Transition metal–nitrogen–carbon (TM–N–C) catalysts have been intensely investigated to tackle the sluggish oxygen reduction reactions (ORRs), but insufficient accessibility of the active sites limits their performance. Here, by using solid ZIF‐L nanorods as self‐sacrifice templates, a ZIF‐phase‐transition strategy is developed to fabricate ZIF‐8 hollow nanorods with open cavities, which can be subsequently converted to atomically dispersed Fe‐N‐C hollow nanorods (denoted as Fe1–N–C HNRs) through rational carbonization and following fixation of iron atoms. The microstructure observation and X‐ray absorption fine structure analysis confirm abundant Fe–N4 active sites are evenly distributed in the carbon skeleton. Thanks to the highly accessible Fe‐N4 active sites provided by the highly porous and open carbon hollow architecture, the Fe1‐N‐C HNRs exhibit superior ORR activity and stability in alkaline and acidic electrolytes with very positive half‐wave potentials of 0.91 and 0.8 V versus RHE, respectively, both of which surpass those of commercial Pt/C. Remarkably, the dynamic current density (JK) of Fe1‐N‐C HNRs at 0.85 V versus RHE in alkaline media delivers a record value of 148 mA cm−2, 21 times higher than that of Pt/C. The assembled Zn‐air battery using Fe1–N–C HNRs as cathode catalyst exhibits a high peak power density of 208 mW cm−2.

Single‐atom Fe‐N‐C (denoted as Fe1‐N‐C) catalysts exhibit inadequate bifunctional activities to conquer the sluggish oxygen reduction and evolution reaction (ORR/OER), hindering their practical applications in rechargeable Zn‐air batteries (ZABs). Here, by employing Fe1‐N‐C hollow nanorods as ORR‐active support, OER‐active NiFe‐layered double hydroxide (NiFe‐LDH) nanodots are evenly decorated through a spatially confined process to form NiFe‐LDH/Fe1‐N‐C heterostructure hollow nanorods with abundant accessible catalytic sites. The NiFe‐LDH/Fe1‐N‐C heterostructure not only enhances the ORR activity of pristine Fe1‐N‐C but also realizes efficient bifunctional ORR/OER activity in one monolithic catalyst. Theoretical calculations reveal that introducing NiFe‐LDH nanodots results in donation of electrons to the Fe1‐N‐C matrix and thus lowers the Fe‐d band center of the Fe‐N4 sites, dramatically narrowing the energy barriers of the ORR rate‐limiting steps. As a result, NiFe‐LDH/Fe1‐N‐C nanorods deliver remarkable ORR activity with a half‐wave potential of 0.90 V versus reversible hydrogen electrode, surpassing bare Fe1‐N‐C and commercial Pt/C. Impressively, the integrated NiFe‐LDH/Fe1‐N‐C catalysts show outstanding bifunctional performance with a small overpotential gap of only 0.65 V. The liquid‐state ZABs with NiFe‐LDH/Fe1‐N‐C as an air‐cathode catalyst deliver a peak power density of 205 mW cm−2 and long‐term cycling stability of up to 400 h.

Design and synthesis of non-precious-metal single-atom catalysts with favorable coordination environments and abundant accessible active sites to boost the sluggish oxygen reduction reactions (ORRs) is highly desirable for both fuel...

Development of bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) are urgently needed for advanced energy storage and conversion devices including rechargeable Zn-air batteries. Herein,...

Bifunctional Oxygen Catalysts In article number 2203609, Fei‐Xiang Ma, Cheng‐Yan Xu, and co‐workers design a NiFe‐LDH/Fe1‐N‐C heterostructure to achieve bifunctional oxygen reduction reaction/oxygen evolution reaction activity in one monolithic catalyst, in which NiFe‐LDH can regulate the electronic structures of atomic Fe‐N4 sites by donating electrons.