Isolated single iron atoms anchored on a N, S-codoped hierarchically ordered porous carbon framework for highly efficient oxygen reduction

Abstract

Atomically dispersed metal catalysts are promising candidates for the oxygen reduction reaction (ORR) and for achieving efficient energy conversion. However, rational design of single atom catalysts (SACs) with high-efficiency ORR catalytic activity and superior stability is still crucial yet challenging. Herein, an in situ gas-foaming methodology is presented for constructing single Fe atoms dispersed on a N, S-codoped (Fe_SA/NSC) hierarchically ordered porous carbon (HOPC) framework via one-step pyrolysis of dopamine (DA)/Fe³⁺ complexes and thiourea in SBA-15 channels. HOPC structures (facilitating active site access and mass transfer) and optimized FeN₄S₂ catalytic centers make Fe_SA/NSC exhibit high ORR activity with a half-wave potential (E_1/2) of 0.91 V, fuel selectivity and long-term stability (3 mV negative shift after 5000 potential cycles) in 0.1 M KOH. It even shows comparable ORR catalytic activity (E_1/2 = 0.78 V) to the Pt/C catalyst in acidic electrolytes. As the air electrode in zinc–air batteries, Fe_SA/NSC demonstrates superior power density, long-term discharge stability and specific capacity to the commercial Pt/C catalyst. Thus, Fe_SA/NSC is a promising non-platinum-group metal ORR catalyst for the ORR and application in zinc–air batteries.