Durable and Active Nitrogen‐Coordinated Iron Single‐Atom Catalyst for Proton Exchange Membrane Fuel Cells Through Carbon Encapsulation
Geumbi Na, Wonchan Hwang, Heejong Shin, Subin Park, Ji Eun Park, Jongmin Lee, Yoojin Shin, Hosung Choi, Jaehyuk Shim, Kyungbeen Yeom, Yung‐Eun Sung
Abstract
Abstract Significant advancements in the activity of nitrogen‐coordinated iron single‐atom catalysts (Fe–N–C) have attracted attention as potential alternatives to Pt‐based cathodes in proton exchange membrane fuel cells. However, their limited stability in acidic environments hinders their practical application. Moreover, achieving a synchronous enhancement of both the activity and stability of the Fe sites while preventing demetallation or carbon corrosion remains a formidable challenge. Herein, a synthesis method for Fe–N–C is introduced that exhibits remarkable durability, featuring a protective carbon encapsulation formed by applying an additional heterocyclic organic compound coating. It is demonstrated that stability can be enhanced by converting edge‐rich Fe sites into highly stable FeN 4 moieties through precise control of the robustness and packing density of the carbon encapsulation. Furthermore, electrochemical redox behavior along with in situ spectroscopies and online differential electrochemical mass spectrometry provide insights into the structural characteristics of each Fe site and their stabilities. The accelerated stress testing and a long‐term test (>100 h) exhibit that the robust carbon encapsulation can successfully prevent corrosion of carbon support and ensure durable Fe sites during operation.