A plasma-catalytic system with MgO/NiO/Ni cathode for SF6 degradation

Abstract

In this work, a plasma-catalytic system in DC discharge with MgO/NiO/Ni (MNN) cathode is proposed for the degradation of SF6 greenhouse gas. The discharge power with MNN cathode is significantly increased compared with Ni cathode due to its good electron emission characteristics, and an effective and stable SF6 degradation performance is achieved in this multi-needle plate discharge system. Besides, surface discharge occurs on the MNN cathode in addition to the needle tips, which is believed to be conducive to the catalytic decomposition of SF6 on the MgO surface. Nontoxic products of MgF2 and MgSO4 are detected on the MgO layer after discharge from various characterizations (XRD, XPS, FTIR and Raman, etc.), suggesting that there is a series of catalytic reactions between SF6/intermediates and MgO. The addition of appropriate O2 (O2:SF6 = 1:1) in the background is not only conducive to the defluorination decomposition of SF6 in ionization region, but also O atom generated from O2 discharge promotes the formation of MgF2 and MgSO4, thus resulting in an effective SF6 degradation performance. Then, the possible degradation mechanism of SF6 in gas phase and on the MgO layer is discussed and the possible degradation pathways are proposed. This research first demonstrates the effectiveness of enabling degrading SF6 gases in a plasma-catalytic system with MNN cathode.