Global model of plasma-activated water over long time scale: Pulsed discharge and afterglow

Plasma-activated water (PAW) has been utilised in various application fields, and a deep understanding on the plasma chemistry is the foundation of application-orientated optimisation. In this paper, a global model is built to study the chemical properties of PAW produced by a dielectric barrier discharge that is powered by nanosecond voltage pulses. The applied voltage is firstly repeated with 10 kHz frequency for 100 s, and then shut down for 200 s afterglow, providing a long-term evolution regarding the production and consumption of some typical reactive oxygen/nitrogen species (RONS) in PAW. The calculated results agree principally with experimental measurements from literature. During the pulsed discharge, the water gradually acidises, and the long-lived species accumulate; while in the afterglow, most of the aqueous RONS decay rapidly, except for O-3aq, NO3aq-, H2O2aq and N2Oaq, which might be the main sources to sustain long-term effects. Furthermore, the effects of applied voltage and gap distance on RONS are investigated. Correlation analyses from Pearson correlation coefficient indicate that gaseous RONS are more sensitive to the gap distance, while the aqueous ones are more sensitive to the voltage amplitude, suggesting the possibility to independently regulating the gaseous and aqueous chemistry.