Solvent-Free Surface Engineering of Gas Diffusion Electrodes via Initiated Chemical Vapor Deposition for Durable...

Gas diffusion electrodes (GDEs) in rechargeable zinc-air (Zn-air) batteries often suffer from catalyst dissolution, electrolyte flooding, and degradation of the gas-liquid interface, which severely limit long-term cycling stability. Here, we report a solvent-free surface-engineering strategy based on initiated chemical vapor deposition (iCVD) to construct a dual-functional interfacial architecture within the GDE. A hydrophilic poly-(glycidyl methacrylate) (poly-(GMA)) interlayer was conformally deposited at the electrolyte interface to enhance electrolyte uptake and ionic transport, while a hydrophobic poly-(2-(perfluorohexyl)-ethyl acrylate) (poly-(PFHEA)) layer was introduced on the air side to preserve gas permeability. The optimized poly-(GMA) coating exhibited high electrolyte uptake (291 ± 8%) and enhanced ionic conductivity (1.61 mS cm^-1), more than doubling that of the unmodified substrate. Incorporation of this interlayer within the GDE architecture reduced ohmic resistance and improved interfacial stability and transport characteristics, resulting in enhanced practical electrode performance. When integrated into Zn-air batteries, the modified electrode delivered a reduced charge-discharge voltage gap (0.734 V) and a round-trip efficiency of 60.3%. These findings demonstrate that vapor-phase polymer deposition provides a scalable route to engineer functional interfaces in GDEs, enabling improved stability and electrochemical efficiency in rechargeable Zn-air batteries. This work provides mechanistic insights into how vapor-deposited interfacial layers regulate ion transport and suppress catalyst degradation in gas diffusion electrodes.