Ionomers based on protic ionic liquid for proton-coupled electrochemical reactions

초록

This study explores the use of a [DBU][H2SO4], protic ionic liquid (PIL), as a proton-conductive additive in catalyst layers for proton-coupled electrochemical reactions, aiming to complement or partially replace conventional polymeric ionomers such as Nafion, which has raised increasing concern regarding per-and polyfluoroalkyl substances (PFAS). Electrochemical performance was evaluated using a Pt/C catalyst for two representative electrochemical reactions-the toluene hydrogenation and the hydrogen evolution reaction (HER). Three proton-conducting compositions were compared: Nafion only (1:0), a mixture of Nafion and [DBU] [H2SO4] (0.5:0.5), and [DBU][H2SO4] only (0:1). In both reaction systems, electrodes incorporating the mixed ionomer demonstrated reduced overpotentials, attributed to the higher ionic conductivity of [DBU][H2SO4] compared to Nafion. Beyond overpotential reduction, the Nafion-[DBU][H2SO4] blend also improved faradaic efficiency and operational stability, outperforming the Nafion-only and [DBU][H2SO4]-only configurations. These synergistic improvements arise from the combination of the [DBU][H2SO4]'s efficient proton transport with Nafion's mechanical integrity and interfacial adhesion. Importantly, the partial substitution of fluorinated ionomers with non-fluorinated PILs offers a more sustainable approach to ionomer design. The findings highlight the potential of PILs as co-functional additives that simultaneously enhance electrochemical performance and reduce environmental impact in both organic and aqueous systems.

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