Engineering CoN₄ and FeN₄ Dual Sites with Adjacent Nanoclusters on Flexible Porous Carbon Fibers for Enhanced Electrocatalytic Oxygen Reduction and Evolution

Dual-atom catalysts (DACs) possess tunable electronic structures and efficient atom utilization, making them highly promising for catalyzing the oxygen reduction reaction/oxygen evolution reaction (ORR/OER). However, achieving high catalytic activity and stability for both ORR and OER in DACs remains a challenge. Herein, a flexible membrane of porous carbon fiber anchored with atomically scattered CoN₄/FeN₄ dual sites and adjacent Co₂Fe₂/Fe₅ nanoclusters (Co, Fe-DACs/NCs@PCF) is synthesized. The local geometry and electronic structure of the CoN₄/FeN₄ sites, which act as reaction centers for ORR/OER, are finely regulated by the neighboring Co₂Fe₂/Fe₅ nanoclusters. This unique structure imparts Co, Fe-DACs/NCs@PCF with exceptional activity and durability toward ORR/OER, outperforming the performance of single-atom catalysts containing only CoN₄ or FeN₄ sites, as well as commercial Pt/C and RuO₂ catalysts. Zinc–air battery employing a Co, Fe-DACs/NCs@PCF cathode exhibits outstanding stability, maintaining cyclability for over 1500 h, outperforming a Pt/C + RuO₂ air cathode. Theoretical calculations highlight distinct synergies between Fe₅ (Co₂Fe₂) clusters and FeN₄ (CoN₄) sites, which optimize the coupling strength of Fe(Co)─OH at the potential-determining steps and thus improve ORR (OER) catalytic kinetics. This study lays a theoretical and practical foundation for rational design of heterostructure catalysts featuring coexisting DACs and nanoclusters within porous carbon fibers.