Delgado Hernan E, Elg Daniel T, Bartels David M, Rumbach Paul, Go David B
Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , Indiana 46556 , United States.
Department of Engineering , University of Southern Indiana , Evansville , Indiana 47712 , United States.
Langmuir. 2020 Feb 11;36(5):1156-1164. doi: 10.1021/acs.langmuir.9b03654. Epub 2020 Jan 29.
When a nonthermal plasma and a liquid form part of the same circuit, the liquid may function as a cathode, in which case electrons are emitted from the liquid into the gas to sustain the plasma. As opposed to solid electrodes, the mechanism of this emission has not been established for a liquid, even though various theories have attempted to explain it via chemical processes in the liquid phase. In this work, we tested the effects of the interfacial chemistry on electron emission from water, including the role of pH as well as the hydroxyl radical, the hydrogen atom, the solvated electron, and the presolvated electron; it was found that none of these species are critical to sustain the plasma. We propose an emission mechanism where electrons, generated from ionized water molecules in the uppermost monolayers of solution, are emitted into the plasma directly from the conduction band of the water.
