Plasma-catalyzed hydrogen peroxide synthesis in an H-type electrochemical cell

Hydrogen peroxide (H₂O₂) is a versatile green oxidant widely used in environmental remediation, disinfection, and chemical processing. Plasma electrochemical synthesis offers a catalyst-free and decentralized route for on-site H₂O₂ production directly from water under ambient conditions. In this study, H₂O₂ generation is investigated in a double-layer H-type plasma electrochemical reactor, with systematic evaluation of discharge current, solution flow rate, temperature, and working gas composition. The H₂O₂ concentration increases linearly with increasing discharge current, while competing plasma reactions cause limited electron utilization efficiency. Lower solution flow rates favor higher product accumulation, while elevated temperatures enhance decomposition under circulation conditions. Gas composition plays a decisive role: Ar plasma produces higher H₂O₂ yields than O₂ or N₂, whereas air significantly suppresses H₂O₂ formation due to nitrite-mediated consumption pathways. An optimized Ar/O₂ mixture (54/6 standard cubic centimeters per minute (sccm)) enables enhanced performance, achieving a maximum H₂O₂ concentration of 120 mM (M = mol/L) after 4 h of plasma operation. Although this represents significant progress, a substantial gap remains toward practically usable H₂O₂ concentrations, highlighting the need for further reactor and energy-efficiency optimization.