The ORR mechanism generally follows two main pathways: the direct four-electron pathway and the two-step two-electron pathway. In the four-electron pathway, Oâ is directly reduced to HâO. In the two-electron pathway, Oâ is first reduced to HâOâ, which is then further reduced to HâO. The four-electron pathway is preferred for fuel cells due to its higher efficiency and avoidance of HâOâ, which can degrade fuel cell components.
