What Is the Rate-Limiting Step of Oxygen Reduction Reaction on Fe–N–C Catalysts?

• DOI: 10.1021/jacs.3c09193
• Publication Date: 2023-11-13T17:10:29Z
• Authors: Saerom Yu; Zachary Levell; Zhou Jiang; Xunhua Zhao; Yuanyue Liu
• Keywords: Rate-determining step; Limiting

Oxygen reduction reaction (ORR) is essential to various renewable energy technologies. An important catalyst for ORR single iron atoms embedded in nitrogen-doped graphene (Fe-N-C). However, the rate-limiting step of on Fe-N-C unknown, significantly impeding understanding and improvement. Here, we report activation energies all steps, calculated by ab initio molecular dynamics simulations under constant electrode potential. In contrast common belief that a hydrogenation limits rate, find oxygen molecule replacing adsorbed water Fe. This occurs through concerted motion H2O desorption O2 adsorption, without leaving site bare. Interestingly, despite being an apparent "thermal" process often considered be potential-independent, barrier reduces with can explained stronger Fe-O2 binding weaker Fe-H2O at lower potential, due gaining electrons donating catalyst. Our study offers new insights into highlights importance kinetic studies heterogeneous electrochemistry.