Improving Fuel Cell Performance of FeN_x-Based Catalysts by Introducing Graphitic Microdomains in the Carbon Matrix

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The activity-stability trade-off limits the widespread use of iron-nitrogen-carbon (Fe-N-C) catalysts in fuel cells.
• Developing non-precious metal (non-PGM) catalysts is crucial for advancing fuel cell technology.

Purpose of the Study:

• To engineer an Fe-N-C catalyst that breaks the activity-stability trade-off.
• To enhance the performance and durability of Fe-N-C catalysts for oxygen reduction reactions in fuel cells.

Main Methods:

• Synthesis of an atomically dispersed Fe-N-C catalyst with graphitic microdomains (FeN_x-Gmd) via Fe₃C-catalyzed graphitization.
• Electrochemical testing of the FeN_x-Gmd as a cathode catalyst in fuel cells.
• Accelerated stability testing (10,000 cycles).
• Theoretical calculations to understand structure-activity relationships.

Main Results:

• FeN_x-Gmd catalysts achieved high peak power densities: 1.06 W cm^-2 (H₂/O₂) and 0.55 W cm^-2 (H₂/air).
• Performance ranks among the top non-PGM catalysts reported.
• High graphitic degree correlates with increased FeN_x site activity and stability.
• Post-stability test, power density remained high (0.79 W cm^-2 in H₂/O₂), demonstrating excellent durability.
• The strategy avoids significantly reducing active S1 sites.

Conclusions:

• The FeN_x-Gmd catalyst effectively breaks the activity-stability trade-off in Fe-N-C catalysts.
• Graphitic microdomains enhance both catalytic activity and corrosion resistance.
• This approach offers a new pathway for developing advanced non-PGM fuel cell catalysts.