Recent advances in Fe-N-C single-atom site coupled synergistic catalysts for boosting oxygen reduction reaction

Metal-air batteries,fuel cells,and electrochemical H_(2)O2 production currently attract substantial consideration in the energy sector owing to their efficiency and eco-consciousness.However,their broader use is hindered by the complex oxygen reduction reaction(ORR)that occurs at cathodes and involves intricate electron transfers.Despite the significant ORR performance of platinum-based catalysts,their high cost,operational limitations,and susceptibility to methanol poisoning hinder broader implementation.This emphasizes the need for efficient nonprecious metal-based ORR electrocatalysts.A promising approach involves utilizing single-atom catalysts(SACs)featuring metal-nitrogen-carbon(M-N-C)coordination sites.SACs offer advantages such as optimal utilization of metal atoms,uniform active centers,precisely defined catalytic sites,and robust metal-support interactions.However,the symmetrical electron distribution around the central metal atom of a single-atom site(M-N4)often results in suboptimal ORR performance.This challenge can be addressed by carefully tailoring the surrounding environment of the active center.This review specifically focuses on recent advancements in the Fe-N4 environment within Fe-N-C SACs.It highlights the promising strategy of coupling Fe-N4 sites with metal clusters and/or nanoparticles,which enhances intrinsic activity.By capitalizing on the interplay between Fe-N4 sites and associated species,overall ORR performance improved.The review combines findings from experimental studies and density functional theory simulations,covering synthesis strategies for Fe-N-C coupled synergistic catalysts,characterization techniques,and the influence of associated particles on ORR activity.By offering a comprehensive outlook,the review aims to encourage research into high-efficiency Fe single-atom sites coupled synergistic catalysts for real-world applications in the coming years.