A "Dual Spatial Confinement" Route to Tailor Efficient Dual-Active Sites ORR Catalyst for Rechargeable Zn-Air Batteries.

Dual active center catalysts (DACs) are effective for accelerating the sluggish kinetics of cathodic oxygen reduction reaction (ORR) in rechargeable zinc-air batteries (ZABs). However, their tendency to aggregate severely restrict the catalytic efficiency. Herein, a "dual spatial confinement" route is conceived to develop a family of well-dispersed DACs for boosting ORR activity and ZABs. During pyrolysis, the Zn vacancies generated from Zn-Zeolitic imidazolate framework (Zn-ZIF) precursors facilitate the initial incorporation and confinement of Fe/Co atoms, enabling the formation of uniformly dispersed metal sites. Subsequently, the in-situ grown N-doped carbon nanotubes (CNTs) further regulate the dual active centers (CoFe and CoN), ultimately yielding a highly efficient ORR catalyst. Owing to the synergistic effect between the dual active centers, the optimized CoFe/CoN@CNT-900 catalyst exhibits superior 4e ORR activity. Theoretical calculations demystify that the CoFe/CoN sites co-promote the generation of OH on Co centers, greatly enhance the ORR activity. When applied in rechargeable ZABs, the catalyst delivers a high power density of 168.99 mW cm, a high specific capacity of 904.57 mAh g , and good cycling stability, along with fine rate capability. This work shall light a pathway towards dual active center catalysts with sterling ORR activity.