Self-Doped Sulfur Enhanced the Activity of Fe-N for Oxygen Reduction Reaction

Abstract

The oxygen reduction reaction (ORR) is an important electrochemical reaction for fuel cells and metal-air batteries. A highly-active and stable electrocatalyst is required to improve the sluggish kinetics of the ORR. In this work, a novel electrocatalyst with Fe atoms coordinated on a N-doped carbon support was designed using biowaste (peanut shells) as the source of carbon, sulfur, and nitrogen. Moreover, by controlling the electron-donating/withdrawing properties of the carbon skeleton, an instinctive design strategy that combines sulfur functionalities was used to modify and boost the catalytic activity of Fe-N active sites. The synthesized Fe-N/S-C catalyst exhibited excellent ORR performance, with a half-wave potential of 0.87 V vs RHE, a limiting current density of 5.21 mA cm−2, and an onset potential of 1.13 V in 0.1 M KOH solution. Additionally, this peanut shell-derived Fe-N/S-C catalyst was applied in a zinc-air battery (ZAB) as an air cathode, which displayed a power density of 190 mW cm−2.