plasma. Such plasma-mediated reactions can enable efficient CO2 reuse. We study CO2 and CO plasmas generated by inductively coupled radiofrequency power (30–300 W) at low pressures (6–400 Pa). By varying the argon admixture, we can study the effect of the electron temperature, Te, on the conversion and emission properties using optical emission spectroscopy, mass spectrometry, and electrical probe measurements. Importantly, we can observe several parameters simultaneously: Te, CO2 conversion, chemiluminescence from CO2, and dissociation products and optical emission from several atomic and CO transitions and from the C2 Swan system. On the basis of these results, we establish a correlation between Te, the CO2 conversion, and the optical emission spectra. A low Te enhances CO2 conversion and Swan band emission. In contrast with published studies, our results show that the CO2 and C2 vibrations are not in local equilibrium. This means that the vibrational temperatures of CO2 and C2 should differ.