Interfacial enhancement of O∗ protonation on Fe2N/Fe3C nanoparticles to boost oxygen reduction reaction and the fuel cell in acidic electrolyte

Abstract

Understanding the origin of high activity of Fe–N–C electrocatalysts in oxygen reduction reaction (ORR) is critical but still challenging for developing efficient non-precious metal catalysts in fuel cells and metal-air batteries. Herein, we developed Fe-based ORR catalysts containing highly dispersed interfaces of Fe2N/Fe3C and revealed the origin of its activity by intensively investigating the structure of the catalysts and their correlations with the electrochemical performance. It was found that the Fe2N/Fe3C with a well-matched interface displays a half-wave potential of 0.764 V (vs. RHE) and high current density in acidic electrolytes. In addition, the H2–O2 fuel cell assembled using Fe2N/Fe3C as the cathode exhibits excellent performance with a peak power density of 713 mW/cm−1. The experimental and computational results reveal that the interface of the Fe2N/Fe3C heterojunction is essential for the ORR in acidic electrolytes because it provides a remarkable decrease in the maximum free energy change of O∗ protonation to OH∗.