Rotating ring-disk electrode method to evaluate performance of electrocatalysts in hydrogen peroxide activation via rapid detection of hydroxyl radicals

One-electron electrochemical reduction of hydrogen peroxide (H₂O₂) is an effective way to produce hydroxyl radical (•OH), whose yield is greatly dependent on the performance (activity and selectivity) of electrocatalysts. However, the current method to evaluate the performance of electrocatalysts is limited by time-consuming and less sensitive method of •OH detection. Herein, we propose an online rotating ring disk electrode (RRDE) method to evaluate the performance of electrocatalysts in H₂O₂ activation by rapidly detecting •OH. This method is implemented by determining the current signals on the disk and ring electrodes: the generated •OH from H₂O₂ reduction on the disk electrode (induce negative disk currents) reacts with H₂O₂ to produce superoxide radical (O₂^•−), which migrates to and is oxidized on the ring electrode and generates positive ring currents. The relevance of the ring currents to O₂^•− and •OH is proved by radical quenching tests and kinetic analysis. The performance of five electrocatalysts were evaluated by both the RRDE method and the terephthalic acid (TPA) fluorescence method, and the consistent results verify the applicability of the RRDE method. Hence, this work facilitates the development of high-performance electrocatalysts for H₂O₂ activation and bring insights for RRDE-based electroanalytic chemistry.