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

• The discharge form changes and the discharge power is improved by MgO/NiO/Ni cathode. • MgF 2 and MgSO 4 are detected on MgO layer after discharge, which promotes the decomposition of SF 6 . • Reaction process in gas phase and the catalytic process on MgO surface are discussed. • The possible degradation pathways of SF 6 are determined. In this work, a plasma-catalytic system in DC discharge with MgO/NiO/Ni (MNN) cathode is proposed for the degradation of SF 6 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 SF 6 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 SF 6 on the MgO surface. Nontoxic products of MgF 2 and MgSO 4 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 SF 6 /intermediates and MgO. The addition of appropriate O 2 (O 2 :SF 6 = 1:1) in the background is not only conducive to the defluorination decomposition of SF 6 in ionization region, but also O atom generated from O 2 discharge promotes the formation of MgF 2 and MgSO 4 , thus resulting in an effective SF 6 degradation performance. Then, the possible degradation mechanism of SF 6 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 SF 6 gases in a plasma-catalytic system with MNN cathode.