Simultaneously Engineering the Coordination Environment and Pore Architecture of Metal-Organic Framework-Derived Single-Atomic Iron Catalysts for Ultraefficient Oxygen Reduction.

Abstract

Designing highly efficient and durable electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics for fuel cells and metal-air batteries are highly desirable but challenging. Herein, a facile yet robust strategy is reported to rationally design single iron active centers synergized with local S atoms in metal-organic frameworks derived from hierarchically porous carbon nanorods (Fe/N,S-HC). The cooperative trithiocyanuric acid-based coating not only introduces S atoms that regulate the coordination environment of the active centers, but also facilitates the formation of a hierarchically porous structure. Benefiting from electronic modulation and architectural functionality, Fe/N,S-HC catalyst shows markedly enhanced ORR performance with a half-wave potential (E1/2 ) of 0.912\xa0V and satisfactory long-term durability in alkaline medium, outperforming those of commercial Pt/C. Impressively, Fe/N,S-HC-based Zn-air battery also presents outstanding battery performance and long-term stability. Both electrochemical experimental and density functional theoretical (DFT) calculated results suggest that the FeN4 sites tailored with local S atoms are favorable for the adsorption/desorption of oxygen intermediate, resulting in lower activation energy barrier and ultraefficient oxygen reduction catalytic activity. This work provides an atomic-level combined with porous morphological-level insights into oxygen reduction catalytic property, promoting rational design and development of novel highly efficient single-atom catalysts for the renewable energy applications.