Atomically Dispersed Pentacoordinated‐Zirconium Catalyst with Axial Oxygen Ligand for Oxygen Reduction Reaction.

Single‐atom catalysts (SACs), as promising alternatives to Pt‐based catalysts, suffer from the limited choice of center metals and low single‐atom loading. Here, we report a pentacoordinated Zr‐based SAC with nontrivial axial O ligands (denoted O−Zr−N−C) for oxygen reduction reaction (ORR). The O ligand downshifts the d‐band center of Zr and confers Zr sites with stable local structure and proper adsorption capability for intermediates. Consequently, the ORR performance of O−Zr−N−C prominently surpasses that of commercial Pt/C, achieving a half‐wave potential of 0.91 V vs. reversible hydrogen electrode and outstanding durability (92 % current retention after 130‐hour operation). Moreover, the Zr site shows good resistance towards aggregation, enabling the synthesis of Zr‐based SAC with high loading (9.1 wt%). With the high‐loading catalyst, the zinc‐air battery (ZAB) delivers a record‐high power density of 324 mW cm−2 among those of SAC‐based ZABs. [ABSTRACT FROM AUTHOR]