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

SF6 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 SF6 degradation path in a γ-Al2O3 packed plasma in the presence of H2O or O2.Our experimental results show that both H2O and O2 have a synergetic effect with γ-Al2O3 packing on promoting SF6 degradation, leading to higher stable gas yields than typical spark or corona discharges.H2O or O2 addition promotes SO2 or SO2F2 selectivity, respectively.Density functional theory (DFT) calculations reveal that SO2 generation corresponding with the highest activation barrier is the most critical step toward SF6 degradation.Radicals like H and O generated from H2O or O2 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 SF6 degradation mechanism especially in packed-bed plasma systems.