Elucidating activity-stability trade-offs in nano-fingerprint carbon anchoring single atoms and clusters in oxygen reduction reaction

Hybrid sites (M1+x) that incorporate single atoms (M1) with clusters (Mx) hold great potential for overcoming linear scaling relations in electrocatalysis, but spatial decoupling of M1 from Mx fundamentally hampers intercomponent synergy. Here, we report a composite electrocatalyst (Zn1Fe1+x/f-NC) featuring Fex clusters encapsulated within nano-fingerprint carbon layers and surrounded by densely dispersed Fe/Zn-N4 atomic sites. Decoupling experiments revealed that Fe1/Zn1 atomic sites mainly initiate catalytic activity, while Fex clusters further boost intrinsic activity, whereas nano-fingerprint carbon facilitates the confinement and stabilization of M1+x. The Zn1Fe1+x/f-NC demonstrates competitive oxygen reduction reaction performance, achieving a half-wave potential of 0.93 V and stability over 50 h. Zinc-air batteries with Zn1Fe1+x/f-NC air cathode exhibit a peak power density of 263.82 mW·cm−2 and robust stability exceeding 2200 h at 10 mA cm−2. Density functional theory calculations reveal that the atomic Zn sites, Fex clusters and nano-fingerprint carbon layers jointly enhance the catalytic activity and stability by modulating the electronic structure of Fe-N4 sites and optimizing the adsorption energy of the key intermediate, especially OH*. Hybrid sites of single atoms and clusters promise to overcome scaling relations but are limited by spatial decoupling. Here, the authors report an electrocatalyst (Zn1Fe1+x/f-NC) with Fex clusters and Fe/Zn-N4 sites within nano-fingerprint carbon layers, enhancing ORR and Zn-air battery performance.