Deep Oxidation of NO by a Hybrid System of Plasma–N-Type Semiconductors: High-Energy Electron-Activated “Pseudo Photocatalysis” Behavior

A “pseudo photocatalysis” process, being initiated between plasma and N-type semiconductors in the absence of light, was investigated for NO removal for the first time via dynamic probing of reaction processes by FT-IR spectra. It was demonstrated that N-type semiconductor catalysts could be activated to produce electron–hole (e––h+) pairs by the collision of high-energy electrons (e*) from plasma. Due to the synergy of plasma and N-type semiconductors, major changes were noted in the conversion pathways and products. NO can be directly converted to NO2– and NO3– instead of toxic NO2, owing to the formation of O2– and ·OH present in catalysts. New species like O3 or ·O may be generated from the interaction between catalyst-induced species and radicals in plasma at a higher SIE, leading to deep oxidation of existing NO2 to N2O5. Experiments with added trapping agents confirmed the contribution of e– and h+ from catalysts. A series of possible reactions were proposed to describe reaction pathways and the mechanism of this synergistic effect. We established a novel system and realized an e*-activated “pseudo photocatalysis” behavior, facilitating the deep degradation of NO. We expect that this new strategy would provide a new idea for in-depth analysis of plasma-activated catalysis phenomenon.