Streamer-Based Discharge on Water–Air Interface as a Source of Plasma-Activated Water: Conceptual Design and Basic Performance

Here we propose a geometrical analogue of a surface coplanar DBD electrode system allowing the generation of multiple filamentary discharges expanding along the surface of a thin water layer in a flow-through type reactor. A stable layer of deionized/tap water is maintained by a constant flow and separates active discharge filaments from the submerged metal electrodes. Discharges are produced by the application of periodic bipolar high-voltage pulses with a repetition frequency of tens of hertz and lasting a few microseconds. The duration of the high-voltage pulses combined with the non-zero water conductivity allows a partial transition of the initial cold streamer phase to the hot spark phase. Plasma-induced optical emission analysis showed significant heating of the developed filaments (850 K) and increased electron number density (4·10 17 cm −3 ), proving the streamer to spark transition. The analysis of the dissolved products of the discharges showed the maximum NO 2 − and H 2 O 2 production yields of 35 and 30 mmol·kWh −1 , respectively. The current conceptual design is easily scalable by adding pairs of high voltage and grounded compartments with additional water inlets/outlets or by extending the length of the blade separating two adjacent compartments.