Mechanistic insight into the Fe-atom-pairs for breaking the scaling relation in ORR

Dual-atom catalysts (DACs) show great potential for efficiently regulating multiple reaction pathways and well understanding of the fundamental mechanisms, therefore are expected to break the limitations of single-atom catalysts (SACs) in heterogeneous catalysis. Herein, Fe-DAs/NC with Fe2-N6 moieties was successfully synthesized by pyrolysis of nano-confined Fe-ZIF-8, and further employed as alkaline oxygen reduction reaction (ORR) catalyst. We propose that the two adjacent Fe atoms of Fe2-N6 moiety in Fe-DAs/NC can cooperatively bond the O2 molecule via a dual-side adsorption to boost the initial O2 adsorption and O-O dissociation, meanwhile the individual Fe atom in Fe2-N6 moiety with decreased d-band center can further break the energy barrier limit for efficient desorption of the final OH* intermediate. Due to the synergistic effect of Fe2-N6 moiety, the ORR performances of Fe-DAs/NC were fully improved compared to the single-atom Fe-N4 catalyst. Specifically, FeDAs/NC displays a large half-wave potential of 0.93 V, fast kinetics, high selectivity, and robust stability. And, Fe-DAs/NC-based Zn-air battery shows superior specific capacity, power density, and cycle stability than the commercial Pt/C. Our findings pave the way for rational design of atomically dispersed catalysts and afford an intensive understanding of the relationship between the structure and catalytic mechanism at the atomic scale.

Automated summary

Dual-atom catalysts (DACs) have the potential to efficiently regulate multiple reaction pathways and understand the fundamental mechanisms, breaking the limitations of single-atom catalysts (SACs) in heterogeneous catalysis. Fe-DAs/NC with Fe2-N6 moieties was successfully synthesized and employed as an alkaline oxygen reduction reaction (ORR) catalyst. The ORR performances of Fe-DAs/NC were significantly improved compared to single-atom Fe-N4 catalyst due to the synergistic effect of Fe2-N6 moiety.