Characterization of a capillary plasma reactor for carbon dioxide decomposition

The decomposition of carbon dioxide in a plasma reactor was investigated experimentally, using capillary discharge tubes with a diameter of 0.5 or 3.0 mm and a length of 25, 50, 75, 100 or 150 mm. The chemical composition of the reaction products and the current–voltage characteristics were measured over a pressure range of 3.33–120 Torr, and the CO2 conversion rates and reduced electric fields were calculated. The results show that the influence of downscaling on the reduced electric fields can be well evaluated by adjusting both the current density, i, and the products of the pressure and the tube diameter, pd. However, the characteristics of CO2 decomposition cannot be determined based on i and pd; they are better characterized by i and p. It can be deduced from our experimental results that the CO2 conversion rate is predominated by the electron impact CO2 dissociation and gas phase reverse reactions even in a capillary plasma reactor.