Scalable and Printable Three-Phase Ion Gel Electrocatalyst Device

Abstract

Scalable electrocatalyst systems that are mechanically robust, thermally stable, and compatible with large-area manufacturing are critical for advancing next-generation electrochemical technologies. Here, we present an ion gel-based electrocatalyst device platform capable of stable operation at elevated temperatures beyond the practical limits of many conventional polymer electrolyte systems. The device consists of a polybenzimidazole (PBI)- and 1-hexyl-3-methylimidazolium trifluoromethanesulfonate ([HMIM][OTf])-based ion gel integrated with Au electrodes and graphene- or carbon nanotube-supported Pt catalyst layers, demonstrating compatibility with scalable and solution-processable fabrication methods. Thermogravimetric analysis and infrared spectroscopy confirmed thermal stability beyond 200 °C without significant structural degradation. To demonstrate electrocatalytic operation at elevated temperature, formic acid electrocatalytic decomposition was investigated using formic acid electrooxidation and hydrogen evolution as the half-cell reactions. Under continuous 4 mol % formic acid gas flow at temperatures near 100 °C, the devices sustained stable steady-state electrocatalysis over multiday operation without observable ion gel degradation or device failure. Kinetic analysis revealed that open-circuit behavior differs substantially from conventional gas-phase thermocatalytic formic acid decomposition on Pt, whereas closed-circuit operation followed the expected kinetic trends for Au-limited formic acid electrooxidation suggesting that the observed rates were not governed solely by mass transport. These results demonstrate that ion gel-based electrocatalyst devices provide a thermally durable and manufacturing-compatible platform for elevated-temperature electrochemical applications.