Ultrastable Fe-N-C Fuel Cell Electrocatalysts by Eliminating Non-Coordinating Nitrogen and Regulating Coordination Structures at High Temperatures.

Pyrolyzed Fe-N-C materials have attracted considerable interests as one of the most active noble-metal-free electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Despite significant progress has been made in improving their catalytic activity during past decades, the Fe-N-C catalysts still suffer from fairly poor electrochemical and storage stability, which greatly hurdles their practical application. Here, we develop an effective strategy to greatly improve their catalytic stability in PEMFCs and storage stability by virtue of previously-unexplored high-temperature synthetic chemistry between 1100-1200°C. Pyrolysis at this rarely adopted temperature range not only enables the elimination of less active nitrogen-doped carbon sites that generate detrimental peroxide byproducts but also regulates the coordination structure of Fe-N-C from less stable D1 (O-FeN 4 C 12 ) to a more stable D2 structure (FeN 4 C 10 ). The optimized Fe-N-C catalyst exhibits excellent stability in PEMFCs (> 80% performance retention after 30 hours under H 2 /O 2 condition) and no activity loss after 35-day storage while maintaining a competitive ORR activity and PEMFC performance. This article is protected by copyright. All rights reserved.