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.