CO2 Decomposition in CO2 and CO2/H2 Spark‐like Plasma Discharges at Atmospheric Pressure

Abstract In this work, a spark‐like plasma discharge is ignited in pure CO 2 and in CO 2 /H 2 mixtures to investigate CO formation. Power pulsing is used to limit arc formation to sustain a high current transient “spark‐like” plasma consisting of a mixed mode discharge comprising an initial current pulse (“spark”) followed by a longer‐lived glow mode thorough each half cycle of the applied voltage. In pure CO 2 , the efficiency ranged between 20–50 % for CO 2 conversions between 9–18 % for gas residence times of 100–600 ms. Adding H 2 as a co‐reactant was investigated for a wide range of mixture ratios. The outlet gas was found to produce O 2 ‐free mixtures of CO/H 2 /CO 2 . Conversion rates in CO 2 /H 2 mixtures are found to be similar to pure CO 2 at equivalent residence times. The primary role of H 2 as a co‐reactant is therefore found to be the removal of O 2 formed during dissociation of CO 2 . The energy cost of this dilution resulted in reduced efficiency for CO 2 conversion (from 41 to 18 %), which is correlated to the efficiency drop found for pure CO 2 conversion at lower flows. Opportunities for optimising this small volume “unit‐cell” spark reactor are encouraged by the results presented. This approach could enable deployment of serial or parallel combinations of such reactors capable of dealing cost‐effectively with the conversion of the larger CO 2 and CO 2 /H 2 volumes required in future industry applications.