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

• RRDE was established as an online method to evaluate electrocatalyst performance. • Electrocatalysts active H 2 O 2 to produce •OH and subsequently generate O 2 •− . • Anodic currents on ring electrode due to O 2 •− oxidation were measured. • The RRDE method is verified by terephthalic acid fluorescence detection. One-electron electrochemical reduction of hydrogen peroxide (H 2 O 2 ) 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 H 2 O 2 activation by rapidly detecting •OH. This method is implemented by determining the current signals on the disk and ring electrodes: the generated •OH from H 2 O 2 reduction on the disk electrode (induce negative disk currents) reacts with H 2 O 2 to produce superoxide radical (O 2 •− ), which migrates to and is oxidized on the ring electrode and generates positive ring currents. The relevance of the ring currents to O 2 •− 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 H 2 O 2 activation and bring insights for RRDE-based electroanalytic chemistry.