Investigation on Degradation Path of SF6 in Packed-Bed Plasma: Effect of Plasma-generated Radicals

SF
6
degradation mechanism in non-thermal plasma (NTP) systems is not fully understood due to the formation of a complex physico-chemical reaction network, especially when reactive gases and packing materials are involved. In this work, we conduct a combined experimental and theoretical study to unravel the SF
6
degradation path in a γ-Al
2
O
3
packed plasma in the presence of H
2
O or O
2
. Our experimental results show that both H
2
O and O
2
have a synergetic effect with γ-A1
2
O
3
packing on promoting SF
6
degradation, leading to higher stable gas yields than typical spark or corona discharges. HO or O
2
addition promotes SO
2
or SO
2
F
2
selectivity, respectively. Density functional theory (DFT) calculations reveal that SO
2
generation corresponding with the highest activation barrier is the most critical step toward SF
6
degradation. Radicals like H and O generated from H
2
O or O
2
discharge can significantly promote the degradation process via Eley-Rideal mechanism, affecting key reactions of stable product generation, advancing degradation efficiency. The results of this work could provide insights on further understanding SF
6
degradation mechanism especially in packed-bed plasma systems.