Generation Pathway of Hydroxyl Radical in Fe/N/C-Based Oxygen Reduction Electrocatalysts under Acidic Media

The identification of the generation pathway of ^•OH radical during the oxygen reduction reaction (ORR) is critical because it determines which strategy should be adopted to minimize these corrosive species. In this way, researchers can develop a more stable Fe/N/C ORR catalyst or a catalyst layer in the proton exchange membrane fuel cells (PEMFCs). To date, this critical problem has still been unresolved. Herein, the generation of the ^•OH radical during the acidic ORR was mimicked by using two known pathways, that is, the Fenton (and Fenton-like) and the electrochemical reduction of H₂O₂(H₂O₂-ECR) process. The latter was determined as the main generation pathway of ^•OH radical below 30 °C. As the temperature surpassed 30 °C, the H₂O₂-ECR process began to lose its dominance because of the appearance of a third so-far unknown generation pathway. This work lays a basis for future development of radical elimination strategies to stabilize a Fe/N/C ORR catalyst or a catalyst layer in PEMFCs.