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

Abstract

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.