Investigation of Pulse Parameters on CO2 Splitting to O2 by Dielectric Barrier Discharge Plasma at 1kPa

The low-pressure atmosphere on Mars, rich in CO 2 (~95%), makes the in-situ resource utilization of Martian CO 2 and the improvement of oxidation attract widespread attention. It contributes to the construction of Mars base and support the deep space exploration. In this paper, the repetitive microsecond pulse voltage was used to drive dielectric barrier discharge (DBD) cell. Combined with 1D simulation model and experiment, the effects of electrical parameters (pulse width and pulse rising/falling edge) on CO 2 conversion to O 2 and discharge mechanism under low pressure were studied. The conditions we set are shown as follows: the gap width d is 4mm, the pulse voltage u is 1000V with the frequency of 100kHz, pressure p is 1kPa. The changing electrical parameters are the pulse rising edge (200ns~1000ns) and pulse width (1.5μs~4.5μs). The results show that the discharge mode is glow discharge with obvious cathode fall region, negative glow space and positive column. There are four stages in a single discharge cycle, each stage has different effects on the product. The density of O 2 increases step-like in positive discharge extinction stage, and keeps stable in positive discharge, negative discharge and negative discharge extinction stages. The production of O 2 mainly depends on the recombination reaction of lower energy electrons and CO 2 + (over 95% contribution in a cycle), whose rate can reach the order of 10 -2 mol•m -3 •s -1 . And the electron impact dissociation is dominant in the O 2 consumption pathway. The increase of pulse width is beneficial to the O 2 production, however, it should be noted that the lifetime of electron-ion recombination reaction is less than 15μs. CO 2 + is mainly generated in the positive and negative discharge stages, and the peak reaction rate of collision ionization reaction between higher energy electrons and CO 2 ground state molecules can reach the order of 10 0 mol•m -3 •s -1 . The ion consumption path is mainly in the positive discharge extinction stage: a). CO and O are formed by recombination with electrons, b). C and O 2 are formed by recombination with electrons. By reducing the rising edge and falling edge, the positive and negative discharge is more intense and more electrons with higher energy are generated, which is conducive to CO 2 + generation.