Vapor-Depositing Single-Atom Iron Catalysts on Porous Carbon Nanosheets for Enhanced Oxygen Reduction

Single-atom Fe catalysts (Fe-SACs) are recognized as the effective alternative to platinum-based counterparts for the oxygen reduction reaction (ORR). Maximizing availability efficiency of active sites is of great significance for Fe-SACs in practical application. Herein, an efficient chemical vapor deposition route is developed to generate Fe-SACs on porous carbon nanosheets for ORR. Metal-organic framework (ZIF-8) is converted into highly porous and N,S-co-doped carbon nanosheets as Fe-SACs support. Ferrocene is sublimated and deposited on carbon nanosheet support to generate isolated single-atomic Fe sites. Spectral and microscopic investigations confirm that Fe elements in Fe-SACs are highly dispersed in carbon support and coordinated asymmetrically with nitrogen and sulfur atoms in Fe-N₃S₁ configuration. The optimized Fe-SACs achieve outstanding alkaline ORR activity with a half-wave potential of 0.91 V vs. RHE. After 10 000 cycles, the half-wave potential only shows 16 mV decays. Furthermore, the rechargeable zinc-air batteries assembled with Fe-SACs as the air electrode can show a peak power density of 213 mW cm^-2 and retain a stable voltage plateau over 10 000 charge-discharge cycles. This work affords an efficient strategy for preparing highly exposed Fe-SACs for energy-related applications.