121st General Meeting of the KCS

Type Symposium
Area Recent Trends in Electrocatalyst
Room No. Room 202A
Time THU 16:55-:
Code ELEC1-4
Subject Stability of Fe-N-C catalysts during oxygen reduction
Authors Chang Hyuck Choi
School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Korea
Abstract For catalyzing dioxygen reduction, iron-nitrogen-carbon materials are today the best candidates to replace platinum in proton-exchange membrane fuel cell cathodes. Despite tremendous progress in their activity and site-structure understanding, improved durability is critically needed but challenged by insufficient understanding of their degradation mechanisms during operation. Hydrogen peroxide, a byproduct of the oxygen reduction, severely impairs fuel cell materials, and iron-based catalysts in particular. We reveal that exposure to hydrogen peroxide leaves iron-based catalytic sites untouched but decreases their turnover frequency for oxygen reduction via surface oxidation of carbon, leading to disrupted π-electron network and decreased oxophilicity of iron-based sites. Their turnover frequency is recovered upon electrochemical reduction of the carbon surface, demonstrating the proposed deactivation mechanism. Observed in acidic and alkaline electrolytes, these insights suggest that durable iron-nitrogen-carbon catalysts are within reach if strategies minimizing the amount of hydrogen peroxide or reactive oxygen species produced during oxygen reduction are developed.
E-mail chchoi@gist.ac.kr