Fe/N/C Catalysts with Hierarchical Porous Structure Derived from Fe-doped ZIF-8 for Accelerated ORR Activity

Fe-N-C is considered to be the most promising candidate for catalyzing oxygen reduction reaction (ORR), and its large-scale development is crucial to reducing the cost of proton exchange membrane fuel cells (PEMFCs). However, its simple and efficient synthesis still faces great challenges, and the microstructure changes in the pyrolysis process are not clear. Herein, we report a high-performance Fe-N-C catalyst, which is produced from the high temperature pyrolysis of Fe-doped ZIF-8 precursor. The effect of pyrolysis temperature on the specific surface area, porous structure and graphitization level of Fe-N-C catalyst is systematically studied. Eminently, Fe-N-C 1000, which was obtained via pyrolysis of Fe-ZIF-8 at 1000 °C, possesses highly dispersed Fe-N ₄ active sites on the high surface area polyhedral, ensuring the high intrinsic activity. The simultaneous hierarchically ordered porous architecture provides a wealth of mass transfer channels to improve dynamic performance. It exhibits an outstanding ORR activity in acidic solution (E _1/2 of 0.791 V). High graphitization also enhances its corrosion resistance, showing superior stability (only change 20 mV after 5000 cycles in 0.5M H ₂ SO ₄ ). This work well demonstrates the importance of establishing the structural equilibrium of the catalyst under pyrolysis conditions for efficient ORR.