Mechanistic insights into ultraviolet cathode photoemission-mediated enhancement of atmospheric pressure nanosecond pulsed streamer discharge

Abstract This work presents a novel approach to enhance the discharge intensity and plasma-chemical reactivity of nanosecond pulsed streamer discharge through ultraviolet (UV)-induced cathode photoemission pre-ionization in atmospheric pressure air. The photoemission efficiency of three cathode materials—zinc (Zn), graphite, and stainless steel (SS)—was systematically quantified, revealing a clear hierarchy of Zn > graphite > SS. The work function was identified as the primary factor governing electron emission efficiency, while surface microstructure and UV absorption characteristics were found to further modulate the photoemission dynamics. By establishing the correlation between cathode photoemission efficiency and discharge behavior, cathode photoemission is confirmed as the primary mechanism in discharge enhancement. The electron density multiplication driven by the electron avalanche is amplified by this process, resulting in a significant reduction in breakdown voltage thresholds, an enhancement in discharge intensity, and a prolongation of the discharge duration. Among the tested cathodes, the most pronounced enhancement effects were exhibited by Zn, with a 5.06 A increase in discharge current and an approximately 88.2% improvement in discharge energy, followed by graphite cathodes, while SS cathodes have the weakest effect. Notably, the generation of reactive species is facilitated by this enhanced discharge regime, with the presence of O (3 p 5 P) in atmospheric pressure air, a species that remains undetectable under conventional pulsed discharge conditions.