Probing time-resolved plasma-driven solution electrochemistry in a falling liquid film plasma reactor: Identification of HO2− as a plasma-derived reducing agent.

This article focuses on the investigation of plasma–liquid interfacial chemistry using a novel falling liquid film plasma reactor that enables in situ, time-resolved optical absorption measurements of redox reactions and formate decomposition under controlled convective transport conditions. The study reveals that plasma-induced reactions in thin aqueous films depend strongly on film thickness and pH, with high pH favoring reduction processes mediated by long-lived hydroperoxide ions (HO₂⁻) formed from plasma-produced hydrogen peroxide (H₂O₂). Computational analysis supports the role of HO₂⁻ as a significant reducing agent for ferricyanide, explaining observed slow reduction kinetics on millisecond time scales. Overall, the reactor design and combined experimental and theoretical approach provide new insights into plasma-driven solution electrochemistry and near-interfacial reactive species dynamics.