Nano-Stabilizer Engineering of Rare-Earth Metal Single-Atom Site for Boosted Oxygen Electroreduction and Metal-Air Batteries.

Stabilizing the coordination structure of highly active catalytic sites is an effective strategy for enhancing catalytic performance. Herein, rare-earth metal Pr-based single-atom nano-stabilizer engineering is reported for stabilizing highly active Fe-N4O sites, thereby achieving enhanced activity toward the oxygen reduction reaction and in metal-air batteries. In situ x-ray absorption spectroscopy reveals that the axial O coordination atom of the Fe-N4O site is stabilized by the Pr single-atom nano-stabilizer, which downshifts the d-band center of Fe, facilitates the reduction and desorption of the *OH intermediate, and thus lowers the energy barrier of the rate-determining step-verified via density functional theory calculations. The FePr-ISAS/CN catalyst with the nano-stabilizer exhibits a half-wave potential of 0.921 V versus RHE, 45 and 72 mV higher than those of Fe-ISAS/CN and the commercial Pt/C catalyst. Furthermore, the FePr-ISAS/CN-based Al-air battery achieves a high peak power density of 360 mW cm-2, superior to most reported metal single-atom catalyst-based Al-air batteries. This work reveals the potential of rare-earth metal-based nano-stabilizer engineering for stabilizing the coordination structure of highly active sites and thereby boosting activity in both electrocatalytic ORR and metal-air battery devices.