How important is reactor design for CO2 conversion in warm plasmas?

In this work, we evaluated several new electrode configurations for CO2 conversion in a gliding arc plasmatron (GAP) reactor. Although the reactor design influences the performance, the best results give only slightly higher CO2 conversion than the basic GAP reactor design, which indicates that this reactor may have reached its performance limits. Moreover, we compared our results to those of four completely different plasma reactors, also operating at atmospheric pressure and with contact between the plasma and the electrodes. Surprisingly, the performance of all these warm plasmas is very similar (CO2 conversion around 10 % for an energy efficiency around 30 %). In view of these apparent performance limits regarding the reactor design, we believe further improvements should focus on other aspects, such as the post-plasma-region where the implementation of nozzles or a carbon bed are promising. We summarize the performance of our GAP reactor by comparing the energy efficiency and CO2 conversion for all different plasma reactors reported in literature. We can conclude that the GAP is not the best plasma reactor, but its operation at atmospheric pressure makes it appealing for industrial application. We believe that future efforts should focus on process design, techno-economic assessments and large-scale demonstrations: these will be crucial to assess the real industrial potential of this warm plasma technology.