Investigating the Mechanism and Intermediates of the Oxygen Reduction Reaction

Abstract The Oxygen Reduction Reaction (ORR) plays a crucial role in corrosion mechanisms and the operation of electrochemical energy devices, affecting both stability and efficiency. Despite extensive research, the exact mechanisms and intermediates involved in ORR continue to be subjects of study. The literature reports a range of intermediates and mechanisms, which can be complex and, at times, contradictory. This paper conducts a comprehensive literature review with a primary focus on ORR mechanisms on steel, while also examining platinum, gold, and carbon electrodes. Recent advancements in experimental techniques and theoretical modeling have improved our understanding of ORR, which is essential for corrosion science and energy conversion technologies. This review compiles and analyzes the existing literature on the ORR, focusing on its behavior across different electrodes, including platinum, gold and steel/iron. The study identifies key intermediates such as HO2-, O2-, H2O2, OOH, and OH through electrochemical measurements and in situ spectroscopic methods, mapping their formation and consumption. Understanding these ORR pathways and their interactions with other corrosion processes contributes to the refinement of predictive corrosion models.