Efficient atomically dispersed Fe catalysts with robust three-phase interface for stable seawater-based zinc-air batteries

The use of seawater-based electrolytes in zinc-air batteries (S-ZABs) presents significant economic and social benefits and mitigates the demand for scarce freshwater resources. However, it is challenging to achieve a metal–nitrogen–carbon (M–N–C) catalyst that exhibits high resistance to corrosive Cl – in seawater-based electrolytes and possesses a strengthened binding affinity with O 2 , which enables catalysts with an optimized oxygen reduction reaction (ORR) and enhances the applicability of S-ZABs. Herein, we propose a combined wet chemistry-pyrolysis strategy to obtain atomically dispersed Fe-decorated nitrogen-doped mesoporous carbon spheres (N-MCS-Fe-900). Benefiting from the capacity of the Fe decorations to form the edge-hosted aerophilic FeN 4 -O 2 sites at the optimized three-phase interface, N-MCS-Fe-900 affords the enhanced resistance of the active Fe sites to corrosive Cl – , as well as improved interaction with O 2 , thereby facilitating the ORR process. As expected, the N-MCS-Fe-900 delivers high half wave potential of 0.90 V and kinetic current density of 18.61 mA cm −2 at 0.85 V in seawater-based 0.1 M KOH. More importantly, the S-ZABs equipped with N-MCS-Fe-900 exhibited long-term stability under a high current density for over 140 h without voltage decay. Theoretical calculations and electrochemical performance evaluations collectively revealed the superior catalytic efficacy and genesis of this activity in N-MCS-Fe-900, which features edge-hosted FeN 4 -O 2 sites at the stable three-phase interface in seawater electrolytes. This study provides new insights for the advancement of ORR catalysts in sustainable energy conversion technologies for seawater-based electrolytes. This work proposes a strategy to construct the edge-hosted aerophilic FeN 4 -O 2 sites at the optimized three-phase interface, N-MCS-Fe-900 affords the enhanced resistance of the active Fe sites to corrosive Cl - , as well as improved interaction with O 2 , thereby facilitating the ORR process and hitting the spot of long-term stability under high current density over 140 h for seawater-based ZABs.