Iron redox behavior and oxygen reduction activity of Fe-N-C electrocatalysts in different electrolytes. (1st March 2023)

• Record Type: Journal Article
• Authors: Wang, Xiaoping; Ferrandon, Magali; Park, Jae Hyung; Shen, Jing-Jing; Kropf, A. Jeremy; Zhang, Hanguang; Zelenay, Piotr; Myers, Deborah J.
• Is Part Of: Electrochimica acta. Volume 443(2023)
• Publication Date: 2023-03-01
• Subjects: Polymer electrolyte fuel cells -- PGM-free Fe-N-C electrocatalyst -- ORR activity -- Fe redox couple -- Sulfuric acid electrolyte -- Perchloric acid electrolyte -- Cavity microelectrode; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2023.141934
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: The iron redox behavior and oxygen reduction reaction (ORR) activity of Fe-N-C ORR electrocatalysts synthesized by a variety of techniques were investigated as a function of the identity of the electrolyte anion (bisulfate/sulfate or perchlorate) at a constant pH. In situ X-ray absorption spectroscopy data support the assignment of the redox peaks in the voltammograms to the Fe 3+ /Fe 2+ redox couple. It was found that for a given Fe-N-C catalyst, there is a correlation between the Fe redox couple peak potential and the ORR activity in perchloric acid electrolyte, but not in sulfuric acid electrolyte. While a higher Fe redox couple potential (≥ 110 mV higher) was observed in perchloric acid electrolyte, a higher ORR activity was obtained in sulfuric acid electrolyte. The higher ORR activity observed in sulfuric acid than perchloric acid was correlated with the higher peak current and larger faradaic charge for the Fe redox couple. A study of the Fe redox behavior using a cavity microelectrode, eliminating the impact of ionomer, showed that the interaction of H2 SO4 with Fe-N-C is stronger than that of HClO4 and that Fe redox in both electrolytes is a reversible surface electrochemical reaction.