SF 6 Degradation in a γ-Al 2 O 3 Packed DBD System: Effects of Hydration, Reactive Gases and Plasma-Induced Surface Charges

Packed-bed DBD (PB-DBD) plasmas hold promise for effective degradation of greenhouse gases like SF 6 . In this work, we conducted a combined experimental and theoretical study to investigate the effect of the packing surface structure and the plasma surface discharge on the SF 6 degradation in a γ-Al 2 O 3 packing DBD system. Experimental results show that both the hydration effect of the surface (upon moisture) and the presence of excessive reactive gases in the plasma can significantly reduce the SF 6 degradation, but they hardly change the discharge behavior. DFT results show that the pre-adsorption of species such as H, OH, H 2 O and O 2 can occupy the active sites (Al III site) which negatively impacts the SF 6 adsorption. H 2 O molecules pre-adsorbed at neighboring sites can promote the activation of SF 6 molecules and lower the reaction barrier for the S-F bond-breaking process. Surface-induced charges and local external electric fields caused by the plasma can both improve the SF 6 adsorption and enhance the elongation of the S-F bonds. Our results indicate that both the surface structure of the packing material and the plasma surface discharge are crucial for SF 6 degradation performance, and the packing beads should be kept dry during the degradation. This work helps to understand the underlying mechanisms of SF 6 degradation in a PB-DBD system.